Alumis completes merger with ACELYRIN at 0.4814 shares per ACELYRIN share

Alumis Inc. (Nasdaq: ALMS) said on May 21, 2025 that it has completed its merger with ACELYRIN, Inc. Each ACELYRIN stockholder will receive 0.4814 shares of Alumis common stock for each ACELYRIN share owned. ACELYRIN common stock has ceased trading and will no longer be listed on the Nasdaq Global Select Market.

A ratio that moved

The merger agreement signed on February 6, 2025 set the exchange ratio at 0.4274 shares of Alumis voting common stock for each ACELYRIN share. Alumis repeated that figure in its annual report, filed March 19, 2025. The closing release uses 0.4814 and does not say why the ratio differs. The release also does not restate the combined ownership split. The annual report said that, on a fully diluted basis as of January 31, 2025, Alumis holders would own about 55% of the combined company and ACELYRIN holders about 45%.

The agreement set July 7, 2025 as the date after which either company could terminate if the deal had not closed. It also provided for termination fees of $10.0 million in certain circumstances, including a termination to accept a superior proposal. The deal closed before that date.

Financial position after the close

Alumis's chief executive, Martin Babler, said the combination gives the company "a cash runway that now extends into 2027." The release describes a "significantly strengthened balance sheet." It does not give the combined cash balance, the net loss or the cash used in operations, so the runway cannot be checked against spending in this release.

Morgan Stanley & Co. LLC was financial advisor to Alumis, and Cooley LLP was its legal counsel. Guggenheim Securities, LLC advised ACELYRIN, with Fenwick & West LLP and Paul Hastings LLP as its legal counsel.

The pipeline still depends on trials

The annual report describes ESK-001, an oral TYK2 inhibitor, as having shown "significant therapeutic effect" in its Phase 2 program in moderate-to-severe plaque psoriasis. The report says the company has started the Phase 3 ONWARD program, which includes two parallel Phase 3 trials, and expects topline results from them in the first quarter of 2026. Results from a Phase 2 trial in systemic lupus erythematosus are expected in 2026. The open-label extension of the psoriasis Phase 2 trial is still running. The Phase 2 psoriasis results are the company's own description, and the Phase 3 trials have not yet reported.

The annual report also covers A-005, a central nervous system penetrant TYK2 inhibitor. Its human data so far come from a Phase 1 trial in healthy volunteers, which started in April 2024, with initial results reported in December 2024. The closing release adds no new clinical data.

Lonigutamab, the ACELYRIN program, is the least clear part of the record. The closing release still lists it among the pipeline programs and describes it as a subcutaneously delivered therapy for thyroid eye disease. It does not say whether the program will continue, be cut or be changed.

What the closing leaves open

The release gives no total of shares issued and no post-closing ownership table. It also does not give a new timetable for the psoriasis readouts beyond the first quarter of 2026 that the annual report gave. The gap between 0.4274 and 0.4814 stays unexplained in the release, and the annual report predates the change.

The release describes the combined company as a leading clinical-stage biopharma company with a differentiated portfolio and a strong balance sheet. Those are the company's words. The release does not compare the portfolio with any competing program, and it does not spell out what a failed Phase 3 trial would mean for the combined company.

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