The Company is party to a collaboration and license agreement with Shionogi whereby Shionogi is responsible for all clinical development and regulatory filings for zuranolone in MDD and other indications in Japan, the Republic of Korea (South Korea), and Taiwan (together, the Shionogi Territory) and would be responsible for commercialization of zuranolone in the Shionogi Territory, to the extent zuranolone is successfully developed and obtains marketing approval in any of the countries within the Shionogi Territory. At the time of execution of the Shionogi Collaboration Agreement in 2018, Shionogi was required to make an upfront payment to Sage of $90.0 million, and the Company was eligible to receive additional payments of up to $470.0 million if certain regulatory and commercial milestones are achieved by Shionogi. As of March 31, 2026, the remaining potential future milestone payments include up to $40.0 million for the achievement of specified regulatory milestones, up to $10.0 million for the achievement of specified commercialization milestones, and up to $385.0 million for the achievement of specified net sales milestones. The Company is also eligible to receive tiered royalties on sales of zuranolone in the Shionogi Territory, if development efforts are successful, with tiers averaging in the low to mid-twenty percent range, subject to other terms of the agreement. As between the Company and Shionogi, the Company maintains exclusive rights to develop and commercialize

zuranolone outside of the Shionogi Territory. The upfront cash payment and any payments for milestones and royalties are non-refundable and non-creditable. Due to the uncertainty of pharmaceutical development and the high historical failure rates generally associated with drug development, the Company may not receive any milestone payments or any royalty payments from Shionogi. In the fourth quarter of 2025, Shionogi received approval from the Pharmaceuticals and Medical Devices Agency for the manufacturing and marketing of a product containing zuranolone in Japan for the treatment of MDD. Shionogi announced the first commercial sale of ZURZUVAE in Japan in the first quarter of 2026. No product containing zuranolone is approved for the treatment of MDD in the United States.

Under the clinical supply agreement, the Company is obligated to manufacture and supply to Shionogi (i) clinical quantities of API reasonably required by Shionogi for the development of licensed products in the Shionogi Territory under the collaboration and license agreement and (ii) quantities of drug product reasonably required for use by Shionogi in Phase 1 clinical trials of zuranolone in the Shionogi Territory under the collaboration and license agreement, in the quantities agreed to by the parties. A commercial supply agreement has not yet been entered into and the parties are operating under the provisions of the existing clinical supply agreement.

Under the terms of the Biogen Collaboration Agreement, the Company granted Biogen a co-exclusive license to develop and commercialize SAGE-217 products in the U.S., an exclusive license to develop and commercialize SAGE-217 products in all countries of the world other than the U.S. and the Shionogi Territory. The Company refers to the territories outside the U.S. to which Biogen has rights under the Biogen Collaboration Agreement with respect to SAGE-217 as the Biogen Territory.

Development and commercialization activities in the U.S. under the Biogen Collaboration Agreement are conducted pursuant to plans agreed to by the Company and Biogen and overseen by a joint steering committee that consists of an equal number of representatives of each party. The Company and Biogen share equally in the costs for development and commercialization, as well as the profits and losses upon FDA approval and commencement of product sales, in the U.S., subject to the Company’s opt-out right described below. Biogen is solely responsible for all development activities and costs related to any development and commercialization of SAGE-217 products for the Biogen Territory, and the Company will receive royalties on any sales in the Biogen Territory, as mentioned above. Biogen is the principal and records sales of SAGE-217 products globally. The Company is obligated to supply API and bulk drug product for the Biogen Territory and API, bulk drug product and final drug product for the U.S. to support development and commercialization activities. Biogen has the right to assume manufacturing responsibilities for API for the Biogen Territory at any time during the term of the Biogen Collaboration Agreement, and the Biogen Collaboration Agreement further provides that Biogen will, within a reasonable period of time, assume manufacturing responsibility for bulk drug product for the Biogen Territory.

Unless terminated earlier, the Biogen Collaboration Agreement will continue on a country-by-country basis until the date on which (a) in any country in the Biogen Territory, the royalty term has expired in such country, and (b) for the U.S., the parties agree to permanently cease to commercialize. Biogen also has the right to terminate the Biogen Collaboration Agreement for convenience in its entirety or as to a particular region, upon advance written notice. The Company has an opt-out right to convert the co-exclusive license in the U.S. to an exclusive license to Biogen. Following the exercise of the opt-out right, the Company would no longer share equally in the profits and losses in the U.S. and would be entitled to receive certain royalty payments at percentage rates ranging from the low to high twenties and additional sales milestones.

While Biogen is considered the principal in transactions with customers for the sale of ZURZUVAE globally, the Company is also engaged in significant commercialization activities, including maintaining its own U.S. direct sales force. The Company presents its proportionate share of Biogen’s ZURZUVAE sales to customers in the U.S. as Collaboration revenue (ZURZUVAE) within the condensed consolidated statements of loss. Payments to or reimbursements from Biogen related to the agreement of the parties to share equally in all revenue and costs are accounted for as an increase to Collaboration revenue (ZURZUVAE), an increase to or reduction of Cost of revenues, Research and development expenses, or Selling, general and administrative expenses, in the condensed consolidated statements of loss, depending on the nature of the activity.