Werewolf Therapeutics Agrees to Merge With Ambros at $500 Million Implied Valuation

Werewolf Therapeutics has agreed to merge with privately held Ambros Therapeutics in an all-stock deal that assigns Ambros an implied value of $500 million before a concurrent financing and Werewolf an implied value of $47.5 million. The combined company is expected to operate under the Ambros Therapeutics name, remain listed on Nasdaq and trade under the ticker symbol AMBX after the merger closes.

Existing Ambros stockholders are expected to own about 71.7% of the combined company, investors in a new $150 million private placement about 21.5%, and pre-merger Werewolf stockholders about 6.8%, excluding Werewolf holders that also invest in the financing. Those percentages can change based on Werewolf’s net cash at closing, giving the public company’s final balance sheet a direct role in how ownership is divided.

Ambros will become the operating center of the public company

The companies said in their merger announcement that Werewolf will issue common shares, or pre-funded warrants in place of shares in some cases, to Ambros stockholders. Ambros will then become a wholly owned subsidiary of Werewolf, but the surviving public business will use the Ambros name and will be led by Ambros management.

Joseph “Jay” Hagan is expected to serve as chief executive officer of the combined company, with Cris Calsada as chief financial officer, Gail Cawkwell as chief medical officer, Christopher Aker as general counsel and Kunal Kishnani as senior vice president of corporate development. Members of Ambros’ existing board are also expected to become directors of the combined company. The leadership structure puts Ambros and its late-stage drug program at the center of the listed entity.

Eligible pre-merger Werewolf holders are also expected to receive a contingent value right tied to net proceeds, if any, from future dispositions of Werewolf’s legacy assets. That right is separate from their minority equity stake in the combined company. No payment is guaranteed, and any eventual amount will depend on whether the legacy assets are sold and what proceeds are realized.

The agreement follows months of cost-cutting and a strategic review at Werewolf. In its latest quarterly filing, Werewolf said it began evaluating alternatives in February 2026, including a company sale, merger, asset sale, licensing arrangement or collaboration. It also disclosed workforce reductions in February and May as it cut spending and conserved capital.

Werewolf reported $22.0 million of cash and cash equivalents at June 30, 2026. The filing said those resources were not expected to fund operations for 12 months from the date the quarterly report was issued. Werewolf had also repaid its K2 HealthVentures term loan in May, eliminating the outstanding debt under that facility but recording a $3.4 million loss on extinguishment.

Neridronate and CRPS-RISE are the focus of the merger

Ambros’ lead program is neridronate, a bisphosphonate being studied for complex regional pain syndrome type 1, or CRPS-1. The company describes CRPS-1 as a rare and severely painful condition that often begins after an injury to a limb and can progress from an early warm, inflamed phase to a chronic phase with persistent pain and functional impairment.

The Phase 3 CRPS-RISE study is already recruiting. The ClinicalTrials.gov record lists an estimated enrollment of 270 adults and describes the study as randomized, triple-blind and placebo-controlled. Participants are assigned to intravenous neridronate or placebo, with four infusions given over 10 days and a primary endpoint measuring the change in pain intensity from baseline to week 12.

The timing of CRPS-RISE is central to the capital plan because the combined company will be focused on advancing neridronate through its pivotal study and toward a possible U.S. filing. ClinicalTrials.gov lists the study’s primary completion for December 2027 and study completion for January 2028, while Ambros says it expects topline Phase 3 results in 2028.

Ambros says neridronate has received Breakthrough Therapy, Fast Track and Orphan Drug designations from the U.S. Food and Drug Administration for CRPS. FDA’s orphan-drug database separately lists neridronate as designated for treatment of complex regional pain syndrome and shows that it is not approved by the FDA for the orphan indication. Ambros has said, based on its interactions with the agency, that positive results from a single pivotal study such as CRPS-RISE could potentially support a U.S. approval application, but the company also acknowledges that the FDA could require additional data or clinical work.

Neridronate was developed by Abiogen Pharma and is already approved in Italy for CRPS and other indications, according to Ambros. The company says the drug has been administered to about 600,000 patients across approved indications in Italy. That history provides a body of prior use, but it does not remove the clinical and regulatory risk attached to the U.S. Phase 3 program.

The $150 million placement is intended to carry the program through a 2028 readout

Alongside the merger, the companies secured commitments for an oversubscribed $150 million private placement that is expected to close at the same time. RA Capital Management and Janus Henderson Investors are co-leading the financing, with participation from several other health care-focused investment firms. Werewolf is expected to issue common stock and pre-funded warrants for the gross proceeds.

Ambros expects the new capital to fund the combined company through the CRPS-RISE topline results and a planned new drug application to the FDA, with cash runway into the first half of 2029. That runway estimate depends on the merger and financing closing as planned, the trial progressing on schedule and spending remaining within management’s assumptions. The companies list those factors among the risks that could cause actual timing or funding needs to differ.

For legacy Werewolf holders, the expected 6.8% stake comes after the new investors receive roughly 21.5% of the combined company. The public listing will therefore be centered on Ambros’ drug program and the new financing rather than continuing primarily as the former Werewolf oncology business. The contingent value right preserves a separate claim on possible proceeds from Werewolf’s pre-merger assets.

Both boards have approved the merger, but the companies still need stockholder approvals, Nasdaq approval for the new shares, an effective Form S-4 registration statement and other closing conditions. They currently expect the merger to close by the first quarter of 2027. Before then, Werewolf is expected to file a proxy statement and prospectus with the SEC that will provide fuller details on the exchange ratio, ownership adjustments, voting process and the rights attached to the legacy-asset contingent value right.

CRPS-RISE is expected to reach primary completion near the end of 2027, with Ambros targeting topline results in 2028. That readout will determine whether the newly financed public company can advance neridronate toward a potential U.S. filing.