SC TO-T/A

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Schedule TO

Tender Offer Statement under Section 14(d)(1) or 13(e)(1)

of the Securities Exchange Act of 1934

(AMENDMENT NO. 1)

Myogen, Inc.

(Name of Subject Company (Issuer))

Mustang Merger Sub, Inc. (Offeror)

Gilead Sciences, Inc. (Parent of Offeror)

(Names of Filing Persons)

COMMON STOCK, PAR VALUE $0.001 PER SHARE

(Title of Class of Securities)

62856E104

(CUSIP Number of Class of Securities)

Gregg H. Alton, Esq.

Senior Vice President and General Counsel

Gilead Sciences, Inc.

333 Lakeside Drive

Foster City, California 94404

Tel: (650) 574-3000

(Name, address, and telephone number of person authorized to receive notices

and communications on behalf of filing persons)

with copies to:

David A. Lipkin, Esq.

Michelle Sonu Park, Esq.

Tali Sealman Tene, Esq.

Cooley Godward Kronish LLP

Five Palo Alto Square

3000 El Camino Real

Palo Alto, CA 94306-2155

Tel: (650) 843-5000

Fax: (650) 849-7400

Calculation of Filing Fee

Transaction valuation(1)	Amount of filing fee(2)
$2,435,406,435	$260,588.49

(1) Estimated solely for the purpose of calculating the registration fee in accordance with the Securities Exchange Act of 1934, as amended, based on the product of (i) $52.50 (i.e. the tender offer price) and (ii) 46,388,694, the estimated maximum number of shares of Myogen common stock to be acquired in the tender offer (which number is composed of 43,440,061 shares of Myogen common stock outstanding as of October 11, 2006, 1,967,675 shares of Myogen common stock issuable upon the exercise of outstanding options that are or will become vested and exercisable before November 10, 2006 and 980,958 shares of Myogen common stock issuable upon the exercise of outstanding warrants).

(2) The amount of the filing fee calculated in accordance with the Securities Exchange Act of 1934, as amended, equals $107 for each $1,000,000 of value.

x Check the box if any part of the fee is offset as provided by Rule 0-11(a)(2) and identify the filing with which the offsetting fee was previously paid. Identify the previous filing by registration statement number or the form or schedule and the date of its filing.

Amount Previously Paid: $260,588.49	Filing Party: Mustang Merger Sub, Inc. and Gilead Sciences, Inc.
Form or Registration No.: SC TO-T	Date Filed: October 16, 2006

¨ Check the box if the filing relates to preliminary communications made before the commencement of a tender offer.

Check the appropriate boxes below to designate any transactions to which the statement relates:

x third-party tender offer subject to Rule 14d-1.

¨ issuer tender offer subject to Rule 13e-4.

¨ going-private transaction subject to Rule 13e-3.

¨ amendment to Schedule 13D under Rule 13d-2.

Check the following box if the filing is a final amendment reporting the results of the tender offer:  ¨

This Amendment No. 1 (the “Amendment”) amends and supplements the Tender Offer Statement on Schedule TO (the “Schedule TO”), filed initially with the Securities and Exchange Commission on October 16, 2006 by Mustang Merger Sub, Inc., a Delaware corporation (the “Purchaser”) and a wholly owned subsidiary of Gilead Sciences, Inc., a Delaware corporation (“Gilead”), and Gilead relating to the tender offer by the Purchaser to purchase all of the outstanding shares of common stock, par value $0.001 per share, of Myogen, Inc., a Delaware corporation (the “Company”), at a purchase price of $52.50 per share, net to the seller in cash, without interest thereon, upon the terms and subject to the conditions set forth in the Offer to Purchase, dated October 16, 2006, and in the Letter of Transmittal, copies of which were filed with the Schedule TO as Exhibits (a)(1) and (a)(2), respectively. Capitalized terms used and not otherwise defined herein shall have the meanings assigned to such terms in the Offer to Purchase or in the Schedule TO. This Amendment is being filed on behalf of the Purchaser and Gilead.

ITEM 11. ADDITIONAL INFORMATION

Sections (a)(2) and (a)(3) of Item 11 are hereby amended and supplemented to include the following:

The required waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended (the “HSR Act”), with respect to the Offer has been terminated by the United States Federal Trade Commission prior to expiration of the full waiting period. On October 26, 2006, Gilead issued a press release announcing that the required waiting period under the HSR Act had been terminated. A copy of the press release is attached hereto as Exhibit (a)(9).

ITEM 12. EXHIBITS

Exhibit No.	Document
(a)(1)*	Offer to Purchase, dated October 16, 2006.
(a)(2)*	Form of Letter of Transmittal.
(a)(3)*	Form of Notice of Guaranteed Delivery.
(a)(4)*	Form of Letter from the Information Agent to Brokers, Dealers, Banks, Trust Companies and Other Nominees.
(a)(5)*	Form of Letter to Clients for use by Brokers, Dealers, Banks, Trust Companies and Other Nominees.
(a)(6)*	Guidelines for Certification of Taxpayer Identification Number on Substitute Form W-9.
(a)(7)*	Joint Press Release issued by Gilead Sciences, Inc. and Myogen, Inc. on October 2, 2006.
(a)(8)*	Summary Newspaper Advertisement published in The Wall Street Journal on October 16, 2006.
(a)(9)	Press Release issued by Gilead Sciences, Inc. on October 26, 2006.
(b)	Not applicable.
(d)(1)*	Agreement and Plan of Merger, dated as of October 1, 2006, by and among Gilead Sciences, Inc., Mustang Merger Sub, Inc. and Myogen, Inc.
(d)(2)*	Mutual Confidential Disclosure Agreement, dated as of May 19, 2006, by and between Gilead Sciences, Inc. and Myogen, Inc.
(d)(3)*	Confidentiality and Exclusivity Agreement, dated August 3, 2006, between Gilead Sciences, Inc. and Myogen, Inc.
(g)	Not applicable.
(h)	Not applicable.

* Previously filed

SIGNATURES

After due inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

MUSTANG MERGER SUB, INC.
By:	/s/ JOHN F. MILLIGAN, PH.D.
Name:	John F. Milligan, Ph.D.
Title:	President and Chief Financial Officer

GILEAD SCIENCES, INC.
By:	/s/ JOHN F. MILLIGAN, PH.D.
Name:	John F. Milligan, Ph.D.
Title:	Executive Vice President and Chief Financial Officer
	Dated: October 26, 2006

INDEX TO EXHIBITS

Exhibit No.	Document
(a)(1)*	Offer to Purchase, dated October 16, 2006.
(a)(2)*	Form of Letter of Transmittal.
(a)(3)*	Form of Notice of Guaranteed Delivery.
(a)(4)*	Form of Letter from the Information Agent to Brokers, Dealers, Banks, Trust Companies and Other Nominees.
(a)(5)*	Form of Letter to Clients for use by Brokers, Dealers, Banks, Trust Companies and Other Nominees.
(a)(6)*	Guidelines for Certification of Taxpayer Identification Number on Substitute Form W-9.
(a)(7)*	Joint Press Release issued by Gilead Sciences, Inc. and Myogen, Inc. on October 2, 2006.
(a)(8)*	Summary Newspaper Advertisement published in The Wall Street Journal on October 16, 2006.
(a)(9)	Press Release issued by Gilead Sciences, Inc. on October 26, 2006.
(b)	Not applicable.
(d)(1)*	Agreement and Plan of Merger, dated as of October 1, 2006, by and among Gilead Sciences, Inc., Mustang Merger Sub, Inc. and Myogen, Inc.
(d)(2)*	Mutual Confidential Disclosure Agreement, dated as of May 19, 2006, by and between Gilead Sciences, Inc. and Myogen, Inc.
(d)(3)*	Confidentiality and Exclusivity Agreement, dated August 3, 2006, between Gilead Sciences, Inc. and Myogen, Inc.
(g)	Not applicable.
(h)	Not applicable.

* Previously filed

EX-99.(A)(9)

Exhibit (a)(9)

CONTACTS: Susan Hubbard, Investors (650) 522-5715   Amy Flood, Media (650) 522-5643

For Immediate Release

GILEAD SCIENCES ANNOUNCES EARLY TERMINATION OF

HART-SCOTT-RODINO WAITING PERIOD

Foster City, CA, October 26, 2006 – Gilead Sciences, Inc. (Nasdaq: GILD) today announced that the required waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 with respect to Gilead’s cash tender offer for Myogen, Inc. (Nasdaq: MYOG) has been terminated by the United States Federal Trade Commission prior to the expiration of the waiting period.

The tender offer is expected to close by the end of the fourth quarter of 2006, subject to customary closing conditions. As previously announced, unless the tender offer is extended, the tender offer and withdrawal rights will expire at 12:00 midnight, New York City time, on Friday, November 10, 2006.

This announcement is neither an offer to purchase nor a solicitation of an offer to sell Myogen shares. The tender offer can only be made through an offer to purchase, letter of transmittal and related tender offer materials. The tender offer materials, certain other offer materials, and the solicitation/recommendation statement have been sent to all stockholders of Myogen and also are available free of charge at the SEC’s website at www.sec.gov.

About Gilead Sciences

Gilead Sciences is a biopharmaceutical company that discovers, develops and commercializes innovative therapeutics in areas of unmet medical need. The company’s mission is to advance the care of patients suffering from life-threatening diseases worldwide. Headquartered in Foster City, California, Gilead has operations in North America, Europe and Australia. For more information on Gilead Sciences, please visit the company’s website at www.gilead.com or call Gilead Public Affairs at 1-800-GILEAD-5 or 1-650-574-3000.

Forward-Looking Statements

This press release includes forward-looking statements, within the meaning of the Private Securities Litigation Reform Act of 1995, that are subject to risks, uncertainties and other factors including the risk that the acquisition of Myogen will not be consummated as the transaction is subject to certain closing conditions. For example, the ability of the parties to close the tender offer by the end of 2006 will depend on a number of factors outside the parties’ control, including the satisfaction of closing conditions. These risks, uncertainties and other factors, and the general risks associated with Gilead’s business as described in reports and other documents filed with the Securities and Exchange Commission, could cause actual results to differ materially from those referred to in the forward-looking statements. The reader is cautioned not to rely on these forward-looking statements. All forward-looking statements are based on information currently available to Gilead and Gilead assumes no obligation to update any such forward-looking statements or other statements included in this press release.

- more -

Gilead Sciences, Inc. 333 Lakeside Drive Foster City, CA 94404 USA www.gilead.com

phone 650 574 3000 facsimile 650 578 9264

October 26, 2006 Page 2

Additional Information and Where to Find It

This announcement is neither an offer to purchase nor a solicitation of an offer to sell shares of Myogen. Myogen stockholders are urged to read the relevant tender offer documents because they contain important information that stockholders should consider before making any decision regarding tendering their shares. Gilead has filed tender offer materials with the U.S. Securities and Exchange Commission, and Myogen has filed a Solicitation/Recommendation Statement with respect to the offer. The tender offer materials (including an Offer to Purchase, a related Letter of Transmittal and certain other offer documents) and the Solicitation/Recommendation Statement contain important information, which should be read carefully before any decision is made with respect to the tender offer. The Offer to Purchase, the related Letter of Transmittal and certain other offer documents, as well as the Solicitation/Recommendation Statement, have been made available to all stockholders of Myogen at no expense to them, and are available for free at the Commission’s web site at www.sec.gov. Free copies of the Offer to Purchase, the related Letter of Transmittal and certain other offering documents are available from Gilead by mailing requests for such materials to Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, attention: Investor Relations.

In addition to the Offer to Purchase, the related Letter of Transmittal and certain other offer documents, as well as the Solicitation/Recommendation Statement, Gilead and Myogen file annual, quarterly and special reports, proxy statements and other information with the Securities and Exchange Commission. You may read and copy any reports, statements or other information filed by Gilead or Myogen at the SEC public reference room at 100 F Street, N.E., Washington, D.C. 20549. Please call the Commission at 1-800-SEC-0330 for further information on the public reference room. Gilead’s and Myogen’s filings with the Commission are also available to the public from commercial document-retrieval services and at the website maintained by the Commission at www.sec.gov.

Interests of Certain Persons in the Offer and the Merger

Gilead will be, and certain other persons may be, soliciting Myogen stockholders to tender their shares into the tender offer. The directors and executive officers of Gilead and the directors and executive officers of Myogen may be deemed to be participants in Gilead’s solicitation of Myogen’s stockholders to tender their shares into the tender offer.

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