Teijin Agreement	12 Months Ended
Dec. 31, 2018
License And Supply Agreement [Abstract]
Teijin Agreement	6. Teijin Agreement In August 2016, the Company, entered into an Exclusive License and Supply Agreement (the “Agreement”) with Teijin Limited, or Teijin, a pharmaceutical company based in Japan, pursuant to which the Company granted to Teijin an exclusive license to develop, use, sell, offer for sale, import, and otherwise commercialize, in Japan, any pharmaceutical product incorporating somavaratan (VRS-317), while the Company retains exclusive rights to somavaratan in the rest of the world. In exchange for such rights, the Company received an upfront payment of $40.0 million from Teijin, as well as the potential to receive a development milestone of $35.0 million, regulatory milestones of up to $55.0 million, and sales milestones of up to $35.0 million, in addition to sales-based payments. Under the Agreement, the development and commercialization of somavaratan products in Japan would have been overseen by a joint steering committee composed of representatives of Teijin and the Company. The Company would have been responsible for completing (at the Company’s expense) all ongoing clinical studies, including the current pediatric Growth Hormone Deficiency (GHD) Phase 2/3 trial, and its related long-term safety study, and the Company would have also been responsible for a portion of the costs associated with any additional trials, if they are required by the Japanese authorities for approval of the Marketing Authorization Application, or MAA, in Japan in the pediatric indication, up to a cap on our share of such costs of $5.0 million. Following the MAA submission in Japan, Teijin would have been responsible for conducting any additional Japanese studies for the pediatric or any other indications, at its own expense. In September 2017, the Phase 3 VELOCITY trial of somavaratan failed to reach its primary endpoint. As a result, because Japanese approval relied upon a positive Phase 3 Velocity trial result, the Japan pediatric GHD Phase 3 trial and its related long-term safety study have been discontinued. In January 2018, the Company received notice from Teijin that it was, pursuant to the agreement’s terms, terminating the Agreement, effective as of January 31, 2018. The notice of termination followed discussions between the Company and Teijin regarding the failure of the Company’s Phase 3 VELOCITY trial to meet its primary endpoint during which the Company and Teijin determined that continuing with the Agreement was no longer in the best interests of either party. Under the Agreement, the Company had granted to Teijin an exclusive license to develop, use, sell, offer for sale, import and otherwise commercialize, in Japan, any pharmaceutical product incorporating somavaratan (VRS-317). In exchange for such rights, the Company received an upfront fixed and non-refundable payment of $40 million from Teijin and could potentially have also received up to $125 million in development, regulatory and sales milestone payments, in addition to transfer pricing and a royalty calculated on net sales in Japan. The termination is not associated with any early termination penalty or any further payments by either party. Upon termination of the license agreement, the Company assessed whether to recognize the upfront payment as revenue in accordance with ASC 605-25 Multiple-Element Arrangements, as of December 31, 2017. From receipt of the $40.0 million in August 2016 through September 30, 2017, the Company concluded that persuasive evidence of an arrangement did not yet exist as certain key economic terms that may have significantly impacted economics of the Agreement were yet to be negotiated and finalized by the parties as part of the commercial supply agreement. The Company reviewed the Agreement noting that remaining efforts made by the Company from October 2017 through January 2018 were not deemed a deliverable under the Agreement. These remaining efforts consisted solely of activities related to shutting down the clinical sites because of the VELOCITY trial failing to meet its primary endpoint. The actions undertaken to close sites would have occurred with or without a third party and were not an obligation specific to, nor were they described, in the agreement. As such, the Company’s obligations under the Agreement were substantively complete at December 31, 2017.

Teijin Agreement

12 Months Ended

Dec. 31, 2018

License And Supply Agreement [Abstract]

6. Teijin Agreement

In August 2016, the Company, entered into an Exclusive License and Supply Agreement (the “Agreement”) with Teijin Limited, or Teijin, a pharmaceutical company based in Japan, pursuant to which the Company granted to Teijin an exclusive license to develop, use, sell, offer for sale, import, and otherwise commercialize, in Japan, any pharmaceutical product incorporating somavaratan (VRS-317), while the Company retains exclusive rights to somavaratan in the rest of the world. In exchange for such rights, the Company received an upfront payment of $40.0 million from Teijin, as well as the potential to receive a development milestone of $35.0 million, regulatory milestones of up to $55.0 million, and sales milestones of up to $35.0 million, in addition to sales-based payments.

Under the Agreement, the development and commercialization of somavaratan products in Japan would have been overseen by a joint steering committee composed of representatives of Teijin and the Company. The Company would have been responsible for completing (at the Company’s expense) all ongoing clinical studies, including the current pediatric Growth Hormone Deficiency (GHD) Phase 2/3 trial, and its related long-term safety study, and the Company would have also been responsible for a portion of the costs associated with any additional trials, if they are required by the Japanese authorities for approval of the Marketing Authorization Application, or MAA, in Japan in the pediatric indication, up to a cap on our share of such costs of $5.0 million. Following the MAA submission in Japan, Teijin would have been responsible for conducting any additional Japanese studies for the pediatric or any other indications, at its own expense.

In September 2017, the Phase 3 VELOCITY trial of somavaratan failed to reach its primary endpoint. As a result, because Japanese approval relied upon a positive Phase 3 Velocity trial result, the Japan pediatric GHD Phase 3 trial and its related long-term safety study have been discontinued. In January 2018, the Company received notice from Teijin that it was, pursuant to the agreement’s terms, terminating the Agreement, effective as of January 31, 2018. The notice of termination followed discussions between the Company and Teijin regarding the failure of the Company’s Phase 3 VELOCITY trial to meet its primary endpoint during which the Company and Teijin determined that continuing with the Agreement was no longer in the best interests of either party.

Under the Agreement, the Company had granted to Teijin an exclusive license to develop, use, sell, offer for sale, import and otherwise commercialize, in Japan, any pharmaceutical product incorporating somavaratan (VRS-317). In exchange for such rights, the Company received an upfront fixed and non-refundable payment of $40 million from Teijin and could potentially have also received up to $125 million in development, regulatory and sales milestone payments, in addition to transfer pricing and a royalty calculated on net sales in Japan. The termination is not associated with any early termination penalty or any further payments by either party.

Upon termination of the license agreement, the Company assessed whether to recognize the upfront payment as revenue in accordance with ASC 605-25 Multiple-Element Arrangements, as of December 31, 2017. From receipt of the $40.0 million in August 2016 through September 30, 2017, the Company concluded that persuasive evidence of an arrangement did not yet exist as certain key economic terms that may have significantly impacted economics of the Agreement were yet to be negotiated and finalized by the parties as part of the commercial supply agreement. The Company reviewed the Agreement noting that remaining efforts made by the Company from October 2017 through January 2018 were not deemed a deliverable under the Agreement. These remaining efforts consisted solely of activities related to shutting down the clinical sites because of the VELOCITY trial failing to meet its primary endpoint. The actions undertaken to close sites would have occurred with or without a third party and were not an obligation specific to, nor were they described, in the agreement. As such, the Company’s obligations under the Agreement were substantively complete at December 31, 2017.