Werewolf Therapeutics and Ambros Therapeutics agree to merge, plan $150M private placement

Werewolf Therapeutics, Inc. (Nasdaq: HOWL) and Ambros Therapeutics, Inc. announced on August 21, 2026 that the two companies signed a definitive agreement to combine in a transaction structured entirely as a stock swap.¹ Following the close, the surviving entity will take the Ambros Therapeutics name, be based in San Diego, and is expected to list under the ticker "AMBX."¹

Alongside the merger, the companies secured commitments for an oversubscribed private placement of $150 million led by RA Capital Management and Janus Henderson Investors.¹ Werewolf disclosed that closing requires, among other conditions, that the private placement deliver at least $100.0 million in cash proceeds to Werewolf.¹

The combined company's lead asset is neridronate, a bisphosphonate being tested in the Phase 3 "CRPS-RISE" trial. Under the protocol, the study will enroll roughly 270 participants randomized evenly to intravenous neridronate or placebo.¹ Dosing calls for four IV infusions given across 10 days, either 100 mg of neridronate per dose for a 400 mg cumulative dose or a matching placebo regimen, followed by observation through week 12.¹ The trial's main efficacy measure is the shift in pain severity from baseline to week 12, scored on an 11-point rating scale.¹

Regarding regulatory status, Ambros said its discussions with the FDA support the view that a single successful pivotal trial could be enough for U.S. approval.¹ Financial terms value Ambros at $500 million before the private placement and Werewolf at $47.5 million.¹ Post-closing ownership is expected to split roughly 6.8% to existing Werewolf holders, 71.7% to Ambros holders, and 21.5% to the new private placement investors.¹

The transaction has received board approval from both companies and is targeted to close by the first quarter of 2027, pending stockholder votes and other customary conditions.¹ Ambros expects to report topline CRPS-RISE data in 2028.¹