San Diego-based Ambros Therapeutics is merging with Waltham, Massachusetts-based Werewolf Therapeutics (Nasdaq: HOWL) in an all-stock transaction, with a concurrent USD 150 million oversubscribed private placement. The deal allows Ambros a reverse merger to access public markets while providing funds to advance neridronate, a bisphosphonate with FDA Breakthrough Therapy, Fast Track, and Orphan Drug designations, through a pivotal Phase III trial in complex regional pain syndrome type 1 (CRPS-1). The combined company will operate as Ambros Therapeutics, trade on Nasdaq under the ticker AMBX, and be led by the existing Ambros management team.
Under the merger terms, pre-merger Ambros stockholders will hold approximately 71.7% of the combined company, private placement investors approximately 21.5%, and pre-merger Werewolf stockholders approximately 6.8%, with the percentages subject to adjustment based on Werewolf's net cash at closing. Ambros carries an implied pre-money valuation of USD 500 million; Werewolf is valued at USD 47.5 million. The private placement, co-led by RA Capital Management and Janus Henderson Investors, includes Aberdeen Investments, Adage Capital Partners, ADAR1 Capital Management, Balyasny Asset Management, and Sphera Healthcare, among others, and is sized to fund operations through Phase III topline data and a planned New Drug Application (NDA) submission, with cash runway into H1 2029. Pre-merger Werewolf stockholders will also receive a contingent value right (CVR) entitling them to proceeds from any disposition of Werewolf's legacy oncology assets. The transaction has received board approval from both companies and is expected to close by Q1 2027, subject to stockholder approvals and Nasdaq listing approval.
Neridronate, originally developed by Italy's Abiogen Pharma S.p.A., is a bisphosphonate approved in Italy for CRPS, osteogenesis imperfecta, and Paget's disease and has been administered to approximately 600,000 patients. Ambros holds exclusive US rights to the drug for CRPS-1, for which no pharmacological therapy is currently FDA-approved.
The ongoing CRPS-RISE Phase III trial is enrolling approximately 270 patients with warm-phase CRPS-1 who test positive by triple-phase bone scan, an enrichment strategy intended to identify patients more likely to respond based on neridronate's proposed mechanism and previous clinical findings. The primary endpoint is change in pain intensity at Week 12, with topline results expected in 2028. Ambros said FDA has indicated that a single successful pivotal trial could potentially support an NDA. Neridronate has received Breakthrough Therapy, Fast Track, and Orphan Drug designations from FDA.