Werewolf to Merge With Ambros, Raises $150 Million

Rare Daily Staff

Werewolf Therapeutics said it will merge with privately held Ambros Therapeutics and that it raised $150 million in an oversubscribed private placement, pivoting the Nasdaq-listed company toward the late-stage development of neridronate for complex regional pain syndrome type 1, a rare condition.

Under the all-stock transaction, the combined company will operate as Ambros Therapeutics, be headquartered in San Diego, and is expected to trade on Nasdaq under the ticker AMBX. The deal is expected to close in the first quarter of 2027, subject to shareholder approvals, Nasdaq listing approval, and other customary conditions.

The transaction gives Ambros access to public-market infrastructure and financing to complete its pivotal CRPS-RISE Phase 3 trial of intravenous neridronate, a bisphosphonate already marketed in Italy for CRPS and other bone-related conditions. Ambros expects to report topline data from the trial in 2028 and said the new capital should fund operations through a planned U.S. new drug application submission, extending its runway into the first half of 2029.

CRPS-1 is a severely painful, debilitating rare disease that typically follows a limb injury. The condition is characterized by intense, continuous pain in an affected limb, such as an arm, leg, hand, or foot. Patients with CRPS-1 often experience an evolving disease course that begins with a warm phase, which typically predominates during the first year after onset. During this phase, inflammation and other mechanisms can make the affected limb red, swollen, warm, and hypersensitive to pain.

In many patients, the disease progresses to a chronic cold phase, in which the affected limb changes in appearance and patients face ongoing, debilitating pain. There are currently no FDA-approved medicines for this high-unmet-need patient population.

Neridronate was developed by Abiogen Pharma. Clinical studies have demonstrated lasting pain reduction, along with improvements in other CRPS-related symptoms. Beyond CRPS, neridronate is also approved in Italy for osteogenesis imperfecta and Paget’s disease. The FDA has granted neridronate Breakthrough Therapy, Fast Track, and Orphan Drug designations for the treatment of CRPS.

The $150 million private placement was co-led by RA Capital Management and Janus Henderson Investors. Other participants include Aberdeen Investments, Adage Capital Partners, ADAR1 Capital Management, Affinity Asset Advisors, Arkin Bio Capital, Balyasny Asset Management, Enavate Sciences, SilverArc Capital, Sphera Healthcare, and Woodline Partners.

The merger terms assign an implied pre-financing value of $500 million to Ambros and $47.5 million to Werewolf. After closing, Ambros shareholders are expected to own approximately 71.7 percent of the combined company, financing investors 21.5 percent, and existing Werewolf shareholders 6.8 percent, subject to adjustments tied to Werewolf’s net cash at closing.

Existing Werewolf shareholders will also receive contingent value rights tied to any net proceeds from dispositions of Werewolf’s legacy assets. Werewolf had been developing conditionally activated cytokine therapies, including its IL-2 candidate WTX-124 and IL-12 candidate WTX-330, through its PREDATOR platform.

Ambros Chief Executive Officer Jay Hagan will lead the combined company, alongside Chief Financial Officer Cris Calsada, Chief Medical Officer Gail Cawkwell, General Counsel Christopher Aker, and Senior Vice President of Corporate Development Kunal Kishnani. Ambros’ current board members are expected to join the combined company’s board.

Photo: Ambros Chief Executive Officer Jay Hagan