Results of Operations and Financial Condition. On July 29, 2026, Biogen Inc. issued a press release announcing its results of operations and financial condition for the second quarter ended June 30, 2026. A copy of the press release is furnished as Exhibit 99.1 and is incorporated herein by reference. The press release is being furnished pursuant to

Results of Operations and Financial Condition Biogen Inc. (Biogen) expects that its GAAP and non-GAAP results for the second quarter of 2026 will include acquired in-process research and development, upfront and milestone expense of approximately $164 million on a pre-tax basis. The estimated charge is expected to impact GAAP and non-GAAP net income per diluted share for the second quarter of 2026 by approximately $0.95 per share. Additionally, Biogen anticipates its GAAP and non-GAAP results…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement. The information set forth in

Completion of Acquisition or Disposition of Assets. Pursuant to the Merger Agreement, on April 14, 2026, Purchaser commenced a tender offer (the “Offer”) to acquire any and all of the issued and outstanding Shares, in exchange for (i) $41.00 per Share, net to the seller in cash, without interest and subject to reduction for any applicable tax withholding (the “Cash Amount”), plus (ii) one contractual, non-transferable contingent value right per Share (each, a “CVR”) representing the right to…

Entry into a Material Definitive Agreement. CVR Agreement As previously disclosed, on March 31, 2026, Biogen Inc., a Delaware corporation (“Biogen”), entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Apellis Pharmaceuticals, Inc., a Delaware corporation (“Apellis”), and Aspen Purchaser Sub, Inc., a Delaware corporation and a wholly owned subsidiary of Biogen (“Purchaser”). Pursuant to the Merger Agreement and in connection with the irrevocable acceptance for payment b…

Results of Operations and Financial Condition. On April 29, 2026, Biogen Inc. issued a press release announcing its results of operations and financial condition for the first quarter ended March 31, 2026. A copy of the press release is furnished as Exhibit 99.1 and is incorporated herein by reference. The press release is being furnished pursuant to

Results of Operations and Financial Condition Biogen Inc. (Biogen) expects that its GAAP and non-GAAP results for the first quarter of 2026 will include acquired in-process research and development, upfront and milestone expense of approximately $34 million on a pre-tax basis. The estimated charge is expected to impact GAAP and non-GAAP net income per diluted share for the first quarter of 2026 by approximately $0.19 per share. Acquired in-process research and development, upfront and milesto…

Other Events. Press Release On March 31, 2026, Biogen and Apellis issued a joint press release announcing the entry into the Merger Agreement. A copy of the press release is attached as Exhibit 99.2 hereto and is incorporated herein by reference. Investor Webcast Presentation On March 31, 2026, Biogen held an investor webcast presentation announcing the Merger. A copy of the investor webcast presentation relating to the Merger is attached as Exhibit 99.3 to this Current Report on Form 8-K and…

Entry into a Material Definitive Agreement. Agreement and Plan of Merger On March 31, 2026, Biogen Inc., a Delaware corporation (“Biogen”), entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Apellis Pharmaceuticals, Inc., a Delaware corporation (“Apellis”), and Aspen Purchaser Sub, Inc., a Delaware corporation and a wholly owned subsidiary of Biogen (“Purchaser”). Pursuant to the Merger Agreement, and upon the terms and subject to the conditions therein, Purchaser will…

Chief Legal Officer — Susan H. Alexander: Susan H. Alexander, Chief Legal Officer, will depart from the Company effective as of end May, 2026.

Chair of the Board of Directors — Caroline Dorsa: Ms. Dorsa decided not to stand for re-election to the Board.

Results of Operations and Financial Condition. On February 6, 2026, Biogen Inc. issued a press release announcing its results of operations and financial condition for the fourth quarter and year ended December 31, 2025. A copy of the press release is furnished as Exhibit 99.1 and is incorporated herein by reference. The press release is being furnished pursuant to

Results of Operations and Financial Condition Biogen Inc. (Biogen) expects that its GAAP and non-GAAP results for the fourth quarter of 2025 will include acquired in-process research and development, upfront and milestone expense of approximately $222 million on a pre-tax basis. The estimated charge is expected to impact GAAP and non-GAAP net income per diluted share for the fourth quarter 2025 by approximately $1.26 per share. During the first quarter of 2025 we began presenting acquired in-…

Results of Operations and Financial Condition. On October 30, 2025, Biogen Inc. issued a press release announcing its results of operations and financial condition for the third quarter ended September 30, 2025. A copy of the press release is furnished as Exhibit 99.1 and is incorporated herein by reference. The press release is being furnished pursuant to

Results of Operations and Financial Condition Biogen Inc. (Biogen) expects that its GAAP and non-GAAP results for the third quarter of 2025 will include acquired in-process research and development, upfront and milestone expense of approximately $2 million on a pre-tax basis. The estimated charge is expected to impact GAAP and non-GAAP net income per diluted share for the third quarter 2025 by approximately ($0.01) per share. During the first quarter of 2025 we began presenting acquired in-pr…

Results of Operations and Financial Condition. On July 31, 2025, Biogen Inc. issued a press release announcing its results of operations and financial condition for the second quarter ended June 30, 2025. A copy of the press release is furnished as Exhibit 99.1 and is incorporated herein by reference. The press release is being furnished pursuant to

Results of Operations and Financial Condition Biogen Inc. (Biogen) expects that its GAAP and non-GAAP results for the second quarter of 2025 will include acquired in-process research and development, upfront and milestone expense of approximately $46 million on a pre-tax basis. The estimated charge is expected to impact GAAP and non-GAAP net income per diluted share for the second quarter 2025 by approximately ($0.26) per share. During the first quarter of 2025 we began presenting acquired in…

Other Events. On May 6, 2025, Biogen Inc. (the “Company”) entered into an Underwriting Agreement (the “Underwriting Agreement”) with BofA Securities, Inc., Citigroup Global Markets Inc. and J.P. Morgan Securities LLC, as representatives of the several underwriters named in Schedule I thereto, relating to the issuance and sale of $1.75 billion aggregate principal amount of notes, consisting of $400 million aggregate principal amount of 5.050% Senior Notes due 2031 (the “2031 Notes”), $650 mill…

Results of Operations and Financial Condition. On May 1, 2025, Biogen Inc. issued a press release announcing its results of operations and financial condition for the first quarter ended March 31, 2025. A copy of the press release is furnished as Exhibit 99.1 and is incorporated herein by reference. The press release is being furnished pursuant to

Results of Operations and Financial Condition. On February 12, 2025, Biogen Inc. issued a press release announcing its results of operations and financial condition for the fourth quarter and year ended December 31, 2024. A copy of the press release is furnished as Exhibit 99.1 and is incorporated herein by reference. The press release is being furnished pursuant to

Vice President, Chief Accounting Officer & Global Corporate Controller — Sean Godbout: Sean Godbout was promoted to Vice President, Chief Accounting Officer & Global Corporate Controller.

Chief Financial Officer — Michael McDonnell: Michael McDonnell is retiring as CFO, and Robin Kramer has been appointed as the new CFO.

Results of Operations and Financial Condition. On October 30, 2024, Biogen Inc. issued a press release announcing its results of operations and financial condition for the third quarter ended September 30, 2024. A copy of the press release is furnished as Exhibit 99.1 and is incorporated herein by reference. The press release is being furnished pursuant to

Director — Lloyd B. Minor, M.D. and Sir Menelas (Mene) Pangalos, Ph.D.: Two new directors were appointed to the Board of Directors.

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information included in