BIOGEN INC. → Sage Therapeutics, Inc.

Item 4 of the Schedule 13D is hereby amended and supplemented by adding the following: From March 2025 through May 2025, the Reporting Persons engaged in discussions and diligence with the Issuer with respect to a potential sale of the Issuer to the Reporting Persons. On May 5, 2025, the Reporting Persons submitted to representatives of the Issuer a non-binding proposal to acquire all of the outstanding shares of Common Stock not owned by the Reporting Persons or their subsidiaries for an upfront payment of $9.00 per share in cash and one contingent value right per share representing the right to receive $2.00 in cash upon annual net sales of ZURZUVAE in the U.S. in a calendar year first equaling or exceeding $450 million and $2.00 in cash upon annual net sales of ZURZUVAE in the U.S. in a calendar year first equaling or exceeding $700 million (the "May 5 Proposal"). The May 5 Proposal was submitted subject to resolution of specific diligence matters. After the May 5 Proposal, representatives of the Reporting Persons and representatives of the Issuer continued to engage in discussions and diligence with respect to a potential transaction (including with respect to such specific diligence matters). On May 15, 2025, the Issuer terminated all discussions and diligence with respect to a potential transaction with the Reporting Persons. On June 16, 2025, the Issuer announced that it entered into an Agreement and Plan of Merger (the "Merger Agreement"), dated June 13, 2025, with Supernus Pharmaceuticals, Inc., a Delaware corporation ("Parent"), and Saphire, Inc., a Delaware corporation and a wholly owned subsidiary of Parent ("Purchaser"), pursuant to which, upon the terms and subject to the conditions therein, Purchaser will commence a tender offer (the "Offer") to acquire all of the Issuer's issued and outstanding Common Stock in exchange for $8.50 per share in cash plus one contingent value right per share representing the right to receive up to $3.50 per share upon the satisfaction of certain milestones. On July 2, 2025, Purchaser commenced the Offer, which Offer is currently scheduled to expire at one minute following 11:59 P.M., Eastern Time, on July 30, 2025, unless extended or earlier terminated (the "Offer Expiration Time"). At or before the Offer Expiration Time, the Reporting Persons intend to tender all or a portion of the Common Stock held by the Reporting Persons to Purchaser in the Offer or to dispose of all or a portion of the Common Stock held by the Reporting Persons. The Reporting Persons do not intend to disclose developments with respect to the foregoing, except as required by applicable law.