Werewolf and Ambros Therapeutics Announce Merger to Advance Neridronate as Potential First FDA-Approved Treatment for CRPS-1
核心洞察
Werewolf Therapeutics and Ambros Therapeutics (搜索) entered into a definitive all-stock merger to create a Nasdaq-listed, late-stage biotech focused on neridronate for CRPS-1.
The combined company secured an oversubscribed $150 million private placement co-led by RA Capital Management and Janus Henderson Investors, funding operations into the first half of 2029.
Neridronate, a bisphosphonate with Breakthrough Therapy, Fast Track, and Orphan Drug designations, is being evaluated in the pivotal CRPS-RISE Phase 3 trial with topline data expected in 2028.
Werewolf Therapeutics, Inc. (Nasdaq: HOWL) and Ambros Therapeutics (搜索), Inc. announced on August 21, 2026 that they have entered into a definitive merger agreement to combine the companies in an all-stock transaction. The combined company will focus on advancing Ambros Therapeutics' neridronate development program in Complex Regional Pain Syndrome Type 1 (搜索) (CRPS-1, formerly known as Reflex Sympathetic Dystrophy). Upon completion of the merger, the combined company will operate as Ambros Therapeutics, headquartered in San Diego, California, and is expected to trade under the Nasdaq ticker symbol "AMBX."
The transaction is expected to close by the first quarter of 2027, subject to approval by stockholders of each company, Nasdaq listing approval, effectiveness of the registration statement on Form S-4, and other customary closing conditions.
A Potential First-in-Class Therapy for an Orphan Disease
Neridronate is a differentiated bisphosphonate developed by Abiogen Pharma (搜索) S.p.A. that is already approved and marketed in Italy for the treatment of CRPS, as well as for osteogenesis imperfecta (搜索) and Paget's disease (搜索). The drug has been administered to approximately 600,000 patients across its approved indications in Italy, providing an extensive prior clinical experience and a well-established safety and tolerability profile.
CRPS-1 is a severely painful, debilitating orphan disease typically following a limb injury, affecting an estimated 65,000 newly diagnosed people in the United States each year. There are currently no FDA-approved medicines available to treat this high-unmet-need patient population. The condition is characterized by intense, continuous pain in the affected limb, such as the arm, leg, hand, or foot. Patients often experience an evolving condition commencing with a "warm" phase that typically predominates in the first year after onset, during which inflammation and other mechanisms cause the affected limb to become red, swollen, warm, and hypersensitive to pain. In many patients, the disease progresses to a chronic "cold" phase with ongoing, debilitating pain.
Recognizing its potential, the FDA has granted neridronate Breakthrough Therapy, Fast Track, and Orphan Drug designations for the treatment of CRPS.
"We are uniquely positioned to be advancing neridronate, a differentiated bisphosphonate with extensive prior clinical experience, in an FDA-aligned single Phase 3 trial supporting potential regulatory approval in patients with CRPS-1, a debilitating orphan disease with no currently FDA-approved therapy," said Jay Hagan, Chief Executive Officer of Ambros Therapeutics (搜索).
The CRPS-RISE Pivotal Trial
Neridronate is advancing in the pivotal CRPS-RISE Phase 3 clinical trial, a multicenter, randomized, triple-blind, placebo-controlled study designed to assess the efficacy, safety, and tolerability of neridronate in patients with warm CRPS-1. The trial will evaluate approximately 270 participants randomized 1:1 to receive either intravenous (IV) neridronate or placebo.
To be eligible, participants must have a confirmed CRPS-1 diagnosis per the Budapest Clinical Criteria, a known precipitating event (such as fracture, sprain, or contusion), CRPS-1 duration of 6 months or less, and moderate to severe pain. Additionally, participants must have characteristics that Ambros Therapeutics (搜索) believes make them more likely responders to neridronate treatment: a positive triple-phase bone scan (TPBS) and specific attributes of the warm CRPS-1 subtype.
Following an initial screening period of two to six weeks, participants will receive four IV infusions over 10 days of either 100 mg neridronate (400 mg total dose) or placebo, followed by a post-treatment period through week 12. The primary efficacy endpoint is change in pain intensity from baseline to week 12 as measured on an 11-point Numerical Rating Scale. Key secondary endpoints include other measures of pain reduction and patient-reported outcomes. The program also includes a registry for long-term outcomes and an opportunity for CRPS-RISE participants with active disease who completed the study to receive neridronate.
CRPS-RISE leverages a precision medicine approach focused on diagnosed CRPS-1 patients in the warm phase of the disease with positive triple-phase bone scans, whose disease biology most closely aligns with neridronate's proposed mechanism and where prior clinical evidence suggests the treatment effect may be greatest.
Based on interactions with the FDA, Ambros Therapeutics (搜索) believes that positive results from a single pivotal trial such as CRPS-RISE could support potential U.S. approval. The company anticipates reporting topline data from CRPS-RISE in 2028. Along with Orphan Designation, Ambros Therapeutics' intellectual property portfolio supports the potential for neridronate's U.S. market exclusivity through 2045.
Financing and Ownership Structure
In connection with the proposed merger, the companies secured commitments for an oversubscribed concurrent private placement of $150 million from a syndicate of leading healthcare-dedicated investors co-led by RA Capital Management and Janus Henderson Investors. The private placement includes participation from Aberdeen Investments, Adage Capital Partners, L.P., ADAR1 Capital Management, Affinity Asset Advisors, LLC, Arkin Bio Capital, Balyasny Asset Management, Patient Square Capital's platform Enavate Sciences, SilverArc Capital, Sphera Healthcare, and Woodline Partners LP, as well as other new and existing investors.
The private placement is expected to close concurrently with the proposed merger, at which time Werewolf Therapeutics will issue common stock and pre-funded warrants for aggregate gross proceeds of $150 million. Ambros Therapeutics (搜索) expects the combined company to be fully funded through topline results from the pivotal CRPS-RISE Phase 3 clinical trial expected in 2028 and a planned New Drug Application (NDA) submission to the FDA, with cash runway into the first half of 2029.
The exchange ratio is based on an implied value of Ambros Therapeutics (搜索) of $500 million (before giving effect to the concurrent private placement) and an implied value of Werewolf Therapeutics of $47.5 million. Pre-merger Werewolf Therapeutics stockholders (other than those investors participating in the private placement) are expected to own approximately 6.8% of the combined company, pre-merger Ambros Therapeutics stockholders approximately 71.7%, and investors participating in the private placement approximately 21.5%. These percentages are subject to adjustment based on the amount of Werewolf Therapeutics' net cash at the time of closing.
"Following a comprehensive review of strategic options, management and the board of directors believe a merger with Ambros Therapeutics (搜索) is in the best interest of Werewolf Therapeutics' stockholders," said Daniel J. Hicklin, Ph.D., President and Chief Executive Officer of Werewolf Therapeutics. "Neridronate, which has received the FDA's Breakthrough Therapy, Fast Track, and Orphan Drug designations, is a differentiated bisphosphonate with the potential to redefine the standard of care for patients with CRPS-1."
Leadership and Organization
Upon closing of the proposed transaction, the combined company will be led by current members of the Ambros Therapeutics (搜索) leadership team, including Joseph (Jay) Hagan as Chief Executive Officer, Cris Calsada as Chief Financial Officer, Gail Cawkwell, M.D., Ph.D., as Chief Medical Officer, Christopher Aker as General Counsel, and Kunal Kishnani as SVP of Corporate Development. Members of Ambros Therapeutics' existing board of directors will become directors of the combined company.
Werewolf Therapeutics is an innovative biopharmaceutical company pioneering the development of conditionally activated INDUKINE molecules through its proprietary PREDATOR platform for the treatment of cancer and other immune-mediated conditions. Its most advanced clinical-stage product candidates, WTX-124 and WTX-330, are systemically delivered, conditionally activated Interleukin-2 and Interleukin-12 INDUKINE molecules, respectively, for the treatment of solid tumors. Existing Werewolf Therapeutics stockholders will also be issued a contingent value right representing the right to receive certain payments from net proceeds related to dispositions of Werewolf Therapeutics' pre-transaction legacy assets.