Alumis and ACELYRIN, INC. Merger Progresses

Alumis and Acelyrin, both clinical-stage biopharmaceutical companies, are proceeding with a proposed all-stock merger. They have jointly filed a definitive proxy statement/prospectus with the United States — United States Securities and Exchange Commission, and special stockholder meetings are scheduled for May 13, 2025, for both companies to vote on the transaction. The boards of both companies unanimously recommend the merger, which is expected to close in the second quarter of 2025. The merger aims to create a leading clinical-stage immunology company with a differentiated late-stage portfolio of therapies and a strong balance sheet, providing a cash runway into 2027. Initially, Alumis stockholders were to own 55% and Acelyrin stockholders 45% of the combined company. However, an amendment to the merger agreement was announced on April 21, 2025, increasing Acelyrin stockholders' ownership to approximately 48% and Alumis stockholders' ownership to approximately 52% in the combined company. This revision was made in response to market conditions and investor expectations, and to maximize value for Acelyrin stockholders, especially after a rapid accumulation of Acelyrin stock by Tang Capital led Acelyrin to adopt a limited duration rights plan. Institutional Shareholder Services has recommended that Acelyrin stockholders vote 'FOR' the merger.