Waltham, Massachusetts, USA, and San Diego, California, USA, August 21, 2026
Werewolf Therapeutics and Ambros Therapeutics have announced a definitive agreement to combine the two companies in an all-stock merger, creating a late-stage biotechnology company focused on advancing neridronate as a potential treatment for Complex Regional Pain Syndrome Type 1 (CRPS-1). The transaction is accompanied by an oversubscribed $150 million private placement from a syndicate of healthcare-focused investors. Following completion of the proposed merger, the combined company is expected to operate as Ambros Therapeutics, headquartered in San Diego, California, and is expected to trade on Nasdaq under the ticker symbol “AMBX.” The transaction is designed to provide funding for the ongoing development of neridronate and support the program through pivotal Phase 3 results and a potential New Drug Application (NDA) submission to the U.S. Food and Drug Administration (FDA).
$150 Million Financing Supports Late-Stage Development
The proposed merger brings together Ambros Therapeutics’ clinical-stage development program with Werewolf Therapeutics’ publicly listed biotechnology platform. In connection with the transaction, the companies secured commitments for an oversubscribed $150 million private placement, co-led by RA Capital Management and Janus Henderson Investors, with participation from additional healthcare-focused investors. The financing is expected to close concurrently with the merger and is intended to provide the combined company with sufficient resources to reach topline results from the CRPS-RISE Phase 3 trial, expected in 2028, and support a planned NDA submission. The company expects the resulting cash runway to extend into the first half of 2029, giving the development program financial support through important clinical and regulatory milestones. The merger is expected to close by the first quarter of 2027, subject to customary closing conditions, including approval from the stockholders of both companies, effectiveness of a Form S-4 registration statement, and approval for listing the relevant shares on Nasdaq. Under the proposed transaction, Ambros Therapeutics would become a wholly owned subsidiary of Werewolf Therapeutics, with former Ambros stockholders expected to hold the majority of the combined company’s ownership.
Neridronate Advances in Pivotal CRPS-1 Trial
The central scientific asset of the combination is neridronate, a differentiated bisphosphonate being developed for CRPS-1, a debilitating orphan disease associated with severe and persistent pain. According to the companies, approximately 65,000 people are newly diagnosed with CRPS-1 in the United States each year, and there are currently no FDA-approved medicines specifically available for the condition. Neridronate has already been approved and marketed in Italy for CRPS and other indications, including osteogenesis imperfecta and Paget’s disease, and has been administered to approximately 600,000 patients across its approved indications. The FDA has granted the program Breakthrough Therapy, Fast Track, and Orphan Drug designations for CRPS.Neridronate is currently being evaluated in the CRPS-RISE Phase 3 clinical trial, a multicenter, randomized, triple-blind, placebo-controlled study designed to assess its efficacy, safety, and tolerability in patients with warm CRPS-1. The trial is expected to enroll approximately 270 participants, randomized to receive intravenous neridronate or placebo. The primary efficacy endpoint is the change in pain intensity from baseline to Week 12, measured using an 11-point Numerical Rating Scale, while secondary endpoints include additional pain measures and patient-reported outcomes.
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FDA Alignment Creates Potential Regulatory Pathway
A key feature of the development strategy is the companies’ stated alignment with the FDA, under which a successful single pivotal Phase 3 trial could potentially support U.S. approval of neridronate for CRPS-1. Ambros expects to report topline CRPS-RISE results in 2028 and pursue a potential NDA submission based on the clinical data and regulatory requirements. The company also states that its intellectual property portfolio could support potential U.S. market exclusivity through 2045. The proposed combination therefore represents more than a corporate transaction, bringing together late-stage clinical development, regulatory strategy, pharmaceutical financing, and biotechnology expertise around a therapy targeting a significant unmet medical need. If successfully completed and supported by positive clinical results, the merger could establish Ambros Therapeutics as a focused late-stage biotechnology company positioned to advance neridronate toward potential FDA approval for CRPS-1.
Source: Werewolf Therapeutics, Ambros Therapeutics press relese
