Item 4 — Purpose of Transaction
Item 4 of the Prior Schedule 13D is hereby amended and supplemented by adding the following at the end thereof: As previously disclosed, on March 31, 2026, Biogen entered into an Agreement and Plan of Merger (the "Merger Agreement") with Apellis and Aspen Purchaser Sub, Inc., a Delaware corporation and a wholly owned subsidiary of Biogen ("Purchaser"). Pursuant to the Merger Agreement, on April 14, 2026, Purchaser commenced a tender offer (the "Offer") to acquire any and all 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 receive contingent cash payments of up to an aggregate of $4.00 in cash, without interest and subject to reduction for any applicable tax withholding, upon the achievement of certain specified milestones, in each case upon the terms and subject to the conditions set forth in the Offer to Purchase, dated April 14, 2026 (as amended or supplemented from time to time, the "Offer to Purchase") and in the related Letter of Transmittal. As a result of the satisfaction of the Minimum Condition (as defined in the Offer) and each of the other conditions to the Offer, on May 14, 2026, Purchaser irrevocably accepted for payment all Shares that were validly tendered (and not validly withdrawn) pursuant to the Offer. Following the completion of the Offer, on May 14, 2026, pursuant to the terms of the Merger Agreement, Purchaser merged with and into Apellis, without a vote of the stockholders of Apellis in accordance with Section 251(h) of the General Corporation Law of the State of Delaware, with Apellis continuing as the surviving corporation of the merger and as a wholly owned subsidiary of Biogen (the "Merger").