Commitments and Contingencies	6 Months Ended
Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies *License Agreement with StrideBio LLC* On April 13, 2017, the Company and its affiliates entered into a development and option agreement with StrideBio LLC (“StrideBio”), to research and develop novel adeno-associated virus capsids. Pursuant to the license agreement, the Company made a one-time upfront payment of $0.5 million to StrideBio, an achieved milestone payment of $0.3 million and is required to pay StrideBio up to $3.0 million upon the achievement of research milestones. Under the agreement, the Company is also contingently obligated to purchase a convertible note in the amount of $0.5 million, which was deemed to be fair value as of the date the investment was executed in the third quarter. The terms of this investment are further disclosed in Note 12. *Operating Leases* In March 2017, the Company subleased a portion of one research and office facility to a third party effective April 1, 2017. The sublease term is less than the remaining term under the original lease, and as a result, the Company does not believe it has met a cease use date as it may re-enter the space following the sublease. Payments to be received from the sublessee are approximately $2.8 million and will offset scheduled rent payments due to the landlord under the original lease for the sublease term. *Litigation* The Company licenses a U.S. patent application that is currently subject to interference proceedings declared by the Patent Trial and Appeal Board (“PTAB”) of the U.S. Patent and Trademark Office. Following motions by the parties and other procedural matters, the PTAB concluded in February 2017 that the declared interference should be dismissed because the claim sets of the two parties were not directed to the same patentable invention in accordance with the PTAB’s two-way test for patent interferences. In April 2017, the regents of the University of California (“California”) appealed the PTAB decision to the U.S. Court of Appeals for the Federal Circuit. In the appeal, California is seeking review and reversal of the PTAB’s February 2017 decision, which terminated the interference without determining which inventors actually invented the use of the CRISPR/Cas9 genome editing technology in eukaryotic cells. Under the Invention Management Agreement signed on December 15, 2016, the Company is obligated to share costs related to patent maintenance, defense and prosecution. During the three and six months ended June 30, 2017, the Company incurred $0.5 million and $1.0 million, respectively, in shared costs. During the three and six months ended June 30, 2016, the Company incurred $0.3 million, and $0.8 million, respectively, in shared costs. The Company had accrued legal costs from the cost sharing of $0.8 million and $2.8 million as of June 30, 2017 and December 31, 2016, respectively.

6. Commitments and Contingencies

License Agreement with StrideBio LLC

On April 13, 2017, the Company and its affiliates entered into a development and option agreement with StrideBio LLC (“StrideBio”), to research and develop novel adeno-associated virus capsids. Pursuant to the license agreement, the Company made a one-time upfront payment of $0.5 million to StrideBio, an achieved milestone payment of $0.3 million and is required to pay StrideBio up to $3.0 million upon the achievement of research milestones. Under the agreement, the Company is also contingently obligated to purchase a convertible note in the amount of $0.5 million, which was deemed to be fair value as of the date the investment was executed in the third quarter. The terms of this investment are further disclosed in Note 12.

Operating Leases

In March 2017, the Company subleased a portion of one research and office facility to a third party effective April 1, 2017. The sublease term is less than the remaining term under the original lease, and as a result, the Company does not believe it has met a cease use date as it may re-enter the space following the sublease. Payments to be received from the sublessee are approximately $2.8 million and will offset scheduled rent payments due to the landlord under the original lease for the sublease term.

Litigation

The Company licenses a U.S. patent application that is currently subject to interference proceedings declared by the Patent Trial and Appeal Board (“PTAB”) of the U.S. Patent and Trademark Office. Following motions by the parties and other procedural matters, the PTAB concluded in February 2017 that the declared interference should be dismissed because the claim sets of the two parties were not directed to the same patentable invention in accordance with the PTAB’s two-way test for patent interferences. In April 2017, the regents of the University of California (“California”) appealed the PTAB decision to the U.S. Court of Appeals for the Federal Circuit. In the appeal, California is seeking review and reversal of the PTAB’s February 2017 decision, which terminated the interference without determining which inventors actually invented the use of the CRISPR/Cas9 genome editing technology in eukaryotic cells.

Under the Invention Management Agreement signed on December 15, 2016, the Company is obligated to share costs related to patent maintenance, defense and prosecution. During the three and six months ended June 30, 2017, the Company incurred $0.5 million and $1.0 million, respectively, in shared costs. During the three and six months ended June 30, 2016, the Company incurred $0.3 million, and $0.8 million, respectively, in shared costs. The Company had accrued legal costs from the cost sharing of $0.8 million and $2.8 million as of June 30, 2017 and December 31, 2016, respectively.