Alumis agrees to all-stock merger with ACELYRIN, with pro forma cash of about $737 million

Alumis Inc. (Nasdaq: ALMS) agreed on February 6, 2025 to acquire ACELYRIN, INC. (Nasdaq: SLRN) in an all-stock merger. Each ACELYRIN share would convert into 0.4274 shares of Alumis common stock. The companies expect Alumis stockholders to own about 55% of the combined company and ACELYRIN stockholders about 45%, on a fully diluted basis. Closing is expected in the second quarter of 2025.

The terms and what must happen first

In a Form 8-K filed February 6, 2025, Alumis reports an Agreement and Plan of Merger with ACELYRIN and Arrow Merger Sub, Inc., a wholly owned subsidiary of Alumis. Merger Sub will merge into ACELYRIN, which will survive as a wholly owned subsidiary of Alumis. Special committees of independent directors at both companies recommended the deal. ACELYRIN options with an exercise price of $18.00 or less convert into Alumis options, and those above $18.00 are cancelled without payment.

The deal needs an effective registration statement on Form S-4 and approval from a majority of ACELYRIN's outstanding shares. It also needs approval from a majority of the votes cast by Alumis stockholders on issuing the new shares. Either party can end the agreement if the merger has not closed by July 7, 2025. Either company must pay the other a termination fee of $10 million in certain cases, including ending the deal to accept a superior proposal. After closing, the Alumis board would grow to nine directors, two of them designated by ACELYRIN, and the combined company would keep the Alumis name and executive team.

Voting agreements lock in much of the outcome before any vote. ACELYRIN stockholders who signed, including entities affiliated with Westlake Village BioPartners, AyurMaya Capital Management and Access Industries, plus Beth Seidenberg, Dan Becker and ACELYRIN Chief Executive Officer Mina Kim, held approximately 24% of its outstanding shares as of January 31, 2025. Alumis stockholders who signed held approximately 62% of its outstanding common stock on the same date.

Cash that is not yet audited

Both companies gave cash figures on a preliminary basis as of December 31, 2024. Alumis had approximately $289 million of cash, cash equivalents and marketable securities, and ACELYRIN approximately $448 million. The pro forma cash position is approximately $737 million. The filing and release say those numbers are subject to the completion of each company's financial closing procedures and to audit and review adjustments. Alumis says the combined cash provides runway into 2027, beyond several expected clinical readouts.

What the cash is for

Alumis' lead candidate, ESK-001, is an oral TYK2 inhibitor in the Phase 3 ONWARD program for moderate-to-severe plaque psoriasis and the Phase 2b LUMUS trial for systemic lupus erythematosus. Topline data from ONWARD are expected in the first half of 2026, and LUMUS data in 2026. Neither readout has happened as of this filing, so the deal rests on data that are still to come.

ACELYRIN's lead program is lonigutamab, a subcutaneous anti-IGF-1R antibody in a Phase 2 trial for thyroid eye disease. The release says the combined company is evaluating the development plan for lonigutamab "to confirm differentiation in a capital efficient manner." That means the asset ACELYRIN brings to the deal is under review, and the filing does not say what the review could lead to.

Advisers

Morgan Stanley & Co. LLC is financial adviser to Alumis, and Cooley LLP is its legal counsel. Guggenheim Securities, LLC is financial adviser to ACELYRIN, and Fenwick & West LLP is its legal counsel. The 8-K does not name a placement agent or underwriter for the share issue.

The company's own framing is that the merger creates a company with more runway and more late-stage programs. The release calls it a combination that gives the company "financial flexibility" to advance a larger late-stage pipeline. Against that, both cash figures are preliminary, the lead program on one side is under review, and the lead readout on the other side is not yet in.

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