License and Collaboration Agreements	12 Months Ended
Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License and Collaboration Agreements	License and Collaboration Agreements (A) Oxford BioMedica License Agreement: On June 5, 2018, the Company, through its wholly owned subsidiary, ASG, entered into an exclusive license agreement (the "Oxford Agreement") with Oxford BioMedica (UK) Ltd. ("Oxford"), pursuant to which the Company received a worldwide, exclusive, royalty-bearing, sub-licensable license under certain patents and other intellectual property controlled by Oxford to develop and commercialize AXO-Lenti-PD and related gene therapy products for all diseases and conditions. In June 2018, as consideration for the license, the Company made an upfront nonrefundable payment to Oxford of $30.0 million, $5.0 million of which was applied as a credit against the process development work and clinical supply that Oxford is obligated to provide to the Company over the term of the Oxford Agreement. Under the terms of the Oxford Agreement, the Company could be obligated to make payments to Oxford totaling up to $55.0 million upon the achievement of specified development milestones and $757.5 million upon the achievement of specified regulatory and sales milestones. In April 2019, certain development milestones were achieved resulting in a $13.0 million net payment due to Oxford. The Company will also be obligated to pay Oxford a tiered royalty from 7% to 10%, based on yearly aggregate net sales of the underlying gene therapy products, subject to specified reductions upon the occurrence of certain events as set forth in the Oxford Agreement. These royalties are required to be paid, on a product-by-product and country-by-country basis, until the latest to occur of the expiration of the last to expire valid claim of a licensed patent covering such product in such country, the expiration of regulatory exclusivity for such product in such country, or 10 years after the first commercial sale of such product in such country. The Company is solely responsible, at its expense, for all activities related to the development and commercialization of the gene therapy products underlying the Oxford Agreement. Pursuant to the Oxford Agreement, the Company is required to use commercially reasonable efforts to develop, obtain regulatory approval of, and commercialize a gene therapy product underlying the Oxford Agreement in the United States and at least one major market country in Europe. In addition, the Company is required to meet certain diligence milestones and to include at least one U.S.-based clinical trial site in a pivotal study of a gene therapy product underlying the Oxford Agreement. If the Company fails to meet any of these specified development milestones, it may cure such failure by paying Oxford certain fees, which range from $0.5 million to $1.0 million. The Company evaluated the Oxford Agreement and determined that the acquired set of assets and activities did not meet the definition of a business and thus the transaction was not considered a business combination. The Company determined that the in-process research and development ("IPR&D") had not reached technological feasibility and therefore has no alternative future use. Accordingly, $25.0 million of the $30.0 million upfront nonrefundable payment to Oxford under the Oxford Agreement was recorded as research and development expense in the Company's consolidated statements of operations during the year ended March 31, 2019. As the remaining $5.0 million of the upfront payment under the licensing agreement represents a nonrefundable payment for process development work and clinical supply that Oxford is obligated to provide over the term of the Oxford Agreement, the Company fully capitalized this portion of the payment upon execution, with $1.7 million remaining capitalized within prepaid expenses and other current assets in its consolidated balance sheet as of March 31, 2020, which will be recorded to research and development expense as the process development work and clinical supply are provided by Oxford. The Company has the right to terminate the Oxford Agreement at any time upon two months' advance written notice prior to the first commercial sale of a product, or for a specified period of advance written notice after the first commercial sale of a product. Either party may terminate the Oxford Agreement for the other party's uncured material breach or with respect to a failure to make a required payment. Additionally, during the years ended March 31, 2020 and March 31, 2019 respectively, the Company incurred $9.2 million and $5.3 million of AXO-Lenti-PD program-specific costs, excluding the upfront nonrefundable payment and development milestones achieved, within research and development expenses in its consolidated statements of operations and paid a total of $15.2 million and $31.5 million to Oxford, including the upfront nonrefundable payment. (B) Benitec Biopharma License and Collaboration Agreement: In July 2018, the Company, through its wholly owned subsidiary, ASG, entered into a license and collaboration agreement (the "Benitec Agreement") with Benitec Biopharma Limited ("Benitec"), pursuant to which the Company made an upfront payment of $10.0 million and received a worldwide, exclusive, royalty-bearing, sub-licensable license under certain patents and other intellectual property controlled by Benitec to develop and commercialize investigational gene therapy AXO-AAV-OPMD and related gene therapy products (collectively, the "AXO-AAV-OPMD Program") for all diseases and conditions. The Company terminated the Benitec Agreement in its entirety, effective September 3, 2019. The Company evaluated the Benitec Agreement and determined that the acquired set of assets and activities did not meet the definition of a business and thus the transaction was not considered a business combination. The Company determined that the IPR&D had not reached technological feasibility and therefore has no alternative future use. Accordingly, the $10.0 million upfront nonrefundable payment was recorded as research and development expense in the Company's consolidated statements of operations during the year ended March 31, 2019. During the years ended March 31, 2020 and March 31, 2019, respectively, the Company also incurred $1.8 million and $4.6 million of AXO-AAV-OPMD program-specific costs within research and development expenses in its consolidated statements of operations and paid a total of $2.8 million and $12.1 million to Benitec, including the upfront nonrefundable payment. (C) The University of Massachusetts Medical School Exclusive License Agreement: In December 2018, the Company, through its wholly owned subsidiary, ASG, entered into an exclusive license agreement (the "UMMS Agreement"), with the University of Massachusetts Medical School ("UMMS") pursuant to which the Company received a worldwide, royalty-bearing, sub-licensable license under certain patent applications and any patents issuing therefrom, biological materials and know-how controlled by UMMS to develop and commercialize gene therapy product candidates, including AXO-AAV-GM1 and AXO-AAV-GM2, for the treatment of GM1 gangliosidosis and GM2 gangliosidosis (including Tay-Sachs disease and Sandhoff disease), respectively. This license is exclusive with respect to patents and biological materials and non-exclusive with respect to know-how and is subject to UMMS' retained rights for academic research, teaching and non-commercial patient care purposes, as well as to certain pre-existing rights of the U.S. government. Under the UMMS Agreement, the Company is solely responsible, at its expense, for the research, development and commercialization of the licensed gene therapy product candidates. The Company will reimburse UMMS for payments made by UMMS for the manufacture of clinical trial materials for the Company, up to a specified amount. The Company is obligated to use diligent efforts to develop and commercialize the licensed gene therapy product candidates and is required to achieve certain development and commercial milestones in accordance with the timeline set forth in the agreement. The Company evaluated the UMMS Agreement and determined that the acquired set of assets and activities did not meet the definition of a business and thus the transaction was not considered a business combination. The Company determined that the IPR&D had not reached technological feasibility and therefore has no alternative future use. Accordingly, the upfront payment of $10.0 million made from the Company to UMMS was recorded as research and development expense in the Company's consolidated statements of operations during the year ended March 31, 2019. In addition, the Company could be obligated to make payments to UMMS totaling up to $24.5 million upon the achievement of specified development and regulatory milestones and $39.8 million upon the achievement of specified commercial milestones. In February 2019, certain development and regulatory milestones were achieved resulting in a $1.0 million payment due to UMMS, and in October 2019, further development and regulatory milestones were achieved resulting in an additional $1.0 million payment due to UMMS. The Company is also obligated to pay UMMS tiered mid-single digit royalties based on yearly net sales of the licensed products, subject to a specified annual minimum amount. Additionally, the Company will pay UMMS a percentage of any revenues it receives from any third-party sublicenses to licensed products at rates ranging in the mid-single digits to mid-teens. The UMMS Agreement will expire upon the expiration of the Company's obligations to make royalty payments to UMMS, which continues until the later of the expiration of licensed patents and any applicable orphan designation exclusivity and 10 years after the first commercial sale of the licensed products. Upon such expiration, the licenses granted to the Company by UMMS will automatically convert to perpetual, irrevocable, worldwide royalty-free licenses. The Company has the right to terminate the UMMS Agreement at any time upon 90 days' advance written notice to UMMS. Either party may terminate the UMMS Agreement for the other party's uncured material breach upon 60 days' advance written notice, including in the event that UMMS reasonably determines the Company has not fulfilled its diligence obligations. During the years ended March 31, 2020 and March 31, 2019, respectively, the Company incurred $8.8 million and $1.2 million of program-specific costs excluding development and regulatory milestones achieved related to AXO-AAV-GM1 and AXO-AAV-GM2 within research and development expenses in its consolidated statements of operations and paid a total of $3.0 million and $10.2 million to UMMS, including the upfront payment.

License and Collaboration Agreements

(A) Oxford BioMedica License Agreement:

On June 5, 2018, the Company, through its wholly owned subsidiary, ASG, entered into an exclusive license agreement (the "Oxford Agreement") with Oxford BioMedica (UK) Ltd. ("Oxford"), pursuant to which the Company received a worldwide, exclusive, royalty-bearing, sub-licensable license under certain patents and other intellectual property controlled by Oxford to develop and commercialize AXO-Lenti-PD and related gene therapy products for all diseases and conditions. In June 2018, as consideration for the license, the Company made an upfront nonrefundable payment to Oxford of $30.0 million, $5.0 million of which was applied as a credit against the process development work and clinical supply that Oxford is obligated to provide to the Company over the term of the Oxford Agreement. Under the terms of the Oxford Agreement, the Company could be obligated to make payments to Oxford totaling up to $55.0 million upon the achievement of specified development milestones and $757.5 million upon the achievement of specified regulatory and sales milestones. In April 2019, certain development milestones were achieved resulting in a $13.0 million net payment due to Oxford. The Company will also be obligated to pay Oxford a tiered royalty from 7% to 10%, based on yearly aggregate net sales of the underlying gene therapy products, subject to specified reductions upon the occurrence of certain events as set forth in the Oxford Agreement. These royalties are required to be paid, on a product-by-product and country-by-country basis, until the latest to occur of the expiration of the last to expire valid claim of a licensed patent covering such product in such country, the expiration of regulatory exclusivity for such product in such country, or 10 years after the first commercial sale of such product in such country.

The Company is solely responsible, at its expense, for all activities related to the development and commercialization of the gene therapy products underlying the Oxford Agreement. Pursuant to the Oxford Agreement, the Company is required to use commercially reasonable efforts to develop, obtain regulatory approval of, and commercialize a gene therapy product underlying the Oxford Agreement in the United States and at least one major market country in Europe. In addition, the Company is required to meet certain diligence milestones and to include at least one U.S.-based clinical trial site in a pivotal study of a gene therapy product underlying the Oxford Agreement. If the Company fails to meet any of these specified development milestones, it may cure such failure by paying Oxford certain fees, which range from $0.5 million to $1.0 million.

The Company evaluated the Oxford Agreement and determined that the acquired set of assets and activities did not meet the definition of a business and thus the transaction was not considered a business combination. The Company determined that the in-process research and development ("IPR&D") had not reached technological feasibility and therefore has no alternative future use. Accordingly, $25.0 million of the $30.0 million upfront nonrefundable payment to Oxford under the Oxford Agreement was recorded as research and development expense in the Company's consolidated statements of operations during the year ended March 31, 2019. As the remaining $5.0 million of the upfront payment under the licensing agreement represents a nonrefundable payment for process development work and clinical supply that Oxford is obligated to provide over the term of the Oxford Agreement, the Company fully capitalized this portion of the payment upon execution, with $1.7 million remaining capitalized within prepaid expenses and other current assets in its consolidated balance sheet as of March 31, 2020, which will be recorded to research and development expense as the process development work and clinical supply are provided by Oxford. The Company has the right to terminate the Oxford Agreement at any time upon two months' advance written notice prior to the first commercial sale of a product, or for a specified period of advance written notice after the first commercial sale of a product. Either party may terminate the Oxford Agreement for the other party's uncured material breach or with respect to a failure to make a required payment.

Additionally, during the years ended March 31, 2020 and March 31, 2019 respectively, the Company incurred $9.2 million and $5.3 million of AXO-Lenti-PD program-specific costs, excluding the upfront nonrefundable payment and development milestones achieved, within research and development expenses in its consolidated statements of operations and paid a total of $15.2 million and $31.5 million to Oxford, including the upfront nonrefundable payment.

(B) Benitec Biopharma License and Collaboration Agreement:

In July 2018, the Company, through its wholly owned subsidiary, ASG, entered into a license and collaboration agreement (the "Benitec Agreement") with Benitec Biopharma Limited ("Benitec"), pursuant to which the Company made an upfront payment of $10.0 million and received a worldwide, exclusive, royalty-bearing, sub-licensable license under certain patents and other intellectual property controlled by Benitec to develop and commercialize investigational gene therapy AXO-AAV-OPMD and related gene therapy products (collectively, the "AXO-AAV-OPMD Program") for all diseases and conditions. The Company terminated the Benitec Agreement in its entirety, effective September 3, 2019.

The Company evaluated the Benitec Agreement and determined that the acquired set of assets and activities did not meet the definition of a business and thus the transaction was not considered a business combination. The Company determined that the IPR&D had not reached technological feasibility and therefore has no alternative future use. Accordingly, the $10.0 million upfront nonrefundable payment was recorded as research and development expense in the Company's consolidated statements of operations during the year ended March 31, 2019. During the years ended March 31, 2020 and March 31, 2019, respectively, the Company also incurred $1.8 million and $4.6 million of AXO-AAV-OPMD program-specific costs within research and development expenses in its consolidated statements of operations and paid a total of $2.8 million and $12.1 million to Benitec, including the upfront nonrefundable payment.

In December 2018, the Company, through its wholly owned subsidiary, ASG, entered into an exclusive license agreement (the "UMMS Agreement"), with the University of Massachusetts Medical School ("UMMS") pursuant to which the Company received a worldwide, royalty-bearing, sub-licensable license under certain patent applications and any patents issuing therefrom, biological materials and know-how controlled by UMMS to develop and commercialize gene therapy product candidates, including AXO-AAV-GM1 and AXO-AAV-GM2, for the treatment of GM1 gangliosidosis and GM2 gangliosidosis (including Tay-Sachs disease and Sandhoff disease), respectively. This license is exclusive with respect to patents and biological materials and non-exclusive with respect to know-how and is subject to UMMS' retained rights for academic research, teaching and non-commercial patient care purposes, as well as to certain pre-existing rights of the U.S. government.

Under the UMMS Agreement, the Company is solely responsible, at its expense, for the research, development and commercialization of the licensed gene therapy product candidates. The Company will reimburse UMMS for payments made by UMMS for the manufacture of clinical trial materials for the Company, up to a specified amount. The Company is obligated to use diligent efforts to develop and commercialize the licensed gene therapy product candidates and is required to achieve certain development and commercial milestones in accordance with the timeline set forth in the agreement.

The Company evaluated the UMMS Agreement and determined that the acquired set of assets and activities did not meet the definition of a business and thus the transaction was not considered a business combination. The Company determined that the IPR&D had not reached technological feasibility and therefore has no alternative future use. Accordingly, the upfront payment of $10.0 million made from the Company to UMMS was recorded as research and development expense in the Company's consolidated statements of operations during the year ended March 31, 2019. In addition, the Company could be obligated to make payments to UMMS totaling up to $24.5 million upon the achievement of specified development and regulatory milestones and $39.8 million upon the achievement of specified commercial milestones. In February 2019, certain development and regulatory milestones were achieved resulting in a $1.0 million payment due to UMMS, and in October 2019, further development and regulatory milestones were achieved resulting in an additional $1.0 million payment due to UMMS. The Company is also obligated to pay UMMS tiered mid-single digit royalties based on yearly net sales of the licensed products, subject to a specified annual minimum amount. Additionally, the Company will pay UMMS a percentage of any revenues it receives from any third-party sublicenses to licensed products at rates ranging in the mid-single digits to mid-teens.

The UMMS Agreement will expire upon the expiration of the Company's obligations to make royalty payments to UMMS, which continues until the later of the expiration of licensed patents and any applicable orphan designation exclusivity and 10 years after the first commercial sale of the licensed products. Upon such expiration, the licenses granted to the Company by UMMS will automatically convert to perpetual, irrevocable, worldwide royalty-free licenses. The Company has the right to terminate the UMMS Agreement at any time upon 90 days' advance written notice to UMMS. Either party may terminate the UMMS Agreement for the other party's uncured material breach upon 60 days' advance written notice, including in the event that UMMS reasonably determines the Company has not fulfilled its diligence obligations.

During the years ended March 31, 2020 and March 31, 2019, respectively, the Company incurred $8.8 million and $1.2 million of program-specific costs excluding development and regulatory milestones achieved related to AXO-AAV-GM1 and AXO-AAV-GM2 within research and development expenses in its consolidated statements of operations and paid a total of $3.0 million and $10.2 million to UMMS, including the upfront payment.