As filed with the Securities and Exchange Commission on August 14, 2013

Registration No. 333-          

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

HYPERION THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

Delaware	2834	61-1512713
(State or other jurisdiction of incorporation or organization)	(Primary standard industrial classification code number)	(I.R.S. Employer Identification Number)

601 Gateway Boulevard, Suite 200

South San Francisco, California 94080

(650) 745-7802

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Donald J. Santel

Chief Executive Officer

Hyperion Therapeutics, Inc.

601 Gateway Boulevard, Suite 200

South San Francisco, California 94080

(650) 745-7802

(Name, address, including zip code, and telephone number, including area code, of agent for service)

with copies to:

Laura A. Berezin

Hogan Lovells US LLP

525 University Avenue

Palo Alto, CA 94301

(650) 463-4000

Approximate date of commencement of proposed sale to the public: From time to time on or after the effective date of this Registration Statement.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box.    ¨

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box.    x

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    ¨

If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.    ¨

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.    ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

Large accelerated filer	¨	Accelerated filer	¨
Non-accelerated filer	x  (Do not check if a smaller reporting company)	Smaller reporting company	¨

CALCULATION OF REGISTRATION FEE

Title of each class of securities to be registered	Amount to be Registered(1)	Proposed Maximum Offering Price per Unit(2)	Proposed Maximum Aggregate Offering Price	Amount of Registration Fee(3)
Primary Offering:
Common Stock, par value $0.0001 per share	—	—	—	—
Preferred Stock, par value $0.0001 per share	—	—	—	—
Debt Securities	—	—	—	—
Warrants	—	—	—	—
Units
Total	—	—	$150,000,000(2)(3)	$20,460
Secondary Offering:
Common Stock, par value $0.0001 per share	8,727,000(4)	24.525(5)	214,029,675(5)	$29,194
Total				$49,654

(1) With respect to the primary offering, an indeterminate aggregate initial offering price and number or amount of the securities of each identified class is being registered as may from time to time be issued at currently indeterminable prices and as may be issuable upon conversion, redemption, repurchase, exchange or exercise of any of the securities registered hereunder. Separate consideration may or may not be received for securities that are issuable on exercise, conversion or exchange of other securities or that are issued in units. Securities registered hereby may be sold separately, together or in units with other securities registered hereby.

(2) With respect to the primary offering, the proposed maximum offering price will be determined from time to time by the registrant in connection with the issuance by the registrant of the securities registered hereunder, and is not specified as to each class of security pursuant to General Instruction II.D. of Form S-3 under the Securities Act of 1933, as amended (the “Securities Act”).

(3) Calculated pursuant to Rule 457(o) under the Securities Act based on the proposed maximum aggregate offering price.

(4) In addition, pursuant to Rule 416(a) under the Securities Act, the shares of common stock being registered for the selling stockholders hereunder include such indeterminate number of shares as may be issuable as a result of stock splits, stock dividends or similar transactions.

(5) Calculated pursuant to Rule 457(c) under the Securities Act solely for the purpose of calculating the registration fee, based upon the average of the high and low sales prices of the Registrant’s common stock on August 12, 2013, as reported on the NASDAQ Global Market. The proposed maximum offering price per share of common stock will be determined from time to time by the selling stockholder in connection with, and at the time of, the sale by the selling stockholder of the securities registered hereunder.

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment, which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

EXPLANATORY NOTE

This registration statement contains two prospectuses:

• a base prospectus which covers both (i) the offering, issuance and sale by the registrant of up to a maximum aggregate offering price of $150,000,000 of the registrant’s common stock, preferred stock, debt securities, warrants and/or units and (ii) sales of common stock by certain selling stockholders; and

• a sales agreement prospectus covering the offering, issuance and sale by the registrant of up to a maximum aggregate offering price of $50,000,000 of the registrant’s common stock that may be issued and sold under a sales agreement with Cantor Fitzgerald & Co.

The base prospectus immediately follows this explanatory note. The sales agreement prospectus immediately follows the base prospectus. The common stock that may be offered, issued and sold by the registrant under the sales agreement prospectus is included in the $150,000,000 of securities that may be offered, issued and sold by the registrant under the base prospectus.

The information in this prospectus is not complete and may be changed. Neither we nor any selling stockholder may sell any of these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

Subject to Completion, dated August 14, 2013.

PROSPECTUS

$150,000,000

Common Stock

Debt Securities

Preferred Stock

Warrants

Units

8,727,000 Shares of Common Stock Offered by the Selling Stockholders

We may offer and sell up to $150,000,000 in the aggregate of the securities identified above from time to time in one or more offerings. In addition, the selling stockholders named in this prospectus may offer and sell up to an aggregate of 8,727,000 shares of common stock, from time to time, on the terms described in this prospectus or in the applicable prospectus supplement, if any. This prospectus provides you with a general description of the securities.

Each time we or the selling stockholders offer and sell securities, we will provide a supplement to this prospectus (which includes, but is not limited to, an at-the-market sales agreement prospectus) that contains specific information about the offering and the amounts, prices and terms of the securities. The supplement may also add, update or change information contained in this prospectus with respect to that offering. You should carefully read this prospectus and the applicable prospectus supplement before you invest in any of our securities.

We or the selling stockholders may offer and sell the securities described in this prospectus and any prospectus supplement to or through one or more underwriters, dealers and agents, or directly to purchasers, or through a combination of these methods. If any underwriters, dealers or agents are involved in the sale of any of the securities, their names and any applicable purchase price, fee, commission or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement. See the sections of this prospectus entitled “About this Prospectus” and “Plan of Distribution” for more information. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such securities.

You should read carefully this prospectus, the documents incorporated by reference in this prospectus and any prospectus supplement before you invest. Investing in our common stock involves risks. Please see “Risk Factors” on page 7 for more information.

Our common stock is listed on The NASDAQ Global Market under the symbol “HPTX.” As of August 12, 2013, the closing price of our common stock was $24.94.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is                , 2013.

TABLE OF CONTENTS

	Page
About this Prospectus		1
Where You Can Find More Information		2
Incorporation of Certain Information by Reference		2
Special Note Regarding Forward-looking Statements		4
The Company		5
Risk Factors		7
Use of Proceeds		8
Dividend Policy		8
Ratio of Earnings to Fixed Charges		9
Description of Capital Stock		10
Description of Debt Securities		15
Description of Warrants		26
Description of Units		27
Selling Stockholders		28
Plan of Distribution		29
Legal Matters		32
Experts		32

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ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the U.S. Securities and Exchange Commission, or the SEC, using a “shelf” registration process.

By using a shelf registration statement, we may sell the securities described in this prospectus in one or more offerings up to a total offering price of $150,000,000 and the selling stockholders to be named in a prospectus supplement may sell up to 8,727,000 shares of common stock. Each time that we offer and sell securities, we will provide a prospectus supplement to this prospectus (which term includes, as applicable, the at-the-market sales agreement prospectus filed with the registration statement of which this prospectus forms a part) that contains specific information about the securities being offered and sold and the specific terms of that offering. In addition, if the selling stockholders offer securities to or through underwriters, dealers or agents, their names and other applicable details will be included in a prospectus supplement. The prospectus supplement may also add, update or change information contained in this prospectus with respect to that offering. If there is any inconsistency between the information in this prospectus and the applicable prospectus supplement, you should rely on the prospectus supplement. Before purchasing any securities, you should carefully read both this prospectus and the applicable prospectus supplement, together with the additional information described under the headings “Where You Can Find More Information” and “Incorporation of Certain Information by Reference.”

You should rely only on the information incorporated by reference or provided in this prospectus. We have not authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We will not make an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus and the applicable prospectus supplement to this prospectus is accurate as of the date on its respective cover, and that any information incorporated by reference is accurate only as of the date of the document incorporated by reference, unless we indicate otherwise. Our business, financial condition, results of operations and prospects may have changed since those dates.

Unless the context otherwise requires or as otherwise expressly stated, references in this prospectus to the “Company,” “Hyperion,” “we,” “us” and “our” and similar terms refer to Hyperion Therapeutics, Inc. and our subsidiaries on a consolidated basis, as appropriate in the context.

This prospectus, including the information incorporated by reference into this prospectus, includes trademarks, service marks and trade names owned by us or others. The names Hyperion Therapeutics, Inc.^TM and RAVICTI^® are our trademarks and BUPHENYL^® is our registered trademark. AMMONUL^® is the registered trademark of Ucyclyd Pharma, Inc., a wholly owned subsidiary of Medicis Pharmaceutical Corporation, which became a wholly owned subsidiary of Valeant Pharmaceuticals International, Inc. on December 11, 2012. All other trademarks, trade names and service marks appearing in this prospectus are the property of their respective owners.

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WHERE YOU CAN FIND MORE INFORMATION

We are currently subject to the reporting requirements of the Securities Exchange Act of 1934, as amended, which we refer to as the “Exchange Act” in this prospectus, and in accordance therewith file periodic reports, proxy statements and other information with the Securities and Exchange Commission. You may read and copy (at prescribed rates) any such reports, proxy statements and other information at the SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the operation of the public reference room. Our SEC filings are also available to you on the SEC’s website at http://www.sec.gov and in the Investors section of our website at http://www.hyperiontx.com. Our website and the information contained on that site, or connected to that site, are not incorporated into and are not a part of this prospectus.

This prospectus and any prospectus supplement are part of a registration statement that we filed with the SEC and do not contain all of the information in the registration statement. The full registration statement may be obtained from the SEC or us, as provided below. Forms of the indenture and other documents establishing the terms of the offered securities are or may be filed as exhibits to the registration statement. Statements in this prospectus or any prospectus supplement about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the actual documents for a more complete description of the relevant matters. You may inspect a copy of the registration statement at the SEC’s Public Reference Room in Washington, D.C. or through the SEC’s website, as provided above.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC’s rules allow us to “incorporate by reference” information into this prospectus, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, and subsequent information that we file with the SEC will automatically update and supersede that information. Any statement contained in a previously filed document incorporated by reference will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus modifies or replaces that statement.

We incorporate by reference our documents listed below and any future filings made by us with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act between the date of this prospectus and the termination of the offering of the securities described in this prospectus. We are not, however, incorporating by reference any documents or portions thereof, whether specifically listed below or filed in the future, that are not deemed “filed” with the SEC, including any information furnished pursuant to Items 2.02 or 7.01 of Form 8-K or related exhibits furnished pursuant to Item 9.01 of Form 8-K.

This prospectus and any accompanying prospectus supplement incorporate by reference the documents set forth below that have previously been filed with the SEC:

• our Annual Report on Form 10-K/A for the year ended December 31, 2012, which was filed with the SEC on February 26, 2013;

• our Quarterly Reports on Form 10-Q for the fiscal quarters ended March 31, 2013 and June 30, 2013, which were filed with the SEC on May 10, 2013 and August 14, 2013, respectively;

• our Current Reports on Form 8-K, which were filed with the SEC on January 16, 2013, January 22, 2013, February 1, 2013, February 20, 2013, February 25, 2013 (Item 5.02), April 11, 2013, April 30, 2013, June 3, 2013 and August 12, 2013; and

• the description of our common stock contained in our registration statement on Form 8-A, which was filed on July 25, 2012, including any amendments or reports filed for the purpose of updating the description.

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Any statement contained in a document incorporated by reference in this prospectus shall be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus or in any other subsequently filed document that also is or is deemed to be incorporated by reference in this prospectus modifies or supersedes such statement. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus.

You may obtain copies of any of these filings by contacting us at the address and telephone number indicated below or by contacting the SEC as described above under the section entitled “Where You Can Find More Information.” Documents incorporated by reference are available from us without charge, excluding all exhibits unless an exhibit has been specifically incorporated by reference into this prospectus, by requesting them in writing or by telephone at:

Hyperion Therapeutics, Inc.

Attention: Investor Relations

601 Gateway Boulevard, Suite 200

South San Francisco, California 94080

(650) 745-7802

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, including the documents incorporated by reference herein and therein, and any free writing prospectus that we have authorized for use in connection with this offering contain “forward-looking statements” within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act that involve substantial risks and uncertainties. In some cases you can identify these statements by forward-looking words such as “believe,” “may,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “could,” “would,” “project,” “plan,” “expect,” or similar expressions, or the negative or plural of these words or expressions. These forward-looking statements include, but are not limited to, statements concerning the following:

• the commercial launch of RAVICTI and future sales of RAVICTI, BUPHENYL or any other future products or product candidates;

• our expectations regarding the commercial supply of our UCD products;

• third-party payor reimbursement for RAVICTI and BUPHENYL;

• our estimates regarding anticipated capital requirements and our needs for additional financing;

• the UCD or HE patient market size and market adoption of RAVICTI by physicians and patients;

• the timing or cost of a Phase III trial in HE;

• the development and approval of the use of RAVICTI for additional indications or in combination therapy;

• our expectations regarding licensing, acquisitions and strategic operations;

• impact of accounting standards; and

• repayment of notes payable.

These statements are only current predictions and are subject to known and unknown risks, uncertainties, and other factors that may cause our or our industry’s actual results, levels of activity, performance or achievements to be materially different from those anticipated by the forward-looking statements. We discuss many of these risks in this report in greater detail under the heading “Risk Factors” and elsewhere in this report. You should not rely upon forward-looking statements as predictions of future events.

Although we believe that the expectations reflected in the forward-looking statements are reasonable, we cannot guarantee future results, levels of activity, performance, or achievements. Except as required by law, we are under no duty to update or revise any of the forward-looking statements, whether as a result of new information, future events or otherwise, after the date of this report.

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THE COMPANY

This summary contains a general summary of the information contained in this prospectus. It may not include all the information that is important to you. You should read the entire prospectus, the prospectus supplement delivered with the prospectus, if any, and the documents incorporated by reference before making an investment decision.

Overview

We are a biopharmaceutical company focused on the development and commercialization of novel therapeutics to treat disorders in the areas of orphan diseases and hepatology. We have developed our product, RAVICTI^® (glycerol phenylbutyrate) Oral Liquid, to treat the most prevalent urea cycle disorders, or UCD, and are developing glycerol phenylbutyrate, or GPB, to treat hepatic encephalopathy, or HE, two different diseases in which blood ammonia is elevated. UCD are inherited rare genetic diseases caused by a deficiency of one or more enzymes or protein transporters that constitute the urea cycle, which in a healthy individual removes ammonia through the conversion of ammonia to urea. HE may develop in some patients with liver scarring, known as cirrhosis, or acute liver failure and is a chronic disease which fluctuates in severity and may lead to serious neurological damage. On February 1, 2013, the U.S. Food and Drug Administration, or the FDA, granted approval of RAVICTI for use as a nitrogen-binding agent for chronic management of UCD in adult and pediatric patients greater than two years of age who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. Limitations of use for RAVICTI include treatment of patients with acute hyperammonemia, or HA, crises for whom urgent intervention is typically necessary, patients with N-acetylglutamate synthetase deficiency for whom the safety and efficacy of RAVICTI has not been established, and UCD patients under two months of age for whom RAVICTI is contraindicated due to uncertainty as to whether newborns, who may have immature pancreatic function, can effectively digest RAVICTI. We commercially launched RAVICTI during the first quarter of 2013. On May 1, 2013, we received notification from the FDA that RAVICTI qualified for orphan drug exclusivity.

Pursuant to an amended and restated collaboration agreement with Ucyclyd Pharma, Inc., or Ucyclyd, a subsidiary of Valeant Pharmaceuticals International, Inc., we exercised our option to acquire BUPHENYL and AMMONUL^® (sodium phenylacetate and sodium benzoate) injection 10%/10% from Ucyclyd on April 29, 2013. On May 31, 2013, we received a net payment of $11 million from Ucyclyd, which reflected the $32.0 million contractual purchase price for AMMONUL due to us less the $19.0 million contractual purchase price for BUPHENYL due to Ucyclyd and $2.0 million payment due to Ucyclyd for inventory we purchased from Ucyclyd. We are obligated to pay subsequent milestone and royalty payments to Ucyclyd.

On March 13, 2013, we completed a follow-on offering and issued 2,875,000 shares of our common stock at an offering price of $20.75 per share. In addition, we sold an additional 431,250 shares of common stock directly to our underwriters when they exercised their over-allotment option in full at an offering price of $20.75 per share. We received net proceeds from the offering of $63.7 million, after deducting underwriting discounts and commissions of $4.1 million and expenses of $0.8 million.

On July 31, 2012, we completed our initial public offering, or IPO, and issued 5,000,000 shares of our common stock at an initial offering price of $10.00 per share. We sold an additional 750,000 shares of common stock directly to our underwriters when they exercised their over-allotment option in full at the initial offering price of $10.00 per share. Our shares began trading on the NASDAQ Global Market on July 26, 2012. We received net proceeds from the IPO of $51.3 million, after deducting underwriting discounts and commissions of $4.0 million and expenses of $2.2 million

In April 2012, our Phase II HE trial data was unblinded and the trial met its primary endpoint, which was to demonstrate that the proportion of patients experiencing an HE event was significantly lower on GPB versus placebo, both administered in addition to a standard of care, including lactulose and/or rifaximin. We expect our

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research and development expenses to increase when we initiate a Phase III trial of GPB in HE. We will likely continue to incur significant commercial, sales, marketing and outsourced manufacturing expenses in connection with the commercialization of RAVICTI and BUPHENYL in UCD. These increased expenses as compared to prior years, include payroll related expenses due to the addition of employees in the commercial, manufacturing and regulatory departments, costs related to the initiation and operation of our distribution network, and marketing costs and general infrastructure expenses as we expand our organization.

Our Corporate Information

We were incorporated under the laws of the State of Delaware in November 2006. Our principal executive office is located at 601 Gateway Boulevard, Suite 200, South San Francisco, CA 94080, and our telephone number is (650) 745-7802.

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RISK FACTORS

Investing in our securities involves a high degree of risk. You should carefully consider and evaluate all of the information contained in this prospectus, any accompanying prospectus supplement, and in the documents we incorporate by reference in this prospectus before you decide to purchase our securities. In particular, you should carefully consider and evaluate the risks and uncertainties described in “Part I — Item 1A. Risk Factors” of our most recent Quarterly Report on Form 10-Q, and any subsequent filings with the SEC that we file after the date of this prospectus, and all other information contained or incorporated by reference in this prospectus, as updated by our subsequent filings under the Exchange Act, and the risk factors and other information contained in the applicable prospectus supplement before acquiring any of such securities. Any of the risks and uncertainties set forth therein could materially and adversely affect our business, results of operations and financial condition, which in turn could materially and adversely affect the trading price or value of our securities. As a result, you could lose all or part of your investment.

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USE OF PROCEEDS

Unless otherwise indicated in the prospectus supplement, the net proceeds from the sale of securities offered by this prospectus will be used for general corporate purposes and working capital requirements. We may also use a portion of the net proceeds for the licensing or acquisition of, or the development of, additional product candidates and/or to fund possible investments in and the acquisition of complementary businesses or partnerships. However, we have no present plans with respect to acquisitions as of the date of this prospectus. As a result, unless otherwise indicated in the prospectus supplement, our management will have broad discretion to allocate the net proceeds of the offerings. Pending their ultimate use, we intend to invest the net proceeds in a variety of securities, including commercial paper, government and non-government debt securities and/or money market funds that invest in such securities.

We will not receive proceeds of any sale of securities by selling stockholders.

DIVIDEND POLICY

We have never declared or paid any cash dividends on our capital stock and do not anticipate paying any cash dividends in the foreseeable future. Payment of cash dividends, if any, in the future will be at the discretion of our board of directors and will depend on then-existing conditions, including our financial condition, operating results, contractual restrictions, capital requirements, business prospects and other factors our board of directors may deem relevant.

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RATIO OF EARNINGS TO FIXED CHARGES

The following table sets forth the historical ratios of earnings to fixed charges for the periods indicated. As the ratios of earnings to fixed charges indicate less than one-to-one coverage in each of the years presented, we have provided the coverage deficiency amounts for those periods. You should read these figures in connection with our consolidated financial statements, including the notes to those statements, incorporated by reference in this prospectus. The following table excludes a ratio of earnings to combined fixed charges and preferred stock dividends since we did not have an obligation to pay dividends on any of our preferred stock outstanding for the years ended December 31, 2011, 2010, 2009 or 2008. There was no preferred stock outstanding for the six months ended June 30, 2013 or for the year ended December 31, 2012. See Exhibit 12.1 hereto for additional detail regarding the computation of the deficiency of earnings to cover fixed charges.

(in thousands)	Six  Months Ended June 30, 2013		Year Ended December 31,
			2012			2011			2010			2009			2008
Ratio of earnings to fixed charges(1)		41.6		*			*			*			*			*
Earnings (Deficiency of earnings) available to cover fixed charges	$	16,047	($	32,263	)	($	29,416	)	($	25,453	)	($	13,600	)	($	29,099	)

* We did not record earnings for any of the fiscal years ending December 31, 2012, 2011, 2010, 2009 and 2008. Accordingly, our earnings were insufficient to cover fixed charges for such periods and we are unable to disclose a ratio of earnings to fixed charges for such periods.

(1) For purposes of calculating the ratio of earnings to fixed charges, “earnings” are calculated as follows: (i) adding (a) pre-tax income (loss) from continuing operations; (b) fixed charges; (c) amortization of capitalized interest; (d) distributed income of equity investees; and (e) our share of pre-tax losses of equity investees for which charges arising from guarantees are included in fixed charges; and (ii) then subtracting from such sum (a) interest capitalized and (b) any net income attributable to noncontrolling interests. “Fixed charges” are calculated as the sum of (a) interest costs (both expensed and capitalized), (b) amortization of debt expense and discount or premium relating to any indebtedness and (c) that portion of rental expense that is representative of the interest factor.

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DESCRIPTION OF CAPITAL STOCK

The following, together with the additional information we include in the applicable prospectus supplement, describes the common stock that we may offer under this prospectus, including the material provisions of our amended and restated certificate of incorporation and our amended and restated bylaws, the registration rights agreement to which we and certain of our stockholders are parties and certain provisions of the Delaware General Corporation Law. Because the following is only a summary, it does not contain all of the information that may be important to you. For a complete description, you should refer to our amended and restated certificate of incorporation, amended and restated bylaws and registration rights agreement, copies of which have been filed with the SEC. See “Where You Can Find More Information; Incorporation by Reference.”

General

Our amended and restated certificate of incorporation authorizes us to issue up to 100,000,000 shares of common stock, $0.0001 par value, and 10,000,000 shares of preferred stock, $0.0001 par value. As of August 12, 2013, there were outstanding:

• 20,087,200 shares of common stock outstanding;

• 2,856,224 shares of common stock subject to outstanding options; and

• 274 shares of common stock issuable upon the exercise of outstanding warrants.

Common Stock

Voting Rights.    Each holder of common stock is entitled to one vote for each share on all matters submitted to a vote of the stockholders. The affirmative vote of holders of at least 66% of the voting power of all of the then outstanding shares of capital stock, voting as a single class, will be required to amend certain provisions of our certificate of incorporation, including provisions relating to amending our bylaws, the classified board, the size of the board, removal of directors, director liability, vacancies on the board, special meetings, stockholder notices, actions by written consent and exclusive jurisdiction.

Dividends.    Subject to preferences that may be applicable to any outstanding preferred stock, holders of our common stock are entitled to receive ratably any dividends that may be declared by the board of directors out of funds legally available for that purpose.

Liquidation.    In the event of our liquidation, dissolution or winding up, the holders of our common stock are entitled to share ratably in all assets remaining after payment of liabilities and the liquidation preference of any outstanding preferred stock.

Rights and Preferences.    Holders of our common stock have no preemptive, conversion, subscription or other rights, and there are no redemption or sinking fund provisions applicable to our common stock. The rights, preferences and privileges of the holders of our common stock are subject to and may be adversely affected by the rights of the holders of shares of any series of our preferred stock that we may designate in the future.

Fully Paid and Nonassessable.    All outstanding shares of common stock are fully paid and non-assessable, and the shares of common stock to be issued upon the closing of this offering will be fully paid and non-assessable.

Preferred Stock

Our board of directors has the authority, without further action by our stockholders, to issue up to 10,000,000 shares of preferred stock in one or more series and to fix the number, rights, preferences, privileges and restrictions thereof. These rights, preferences and privileges could include dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, and sinking fund terms, and the number of shares

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constituting any series or the designation of such series, any or all of which may be greater than the rights of common stock. The issuance of our preferred stock could adversely affect the voting power of holders of common stock and the likelihood that such holders will receive dividend payments and payments upon liquidation. In addition, the issuance of preferred stock could have the effect of delaying, deferring or preventing a change of control or other corporate action. The issuance of preferred stock, while providing flexibility in connection with possible acquisitions and other corporate purposes, could, among other things, have the effect of delaying, deferring or preventing a change in control of our company and may adversely affect the market price of our common stock and the voting and other rights of the holders of common stock.

As of the date of this prospectus, no shares of preferred stock are outstanding. The particular terms of any series of preferred stock being offered by us under this prospectus will be described in the applicable prospectus supplement relating to that series of preferred stock. Those terms may include:

• the title and number of shares of the preferred stock being offered;

• the dividend rate (or method of calculation) and the dates on which dividends will be paid;

• whether dividends will be cumulative and, if so, the date from which dividends will begin to accumulate;

• the voting rights, if any, of the preferred stock; and

• any conversion provisions of the preferred stock;

• any redemption, repurchase or sinking fund provisions of the preferred stock;

• the liquidation preference per share of the preferred stock;

• any other relative powers, preferences, rights, qualifications, limitations or restrictions of the preferred stock.

The preferred stock will, when issued, be fully paid and non-assessable.

The description of preferred stock above and the description of the terms of a particular series of preferred stock in the applicable prospectus supplement are not complete. You should refer to the applicable certificate of designations for complete information. The prospectus supplement will also contain a description of U.S. federal income tax consequences relating to the preferred stock, if material.

Voting Rights.    The General Corporation Law of Delaware provides that the holders of preferred stock will have the right to vote separately as a class on any proposal involving fundamental changes in the rights of holders of that preferred stock. This right is in addition to any voting rights that may be provided for in the applicable certificate of designations.

Other.    Our issuance of preferred stock may have the effect of delaying or preventing a change in control. Our issuance of preferred stock could decrease the amount of earnings and assets available for distribution to the holders of common stock or other preferred stock or could adversely affect the rights and powers, including voting rights, of the holders of common stock or other preferred stock. The issuance of preferred stock could have the effect of decreasing the market price of our common stock.

Registration Rights

Holders of 5,772,326 shares of preferred stock, common stock, and common stock and preferred stock issuable upon exercise of warrants, have the right to demand that we file a registration statement or request that their shares be covered by a registration statement that we are otherwise filing, as described below.

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Demand Registration Rights

Holders of a majority of the shares having demand registration rights may make unlimited requests that we register all or a portion of their common stock for sale under the Securities Act on Form S-3, or any successor form, so long as the aggregate price to the public in connection with any such offering is at least $1.0 million.

Incidental Registration Rights

In addition, if at any time after our initial public offering, or IPO, we register any shares of our common stock, the holders of all shares having registration rights are entitled to notice of the registration and to include all or a portion of their common stock in the registration.

Other Provisions

In the event that any registration in which the holders of registrable shares participate pursuant to the registration rights agreement is an underwritten public offering, the number of registrable shares to be included may, in specified circumstances, be limited due to market conditions.

We will pay all registration expenses, other than underwriting discounts and selling commissions, and the reasonable fees and expenses of a single special counsel for the selling stockholders, related to any demand or piggyback registration. The registration rights agreement contains customary cross-indemnification provisions, pursuant to which we are obligated to indemnify the selling stockholders in the event of material misstatements or omissions in the registration statement attributable to us, and they are obligated to indemnify us for material misstatements or omissions in the registration statement attributable to them. The demand, piggyback and Form S-3 registration rights described above will expire, with respect to any particular stockholder, five years after our IPO or when that stockholder can sell all of its shares under Rule 144 of the Securities Act.

Anti-Takeover Provisions

Our Certificate of Incorporation and Bylaws

Our amended and restated certificate of incorporation and amended and restated bylaws include a number of provisions that may deter or impede hostile takeovers or changes of control or management. These provisions include:

• Issuance of undesignated preferred stock.    Our board of directors has the authority, without further action by the stockholders, to issue up to 10,000,000 shares of undesignated preferred stock with rights and preferences, including voting rights, designated from time to time by the board of directors. The existence of authorized but unissued shares of preferred stock enables our board of directors to make it more difficult or to discourage an attempt to obtain control of us by means of a merger, tender offer, proxy contest or otherwise.

• Classified board.    Our amended and restated certificate of incorporation provides for a classified board of directors consisting of three classes of directors, with staggered three-year terms. Only one class of directors will be elected at each annual meeting of our stockholders, with the other classes continuing for the remainder of their respective three-year terms. This provision may have the effect of delaying a change in control of the board of directors.

• Board of directors vacancies.    Our amended and restated certificate of incorporation and amended and restated bylaws authorize only our board of directors to fill vacant directorships. In addition, the number of directors constituting our board of directors may be set only by resolution adopted by a majority vote of our entire board of directors. These provisions prevent a stockholder from increasing the size of our board of directors and gaining control of our board of directors by filling the resulting vacancies with its own nominees.

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• Stockholder action; special meetings of stockholders.    Our amended and restated certificate of incorporation provides that our stockholders may not take action by written consent, but may only take action at annual or special meetings of our stockholders. Stockholders will not be permitted to cumulate their votes for the election of directors. Our amended and restated certificate of incorporation further provides that special meetings of our stockholders may be called only by the chairman of our board of directors or by a majority of our board of directors.

• Advance notice requirements for stockholder proposals and director nominations.    Our amended and restated bylaws provide advance notice procedures for stockholders seeking to bring business before our annual meeting of stockholders, or to nominate candidates for election as directors at our annual meeting of stockholders. Our bylaws also specify certain requirements as to the form and content of a stockholder’s notice. These provisions may make it more difficult for our stockholders to bring matters before our annual meeting of stockholders or to nominate directors at our annual meeting of stockholders.

These provisions are intended to enhance the likelihood of continued stability in the composition of our board of directors and its policies and to discourage certain types of transactions that may involve an actual or threatened acquisition of us. These provisions are designed to reduce our vulnerability to an unsolicited acquisition proposal. The provisions also are intended to discourage certain tactics that may be used in proxy fights. However, these provisions could have the effect of discouraging others from making tender offers for our shares and, as a consequence, they may also reduce fluctuations in the market price of our shares that could result from actual or rumored takeover attempts.

Section 203 of the Delaware General Corporation Law

We are subject to Section 203 of the DGCL, which prohibits a Delaware corporation from engaging in a business combination with any interested stockholder for a period of three years following the date the person became an interested stockholder, with the following exceptions:

• before such date, the board of directors of the corporation approved either the business combination or the transaction that resulted in the stockholder becoming an interested holder;

• upon completion of the transaction that resulted in the stockholder becoming an interested stockholder, the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction began, excluding for purposes of determining the voting stock outstanding (but not the outstanding voting stock owned by the interested stockholder) those shares owned (a) by persons who are directors and also officers and (b) pursuant to employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or

• on or after such date, the business combination is approved by the board of directors and authorized at an annual or special meeting of the stockholders, and not by written consent, by the affirmative vote of at least 66 ²/₃% of the outstanding voting stock that is not owned by the interested stockholder.

In general, Section 203 defines business combination to include the following:

• any merger or consolidation involving the corporation and the interested stockholder;

• any sale, transfer, pledge or other disposition of 10% or more of the assets of the corporation involving the interested stockholder;

• subject to certain exceptions, any transaction that results in the issuance or transfer by the corporation of any stock of the corporation to the interested stockholder;

• any transaction involving the corporation that has the effect of increasing the proportionate share of the stock or any class or series of the corporation beneficially owned by the interested stockholder; or

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• the receipt by the interested stockholder of the benefit of any loans, advances, guarantees, pledges or other financial benefits by or through the corporation.

In general, Section 203 defines an “interested stockholder” as an entity or person who, together with the entity’s or person’s affiliates and associates, beneficially owns, or is an affiliate of the corporation and within three years prior to the time of determination of interested stockholder status did own, 15% or more of the outstanding voting stock of the corporation.

Choice of Forum

Our amended and restated certificate of incorporation provides that the Court of Chancery of the State of Delaware will be the exclusive forum for any derivative action or proceeding brought on our behalf, any action asserting a breach of fiduciary duty owed by any director, officer or employee to us or our stockholders, any action asserting a claim against us arising pursuant to the DGCL or any action asserting a claim against us that is governed by the internal affairs doctrine. However, several lawsuits involving other companies have been brought challenging the validity of choice of forum provisions in certificates of incorporation, and it is possible that a court could rule that such provision is inapplicable or unenforceable.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Continental Stock Transfer & Trust Co.

Listing

Our common stock is listed on the NASDAQ Global Market under the symbol “HPTX.”

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DESCRIPTION OF DEBT SECURITIES

The following description sets forth certain general terms and provisions of the senior debt securities that may be offered by means of this prospectus. The particular terms of the debt securities being offered and the extent to which the general provisions described below apply will be described in a prospectus supplement relating to the debt securities.

Any senior debt securities offered by means of this prospectus will be issued under a senior indenture, as amended or supplemented from time to time, which we refer to as the “Indenture,” between us and such trustee as we may appoint. A form of the Indenture has been filed as an exhibit to the Registration Statement of which this prospectus is a part and will be available for inspection at the corporate trust office of the Trustee (as defined below) or as described above under “Where You Can Find More Information” and “Incorporation of Certain Information by Reference.”

The Indenture is and will be subject to and governed by the Trust Indenture Act of 1939. The description of the Indenture set forth below assumes that we have entered into the Indenture. We will execute and deliver the Indenture when and if we issue debt securities. The statements made in this prospectus relating to the Indenture and the debt securities to be issued under the Indenture are summaries of some provisions of the Indenture and such debt securities. The summaries do not purport to be complete and are subject to, and are qualified in their entirety by reference to, all provisions of the Indenture and such debt securities. Unless otherwise specified, capitalized terms used but not defined in this prospectus have the meanings set forth in the Indenture.

General

The debt securities offered by means of this prospectus will be our direct obligations. Senior debt securities will rank equally in right of payment with our other senior unsecured and unsubordinated debt that may be outstanding from time to time, and will rank senior in right of payment to all of any subordinated debt securities that may be outstanding from time to time.

The Indenture provides that debt securities may be issued without limit as to aggregate principal amount, in one or more series, in each case as may be authorized from time to time by us or as established in one or more indentures supplemental to the Indenture. All debt securities of one series need not be issued at the same time and, unless otherwise provided, a series may be reopened, without the consent of the holders of the debt securities of such series, for issuances of additional debt securities of such series.

The Indenture provides that there may be more than one trustee thereunder, each with respect to one or more series of debt securities (each, a “Trustee”). Any Trustee under the Indenture may resign or be removed with respect to one or more series of debt securities, and a successor Trustee will be appointed by us to act with respect to such series. If two or more persons are acting as Trustee with respect to different series of debt securities, each such Trustee will be a trustee of a trust under the Indenture separate and apart from the trust administered by any other Trustee thereunder, and, except as otherwise indicated herein or therein, any action described to be taken by the Trustee may be taken by each such Trustee with respect to, and only with respect to, the one or more series of debt securities for which it is Trustee under the Indenture.

The prospectus supplement relating to any series of debt securities being offered will contain information on the specific terms of those debt securities, including, without limitation:

• the principal amount offered;

• the title of the securities of the series;

• any limit upon the aggregate principal amount of the securities of the series which may be authenticated and delivered under the Indenture;

• the date or dates on which the principal of the securities is payable;

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• the rate or rates (which may be fixed or variable) at which the securities of the series shall bear interest, if any, the date or dates from which such interest shall accrue, the interest payment dates on which such interest shall be payable and the regular record date for the interest payable on any interest payment date;

• the person to whom any interest shall be payable;

• the place or places where the principal of (and premium, if any) and interest on securities of the series shall be payable, any securities of that series may be surrendered for conversion or exchange and notices and demands to or upon us in respect of the securities of that series and the Indenture may be served;

• the basis upon which any interest shall be calculated if other than that of a 360-day year consisting of twelve 30-day months;

• the period or periods within which, the price or prices at which, the currency or currency unit in which, and the terms and conditions upon which securities of the series may be redeemed, in whole or in part, at our option, if we have such an option;

• the terms, if any, upon which the securities of the series may be convertible into or exchanged for any of our capital stock or other securities or property (including cash or any combination thereof) and the terms and conditions upon which such conversion or exchange may be effected, including, without limitation, the initial conversion or exchange price or rate (or manner of calculation thereof), the portion that is convertible or exchangeable or the method by which any such portion shall be determined, the conversion or exchange period, provisions as to whether conversion or exchange will be at the option of the holders or at our option, the events requiring an adjustment of the conversion or exchange price, and provisions affecting conversion or exchange in the event of the redemption of such securities;

• our obligation, if any, to redeem or purchase securities of the series pursuant to any sinking fund or analogous provisions or at the option of a holder thereof and the period or periods within which, the price or prices at which, the currency or currency unit in which, and the terms and conditions upon which securities of the series shall be redeemed or purchased, in whole or in part, pursuant to such obligation;

• whether securities of the series are to be issued in registered form or bearer form or both, and if in bearer form, whether coupons will be attached to them and whether securities of the series in bearer form may be exchanged for securities of the series issued in registered form, and the circumstances under which and the places at which any such exchanges, if permitted, may be made;

• if the securities of the series are to be issued in bearer form or as one or more global notes representing securities of the series in bearer form, whether certain provisions for the payment of additional interest or tax redemptions shall apply; whether interest with respect to any portion of temporary securities of the series in bearer form payable with respect to any interest payment date prior to the exchange of such temporary securities in bearer form for definitive securities of a series in bearer form shall be paid to any clearing organization with respect to the portion of such temporary securities in bearer form held for its account and, in such event, the terms and conditions (including any certification requirements) upon which any such interest payment received by a clearing organization will be credited to the persons entitled to interest payable on such interest payment date; and the terms upon which a temporary securities in bearer form may be exchanged for one or more definitive securities of the series in bearer form;

• if other than denominations of $1,000 or any integral multiple thereof, the denominations in which securities of the series shall be issuable;

• if other than the Trustee, the identity of each security registrar and/or paying agent;

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• the percentage of the principal amount at which such debt securities will be issued and, if other than the principal amount thereof, the portion of the principal amount of securities of the series which shall be payable upon declaration of acceleration of the maturity thereof pursuant to the Indenture;

• any Events of Default and covenants of the Company with respect to the securities of that series, whether or not such Events of Default or covenants are consistent with the Events of Default or covenants set forth in the Indenture;

• if other than the currency of the United States of America, the currency or currency unit in which payment of the principal of (and premium, if any) or interest, if any, on the securities of that series shall be made or in which securities of that series shall be denominated and the particular provisions applicable thereto;

• if the principal of (and premium, if any) and interest, if any, on the securities of that series are to be payable, at the election of the Company or a holder thereof, in a currency or currency unit other than that in which such securities are denominated or stated to be payable, the period or periods within which, and the terms and conditions upon which, such election may be made, and the time and manner of determining the exchange rate between the currency or currency unit in which such securities are denominated or stated to be payable and the currency or currency unit in which such securities are to be so payable;

• if the amount of payments of principal of (and premium, if any) or interest, if any, on the securities of the series may be determined with reference to an index based on a currency or currency unit other than that in which securities are denominated or stated to be payable or any other index, the manner in which such amounts shall be determined;

• whether such securities will be secured or unsecured and if secured, the nature of the collateral securing the debt securities;

• whether and to what extent the securities of each series will be guaranteed and the identity of the guarantors;

• the terms and conditions, if any, upon which such securities may be subordinated to our other debt;

• whether such securities will be issued in certificated or book-entry form;

• the applicability, if any, of the defeasance and covenant defeasance provisions of the Indenture;

• whether and under what circumstances we will pay any additional amounts on such debt securities in respect of any tax, assessment or governmental charge and, if so, whether we will have the option to redeem such debt securities in lieu of making such payment;

• if securities are to be issued upon the exercise of warrants, the time, manner and place for authentication and delivery; and

• any other terms of the series (which terms shall not be inconsistent with the provisions of the Indenture).

The debt securities may be issued in one or more series with the same or various maturities.

The terms of the debt securities do not afford holders of the debt securities protection in the event of a highly leveraged transaction involving us that may adversely affect holders of the debt securities.

Conversion and Exchange Rights

The prospectus supplement will describe, if applicable, the terms on which you may convert the debt securities into or exchange them for other debt securities, preferred stock, common stock or other securities or property (including cash or any combination thereof). The conversion or exchange may be mandatory or may be at your option. The prospectus supplement will describe how the amount of debt securities, number of shares of preferred stock or common stock, or the amount of other securities or property to be received upon conversion or exchange would be calculated.

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Payment and Transfer or Exchange

Unless we otherwise indicate in the applicable prospectus supplement, we will make payment of the interest on any debt securities on any interest payment date to the person in whose name the debt securities, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest, and at maturity, to the person to whom principal is payable. All amounts of principal of and premium, if any, or interest on the debt securities paid by us that remain unclaimed two years after such payment was due and payable will be repaid to us, and the holders of such debt securities will thereafter look solely to us for payment. See “—Global Securities.”

In accordance with the Indenture, you may transfer or exchange debt securities of a series at the office of the Trustee. No service charge will be made for any registration of transfer or exchange of debt securities, but we may require payment of a sum sufficient to cover any transfer tax or other similar governmental charge payable in connection therewith.

If we designate additional transfer agents, we will name them in the applicable prospectus supplement. We may cancel the designation of any particular transfer agent. We may also approve a change in the office through which any transfer agent acts.

If we redeem less than all of the debt securities of a redeemable series, we will not be required to:

• issue, register the transfer of, or exchange any debt securities of that series during a period beginning at the opening of business 15 days before the day of mailing of a notice of redemption of any debt securities that may be selected for redemption and ending at the close of business on the day of the mailing; or

• register the transfer of or exchange any debt securities so selected for redemption, in whole or in part, except the unredeemed portion of any debt securities we are redeeming in part.

In this “Payment and Transfer or Exchange” section of this prospectus, “you” means direct holders and not indirect holders of debt securities.

Merger and Consolidation

Subject to any terms or conditions specified in the applicable prospectus supplement, so long as any debt securities of any series remain outstanding, we may not merge, consolidate or convey, transfer or lease our properties and assets substantially as an entirety and we will not permit any person to consolidate with or merge into us or convey, transfer or lease its properties and assets substantially as an entirety to us unless:

• the successor person is the Company or another corporation organized and existing under the laws of the United States, any state thereof or the District of Columbia that assumes our obligations on the debt securities and under the Indenture;

• immediately after giving effect to such transaction, we or the successor person would not be in default under the Indenture; and

• we have delivered to the Trustee an officers’ certificate and an opinion of counsel, each stating that such consolidation, merger or transfer and such supplemental indenture (if any) comply with the Indenture.

Certain of our Covenants

In addition to any covenants of the Company with respect to a particular series of debt securities as may be described in the applicable prospectus supplement, we will be subject to the following covenants:

Corporate Existence.    Except as described above under “Merger and Consolidation,” we will be required to do or cause to be done all things necessary to preserve and keep in full force and effect our corporate existence,

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rights (by articles of incorporation, bylaws and statute) and franchises. However, we will not be required to preserve any right or franchise if we determine that its preservation is no longer desirable in the conduct of our business and that its loss is not disadvantageous in any material respect to the holders of the debt securities.

Maintenance of Properties.    We will be required to cause all properties owned by us or any Subsidiary or used or held for use in the conduct of our business or the business of any Subsidiary to be maintained and kept in good condition, repair and working order and supplied with all necessary equipment and will be required to cause to be made all necessary repairs, renewals, replacements, betterments and improvements thereof, as in our judgment may be necessary so that the business carried on in connection with these properties may be conducted at all times. However, we will not be prevented from discontinuing the maintenance of any properties if such discontinuance is, in our judgment, desirable in the conduct of our business or the business of any Subsidiary and is not disadvantageous in any material respect to holders of the debt securities.

Payment of Taxes and Other Claims.    We will be required to pay or discharge, or cause to be paid or discharged, before they become delinquent:

• all material taxes, assessments and governmental charges levied or imposed upon us or any Subsidiary or upon our income, profits or property or the income, profits or property of any Subsidiary; and

• all material lawful claims for labor, materials and supplies which, if unpaid, might by law become a lien upon our property or the property of any Subsidiary.

Except as described above, or as otherwise described in the applicable prospectus supplement, the Indenture does not contain any provisions that would afford holders of the debt securities protection in the event of:

• a highly leveraged or similar transaction involving us;

• a change in control or a change in our management; or

• a reorganization, restructuring, merger or similar transaction involving us that may adversely affect the holders of the debt securities.

In addition, subject to the limitations set forth above and in the applicable prospectus supplement, we may, in the future, enter into certain transactions such as the sale of our properties and assets substantially as an entirety or a merger or consolidation with another entity that could increase the amount of our indebtedness or otherwise adversely affect our financial condition or results of operations, which may have an adverse effect on our ability to service our indebtedness, including the debt securities. We have no present intention of engaging in a highly leveraged or similar transaction involving us.

Events of Default

Unless otherwise provided in the applicable prospectus supplement, an Event of Default with respect to the debt securities is defined in the Indenture as being:

(i) default for 30 days in the payment of any installment of interest on the debt securities;

(ii) default in the payment of any principal of the debt securities;

(iii) default by us in the performance of any other covenants or agreements in the Indenture contained therein for the benefit of the debt securities which shall not have been remedied for a period of 90 days after written notice of such default to us by the Trustee or to us and the Trustee by the holders of at least 25% in aggregate principal amount of the debt securities;

(iv) certain events of bankruptcy, insolvency or reorganization of the Company; or

(v) any other Event of Default specified for a series in the applicable prospectus supplement.

Unless otherwise provided in the applicable prospectus supplement, the Indenture provides that if an Event of Default under clause (i), (ii), (iii) or (v) above shall have occurred and be continuing, either the Trustee or the

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holders of not less than 25% in principal amount of the debt securities may declare the principal of all the debt securities, together with any accrued interest, to be due and payable immediately.

Unless otherwise provided in the applicable prospectus supplement, if an Event of Default under clause (iv) above shall have occurred and be continuing, then the principal of all the debt securities, together with any accrued interest, will be due and payable immediately without any declaration or other act on the part of the Trustee or any holder of a debt security. Upon certain conditions such declaration (including a declaration caused by a default in the payment of principal or interest, the payment for which has subsequently been provided) may be annulled by the holders of a majority in principal amount of the debt securities.

In addition, subject to any terms or conditions specified in the applicable prospectus supplement, prior to the declaration of the acceleration of the maturity of the debt securities, past defaults may be waived by the holders of a majority in principal amount of the debt securities, except a default in the payment of principal of or interest on any debt security or in respect of a covenant or provision of the Indenture which cannot be modified or amended without the approval of the holder of each debt security.

The Indenture contains a provision entitling the Trustee, subject to the duty of the Trustee during default to act with the required standard of care, to be indemnified by the holders of debt securities issued thereunder before proceeding to exercise any right or power under the Indenture at the request of the holders of such debt securities.

The Indenture also provides that the holders of a majority in principal amount of the outstanding securities of a particular series issued thereunder and affected (each series voting as a separate class) may direct the time, method and place of conducting any proceeding for any remedy available to the Trustee, or exercising any trust or power conferred on the Trustee, with respect to the debt securities of such series.

The Indenture contains a covenant that we will file annually with the Trustee a certificate as to the absence of any default or specifying any default that exists.

Satisfaction and Discharge

The Indenture provides that, if the provisions of the relevant Article of the Indenture are made applicable to the debt securities of (or within) any series pursuant to such Indenture, the Indenture will cease to be of further effect (except as to surviving rights of registration of transfer or exchange of debt securities, as expressly provided for in the Indenture) as to all debt securities of such series when:

• either:

• all such debt securities theretofore authenticated and delivered (except lost, stolen or destroyed debt securities that have been replaced or paid) have been delivered to the Trustee for cancellation, or

• with respect to all such debt securities not theretofore delivered to the Trustee for cancellation, we have deposited or caused to be deposited with the Trustee funds or Government Obligations (as defined in the Indenture), or any combination thereof, in an amount sufficient to pay and discharge the entire indebtedness on such debt securities not theretofore delivered to the Trustee for cancellation, for unpaid principal and interest to maturity;

• we have paid all other sums payable by it under the Indenture with respect to such series;

• we have delivered to the Trustee an officers’ certificate and an opinion of counsel each stating that all conditions precedent under the Indenture to the satisfaction and discharge of the Indenture with respect to such series have been complied with; and

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• if such debt securities are not due and payable within one year of the date of such deposit, we have delivered to the Trustee an opinion of counsel to the effect that the holders of the debt securities will not recognize income, gain or loss for federal income tax purposes as a result of such deposit, defeasance and discharge and will be subject to federal income tax on the same amount and in the same manner and at the same times, as would have been the case if such deposit, defeasance and discharge had not occurred.

Defeasance and Covenant Defeasance

The Indenture provides that, if the provisions of the relevant Article of the Indenture are made applicable to the debt securities of (or within) any series pursuant to the Indenture, we may elect either (1) to effect a “defeasance,” in which case it will be discharged from any and all obligations with respect to such debt securities (except for the obligations to register the transfer or exchange of such debt securities, to replace temporary or mutilated, destroyed, lost or stolen debt securities, to maintain an office or agency in respect of such debt securities and to hold moneys for payment in trust), or (2) to effect a “covenant defeasance,” in which case it will be released from its obligations with respect to the covenants described under “— Certain of our Covenants” or, if provided pursuant to the Indenture, its obligations with respect to any other covenant, and any omission to comply with such obligations will not constitute a default or an Event of Default with respect to such debt securities. Such defeasance or covenant defeasance shall be effected upon the irrevocable deposit by us with the applicable trustee, in trust, of an amount, in such currency or currencies in which such debt securities are payable at their stated maturity, or Government Obligations (as described below), or both, applicable to such debt securities which through the scheduled payment of principal and interest in accordance with their terms will provide money in an amount sufficient to pay the principal of (and premium, if any) and interest on such debt securities, and any mandatory sinking fund or analogous payments thereon, on the scheduled due dates therefor.

Such a trust may be established only if, among other things, we have delivered to the applicable trustee an opinion of counsel (as specified in the Indenture) to the effect that the holders of such debt securities will not recognize income, gain or loss for U.S. federal income tax purposes as a result of such defeasance or covenant defeasance and will be subject to U.S. federal income tax on the same amounts, in the same manner and at the same times as would have been the case if such defeasance or covenant defeasance had not occurred.

The Indenture defines “Government Obligations” to mean securities that are (i) direct obligations of the government which issued the currency in which the Securities of a particular series are payable or (ii) obligations of a Person controlled or supervised by and acting as an agency or instrumentality of the government that issued the currency in which the Securities of such series are payable, the payment of which is unconditionally guaranteed by such government, which, in either case, are full faith and credit obligations of such government payable in such currency and are not callable or redeemable at the option of the issuer thereof.

Unless otherwise provided in the applicable supplemental indenture relating to any series of debt securities, if after we have deposited funds or Government Obligations to effect defeasance or covenant defeasance with respect to debt securities of any series the holder of a debt security of such series is entitled to, and does, elect pursuant to the Indenture or the terms of such debt security to receive payment in a currency other than that in which such deposit has been made in respect of such debt security, the indebtedness represented by such debt security and any coupons appertaining thereto shall be deemed to have been, and will be, fully discharged and satisfied through the payment of the principal of (and premium, if any) and interest, if any, on such debt security as they become due out of the proceeds yielded by converting the amount or other property so deposited in respect of such debt security into the currency in which such debt security becomes payable as a result of such election based on the applicable market exchange rate. Unless otherwise provided in the applicable prospectus supplement, all payments of principal of (and premium, if any) and interest on any debt security that is payable in a foreign currency that ceases to be used by its government of issuance shall be made in U.S. dollars. If we effect a covenant defeasance with respect to any debt securities and such debt securities are declared due and payable because of the occurrence of an Event of Default, the amount in such currency in which such debt securities are

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payable, and Government Obligations on deposit with the applicable trustee, will be sufficient to pay amounts due on such debt securities at the time of their stated maturity but may not be sufficient to pay amounts due on such debt securities at the time of the acceleration resulting from such Event of Default. We, however, would remain liable to make payment of such amounts due at the time of acceleration.

The applicable prospectus supplement may further describe the provisions, if any, permitting such defeasance or covenant defeasance, including any modifications to the provisions described above, with respect to the debt securities of or within a particular series.

Modification and Waiver

Unless otherwise specified in the applicable prospectus supplement, modifications and amendments of the Indenture will be permitted only with the consent of the holders of not less than a majority in principal amount of all outstanding debt securities issued under the Indenture which are affected by such modification or amendment. However, no such modification or amendment may, without the consent of the holder of each such debt security affected by the modification or amendment:

• change the stated maturity of the principal of, or any installment of interest on, any debt security or reduce the principal amount thereof or the rate of interest thereon, or change the coin or currency in which any debt security or the interest thereon is payable, or impair the right to institute suit for the enforcement of any such payment after the stated maturity thereof;

• reduce the percentage in principal amount of outstanding debt securities necessary to waive compliance with certain provisions of the Indenture or to waive certain defaults; or

• modify any of the provisions relating to supplemental indentures requiring the consent of holders or relating to the waiver of past defaults or relating to the waiver of certain covenants, except to increase the percentage of outstanding debt securities required for such actions or to provide that certain other provisions of the Indenture cannot be modified or waived without the consent of the holder of each debt security.

Unless otherwise specified in the applicable prospectus supplement, modifications and amendments of the Indenture may be made by us and the respective trustee without the consent of any holder of debt securities for any of the following purposes:

• to evidence the succession of another person as obligor under the Indenture;

• to add to our covenants for the benefit of the holders of all or any series of debt securities or to surrender any right or power conferred upon us in the Indenture;

• to add events of default with respect to any or all series of debt securities;

• to add or change any of the provisions of the Indenture to such extent as necessary to permit or facilitate the issuance of debt securities in bearer form, registrable or not registrable as to principal, and with or without interest coupons;

• to change or eliminate any of the provisions of the Indenture, provided that any such change or elimination shall become effective only when there are no debt securities outstanding of any series created prior to the execution of such supplemental indenture which is entitled to the benefit of such provision;

• to establish the form or terms of debt securities of any series;

• to add guarantees with respect to the debt securities;

• to secure the debt securities;

• to evidence and provide for the acceptance of appointment of a successor trustee with respect to the debt securities of one or more series and to add to or change any of the provisions of the Indenture as necessary to provide for or facilitate the administration of the trusts under the Indenture by more than one trustee;

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• to cure any ambiguity, to correct or supplement any provision in the Indenture which may be defective or inconsistent with any other provision in the Indenture, or to make any other provisions with respect to matters or questions arising under the Indenture which shall not be inconsistent with the provisions of the Indenture;

• to add to the conditions, limitations and restrictions on the authorized amount, form, terms or purposes of issue, authentication and delivery of debt securities;

• to supplement any of the provisions of the Indenture to the extent necessary to permit or facilitate the defeasance and discharge of any series of debt securities if such action does not adversely affect the interests of the holders of the debt securities of such series and any related coupons or any other series of debt securities in any material respect;

• to comply with the requirements of the SEC in order to effect or maintain the qualification of the Indenture under the Trust Indenture Act of 1939; or

• to add or modify any other provision in the Indenture with respect to matters or questions arising under the Indenture which we and the trustee may deem necessary or desirable and which does not materially and adversely affect the legal rights under the Indenture of any holder of debt securities of any series.

Global Securities

Book-Entry; Delivery and Form

Unless otherwise specified in the applicable prospectus supplement, the debt securities of each series will be issued in the form of one or more global debt securities, in definitive, fully registered form without interest coupons, each of which we refer to as a “global security.” Each such global security will be deposited with the trustee as custodian for The Depository Trust Company, or DTC, and registered in the name of Cede & Co., the nominee of DTC.

Investors may hold their interests in a global security directly through DTC if they are DTC participants, or indirectly through organizations that are DTC participants. Except in the limited circumstances described below, holders of debt securities represented by interests in a global security will not be entitled to receive their debt securities in fully registered certificated form.

DTC has advised us as follows: DTC is a limited-purpose trust company organized under New York Banking Law, a “banking organization” within the meaning of the New York Banking Law, a member of the Federal Reserve System, a “clearing corporation” within the meaning of the New York Uniform Commercial Code and a “clearing agency” registered pursuant to the provisions of Section 17A of the Exchange Act. DTC was created to hold securities of institutions that have accounts with DTC (“participants”) and to facilitate the clearance and settlement of securities transactions among its participants in such securities through electronic book-entry changes in accounts of the participants, thereby eliminating the need for physical movement of securities certificates. DTC’s participants include both U.S. and non-U.S. securities brokers and dealers, banks, trust companies, clearing corporations and certain other organizations. Access to DTC’s book-entry system is also available to others such as both U.S. and non-U.S. securities brokers and dealers, banks, trust companies and clearing corporations that clear through or maintain a custodial relationship with a participant, whether directly or indirectly.

Ownership of Beneficial Interests

Upon the issuance of each global security, DTC will credit, on its book-entry registration and transfer system, the respective principal amount of the individual beneficial interests represented by the global security to the accounts of participants. Ownership of beneficial interests in each global security will be limited to participants or persons that may hold interests through participants. Ownership of beneficial interests in each global security will be shown on, and the transfer of those ownership interests will be effected only through,

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records maintained by DTC (with respect to participants’ interests) and such participants (with respect to the owners of beneficial interests in the global security other than participants).

So long as DTC or its nominee is the registered holder and owner of a global security, DTC or such nominee, as the case may be, will be considered the sole legal owner of the debt security represented by the global security for all purposes under the indenture, the debt securities and applicable law. Except as set forth below, owners of beneficial interests in a global security will not be entitled to receive certificated debt securities and will not be considered to be the owners or holders of any debt securities represented by the global security. We understand that under existing industry practice, in the event an owner of a beneficial interest in a global security desires to take any actions that DTC, as the holder of the global security, is entitled to take, DTC would authorize the participants to take such action, and that participants would authorize beneficial owners owning through such participants to take such action or would otherwise act upon the instructions of beneficial owners owning through them. No beneficial owner of an interest in a global security will be able to transfer such interest except in accordance with DTC’s applicable procedures, in addition to those provided for under the indenture. Because DTC can only act on behalf of participants, who in turn act on behalf of others, the ability of a person having a beneficial interest in a global security to pledge that interest to persons that do not participate in the DTC system, or otherwise to take actions in respect of that interest, may be impaired by the lack of a physical certificate representing that interest.

All payments on the debt securities represented by a global security registered in the name of and held by DTC or its nominee will be made to DTC or its nominee, as the case may be, as the registered owner and holder of the global security.

We expect that DTC or its nominee, upon receipt of any payment of principal, premium, if any, or interest in respect of a global security, will credit participants’ accounts with payments in amounts proportionate to their respective beneficial interests in the principal amount of the global security as shown on the records of DTC or its nominee. We also expect that payments by participants to owners of beneficial interests in the global security held through such participants will be governed by standing instructions and customary practices as is now the case with securities held for accounts for customers registered in the names of nominees for such customers. These payments, however, will be the responsibility of such participants and indirect participants, and neither we, the trustee nor any paying agent will have any responsibility or liability for any aspect of the records relating to, or payments made on account of, beneficial ownership interests in any global security or for maintaining, supervising or reviewing any records relating to such beneficial ownership interests or for any other aspect of the relationship between DTC and its participants or the relationship between such participants and the owners of beneficial interests in the global security.

Unless and until it is exchanged in whole or in part for certificated debt securities, each global security may not be transferred except as a whole by DTC to a nominee of DTC or by a nominee of DTC to DTC or another nominee of DTC. Transfers between participants in DTC will be effected in the ordinary way in accordance with DTC rules and will be settled in same-day funds.

We expect that DTC will take any action permitted to be taken by a holder of debt securities only at the direction of one or more participants to whose account the DTC interests in a global security are credited and only in respect of such portion of the aggregate principal amount of the debt securities as to which such participant or participants has or have given such direction. However, if there is an event of default under the debt securities, DTC will exchange each global security for certificated debt securities, which it will distribute to its participants.

Although we expect that DTC will agree to the foregoing procedures in order to facilitate transfers of interests in each global security among participants of DTC, DTC is under no obligation to perform or continue to perform such procedures, and such procedures may be discontinued at any time. Neither the Company, the underwriters or the trustee will have any responsibility for the performance or nonperformance by DTC or its participants or indirect participants of their respective obligations under the rules and procedures governing their operations.

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The indenture provides that the global securities will be exchanged for debt securities in certificated form of like tenor and of an equal principal amount, in authorized denominations in the following limited circumstances:

(1) DTC notifies us that it is unwilling or unable to continue as depository or if DTC ceases to be eligible under the indenture and we do not appoint a successor depository within 90 days;

(2) we determine that the debt securities will no longer be represented by global securities and execute and deliver to the trustee an order to such effect; or

(3) an event of default with respect to the debt securities will have occurred and be continuing.

These certificated debt securities will be registered in such name or names as DTC will instruct the trustee. It is expected that such instructions may be based upon directions received by DTC from participants with respect to ownership of beneficial interests in global securities.

The information in this section of this prospectus concerning DTC and DTC’s book-entry system has been obtained from sources that we believe to be reliable, but we do not take responsibility for this information.

Governing Law

The indenture and the debt securities will be governed by and construed in accordance with the laws of the State of New York, except to the extent that the Trust Indenture Act of 1939 is applicable.

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DESCRIPTION OF WARRANTS

The following, together with the additional information we may include in the applicable prospectus supplement, summarizes the material terms and provisions of the warrants that we may offer under this prospectus and the related warrant agreements and warrant certificates. While the terms summarized below will apply generally to any warrants we may offer, we will describe the particular terms of any series of warrants in more detail in the applicable prospectus supplement.

As of the date of this prospectus, the following warrants are outstanding:

• Comerica Bank Warrant.    Pursuant to our loan and security agreement, dated October 2, 2007, with Comerica Bank, we issued a warrant to purchase 274 shares of our common stock at an exercise price of $1,913.05 per share, or the Comerica Warrant. The Comerica Warrant may be exercised in whole or in part at the option of Comerica Bank at any time prior to expiration on October 2, 2017.

In the future, we may issue warrants for the purchase of common stock, debt securities, preferred stock or any combination of the foregoing securities. Warrants may be issued independently or together with our securities offered by any prospectus supplement. Series of warrants may be issued under a separate warrant agreement. The applicable prospectus supplement will describe the terms of the warrants offered, including but not limited to the following:

• the number of warrants offered;

• the price or prices at which the warrants will be issued;

• the currency or currencies in which the prices of the warrants may be payable;

• securities for which the warrants are exercisable;

• whether the warrants will be issued with any other securities and, if so, the amount and terms of these securities;

• the amount of securities purchasable upon exercise of each warrant and the price at which and the currency or currencies in which the securities may be purchased upon such exercise, and the events or conditions under which the amount of securities may be subject to adjustment;

• the date on which the right to exercise such warrants shall commence and the date on which such right shall expire;

• the circumstances, if any, which will cause the warrants to be deemed to be automatically exercised;

• the minimum or maximum amount of such warrants, if any, that may be exercised at any one time;

• any material risk factors relating to such warrants; and

• any other material terms of such warrants.

Prior to the exercise of any warrants, holders of such warrants will not have any rights of holders of the securities purchasable upon such exercise, including the right to receive payments of dividends, or the right to vote such underlying securities.

Prospective purchasers of warrants should be aware that special United States federal income tax, accounting and other considerations may be applicable to instruments such as warrants. The applicable prospectus supplement will describe such considerations, to the extent they are material, as they apply generally to purchasers of such warrants.

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DESCRIPTION OF UNITS

The following, together with the additional information we may include in the applicable prospectus supplement, summarizes the material terms and provisions of the units that we may offer under this prospectus. While the terms summarized below will apply generally to any units we may offer, we will describe the particular terms of any series of units in more detail in the applicable prospectus supplement.

We may, from time to time, issue units comprised of one or more of the other securities that may be offered under this prospectus, in any combination. Each unit will be issued so that the holder of the unit is also the holder of each security included in the unit. Thus, the holder of a unit will have the rights and obligations of a holder of each included security. The unit agreement under which a unit is issued may provide that the securities included in the unit may not be held or transferred separately at any time, or at any time before a specified date.

Any applicable prospectus supplement will describe:

• the material terms of the units and of the securities comprising the units, including whether and under what circumstances those securities may be held or transferred separately;

• any material provisions relating to the issuance, payment, settlement, transfer or exchange of the units or of the securities comprising the units; and

• any material provisions of the governing unit agreement that differ from those described above.

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SELLING STOCKHOLDERS

This prospectus may also relate to the possible resale by certain of our stockholders of 8,727,000 shares of our common stock that were acquired by such stockholders through several bridge loan financings and a preferred stock financing occurring prior to our IPO in 2012. Information about selling stockholders, if any, including their identities and the common stock to be registered on their behalf, will be set forth in a prospectus supplement, in a post-effective amendment to the registration statement of which this prospectus is a part or in filings we make with the SEC under the Exchange Act that are incorporated by reference into this prospectus. Such selling stockholders may include certain of our significant stockholders, including funds affiliated with Bay City Capital, New Enterprise Associates, Highland Capital Partners and/or Sofinnova Ventures.

All of the common stock to be offered by selling stockholders under the registration statement of which this prospectus is a part is issued and outstanding as of the date of the filing of the registration statement of which this prospectus is a part. Selling stockholders shall not sell any shares of our common stock pursuant to this prospectus until we have identified such selling stockholders and the shares being offering for resale by such selling stockholders in a subsequent prospectus supplement. However, the selling stockholders may sell or transfer all or a portion of their shares of our common stock pursuant to any available exemption from the registration requirements of the Securities Act.

Funds affiliated with Bay City Capital, New Enterprise Associates, Highland Capital Partners and/or Sofinnova Ventures acquired our shares in connection with (i) bridge loan financings in April 2011, May 2011, October 2011 and November 2011, which notes and warrants converted into shares of our common stock upon completion of our IPO, and (ii) in connection with a preferred stock financing round in April 2010, which preferred stock converted into shares of our common stock upon completion of our IPO.

We will pay all expenses incurred with respect to the registration of the securities owned by the selling stockholders, other than underwriting fees, discounts or commissions, which will be borne by the selling stockholders.

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PLAN OF DISTRIBUTION

We, and any selling stockholders, may sell the offered securities in any of the ways described below or in any combination or any other way set forth in an applicable prospectus supplement from time to time:

• to or through underwriters or dealers;

• through one or more agents; or

• directly to purchasers or to a single purchaser.

Each time that we or a selling stockholders sells securities covered by this prospectus, we will provide a prospectus supplement that will describe the method of distribution and set forth the offering terms, including the name or names of any underwriters, dealers or agents, the purchase price of the offered securities and the proceeds to us and/or any selling stockholder from the sale, any underwriting discounts, commissions and other items constituting underwriters’ compensation, any initial public offering price and any underwriting discounts, commissions and other items allowed or reallowed or paid to dealers or agents and any securities exchanges on which the offered securities may be listed.

We or the selling stockholders may use one or more underwriters in the sale of the offered securities, in which case the offered securities will be acquired by the underwriter or underwriters for their own account and may be resold from time to time in one or more transactions either:

• at a fixed price or prices, which may be changed;

• at market prices prevailing at the time of sale;

• at prices related to such prevailing market prices; or

• at negotiated prices.

We or a selling stockholder may directly solicit offers to purchase offered securities. Agents designated by us or a selling stockholder from time to time may also solicit offers to purchase offered securities. Any agent designated by us or a selling stockholder, who may be deemed to be an “underwriter” as that term is defined in the Securities Act, involved in the offer or sale of the offered securities in respect of which this prospectus is delivered will be named, and any commissions payable by us or a selling stockholder to such agent will be set forth in the prospectus supplement.

If a dealer is utilized in the sale of the offered securities in respect of which this prospectus is delivered, we or the selling stockholder will sell the offered securities to the dealer, as principal. The dealer, who may be deemed to be an “underwriter” as that term is defined in the Securities Act, may then resell the offered securities to the public at varying prices to be determined by the dealer at the time of resale.

If an underwriter is, or underwriters are, used in the sale, we or a selling stockholder (if any) will execute an underwriting agreement with the underwriters at the time of sale to the underwriters. The names of the underwriters will be set forth in the prospectus supplement, which will be used by the underwriter to make resales of the offered securities in respect of which this prospectus is delivered to the public. In connection with the sale of offered securities, the underwriter may be deemed to have received compensation from us or the selling stockholder in the form of underwriting discounts or commissions and may also receive commissions from purchasers of offered securities for whom they may act as agents. Underwriters may also sell offered securities to or through dealers, and the dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions from the purchasers for whom they may act as agents.

If so indicated in the applicable prospectus supplement, we or a selling stockholder will authorize underwriters, dealers or other persons to solicit offers by certain institutions to purchase offered securities from us or a selling stockholder at the public offering price set forth in the applicable prospectus supplement pursuant

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to delayed delivery contracts providing for payment and delivery on a future date or dates. Institutions with which these contracts may be made include commercial and savings banks, insurance companies, pension funds, investment companies, educational and charitable institutions and others. The obligations of any purchasers under any delayed delivery contract will not be subject to any conditions except that:

• the purchase of the offered securities shall not at the time of delivery be prohibited under the laws of the jurisdiction to which the purchaser is subject, and

• if the offered securities are also being sold to underwriters, we or a selling stockholder will have sold to the underwriters the offered securities not sold for delayed delivery.

The underwriters, dealers and other persons will not have any responsibility in respect of the validity or performance of such contracts. The prospectus supplement relating to the contracts will set forth the price to be paid for offered securities pursuant to the contracts, the commission payable for solicitation of the contracts and the date or dates in the future for delivery of offered securities pursuant to the contracts.

Offered securities may also be offered and sold, if so indicated in the prospectus supplement, in connection with a remarketing upon their purchase, in accordance with a redemption or repayment pursuant to their terms, or otherwise, by one or more remarketing firms, acting as principals for their own accounts or as agents for us or a selling stockholder. Any remarketing firm will be identified and the terms of its agreement, if any, with us or a selling stockholder and its compensation will be described in the applicable prospectus supplement. Remarketing firms may be deemed to be underwriters in connection with their remarketing of offered securities.

Unless otherwise set forth in the applicable prospectus supplement, the obligations of underwriters to purchase the offered securities will be subject to certain conditions precedent and such underwriters will be obligated to purchase all such securities, if any are purchased. In connection with the offering of securities, we or the selling stockholder may grant to the underwriters an option to purchase additional securities to cover over-allotments at the initial public offering price, with an additional underwriting commission, as may be set forth in the accompanying prospectus supplement. If we or the selling stockholder grants any over-allotment option, the terms of such over-allotment option will be set forth in the prospectus supplement for such securities.

We may engage in at the market offerings into an existing trading market in accordance with Rule 415(a)(4) under the Securities Act. In addition, we may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement so indicates, in connection with those derivatives, the third parties may sell securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third party may use securities pledged by us or borrowed from us or others to settle those sales or to close out any related open borrowings of stock, and may use securities received from us in settlement of those derivatives to close out any related open borrowings of stock. The third party in such sale transactions will be an underwriter and, if not identified in this prospectus, will be named in the applicable prospectus supplement (or a post-effective amendment). In addition, we may otherwise loan or pledge securities to a financial institution or other third party that in turn may sell the securities short using this prospectus and an applicable prospectus supplement. Such financial institution or other third party may transfer its economic short position to investors in our securities or in connection with a concurrent offering of other securities.

Underwriters, dealers, remarketing firms and agents may be entitled, under agreements that may be entered into with us or a selling stockholder, to indemnification by us or a selling stockholder against certain civil liabilities, including liabilities under the Securities Act, or to contribution with respect to payments which they may be required to make in respect thereof and may engage in transactions with, or perform services for, us or the selling stockholder in the ordinary course of business.

Any underwriter may engage in over-allotment, stabilizing transactions, short-covering transactions and penalty bids in accordance with Regulation M under the Securities Exchange Act. Over-allotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the

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underlying security so long as the stabilizing bids do not exceed a specified maximum. Short-covering transactions involve purchases of the securities in the open market after the distribution is completed to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a covering transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of the activities at any time.

The specific terms of any lock-up provisions in respect of any given offering will be described in the applicable prospectus supplement.

The underwriters, dealers and agents may engage in transactions with us, or perform services for us, in the ordinary course of business for which they receive compensation.

The anticipated date of delivery of offered securities will be set forth in the applicable prospectus supplement relating to each offer.

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LEGAL MATTERS

The legal validity of the securities offered by this prospectus will be passed upon for us by Hogan Lovells US LLP, Palo Alto, California. Additional legal matters may be passed upon for us or any underwriters, dealers or agents, by counsel that we will name in the applicable prospectus supplement.

EXPERTS

The consolidated financial statements incorporated in this Prospectus by reference to the Annual Report on Form 10-K/A of Hyperion Therapeutics, Inc. for the year ended December 31, 2012 and the audited historical financial statements of the Buphenyl Product Line (A component of Ucyclyd Phama, Inc.) as of December 31, 2012 and the period from December 11, 2012 through December 31, 2012 included on page 2 of Hyperion Therapeutics, Inc.’s Current Report on Form 8-K/A filed on August 12, 2013 have been so incorporated in reliance on the reports (the report on the Buphenyl Product Line (A component of Ucyclyd Pharma, Inc.) contains an explanatory paragraph stating that the financial statements present only the assets to be acquired and the revenues and direct expenses as explained in Note 1 and 2 to such financial statements) of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

The financial statements of the BUPHENYL Product Line (a component of Ucyclyd Pharma, Inc.) as of December 10, 2012 and December 31, 2011, and the related statements of revenues and direct expenses for the period from January 1, 2012 through December 10, 2012 and the year ended December 31, 2011 appearing in our Current Report Form 8-K/A filed on August 12, 2013, have been audited by Ernst & Young LLP, independent auditors, as set forth in their report thereon, included therein and incorporated by reference herein. Such financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

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The information in this prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

Subject to Completion, dated August 14, 2013.

PROSPECTUS

Up to $50,000,000 of Shares

Common Stock

We have entered into a sales agreement with Cantor Fitzgerald & Co., relating to shares of our common stock offered by this prospectus. In accordance with the terms of the sales agreement, we may offer and sell shares of our common stock having an aggregate offering price of up to $50,000,000 from time to time through Cantor Fitzgerald & Co., acting as agent.

Our common stock is listed on The NASDAQ Global Market under the symbol “HPTX.” On August 12, 2013, the last reported sale price of our common stock on The NASDAQ Global Market was $24.94 per share.

Sales of our common stock, if any, under this prospectus may be made in sales deemed to be “at-the-market” equity offerings as defined in Rule 415 promulgated under the Securities Act of 1933, as amended, or the Securities Act, including sales made directly on or through The NASDAQ Global Market, the existing trading market for our common stock, sales made to or through a market maker other than on an exchange or otherwise, in negotiated transactions at market prices prevailing at the time of sale or at prices related to such prevailing market prices, and/or any other method permitted by law, including in privately negotiated transactions. Cantor Fitzgerald & Co. will act as sales agent on a best efforts basis and use commercially reasonable efforts to sell on our behalf all of the shares of common stock requested to be sold by us, consistent with its normal trading and sales practices, on mutually agreed terms between Cantor Fitzgerald & Co. and us. There is no arrangement for funds to be received in any escrow, trust or similar arrangement.

Cantor Fitzgerald & Co. will be entitled to compensation at a fixed commission rate of 3.0% of the gross sales price per share sold. In connection with the sale of our common stock on our behalf, Cantor Fitzgerald & Co. will be deemed to be an “underwriter” within the meaning of the Securities Act and the compensation of Cantor Fitzgerald & Co. will be deemed to be underwriting commissions or discounts.

You should read carefully this prospectus, the documents incorporated by reference in this prospectus before you invest. Investing in our common stock involves risks. Please see “Risk Factors” on page S-5 for more information.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is                     , 2013.

TABLE OF CONTENTS

	Page
About this Prospectus		S-1
Prospectus Summary		S-2
The Offering		S-4
Risk Factors		S-5
Special Note Regarding Forward-looking Statements		S-6
Use of Proceeds		S-7
Dilution		S-8
Price Range of Common Stock		S-10
Plan of Distribution		S-11
Legal Matters		S-12
Experts		S-12
Where You Can Find More Information		S-12
Information Incorporated by Reference		S-12

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ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we have filed with the Securities and Exchange Commission, or SEC, utilizing a “shelf” registration process. Under the shelf registration process, we may offer shares of our common stock having an aggregate offering price of up to $50,000,000 from time to time under this prospectus at prices and on terms to be determined by market conditions at the time of offering.

We provide information to you about this offering of shares of our common stock in two separate documents that are bound together: (1) this at-the-market sales agreement prospectus, which describes the specific details regarding this offering; and (2) the accompanying base prospectus, which provides general information, some of which may not apply to this offering. Generally, when we refer to this “prospectus,” we are referring to both documents combined. If information in this at-the-market sales agreement prospectus is inconsistent with the accompanying base prospectus, you should rely on this prospectus. However, if any statement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in this prospectus—the statement in the document having the later date modifies or supersedes the earlier statement as our business, financial condition, results of operations and prospects may have changed since the earlier dates.

You should rely only on the information contained in, or incorporated by reference into, this prospectus and in any free writing prospectus that we may authorize for use in connection with this offering. We have not, and Cantor Fitzgerald & Co., or Cantor, has not, authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We are not, and Cantor is not, making an offer to sell or soliciting an offer to buy our securities in any jurisdiction in which an offer or solicitation is not authorized or in which the person making that offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make an offer or solicitation. You should assume that the information appearing in this prospectus, the documents incorporated by reference into this prospectus, and in any free writing prospectus that we may authorize for use in connection with this offering, is accurate only as of the date of those respective documents. Our business, financial condition, results of operations and prospects may have changed since those dates. You should read this prospectus, the documents incorporated by reference into this prospectus, and any free writing prospectus that we may authorize for use in connection with this offering, in their entirety before making an investment decision. You should also read and consider the information in the documents to which we have referred you in the sections of this prospectus entitled “Where You Can Find More Information” and “Incorporation by Reference.”

We are offering to sell, and seeking offers to buy, shares of common stock only in jurisdictions where offers and sales are permitted. The distribution of this prospectus and the offering of the common stock in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of the common stock and the distribution of this prospectus outside the United States. This prospectus does not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

Unless the context otherwise requires or as otherwise expressly stated, references in this prospectus to the “Company,” “Hyperion,” “we,” “us” and “our” and similar terms refer to Hyperion Therapeutics, Inc. and our subsidiaries on a consolidated basis, as appropriate in the context.

This prospectus, including the information incorporated by reference into this prospectus, includes trademarks, service marks and trade names owned by us or others. The names Hyperion Therapeutics, Inc.^TM and RAVICTI^® and BUPHENYL^® are our trademarks. AMMONUL^® is the registered trademark of Ucyclyd Pharma, Inc., a wholly owned subsidiary of Medicis Pharmaceutical Corporation, which became a wholly owned subsidiary of Valeant Pharmaceuticals International, Inc. on December 11, 2012. All other trademarks, service marks and trade names included or incorporated by reference in this prospectus and any free-writing prospectus that we have authorized for use in connection with this offering are the property of their respective owners.

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PROSPECTUS SUMMARY

The items in the following summary are described in more detail elsewhere in this prospectus and in the documents incorporated by reference herein. This summary provides an overview of selected information and does not contain all the information you should consider before investing in our common stock. Therefore, you should read the entire prospectus and any free writing prospectus that we have authorized for use in connection with this offering carefully, including the “Risk Factors” section and other documents or information included or incorporated by reference in this prospectus before making any investment decision.

Our Company

We are a biopharmaceutical company focused on the development and commercialization of novel therapeutics to treat disorders in the areas of orphan diseases and hepatology. We have developed our product, RAVICTI^® (glycerol phenylbutyrate) Oral Liquid, to treat the most prevalent urea cycle disorders, or UCD, and are developing glycerol phenylbutyrate, or GPB, to treat hepatic encephalopathy, or HE, two different diseases in which blood ammonia is elevated. UCD are inherited rare genetic diseases caused by a deficiency of one or more enzymes or protein transporters that constitute the urea cycle, which in a healthy individual removes ammonia through the conversion of ammonia to urea. HE may develop in some patients with liver scarring, known as cirrhosis, or acute liver failure and is a chronic disease which fluctuates in severity and may lead to serious neurological damage. On February 1, 2013, the U.S. Food and Drug Administration, or the FDA, granted approval of RAVICTI for use as a nitrogen-binding agent for chronic management of UCD in adult and pediatric patients greater than two years of age who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. Limitations of use for RAVICTI include treatment of patients with acute hyperammonemia, or HA, crises for whom urgent intervention is typically necessary, patients with N-acetylglutamate synthetase deficiency for whom the safety and efficacy of RAVICTI has not been established, and UCD patients under two months of age for whom RAVICTI is contraindicated due to uncertainty as to whether newborns, who may have immature pancreatic function, can effectively digest RAVICTI. We commercially launched RAVICTI during the first quarter of 2013. On May 1, 2013, we received notification from the FDA that RAVICTI qualified for orphan drug exclusivity.

Pursuant to an amended and restated collaboration agreement with Ucyclyd Pharma, Inc., or Ucyclyd, a subsidiary of Valeant Pharmaceuticals International, Inc., we exercised our option to acquire BUPHENYL and AMMONUL^® (sodium phenylacetate and sodium benzoate) injection 10%/10% from Ucyclyd on April 29, 2013. On May 31, 2013, we received a net payment of $11 million from Ucyclyd, which reflected the $32.0 million contractual purchase price for AMMONUL due to us less the $19.0 million contractual purchase price for BUPHENYL due to Ucyclyd and $2.0 million payment due to Ucyclyd for inventory we purchased from Ucyclyd. We are obligated to pay subsequent milestone and royalty payments to Ucyclyd.

On March 13, 2013, we completed a follow-on offering and issued 2,875,000 shares of our common stock at an offering price of $20.75 per share. In addition, we sold an additional 431,250 shares of common stock directly to our underwriters when they exercised their over-allotment option in full at an offering price of $20.75 per share. We received net proceeds from the offering of $63.7 million, after deducting underwriting discounts and commissions of $4.1 million and expenses of $0.8 million.

On July 31, 2012, we completed our initial public offering, or IPO, and issued 5,000,000 shares of our common stock at an initial offering price of $10.00 per share. We sold an additional 750,000 shares of common stock directly to our underwriters when they exercised their over-allotment option in full at the initial offering price of $10.00 per share. Our shares began trading on the NASDAQ Global Market on July 26, 2012. We received net proceeds from the IPO of $51.3 million, after deducting underwriting discounts and commissions of $4.0 million and expenses of $2.2 million

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In April 2012, our Phase II HE trial data was unblinded and the trial met its primary endpoint, which was to demonstrate that the proportion of patients experiencing an HE event was significantly lower on GPB versus placebo, both administered in addition to a standard of care, including lactulose and/or rifaximin. We expect our research and development expenses to increase when we initiate a Phase III trial of GPB in HE. We will likely continue to incur significant commercial, sales, marketing and outsourced manufacturing expenses in connection with the commercialization of RAVICTI and BUPHENYL in UCD. These increased expenses as compared to prior years, include payroll related expenses due to the addition of employees in the commercial, manufacturing and regulatory departments, costs related to the initiation and operation of our distribution network, and marketing costs and general infrastructure expenses as we expand our organization.

Business Strategy

Our strategy is to commercialize our product portfolio, including RAVICTI and BUPHENYL, for the treatment of UCD and to develop GPB for the treatment of HE and other indications. The key elements of our strategy are to:

• Commercialize RAVICTI and improve patient care in UCD.    We have expanded our sales, marketing, and reimbursement functions to commercialize RAVICTI in the United States. A cornerstone of our strategy is to facilitate the rapid transition of patients from BUPHENYL to RAVICTI with a small, scientifically-focused field team of six sales representatives and three payor account managers, a dedicated call center focused on reimbursement adjudication and compliance support, and a network of specialty pharmacies. Our distribution model is designed to provide patients with access to enhanced services that assist in overcoming challenges in healthcare delivery and in financing treatment posed by therapies that are necessarily expensive. We are seeking opportunities for sales of RAVICTI in UCD outside of the United States.

• Develop GPB for the treatment of HE.    Based on the positive results of our Phase II trial assessing the safety and efficacy of GPB in the treatment of episodic HE and an end of Phase II meeting to discuss those trial results with the FDA, we are currently planning a Phase III clinical trial to begin during the second half of 2014 or early 2015.

• Expand GPB into additional indications.    We may explore the use of GPB in indications other than UCD and HE.

• Acquire additional products and product candidates.    We intend to continue to identify and may license or acquire products or product candidates being developed for orphan diseases and hepatology and fit within our commercial strategy.

• Sell BUPHENYL for appropriate patients.    Market BUPHENYL for use by UCD patients who do not transition to RAVICTI or who otherwise may be ineligible to use RAVICTI.

Our Corporate Information

We were incorporated under the laws of the State of Delaware in November 2006. Our principal executive office is located at 601 Gateway Boulevard, Suite 200, South San Francisco, CA 94080, and our telephone number is (650) 745-7802.

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THE OFFERING

Common stock to be offered by us Shares of our common stock having an aggregate offering price of up to $50,000,000.

Manner of offering “At-the-market” offering that may be made from time to time through our sales agent, Cantor Fitzgerald & Co. See “Plan of Distribution” on page S-10.

Use of proceeds We expect to use the net proceeds from this offering: to fund clinical development for RAVICTI in HE; to fund Phase IV studies in UCD; and for working capital and general corporate purposes. See “Use of Proceeds” on page S-7.

NASDAQ Global Market symbol HPTX

Risk factors You should read the “Risk Factors” section on Page S-5 of this prospectus and in the documents incorporated by reference in this prospectus for a discussion of factors to consider before deciding to purchase shares of our common stock.

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RISK FACTORS

You should consider carefully the risks described below and discussed under the section captioned “Risk Factors” contained in our quarterly report on Form 10-Q and in subsequent reports filed with the SEC, as updated by our subsequent filings under the Securities Exchange Act of 1934, as amended, or the Exchange Act, each of which is incorporated by reference in this prospectus in their entirety, together with other information in this prospectus, and the information and documents incorporated by reference in this prospectus, and any free writing prospectus that we have authorized for use in connection with this offering before you make a decision to invest in our common stock. If any of the following events actually occur, our business, operating results, prospects or financial condition could be materially and adversely affected. This could cause the trading price of our common stock to decline and you may lose all or part of your investment. The risks described below are not the only ones that we face. Additional risks not presently known to us or that we currently deem immaterial may also affect our business operations.

Additional Risks Relating to this Offering

Our management will have broad discretion in the use of the net proceeds from this offering and may allocate the net proceeds from this offering in ways that you and other stockholders may not approve.

Our management will have broad discretion in the use of the net proceeds, including for any of the purposes described in the section entitled “Use of Proceeds,” and you will not have the opportunity as part of your investment decision to assess whether the net proceeds are being used appropriately. Because of the number and variability of factors that will determine our use of the net proceeds from this offering, their ultimate use may vary substantially from their currently intended use. The failure of our management to use these funds effectively could harm our business. Pending their use, we may invest the net proceeds from this offering in short-term, investment-grade, interest-bearing securities. These investments may not yield a favorable return to our stockholders.

You may experience future dilution as a result of future equity offerings.

In order to raise additional capital, we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our common stock at prices that may not be the same as the price per share in this offering. We may sell shares or other securities in any other offering at a price per share that is less than the price per share paid by investors in this offering, and investors purchasing shares or other securities in the future could have rights superior to existing stockholders. The price per share at which we sell additional shares of our common stock, or securities convertible or exchangeable into common stock, in future transactions may be higher or lower than the price per share paid by investors in this offering.

Because we do not intend to declare cash dividends on our shares of common stock in the foreseeable future, stockholders must rely on appreciation of the value of our common stock for any return on their investment.

We have never declared or paid cash dividends on our common stock. We currently anticipate that we will retain future earnings for the development, operation and expansion of our business and do not anticipate declaring or paying any cash dividends in the foreseeable future. As a result, only appreciation of the price of our common stock, if any, will provide a return to investors in this offering.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, including the documents incorporated by reference herein and therein, and any free writing prospectus that we have authorized for use in connection with this offering contain “forward-looking statements” within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act that involve substantial risks and uncertainties. In some cases you can identify these statements by forward-looking words such as “believe,” “may,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “could,” “would,” “project,” “plan,” “expect,” or similar expressions, or the negative or plural of these words or expressions. These forward-looking statements include, but are not limited to, statements concerning the following:

• the commercial launch of RAVICTI and future sales of RAVICTI, BUPHENYL or any other future products or product candidates;

• our expectations regarding the commercial supply of our UCD products;

• third-party payor reimbursement for RAVICTI and BUPHENYL;

• our estimates regarding anticipated capital requirements and our needs for additional financing;

• the UCD or HE patient market size and market adoption of RAVICTI by physicians and patients;

• the timing or cost of a Phase III trial in HE;

• the development and approval of the use of RAVICTI for additional indications or in combination therapy;

• our expectations regarding licensing, acquisitions and strategic operations;

• impact of accounting standards; and

• repayment of notes payable.

These statements are only current predictions and are subject to known and unknown risks, uncertainties, and other factors that may cause our or our industry’s actual results, levels of activity, performance or achievements to be materially different from those anticipated by the forward-looking statements. We discuss many of these risks in this report in greater detail under the heading “Risk Factors” and elsewhere in this report. You should not rely upon forward-looking statements as predictions of future events.

Although we believe that the expectations reflected in the forward-looking statements are reasonable, we cannot guarantee future results, levels of activity, performance, or achievements. Except as required by law, we are under no duty to update or revise any of the forward-looking statements, whether as a result of new information, future events or otherwise, after the date of this report.

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USE OF PROCEEDS

The amount of proceeds from this offering will depend upon the number of shares of our common stock sold and the market price at which they are sold. There can be no assurance that we will be able to sell any shares under or fully utilize the sales agreement with Cantor as a source of financing. Unless otherwise indicated in the prospectus supplement, the net proceeds from the sale of securities offered by this prospectus will be used for general corporate purposes and working capital requirements. We may also use a portion of the net proceeds for the licensing or acquisition of, or the development of, additional product candidates and/or to fund possible investments in and the acquisition of complementary businesses or partnerships. However, we have no present plans with respect to acquisitions as of the date of this prospectus.

The amounts and timing of our actual expenditures will depend on numerous factors, including our development and commercialization efforts with respect to RAVICTI and BUPHENYL, as well as the amount of cash used in our operations. We therefore cannot estimate with certainty the amount of net proceeds to be used for the purposes described above. We may find it necessary or advisable to use the net proceeds for other purposes, and we will have broad discretion in the application of the net proceeds. Pending the uses described above, we plan to invest the net proceeds from this offering in short-term, investment-grade, interest-bearing securities.

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DILUTION

If you invest in our common stock, you will experience immediate and substantial dilution to the extent of the difference between the public offering price of our common stock and the adjusted net tangible book value per share of our common stock immediately after the offering.

Our historical net tangible book value per share is determined by dividing our total tangible assets less total liabilities by the actual number of outstanding shares of our common stock. The historical net tangible book value of our common stock as of June 30, 2013 was $100.1 million, or $4.98 per share.

After giving effect to the sale of $50 million of common stock offered by us at an assumed public offering price of $24.94 per share (the last reported sale price of our common stock on The NASDAQ Global Market on August 12, 2013), after deducting the estimated offering expenses payable by us, our net tangible book value as of June 30, 2013, would have been approximately $148.2 million, or $6.71 per share of common stock. This represents an immediate increase in net tangible book value of $1.73 per share to existing stockholders and an immediate dilution of $18.23 per share to new investors purchasing shares of common stock in this offering at the assumed public offering price. The following table illustrates this dilution on a per share basis:

Assumed public offering price per share			$	24.94
Historical net tangible book value per share as of June 30, 2013	$	4.98
Increase in net tangible book value per share attributable to new investors		1.73
As adjusted net tangible book value per share after this offering				6.71
Dilution per share to new investors			$	18.23

The table above assumes for illustrative purposes that an aggregate of 2,004,811 shares of our common stock are sold at a price of $24.94 per share, the last reported sale price of our common stock on The NASDAQ Global Market on August 12, 2013, for aggregate gross proceeds of approximately $50.0 million. The shares sold in this offering, if any, will be sold from time to time at various prices. Each $1.00 increase in the assumed public offering price of $24.94 per share would increase our as adjusted net tangible book value after this offering by approximately $1.9 million, or approximately $0.02 per share, and the dilution per share to new investors by approximately $19.21 per share, assuming all of our common stock in the aggregate amount of $50 million is sold at that price and after deducting the estimated offering expenses payable by us. Each $1.00 decrease in the assumed public offering price of $24.94 per share would decrease our adjusted net tangible book value after this offering by approximately $2.1 million, or approximately $0.03 per share, and the dilution per share to new investors by approximately $17.26 per share, assuming all of our common stock in the aggregate amount of $50 million is sold at that price and after deducting the estimated offering expenses payable by us.

The information discussed above is illustrative only and will adjust based on the actual public offering price and other terms of this offering determined at pricing.

The above table is based on 20,087,200 shares of common stock outstanding as of June 30, 2013, and excludes:

• 1,584,977 shares of common stock issuable upon the exercise of stock options outstanding as of June 30, 2013, under our 2006 Equity Incentive Plan, or the 2006 Plan, having a weighted average exercise price of $3.67 per share;

• 1,079,747 shares of common stock issuable upon the exercise of stock options outstanding as of June 30, 2013, under our 2012 Omnibus Incentive Plan, or the 2012 Plan, having a weighted average exercise price of $19.62 per share;

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• 749,611 shares of common stock reserved as of June 30, 2013, for future issuance under our 2012 Plan, plus any future increases in the number of shares of common stock reserved for issuance under the 2012 Plan pursuant to evergreen provisions; and

• 274 shares of common stock issuable upon the exercise of warrants outstanding as of June 30, 2013, having a weighted average exercise price of $1,913.05 per share.

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PRICE RANGE OF COMMON STOCK

Our common stock has been trading on The NASDAQ Global Market under the symbol “HPTX” since our IPO on July 26, 2012. Prior to this date, there was no public market for our common stock. The following table sets forth the high and low intraday sale prices per share of our common stock for the periods indicated as reported by The NASDAQ Global Market.

	High		Low
2013
Third Quarter (through August 12, 2013)	$	27.00	$	21.29
Second Quarter		25.94		15.92
First Quarter		26.50		10.84
2012
Fourth Quarter	$	12.00	$	10.00
Third Quarter (beginning July 26, 2012)		11.99		9.95

As of August 12, 2013, we had 23 holders of record of our common stock. The actual number of stockholders is greater than this number of record holders, and includes stockholders who are beneficial owners, but whose shares are held in street name by brokers and other nominees. This number of holders of record also does not include stockholders whose shares may be held in trust by other entities.

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PLAN OF DISTRIBUTION

We have entered into a Controlled Equity Offering^SM sales agreement with Cantor under which we may issue and sell shares of our common stock having an aggregate gross sales price of up to $50,000,000 from time to time through Cantor acting as agent. The sales agreement has been filed as an exhibit to our registration statement on Form S-3 of which this prospectus forms a part.

Upon delivery of a placement notice and subject to the terms and conditions of the sales agreement, Cantor may sell our common stock by any method permitted by law deemed to be an “at-the-market” offering as defined in Rule 415 promulgated under the Securities Act, including sales made directly on The NASDAQ Global Market, on any other existing trading market for our common stock or to or through a market maker. Cantor may also sell our common stock by any other method permitted by law, including in privately negotiated transactions. We may instruct Cantor not to sell common stock if the sales cannot be effected at or above the price designated by us from time to time. We or Cantor may suspend the offering of common stock upon notice and subject to other conditions.

We will pay Cantor commissions, in cash, for its services in acting as agent in the sale of our common stock. Cantor will be entitled to compensation at a fixed commission rate of 3.0% of the aggregate gross sales price per share sold. Because there is no minimum offering amount required as a condition to close this offering, the actual total public offering amount, commissions and proceeds to us, if any, are not determinable at this time. We have also agreed to reimburse Cantor for certain specified expenses, including the fees and disbursements of its legal counsel in an amount not to exceed $50,000. We estimate that the total expenses for the offering, excluding compensation and reimbursements payable to Cantor under the terms of the sales agreement, will be approximately $195,000.

Settlement for sales of common stock will occur on the third business day following the date on which any sales are made, or on some other date that is agreed upon by us and Cantor in connection with a particular transaction, in return for payment of the net proceeds to us. Sales of our common stock as contemplated in this prospectus will be settled through the facilities of The Depository Trust Company or by such other means as we and Cantor may agree upon. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

Cantor will use its commercially reasonable efforts, consistent with its sales and trading practices, to solicit offers to purchase the common stock shares under the terms and subject to the conditions set forth in the sales agreement. In connection with the sale of the common stock on our behalf, Cantor will be deemed to be an “underwriter” within the meaning of the Securities Act and the compensation of Cantor will be deemed to be underwriting commissions or discounts. We have agreed to provide indemnification and contribution to Cantor against certain civil liabilities, including liabilities under the Securities Act.

The offering of our common stock pursuant to the sales agreement will terminate upon the earlier of (i) the sale of all shares of our common stock subject to the sales agreement, or (ii) termination of the sales agreement as permitted therein. We and Cantor may each terminate the sales agreement at any time upon 10 days’ prior notice.

Cantor and its affiliates may in the future provide various investment banking, commercial banking and other financial services for us and our affiliates, for which services they may in the future receive customary fees. To the extent required by Regulation M, Cantor will not engage in any market making activities involving our common stock while the offering is ongoing under this prospectus.

This prospectus in electronic format may be made available on a website maintained by Cantor and Cantor may distribute this prospectus electronically.

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LEGAL MATTERS

The legal validity of the securities offered by this prospectus will be passed upon for us by Hogan Lovells US LLP, Palo Alto, California. Cantor is being represented in connection with this offering by Reed Smith LLP, New York, New York.

EXPERTS

The consolidated financial statements incorporated in this Prospectus by reference to the Annual Report on Form 10-K/A of Hyperion Therapeutics, Inc. for the year ended December 31, 2012 and the audited historical financial statements of the Buphenyl Product Line (A component of Ucyclyd Phama, Inc.) as of December 31, 2012 and the period from December 11, 2012 through December 31, 2012 included on page 2 of Hyperion Therapeutics, Inc.’s Current Report on Form 8-K/A filed on August 12, 2013 have been so incorporated in reliance on the reports (the report on the Buphenyl Product Line (A component of Ucyclyd Pharma, Inc.) contains an explanatory paragraph stating that the financial statements present only the assets to be acquired and the revenues and direct expenses as explained in Note 1 and 2 to such financial statements) of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

The financial statements of the BUPHENYL Product Line (a component of Ucyclyd Pharma, Inc.) as of December 10, 2012 and December 31, 2011, and the related statements of revenues and direct expenses for the period from January 1, 2012 through December 10, 2012 and the year ended December 31, 2011 appearing in our Current Report Form 8-K/A filed on August 12, 2013, have been audited by Ernst & Young LLP, independent auditors, as set forth in their report thereon, included therein and incorporated by reference herein. Such financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a registration statement on Form S-3 under the Securities Act, of which this prospectus forms a part. The rules and regulations of the SEC allow us to omit from this prospectus certain information included in the registration statement. For further information about us and the securities we are offering under this prospectus, you should refer to the registration statement and the exhibits and schedules filed with the registration statement. With respect to the statements contained in this prospectus regarding the contents of any agreement or any other document, in each instance, the statement is qualified in all respects by the complete text of the agreement or document, a copy of which has been filed as an exhibit to the registration statement.

We file reports, proxy statements and other information with the SEC under the Exchange Act. You may read and copy this information from the Public Reference Room of the SEC, 100 F Street, N.E., Room 1580, Washington, D.C. 20549, at prescribed rates. You may obtain information on the operation of the Public Reference Room by calling the SEC at 1-800-SEC-0330. The SEC also maintains an Internet website that contains reports, proxy statements and other information about issuers, like us, that file electronically with the SEC. The address of that website is www.sec.gov.

INFORMATION INCORPORATED BY REFERENCE

The SEC allows us to “incorporate by reference” the information we file with them which means that we can disclose important information to you by referring you to those documents instead of having to repeat the information in this prospectus. The information incorporated by reference is considered to be part of this prospectus, and later information that we file with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below and any future information filed (rather

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than furnished) with the SEC under Sections 13(a), 13(c), 14, or 15(d) of the Exchange Act between the date of this prospectus and the termination of this offering, provided, however, that we are not incorporating any information furnished under Item 2.02 or Item 7.01 or related exhibits furnished pursuant to Item 9.01 of any current report on Form 8-K:

• our Annual Report on Form 10-K/A for the year ended December 31, 2012, which was filed with the SEC on February 26, 2013;

• our Quarterly Reports on Form 10-Q for the fiscal quarters ended March 31, 2013 and June 30, 2013, which were filed with the SEC on May 10, 2013 and August 14, 2013, respectively;

• our Current Reports on Form 8-K, which were filed with the SEC on January 16, 2013, January 22, 2013, February 1, 2013, February 20, 2013, February 25, 2013 (Item 5.02), April 11, 2013, April 30, 2013, June 3, 2013 and August 12, 2013; and

• the description of our common stock contained in our registration statement on Form 8-A, which was filed on July 25, 2012, including any amendments or reports filed for the purpose of updating the description.

These documents may also be accessed on our website at www.hyperiontx.com. Except as otherwise specifically incorporated by reference in this prospectus, information contained in, or accessible through, our website is not a part of this prospectus.

We will furnish without charge to you, upon written or oral request, a copy of any or all of the documents incorporated by reference, including exhibits to these documents by writing or telephoning us at the following address:

Hyperion Therapeutics, Inc.

Attention: Investor Relations

601 Gateway Boulevard, Suite 200

South San Francisco, California 94080

(650) 745-7802

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Up to $50,000,000 of Shares

Common Stock

PROSPECTUS

                , 2013.

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution.

Set forth below is an estimate (except in the case of the SEC registration fee and FINRA fee) of the amount of fees and expenses to be incurred in connection with the issuance and distribution of the offered securities, other than underwriting discounts and commissions.

SEC registration fee	$	49,654
FINRA fee		55,105
Accounting fees and expenses		85,000
Legal fees and expenses		150,000
Transfer agent and registrar fees		3,500
Printing expenses		40,000
Miscellaneous		4,741
Total	$	388,000

Item 15. Indemnification of Directors and Officers.

We are incorporated under the laws of the State of Delaware. Section 102(b)(7) of the Delaware General Corporation Law, or DGCL, provides that a Delaware corporation, in its certificate of incorporation, may limit the personal liability of a director to the corporation or its stockholders for monetary damages for breach of fiduciary duties as a director, except for liability for any:

• transaction from which the director derived an improper personal benefit;

• act or omission not in good faith or that involved intentional misconduct or a knowing violation of law;

• unlawful payment of dividends or redemption of shares; or

• breach of the director’s duty of loyalty to the corporation or its stockholders.

Section 145(a) of the DGCL provides, in general, that a Delaware corporation may indemnify any person who was or is a party, or is threatened to be made a party, to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of the corporation) because that person is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation or other enterprise. The indemnity may include against expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by the person in connection with such action, so long as the person acted in good faith and in a manner he or she reasonably believed was in or not opposed to the corporation’s best interests of the corporation, and, with respect to any criminal action or proceeding, had no reasonable cause to believe his or her conduct was unlawful.

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Section 145(b) of the DGCL provides, in general, that a Delaware corporation may indemnify any person who was or is a party, or is threatened to be made a party, to any threatened, pending or completed action or suit by or in the right of the corporation to obtain a judgment in its favor because the person is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation or other enterprise. The indemnity may include expenses (including attorneys’ fees) actually and reasonably incurred by the person in connection with the defense or settlement of such action, so long as the person acted in good faith and in a manner the person reasonably believed was in or not opposed to the corporation’s best interests, except that no indemnification shall be permitted without judicial approval if a court has determined that the person is to be liable to the corporation with respect to such claim. If a present or former director or officer has been successful in defense of any action referred to above, the corporation must indemnify such officer or director against the expenses (including attorneys’ fees) he or she actually and reasonably incurred in connection with such action.

Section 145(g) of the DGCL provides, in general, that a corporation may purchase and maintain insurance on behalf of any person who is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation or other enterprise against any liability asserted against and incurred by such person, in any such capacity, or arising out of his or her status as such, whether or not the corporation could indemnify the person against such liability under Section 145 of the DGCL.

Our amended and restated certificate of incorporation and our amended and restated bylaws each provide for the indemnification of our directors and officers to the fullest extent permitted under the DGCL.

We have entered into indemnification agreements with our directors and executive officers. These indemnification agreements may require us, among other things, to indemnify each such director and executive officer for some expenses, including attorneys’ fees, judgments, fines and settlement amounts incurred by him in any action or proceeding arising out of his service as one of our directors or executive officers.

We maintain a general liability insurance policy that covers certain liabilities of directors and officers of our corporation arising out of claims based on acts or omissions in their capacities as directors or officers.

Item 16. Exhibits

The exhibits listed on the Index to Exhibits of this registration statement are incorporated herein by reference.

Item 17. Undertakings.

(a) The undersigned registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i) To include any prospectus required by Section 10(a)(3) of the Securities Act of 1933;

(ii) To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission

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pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than 20% change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement;

(iii) To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement;

provided, however, that paragraphs (i), (ii) and (iii) above do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Securities and Exchange Commission by the registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

(2) That, for the purpose of determining any liability under the Securities Act of 1933, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3) To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

(4) That, for the purpose of determining liability under the Securities Act of 1933 to any purchaser,

(i) Each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

(ii) Each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5), or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii), or (x) for the purpose of providing the information required by section 10(a) of the Securities Act of 1933 shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

(5) That, for the purpose of determining liability of the registrant under the Securities Act of 1933 to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i) Any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

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(ii) Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

(iii) The portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

(iv) Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

(b) The undersigned registrant hereby undertakes that, for purposes of determining any liability under the Securities Act of 1933, each filing of the registrant’s annual report pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of the securities at that time shall be deemed to be the initial bona fide offering thereof.

(h) Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act of 1933 and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act of 1933 and will be governed by the final adjudication of such issue.

(j) The undersigned registrant hereby undertakes to file an application for the purpose of determining the eligibility of the trustee to act under subsection (a) of Section 310 of the Trust Indenture Act of 1939 in accordance with the rules and regulations prescribed by the SEC under Section 305(b)(2) of the Trust Indenture Act of 1939.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the city of South San Francisco, in the State of California, on this August 14, 2013.

Hyperion Therapeutics, Inc.
By:	/s/    Donald J. Santel
	Donald J. Santel
	Chief Executive Officer and President

POWER OF ATTORNEY

Each person whose individual signature appears below hereby authorizes and appoints Donald J. Santel and Jeffrey S. Farrow, and each of them, with full power of substitution and resubstitution and full power to act without the other, as his or her true and lawful attorney-in-fact and agent to act in his or her name, place and stead and to execute in the name and on behalf of each person, individually and in each capacity stated below, and to file any and all amendments to this registration statement, including any and all post-effective amendments and amendments thereto, and any subsequent registration statement relating to the same offering as this registration statement that is to be effective upon filing pursuant to Rule 462(b) under the Securities Act of 1933, as amended, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing, ratifying and confirming all that said attorneys-in-fact and agents or any of them or their or his substitute or substitutes may lawfully do or cause to be done by virtue thereof.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities and on the dates indicated.

Signature	Title	Date
/s/  Donald J. Santel         Donald J. Santel	Chief Executive Officer, President and Director (Principal Executive Officer)	August 14, 2013
/s/  Jeffrey S. Farrow         Jeffrey S. Farrow	Chief Financial Officer (Principal Financial and Accounting Officer)	August 14, 2013
/s/  James I. Healy, M.D., Ph.D.         James I. Healy, M.D., Ph.D.	Chairman of the Board	August 14, 2013
/s/  David W. Gryska         David W. Gryska	Director	August 14, 2013
/s/  Bo Jesper Hansen, M.D., Ph.D.         Bo Jesper Hansen, M.D., Ph.D.	Director	August 14, 2013
/s/  Jake R. Nunn         Jake R. Nunn	Director	August 14, 2013

Signature	Title	Date
/s/  Bijan Salehizadeh, M.D.         Bijan Salehizadeh, M.D.	Director	August 14, 2013
/s/  Daniel G. Welch         Daniel G. Welch	Director	August 14, 2013
/s/  Lota S. Zoth         Lota S. Zoth	Director	August 14, 2013

EXHIBIT INDEX

Exhibit Number	Description
1.1	Sales Agreement, dated August 14, 2013, by and between Hyperion Therapeutics, Inc. and Cantor Fitzgerald & Co.
1.2*	Form of Underwriting Agreement.
3.1	Amended and Restated Certificate of Incorporation (incorporated by reference to Exhibit 3.1 to the Current Report on Form 8-K, File No. 001-35614, filed on July 31, 2012)
3.2	Amended and Restated bylaws (incorporated by reference to Exhibit 3.4 to Amendment No. 1 to the Registration Statement on Form S-1, File No. 333-180694, filed on May 24, 2012).
4.1	Specimen common stock certificate (incorporated by reference to Exhibit 4.1 to Amendment No. 3 to the Registration Statement on Form S-1, File No. 333-180694, filed on July 5, 2012).
4.2	Amended and Restated Warrant issued pursuant to the Loan and Security Agreement by and between the Company and Comerica Bank, dated October 2, 2007, and as amended on July 6, 2012 (incorporated by reference to Exhibit 4.2 to Amendment No. 4 to the Registration Statement on Form S-1, File No. 333-180694, filed on July 13, 2012).
4.3	Warrant to Purchase Common Stock, issued to Keelin Reeds, dated December 14, 2007 (incorporated by reference to Exhibit 4.3 to the Registration Statement on Form S-1, File No. 333-180694, filed on April 13, 2012).
4.4	Form of Secured Promissory Note issued pursuant to the Loan and Security Agreement by and among the Company, Silicon Valley Bank and the Lenders listed therein, dated April 19, 2012 (the “SVB Loan and Security Agreement”) (incorporated by reference to Exhibit 4.8 of Amendment No. 1 to the Registration Statement on Form S-1, File No. 333-180694, filed on May 24, 2012).
4.5	Form of Warrant to Purchase Stock issued pursuant to the SVB Loan and Security Agreement (incorporated by reference to Exhibit 4.9 of Amendment No. 1 to the Registration Statement on Form S-1, File No. 333-180694, filed on May 24, 2012).
4.6	Second Amended and Restated Investor Rights Agreement by and among the Company and the investors named therein, dated June 29, 2009 (incorporated by reference to Exhibit 10.1 to the Registrant’s Registration Statement on Form S-1, File No. 333-180694, filed on April 13, 2012).
4.7	Form of Indenture.
4.8*	Form of Note.
4.9*	Form of Warrant.
4.10*	Form of Warrant Agreement.
4.11*	Form of Unit.
4.12*	Form of Unit Agreement.
5.1	Opinion of Hogan Lovells US LLP
12.1	Statement Regarding the Computation of Ratio of Earnings to Fixed Charges.
23.1	Consent of Hogan Lovells US LLP (included in Exhibit 5.1).
23.2	Consent of PricewaterhouseCoopers LLP.
23.3	Consent of PricewaterhouseCoopers LLP.
23.4	Consent of Ernst and Young LLP.
24.1	Power of Attorney (included on signature page to this registration statement).
25.1*	Statement of Eligibility on Form T-1 under the Trust Indenture Act of 1939, as amended, of [TRUSTEE], as trustee under the form of indenture filed as Exhibit 4.7 above.

* To be filed by amendment or incorporated by reference in connection with the offering of the securities.