SUBSEQUENT EVENTS	9 Months Ended
Sep. 30, 2018
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	17. SUBSEQUENT EVENTS On October 8, 2018, the Company exercised an option to license Nationwide Children’s Hospital’s micro-dystrophin gene therapy program for the treatment of DMD under an agreement that was originally executed in December 2016. Upon exercise of the option, the Company made an up-front license payment of $1.0 million and may be liable for up to approximately $29.0 million in development, regulatory and sales milestones for each micro-dystrophin gene therapy product. Furthermore, the Company may be required to make a low-single-digit royalty payments based on net sales of micro-dystrophin gene therapy products subsequent to their commercialization. On October 8, 2018, the Company entered into a manufacturing collaboration agreement (“Paragon Agreement”) with Paragon Bioservices, Inc. (“Paragon”). Pursuant to the terms of the Paragon Agreement, Paragon agreed to provide the Company with dedicated access to clinical and commercial manufacturing capacity for its gene therapy programs. In return, the Company is required to make to Paragon: (i) a one-time $36.0 million payment payable in three installments through March 31, 2019, and (ii) additional payments totaling $2.0 million annually. The term of the Paragon Agreement will continue until the earlier of: (i) the latest expiration date of any commercial supply agreement in effect, or (ii) December 31, 2025. The Company also has the ability to terminate the Paragon Agreement prior to expiration, subject to potential additional financial considerations. On October 15, 2018, the Company entered into a license and collaboration agreement for developing and commercializing LYS-SAF302, a gene therapy to treat Mucopolysaccharidosis type IIIA (“MPS IIIA”) with Lysogene S.A. (“Lysogene”). Under the terms of the license and collaboration agreement, Lysogene will be responsible for completion of the pivotal trial, which is set to commence in the fourth quarter of 2018. The Company will have exclusive rights to commercialize LYS-SAF302 in the U.S. and all territories outside of Europe. Lysogene will retain exclusive commercial rights to LYS-SAF302 in Europe. The Company will be responsible for global manufacturing of LYS-SAF302 and will supply drug products to Lysogene for Europe. Lysogene also granted the Company certain option rights to an additional central nervous system targeted gene therapy candidate. Concurrently with the execution of the license and collaboration agreement, the Company entered into an equity investment agreement with Lysogene. Under the equity investment agreement, the Company purchased 950,606 shares of common stock issued by Lysogene. As a result of execution of the agreements, the Company was liable for a payment of $28.0 million to Lysogene related to the up-front license fee, the option fee, the equity investment and reimbursement to certain development activities. Additionally, the Company may be liable for up to approximately $102.8 million in development, regulatory and sales milestones associated with the license and collaboration agreement. Furthermore, the Company may be required to make tiered royalty payments based on net sales of the LYS-SAF302 product subsequent to its commercialization.

17. SUBSEQUENT EVENTS

On October 8, 2018, the Company exercised an option to license Nationwide Children’s Hospital’s micro-dystrophin gene therapy program for the treatment of DMD under an agreement that was originally executed in December 2016. Upon exercise of the option, the Company made an up-front license payment of $1.0 million and may be liable for up to approximately $29.0 million in development, regulatory and sales milestones for each micro-dystrophin gene therapy product. Furthermore, the Company may be required to make a low-single-digit royalty payments based on net sales of micro-dystrophin gene therapy products subsequent to their commercialization.

On October 8, 2018, the Company entered into a manufacturing collaboration agreement (“Paragon Agreement”) with Paragon Bioservices, Inc. (“Paragon”). Pursuant to the terms of the Paragon Agreement, Paragon agreed to provide the Company with dedicated access to clinical and commercial manufacturing capacity for its gene therapy programs. In return, the Company is required to make to Paragon: (i) a one-time $36.0 million payment payable in three installments through March 31, 2019, and (ii) additional payments totaling $2.0 million annually. The term of the Paragon Agreement will continue until the earlier of: (i) the latest expiration date of any commercial supply agreement in effect, or (ii) December 31, 2025. The Company also has the ability to terminate the Paragon Agreement prior to expiration, subject to potential additional financial considerations.

On October 15, 2018, the Company entered into a license and collaboration agreement for developing and commercializing LYS-SAF302, a gene therapy to treat Mucopolysaccharidosis type IIIA (“MPS IIIA”) with Lysogene S.A. (“Lysogene”). Under the terms of the license and collaboration agreement, Lysogene will be responsible for completion of the pivotal trial, which is set to commence in the fourth quarter of 2018. The Company will have exclusive rights to commercialize LYS-SAF302 in the U.S. and all territories outside of Europe. Lysogene will retain exclusive commercial rights to LYS-SAF302 in Europe. The Company will be responsible for global manufacturing of LYS-SAF302 and will supply drug products to Lysogene for Europe. Lysogene also granted the Company certain option rights to an additional central nervous system targeted gene therapy candidate. Concurrently with the execution of the license and collaboration agreement, the Company entered into an equity investment agreement with Lysogene. Under the equity investment agreement, the Company purchased 950,606 shares of common stock issued by Lysogene. As a result of execution of the agreements, the Company was liable for a payment of $28.0 million to Lysogene related to the up-front license fee, the option fee, the equity investment and reimbursement to certain development activities. Additionally, the Company may be liable for up to approximately $102.8 million in development, regulatory and sales milestones associated with the license and collaboration agreement. Furthermore, the Company may be required to make tiered royalty payments based on net sales of the LYS-SAF302 product subsequent to its commercialization.