Roche License Agreement	3 Months Ended
Mar. 31, 2017
Collaborative Agreement [Abstract]
Roche License Agreements	Roche License Agreement Overview In December 2013, the Company entered into the License Agreement with Roche to develop and commercialize certain antibodies that target α-synuclein, including PRX002. The License Agreement was evaluated under ASC 605-25, "Multiple Element Arrangements". Under this License agreement, the Company recognizes research reimbursement as collaboration revenue as earned. The Company recognized $0.3 million as collaboration revenue for research reimbursement from Roche for the three months ended March 31, 2017, as compared to $0.3 million for the three months ended March 31, 2016. Cost sharing payments to Roche are recorded as R&D expenses. The Company recognized $1.3 million in R&D expenses for payments made to Roche during the three months ended March 31, 2017, as compared to $0.5 million for the three months ended March 31, 2016. Reimbursement for development costs from Roche during the three months ended March 31, 2017 was $0.8 million, as compared to $1.2 million for the three months ended March 31, 2016,which was recognized as an offset to R&D expenses. Under the License Agreement, the Company is eligible to receive milestone payments upon the achievement of development, regulatory and various first commercial sales milestones. Milestone payments are evaluated under ASU No. 2010-17, "Milestone Method of Revenue Recognition". Factors considered in this determination included scientific and regulatory risk that must be overcome to achieve each milestone, the level of effort and investment required to achieve the milestone, and the monetary value attributed to the milestone. Accordingly, the Company recognizes payments related to the achievement of this milestone when the milestone is achieved. The clinical and regulatory milestones under the License Agreement after the point at which the Company could opt-out are not considered to be substantive due to the fact that active participation in the development activities that generate the milestones is not required by the License Agreement, and the Company can opt-out of these activities. There are no refund or claw-back provisions and the milestones are uncertain of occurrence even after the Company has opted out. Based on this determination, these milestones will be recognized similar to the commercial milestone, which will be accounted for as contingent revenue payments with revenue recognized upon achievement of the milestone assuming all revenue recognition criteria are met. The Company did not achieve any of the clinical and regulatory milestones under the License Agreement during the three months ended March 31, 2017 and 2016.

Roche License Agreement

Overview

In December 2013, the Company entered into the License Agreement with Roche to develop and commercialize certain antibodies that target α-synuclein, including PRX002. The License Agreement was evaluated under ASC 605-25, "Multiple Element Arrangements". Under this License agreement, the Company recognizes research reimbursement as collaboration revenue as earned. The Company recognized $0.3 million as collaboration revenue for research reimbursement from Roche for the three months ended March 31, 2017, as compared to $0.3 million for the three months ended March 31, 2016. Cost sharing payments to Roche are recorded as R&D expenses. The Company recognized $1.3 million in R&D expenses for payments made to Roche during the three months ended March 31, 2017, as compared to $0.5 million for the three months ended March 31, 2016. Reimbursement for development costs from Roche during the three months ended March 31, 2017 was $0.8 million, as compared to $1.2 million for the three months ended March 31, 2016,which was recognized as an offset to R&D expenses.

Under the License Agreement, the Company is eligible to receive milestone payments upon the achievement of development, regulatory and various first commercial sales milestones. Milestone payments are evaluated under ASU No. 2010-17, "Milestone Method of Revenue Recognition". Factors considered in this determination included scientific and regulatory risk that must be overcome to achieve each milestone, the level of effort and investment required to achieve the milestone, and the monetary value attributed to the milestone. Accordingly, the Company recognizes payments related to the achievement of this milestone when the milestone is achieved.

The clinical and regulatory milestones under the License Agreement after the point at which the Company could opt-out are not considered to be substantive due to the fact that active participation in the development activities that generate the milestones is not required by the License Agreement, and the Company can opt-out of these activities. There are no refund or claw-back provisions and the milestones are uncertain of occurrence even after the Company has opted out. Based on this determination, these milestones will be recognized similar to the commercial milestone, which will be accounted for as contingent revenue payments with revenue recognized upon achievement of the milestone assuming all revenue recognition criteria are met. The Company did not achieve any of the clinical and regulatory milestones under the License Agreement during the three months ended March 31, 2017 and 2016.