Stockholders' Equity	6 Months Ended
Jun. 30, 2017
Equity [Abstract]
Stockholders' Equity	5. Stockholders’ Equity Preferred Stock The Company is authorized to issue up to 10,000,000 shares of preferred stock, $0.00001 par value per share, with no shares outstanding as of June 30, 2017 and December 31, 2016. The Board of Directors is authorized to designate the terms and conditions of any preferred stock the Company may issue without further action by the stockholders of the Company. Common Stock The Company is authorized to issue up to 300,000,000 shares of common stock, $0.00001 par value per share. In February 2014, the Company entered into a stock purchase agreement with one of its founders. The agreement provided for the purchase of 1,000,000 shares of the Company’s common stock at a price per share of $0.01 in exchange for future services to be rendered to the Company as measured by certain performance criteria. The shares were subject to a repurchase option and were to vest in two tranches of 500,000 shares each, upon achievement of the performance target or upon a triggering event as defined. The Company determined that the fair value of the unrecognized expense was $168,000 at February 20, 2014, the grant date. In May 2015, the Company repurchased 633,810 of these shares at a purchase price of $0.00001 per share. In connection with the repurchase, the Company entered into an amendment to the stock purchase agreement to provide that the remaining 366,190 shares will continue to vest in two tranches of 183,095 shares each, upon achievement of the performance target or upon a triggering event as defined. The pro rata grant date fair value of the unrecognized expense is $61,556. In October 2015, a triggering event became probable of occurrence and was deemed achieved in October 2016; therefore, the Company recorded $30,778 of stock-based compensation expense through December 31, 2016, of which $12,371 and $18,407 was recorded as expense during the years ended December 31, 2016 and 2015, respectively. No similar expense was recognized during the three and six months ended June 30, 2017. The Company will continue to reassess at each reporting period whether it is probable that the performance target will be achieved, and if and when it is deemed probable, the Company will begin to record compensation expense using the fair value to determine stock-based compensation expense in its financial statements over the period the Company estimates the performance target will actually be achieved. On April 13, 2016, the Company completed the Offering pursuant to a registration statement on Form S-1 (File No. 333-208182) that was declared effective on April 7, 2016, and a registration statement on Form S-1MEF (File No. 333-210650) filed pursuant to Rule 462(b) of the Securities Act. In the Offering, the Company sold 7,500,000 shares of its common stock and warrants to purchase up to 7,500,000 shares of its common stock at a public offering price of $1.25 per share of common stock and related warrant. The warrants have an exercise price of $1.50 per share of common stock, were immediately exercisable upon issuance and will expire on April 13, 2021. The Company granted the underwriters for the Offering a 45-day option to purchase up to an additional 1,125,000 shares of its common stock and/or warrants to purchase up to an additional 1,125,000 shares of its common stock to cover over-allotments, if any. Ligand, a related party to the Company, purchased 560,000 shares of the Company’s common stock and warrants to purchase up to 560,000 shares of Company’s common stock in the Offering. On April 13, 2016, the underwriters partially exercised the over-allotment option for warrants to purchase an additional 1,125,000 shares of the Company’s common stock at a public offering price of $0.01 per warrant. Upon the closing of the Offering on April 13, 2016, the Company received net proceeds of $7,754,286, after deducting underwriting discounts, commissions and other offering expenses of $1,631,964. On April 13, 2016, pursuant to the terms of the Loan and Security Agreement, the Company issued the Ligand Shares and the Ligand Warrant to Ligand. The Ligand Warrant has an exercise price of $1.50 per share of the Company’s common stock, was immediately exercisable upon issuance (subject to a limitation on exercise to the extent that any exercise thereof would increase Ligand’s beneficial ownership of the Company’s common stock to greater than 49.9%) and expires on April 13, 2021. The Ligand Shares and the Ligand Warrant were issued to Ligand as a repayment of $1,200,000 of the Company’s obligation under the Ligand Note. On April 27, 2016, the underwriters for the Offering exercised their over-allotment option to purchase 1,125,000 shares of the Company’s common stock at a public offering price of $1.24 per share. On April 29, 2016, the Company sold the 1,125,000 shares to the underwriters pursuant to the over-allotment option and received additional net proceeds of $1,283,400, after deducting underwriting discounts, commissions and other offering expenses of $111,600. On June 20, 2016, the Company entered into the Distribution Agreement with Maxim pursuant to which the Company may offer and sell, from time to time, through Maxim up to 3,748,726 shares of its common stock. Any shares of common stock offered and sold in the Maxim Offering will be issued pursuant to the Company’s registration statement on Form S-3 (File No. 333-212134) filed with the SEC on June 20, 2016 and the prospectus relating to the Maxim Offering that forms a part of the registration statement on Form S-3. The registration statement on Form S-3 was declared effective by the SEC on July 26, 2016. The number of shares of the Company’s common stock eligible for sale under the Distribution Agreement will be subject to the limitations of General Instruction I.B.6 of Form S-3. During the three and six months ended June 30, 2017, the Company sold 0 and 488,388 shares of its common stock, respectively, under the Distribution Agreement resulting in net proceeds to the Company of $0 and $670,031, respectively, after deducting the sales agent’s commission. From the inception of the Distribution Agreement through June 30, 2017, the Company has sold 1,267,237 shares of its common stock under the Distribution Agreement resulting in net proceeds to the Company of $1,626,549, after deducting the sales agent’s commission. On August 24, 2016, the Company entered into the Purchase Agreement, pursuant to which Aspire Capital was committed to purchase up to an aggregate of $12.5 million of shares of the Company’s common stock over the 30-month term of the Purchase Agreement. Upon execution of the Purchase Agreement, the Company issued and sold 333,333 of the Initial Shares at a price per share of $1.50, for an aggregate purchase price of $500,000 to Aspire Capital under the Purchase Agreement. Concurrently with the execution of the Purchase Agreement, and as consideration for Aspire Capital entering into the Purchase Agreement, the Company issued 336,116 of the Commitment Shares to Aspire Capital with a fair value of $440,278, which has been recorded as deferred financing costs and is included within other assets in the accompanying balance sheet as of December 31, 2016. The deferred financing costs were proratably charged to additional paid-in-capital for the Initial Shares, with the remainder of the costs being amortized over the term of the Purchase Agreement as there is no guarantee that additional shares will be sold under the Purchase Agreement. Pursuant to the terms of the Purchase Agreement, the Company was able to, from time to time and subject to certain limitations, direct Aspire Capital to purchase shares of the Company’s common stock using pricing formulas based on average prevailing market prices around the time of each sale. Additionally, the Company and Aspire may not effect any sales of shares of the Company's common stock under the Purchase Agreement during the continuance of an event of default or on any trading day that the closing sale price of its common stock is less than $0.40 per share (subject to adjustment for stock dividends, splits, combinations or similar transactions or events). During the three and six months ended June 30, 2017, 0 and 1,326,991 shares were issued, respectively, pursuant to the Purchase Agreement, resulting in aggregate gross proceeds of $0 and $1,869,512, respectively. From the inception of the Purchase Agreement through June 30, 2017, the Company has sold 1,476,991 shares of its common stock under the Purchase Agreement resulting in aggregate gross proceeds to the Company of $2,042,762, in addition to the Initial Shares and the Commitment Shares. Effective June 19, 2017, the Company terminated the Purchase Agreement, resulting in a write off of the remaining capitalized deferred financing costs relating to the Purchase Agreement of $336,985. On February 8, 2017, the Company entered into the SPA with PoC, pursuant to which, among other things, the Company issued to PoC 1,286,173 shares of its common stock. Under the terms of the SPA, PoC has agreed to fund $1,800,000 in study costs associated with certain clinical studies, including a planned proof-of-concept trial in patients with GSD Ia. Any study costs in excess of that amount will be the Company’s sole responsibility. The Company has accounted for the $1,800,000 as a prepaid expense on the balance sheet. During the three and six months ended June 30, 2017, the Company recorded amortization expense of $357,259 and $399,587, respectively, in clinical study costs related to the SPA with PoC, with a remaining prepaid balance of $1,400,413 on the balance sheet as of June 30, 2017. On June 14, 2017, the Company entered into a securities purchase agreement (the “Securities Purchase Agreement”), with certain accredited investors (the “Purchasers”), pursuant to which the Company sold an aggregate of 3,749,783 shares (the “Shares”), of its common stock in a registered direct offering (the “Registered Direct Offering”). The Shares were offered by the Company pursuant to its shelf registration statement on Form S-3 (File No. 333-212134) filed with the SEC on June 20, 2016, as amended by Amendment No. 1 thereto filed with the SEC on July 26, 2016, and declared effective on July 26, 2016. In a concurrent private placement, the Company also agreed, pursuant to the Securities Purchase Agreement, to issue and sell to each of the Purchasers a warrant to purchase 0.75 shares of common stock (the “Warrants”), for each share of common stock purchased by a Purchaser in the Registered Direct Offering (the “Private Placement”) and, together with the Registered Direct Offering, (the “Offerings”). The exercise price of the Warrants is $1.30 per share, subject to adjustment as provided therein, and will be exercisable beginning on December 19, 2017 through December 19, 2022. The combined purchase price for one Share and one Warrant to purchase 0.75 shares of common stock in the Offerings was $1.15. The closing of the Offerings occurred on June 19, 2017. The estimated aggregate net proceeds from the Offerings, after deducting the placement agents’ fees and other estimated offering expenses, were approximately $3.9 million.

5. Stockholders’ Equity

Preferred Stock

The Company is authorized to issue up to 10,000,000 shares of preferred stock, $0.00001 par value per share, with no shares outstanding as of June 30, 2017 and December 31, 2016. The Board of Directors is authorized to designate the terms and conditions of any preferred stock the Company may issue without further action by the stockholders of the Company.

Common Stock

The Company is authorized to issue up to 300,000,000 shares of common stock, $0.00001 par value per share.

In February 2014, the Company entered into a stock purchase agreement with one of its founders. The agreement provided for the purchase of 1,000,000 shares of the Company’s common stock at a price per share of $0.01 in exchange for future services to be rendered to the Company as measured by certain performance criteria. The shares were subject to a repurchase option and were to vest in two tranches of 500,000 shares each, upon achievement of the performance target or upon a triggering event as defined.

The Company determined that the fair value of the unrecognized expense was $168,000 at February 20, 2014, the grant date. In May 2015, the Company repurchased 633,810 of these shares at a purchase price of $0.00001 per share. In connection with the repurchase, the Company entered into an amendment to the stock purchase agreement to provide that the remaining 366,190 shares will continue to vest in two tranches of 183,095 shares each, upon achievement of the performance target or upon a triggering event as defined. The pro rata grant date fair value of the unrecognized expense is $61,556. In October 2015, a triggering event became probable of occurrence and was deemed achieved in October 2016; therefore, the Company recorded $30,778 of stock-based compensation expense through December 31, 2016, of which $12,371 and $18,407 was recorded as expense during the years ended December 31, 2016 and 2015, respectively. No similar expense was recognized during the three and six months ended June 30, 2017. The Company will continue to reassess at each reporting period whether it is probable that the performance target will be achieved, and if and when it is deemed probable, the Company will begin to record compensation expense using the fair value to determine stock-based compensation expense in its financial statements over the period the Company estimates the performance target will actually be achieved.

On April 13, 2016, the Company completed the Offering pursuant to a registration statement on Form S-1 (File No. 333-208182) that was declared effective on April 7, 2016, and a registration statement on Form S-1MEF (File No. 333-210650) filed pursuant to Rule 462(b) of the Securities Act. In the Offering, the Company sold 7,500,000 shares of its common stock and warrants to purchase up to 7,500,000 shares of its common stock at a public offering price of $1.25 per share of common stock and related warrant. The warrants have an exercise price of $1.50 per share of common stock, were immediately exercisable upon issuance and will expire on April 13, 2021. The Company granted the underwriters for the Offering a 45-day option to purchase up to an additional 1,125,000 shares of its common stock and/or warrants to purchase up to an additional 1,125,000 shares of its common stock to cover over-allotments, if any. Ligand, a related party to the Company, purchased 560,000 shares of the Company’s common stock and warrants to purchase up to 560,000 shares of Company’s common stock in the Offering. On April 13, 2016, the underwriters partially exercised the over-allotment option for warrants to purchase an additional 1,125,000 shares of the Company’s common stock at a public offering price of $0.01 per warrant. Upon the closing of the Offering on April 13, 2016, the Company received net proceeds of $7,754,286, after deducting underwriting discounts, commissions and other offering expenses of $1,631,964.

On April 13, 2016, pursuant to the terms of the Loan and Security Agreement, the Company issued the Ligand Shares and the Ligand Warrant to Ligand. The Ligand Warrant has an exercise price of $1.50 per share of the Company’s common stock, was immediately exercisable upon issuance (subject to a limitation on exercise to the extent that any exercise thereof would increase Ligand’s beneficial ownership of the Company’s common stock to greater than 49.9%) and expires on April 13, 2021. The Ligand Shares and the Ligand Warrant were issued to Ligand as a repayment of $1,200,000 of the Company’s obligation under the Ligand Note.

On April 27, 2016, the underwriters for the Offering exercised their over-allotment option to purchase 1,125,000 shares of the Company’s common stock at a public offering price of $1.24 per share. On April 29, 2016, the Company sold the 1,125,000 shares to the underwriters pursuant to the over-allotment option and received additional net proceeds of $1,283,400, after deducting underwriting discounts, commissions and other offering expenses of $111,600.

On June 20, 2016, the Company entered into the Distribution Agreement with Maxim pursuant to which the Company may offer and sell, from time to time, through Maxim up to 3,748,726 shares of its common stock. Any shares of common stock offered and sold in the Maxim Offering will be issued pursuant to the Company’s registration statement on Form S-3 (File No. 333-212134) filed with the SEC on June 20, 2016 and the prospectus relating to the Maxim Offering that forms a part of the registration statement on Form S-3. The registration statement on Form S-3 was declared effective by the SEC on July 26, 2016. The number of shares of the Company’s common stock eligible for sale under the Distribution Agreement will be subject to the limitations of General Instruction I.B.6 of Form S-3. During the three and six months ended June 30, 2017, the Company sold 0 and 488,388 shares of its common stock, respectively, under the Distribution Agreement resulting in net proceeds to the Company of $0 and $670,031, respectively, after deducting the sales agent’s commission. From the inception of the Distribution Agreement through June 30, 2017, the Company has sold 1,267,237 shares of its common stock under the Distribution Agreement resulting in net proceeds to the Company of $1,626,549, after deducting the sales agent’s commission.

On August 24, 2016, the Company entered into the Purchase Agreement, pursuant to which Aspire Capital was committed to purchase up to an aggregate of $12.5 million of shares of the Company’s common stock over the 30-month term of the Purchase Agreement. Upon execution of the Purchase Agreement, the Company issued and sold 333,333 of the Initial Shares at a price per share of $1.50, for an aggregate purchase price of $500,000 to Aspire Capital under the Purchase Agreement. Concurrently with the execution of the Purchase Agreement, and as consideration for Aspire Capital entering into the Purchase Agreement, the Company issued 336,116 of the Commitment Shares to Aspire Capital with a fair value of $440,278, which has been recorded as deferred financing costs and is included within other assets in the accompanying balance sheet as of December 31, 2016. The deferred financing costs were proratably charged to additional paid-in-capital for the Initial Shares, with the remainder of the costs being amortized over the term of the Purchase Agreement as there is no guarantee that additional shares will be sold under the Purchase Agreement. Pursuant to the terms of the Purchase Agreement, the Company was able to, from time to time and subject to certain limitations, direct Aspire Capital to purchase shares of the Company’s common stock using pricing formulas based on average prevailing market prices around the time of each sale. Additionally, the Company and Aspire may not effect any sales of shares of the Company's common stock under the Purchase Agreement during the continuance of an event of default or on any trading day that the closing sale price of its common stock is less than $0.40 per share (subject to adjustment for stock dividends, splits, combinations or similar transactions or events). During the three and six months ended June 30, 2017, 0 and 1,326,991 shares were issued, respectively, pursuant to the Purchase Agreement, resulting in aggregate gross proceeds of $0 and $1,869,512, respectively. From the inception of the Purchase Agreement through June 30, 2017, the Company has sold 1,476,991 shares of its common stock under the Purchase Agreement resulting in aggregate gross proceeds to the Company of $2,042,762, in addition to the Initial Shares and the Commitment Shares. Effective June 19, 2017, the Company terminated the Purchase Agreement, resulting in a write off of the remaining capitalized deferred financing costs relating to the Purchase Agreement of $336,985.

On February 8, 2017, the Company entered into the SPA with PoC, pursuant to which, among other things, the Company issued to PoC 1,286,173 shares of its common stock. Under the terms of the SPA, PoC has agreed to fund $1,800,000 in study costs associated with certain clinical studies, including a planned proof-of-concept trial in patients with GSD Ia. Any study costs in excess of that amount will be the Company’s sole responsibility. The Company has accounted for the $1,800,000 as a prepaid expense on the balance sheet. During the three and six months ended June 30, 2017, the Company recorded amortization expense of $357,259 and $399,587, respectively, in clinical study costs related to the SPA with PoC, with a remaining prepaid balance of $1,400,413 on the balance sheet as of June 30, 2017.

On June 14, 2017, the Company entered into a securities purchase agreement (the “Securities Purchase Agreement”), with certain accredited investors (the “Purchasers”), pursuant to which the Company sold an aggregate of 3,749,783 shares (the “Shares”), of its common stock in a registered direct offering (the “Registered Direct Offering”). The Shares were offered by the Company pursuant to its shelf registration statement on Form S-3 (File No. 333-212134) filed with the SEC on June 20, 2016, as amended by Amendment No. 1 thereto filed with the SEC on July 26, 2016, and declared effective on July 26, 2016. In a concurrent private placement, the Company also agreed, pursuant to the Securities Purchase Agreement, to issue and sell to each of the Purchasers a warrant to purchase 0.75 shares of common stock (the “Warrants”), for each share of common stock purchased by a Purchaser in the Registered Direct Offering (the “Private Placement”) and, together with the Registered Direct Offering, (the “Offerings”). The exercise price of the Warrants is $1.30 per share, subject to adjustment as provided therein, and will be exercisable beginning on December 19, 2017 through December 19, 2022. The combined purchase price for one Share and one Warrant to purchase 0.75 shares of common stock in the Offerings was $1.15. The closing of the Offerings occurred on June 19, 2017. The estimated aggregate net proceeds from the Offerings, after deducting the placement agents’ fees and other estimated offering expenses, were approximately $3.9 million.