Ambros Therapeutics and Werewolf Therapeutics have entered into an all-stock merger agreement alongside a concurrent $150 million private placement. The transaction is intended to provide funding through the continued development of Ambros’ lead drug candidate, neridronate, for complex regional pain syndrome type 1 (CRPS-1).
The combined company will operate under the Ambros name and retain Ambros’ leadership team, led by Chief Executive Officer Jay Hagan. The merger has been approved by the boards of directors of both companies.
According to the companies, the financing was oversubscribed and will be co-led by RA Capital Management and Janus Henderson Investors. Following completion of the merger and financing, Ambros expects its cash runway to extend into the first half of 2029. During that period, the company expects to report Phase 3 data for neridronate and submit the therapy for FDA approval.
Werewolf Ends Strategic Alternatives Process
The agreement follows a period in which Werewolf Therapeutics explored strategic alternatives. The Massachusetts-based biotechnology company began that process in February 2026 after its cash runway fell to less than one year. Werewolf had previously emerged from stealth with $56 million in funding, raised a $72 million Series B round and completed a $120 million initial public offering in 2021.
As part of efforts to extend operations, the company sold assets to Jazz Pharmaceuticals and Merck KGaA while seeking a buyer for its Nasdaq listing. Under the merger terms, former Werewolf shareholders are expected to own approximately 7% of the combined company. The remaining ownership will be held by Ambros investors and participants in the private placement. The companies stated that Ambros and Werewolf have pre-transaction values of $500 million and $47.5 million, respectively.
Late-Stage Trial Evaluates Neridronate in CRPS-1 Patients
Ambros’ lead program focuses on neridronate, an aminobisphosphonate being studied as a non-opioid treatment for CRPS-1, a condition marked by persistent and debilitating pain. The disorder was previously known as reflex sympathetic dystrophy.
The ongoing Phase 3 trial is evaluating four 400-mg infusions of neridronate administered over 10 days. Approximately 270 participants are expected to be enrolled. Researchers are comparing neridronate with placebo, with the primary endpoint measuring the change in pain intensity from baseline to Week 12.
Neridronate was originally developed by Italy’s Abiogen Pharma and later licensed by Ambros. The drug has received breakthrough therapy, fast track and orphan drug designations from the U.S. Food and Drug Administration.
Earlier Research Informs Current Development Strategy
The Phase 3 program builds on previous research conducted in Italy. In 2013, researchers reported significant reductions in pain among CRPS-1 patients who received four 100-mg infusions of neridronate over a 10-day period.
Drawing on findings from earlier studies, Ambros has limited enrollment in the current trial to patients with the warm subtype of CRPS-1 and a positive triple-phase bone scan. The company has said this subgroup includes the patients most likely to benefit from neridronate.
According to the federal clinical trials registry, the study is expected to conclude around the end of 2027 or the beginning of 2028. If successful, the program could lead to the first FDA-approved treatment specifically for CRPS-1. Ambros estimates that the condition affects between 50,000 and 70,000 people annually in the United States.
The merger is expected to support continued development of neridronate as Ambros advances the program toward the completion of its Phase 3 study and a potential regulatory submission.
Ambros Therapeutics is moving forward with its lead drug candidate, neridronate, in a pivotal Phase 3 clinical trial for complex regional pain syndrome type 1 (CRPS-1).
CRPS-1 Remains a Difficult Condition to Treat
Complex regional pain syndrome type 1 can develop after an injury, surgery, fracture, or other physical trauma. Patients may experience persistent pain alongside swelling, sensitivity to touch, changes in skin temperature, and impaired movement.
The condition can vary significantly between individuals, making diagnosis and treatment particularly challenging.
Focus on Earlier Disease
The clinical program is focusing on patients in an earlier stage of the condition. Researchers believe that treating patients before symptoms become more established could potentially provide an opportunity to influence disease progression and improve functional outcomes.
Study Design
The pivotal trial uses a randomized and placebo-controlled design, allowing researchers to compare outcomes between participants receiving the investigational treatment and those receiving placebo.
Participants receive a short course of intravenous treatment and are then monitored over an extended period to evaluate pain and other clinical measures.
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