License Agreements	9 Months Ended
Sep. 30, 2018
License Agreements [Abstract]
License Agreements	10. License Agreements In May 2018, the Company signed an Exclusivity Deed (the “Deed”) with Neuren Pharmaceuticals Limited (“Neuren”) that provided for exclusive negotiations for a period of three months from the date of the Deed. Under the terms of the Deed, the Company invested $3.1 million to subscribe for 1,330,000 shares of the company and paid $0.9 million for the exclusive right to negotiate a deal with Neuren, which was recorded in selling, general and administrative expenses in the Condensed Consolidated Statements of Operations for the nine months ended September 30, 2018. At September 30, 2018, the Company continues to hold the equity securities as a strategic investment in which the Company does not have a controlling interest or significant influence. Publicly held equity securities are measured using quoted prices in their respective active markets with changes recorded through other expense on the statements of operations. Net loss on strategic investments recognized in other expense in the Condensed Consolidated Statements of Operations in the three and nine months ended September 30, 2018 was $1.7 million and $2.0 million, respectively. As of September 30, 2018, the aggregate carrying amount of the Company’s strategic equity investment was $1.2 million included in other assets on the Condensed Consolidated Balance Sheets. In August 2018, the Company entered into a license agreement with Neuren and obtained exclusive North American rights to develop and commercialize trofinetide for Rett syndrome and other indications. Under the terms of the agreement, Neuren received an upfront payment of $10.0 million and is eligible to receive milestone payments of up to $455.0 million, based on the achievement of certain development and annual net sales milestones. In addition, Neuren is eligible to receive tiered, escalating, double-digit percentage royalties based on net sales. The license agreement was accounted for as an asset acquisition and the upfront cash payment of $10.0 million has been recorded in research and development expenses in the Condensed Consolidated Statements of Operations for the three and nine months ended September 30, 2018, as there is no alternative use for the asset.

10. License Agreements

In May 2018, the Company signed an Exclusivity Deed (the “Deed”) with Neuren Pharmaceuticals Limited (“Neuren”) that provided for exclusive negotiations for a period of three months from the date of the Deed. Under the terms of the Deed, the Company invested $3.1 million to subscribe for 1,330,000 shares of the company and paid $0.9 million for the exclusive right to negotiate a deal with Neuren, which was recorded in selling, general and administrative expenses in the Condensed Consolidated Statements of Operations for the nine months ended September 30, 2018. At September 30, 2018, the Company continues to hold the equity securities as a strategic investment in which the Company does not have a controlling interest or significant influence. Publicly held equity securities are measured using quoted prices in their respective active markets with changes recorded through other expense on the statements of operations. Net loss on strategic investments recognized in other expense in the Condensed Consolidated Statements of Operations in the three and nine months ended September 30, 2018 was $1.7 million and $2.0 million, respectively. As of September 30, 2018, the aggregate carrying amount of the Company’s strategic equity investment was $1.2 million included in other assets on the Condensed Consolidated Balance Sheets.

In August 2018, the Company entered into a license agreement with Neuren and obtained exclusive North American rights to develop and commercialize trofinetide for Rett syndrome and other indications. Under the terms of the agreement, Neuren received an upfront payment of $10.0 million and is eligible to receive milestone payments of up to $455.0 million, based on the achievement of certain development and annual net sales milestones. In addition, Neuren is eligible to receive tiered, escalating, double-digit percentage royalties based on net sales. The license agreement was accounted for as an asset acquisition and the upfront cash payment of $10.0 million has been recorded in research and development expenses in the Condensed Consolidated Statements of Operations for the three and nine months ended September 30, 2018, as there is no alternative use for the asset.