Organization, Business and Basis of Presentation	12 Months Ended
Dec. 31, 2015
Accounting Policies [Abstract]
Organization, Business and Basis of Presentation	1. Organization, Business and Basis of Presentation Organization and Business We were incorporated in the state of Delaware on September 8, 2005. We are focused on the discovery and clinical development of innovative medicines for patients suffering from severe rare diseases. Initial Public Offering On May 12, 2015, we completed our initial public offering (IPO) of 6,164,000 shares of common stock at $14.00 per share, resulting in gross proceeds of approximately $86.3 million and net proceeds of $75.9 million, after underwriting and other expenses of approximately $10.4 million (consisting of approximately $6.0 million in underwriting discounts and commissions and approximately $4.4 million in other offering expenses). In connection with the IPO, all outstanding shares of redeemable convertible preferred stock were converted into 16,279,859 shares of our common stock and warrants to purchase 206,581 shares of redeemable convertible preferred stock were converted into warrants to purchase 25,970 shares of our common stock with a resultant reclassification of the warrant liabilities to additional paid-in capital. In addition, we filed an amended and restated certificate of incorporation on May 12, 2015, authorizing 150,000,000 shares of common stock and 7,285,456 shares of preferred stock, 5,000,000 of which is undesignated preferred stock. Upon the closing of the IPO, 1,574,566 shares of common stock were reserved for future issuance under the 2015 Stock Option and Incentive Plan (the 2015 Plan) and 227,623 shares of common stock were reserved for future issuance under the 2015 Employee Stock Purchase Plan (the 2015 ESPP). Principles of Consolidation Our consolidated financial statements include our accounts, our 98% majority-owned subsidiary in Hong Kong, Pangu BioPharma Limited (Pangu BioPharma). All intercompany transactions and balances are eliminated in consolidation. Reverse Stock Split On May 5, 2015, we filed an amendment to our amended and restated certificate of incorporation to effect a one-for-7.95413 reverse stock split of our common stock (the Reverse Stock Split). The par value and the authorized shares of the common and convertible preferred stock were not adjusted as a result of the Reverse Stock Split. All share information has been retroactively restated to reflect the Reverse Stock Split. Use of Estimates Our consolidated financial statements are prepared in accordance with generally accepted accounting principles (GAAP). The preparation of our consolidated financial statements requires us to make estimates and assumptions that impact the reported amounts of assets, liabilities and expenses and the disclosure of contingent assets and liabilities in our consolidated financial statements and accompanying notes. The most significant estimates in our consolidated financial statements relate to the fair value of equity issuances and awards, and clinical trial and research and development expenses. Although these estimates are based on our knowledge of current events and actions we may undertake in the future, actual results may ultimately differ materially from these estimates and assumptions. Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. We view our operations and manage our business in one operating segment.

1. Organization, Business and Basis of Presentation

Organization and Business

We were incorporated in the state of Delaware on September 8, 2005. We are focused on the discovery and clinical development of innovative medicines for patients suffering from severe rare diseases.

Initial Public Offering

On May 12, 2015, we completed our initial public offering (IPO) of 6,164,000 shares of common stock at $14.00 per share, resulting in gross proceeds of approximately $86.3 million and net proceeds of $75.9 million, after underwriting and other expenses of approximately $10.4 million (consisting of approximately $6.0 million in underwriting discounts and commissions and approximately $4.4 million in other offering expenses). In connection with the IPO, all outstanding shares of redeemable convertible preferred stock were converted into 16,279,859 shares of our common stock and warrants to purchase 206,581 shares of redeemable convertible preferred stock were converted into warrants to purchase 25,970 shares of our common stock with a resultant reclassification of the warrant liabilities to additional paid-in capital. In addition, we filed an amended and restated certificate of incorporation on May 12, 2015, authorizing 150,000,000 shares of common stock and 7,285,456 shares of preferred stock, 5,000,000 of which is undesignated preferred stock.

Upon the closing of the IPO, 1,574,566 shares of common stock were reserved for future issuance under the 2015 Stock Option and Incentive Plan (the 2015 Plan) and 227,623 shares of common stock were reserved for future issuance under the 2015 Employee Stock Purchase Plan (the 2015 ESPP).

Principles of Consolidation

Our consolidated financial statements include our accounts, our 98% majority-owned subsidiary in Hong Kong, Pangu BioPharma Limited (Pangu BioPharma). All intercompany transactions and balances are eliminated in consolidation.

Reverse Stock Split

On May 5, 2015, we filed an amendment to our amended and restated certificate of incorporation to effect a one-for-7.95413 reverse stock split of our common stock (the Reverse Stock Split). The par value and the authorized shares of the common and convertible preferred stock were not adjusted as a result of the Reverse Stock Split. All share information has been retroactively restated to reflect the Reverse Stock Split.

Use of Estimates

Our consolidated financial statements are prepared in accordance with generally accepted accounting principles (GAAP). The preparation of our consolidated financial statements requires us to make estimates and assumptions that impact the reported amounts of assets, liabilities and expenses and the disclosure of contingent assets and liabilities in our consolidated financial statements and accompanying notes. The most significant estimates in our consolidated financial statements relate to the fair value of equity issuances and awards, and clinical trial and research and development expenses. Although these estimates are based on our knowledge of current events and actions we may undertake in the future, actual results may ultimately differ materially from these estimates and assumptions.

Segment Reporting

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. We view our operations and manage our business in one operating segment.