HOWL Reverse-Merges With Ambros to Take Neridronate Public

Werewolf Therapeutics (Nasdaq: HOWL) is handing its public listing to a chronic-pain startup. On August 21, Werewolf and Ambros Therapeutics announced an all-stock reverse merger that gives Ambros shareholders 71.7% of the combined company and refocuses it on neridronate, a bisphosphonate for Complex Regional Pain Syndrome Type 1 (CRPS-1) that is already approved in Italy but has no US clearance.

The merged company, valued at roughly $500 million, will operate as Ambros Therapeutics and trade on Nasdaq under the ticker AMBX. Existing Werewolf shareholders keep 6.8%, and investors in a concurrent, oversubscribed $150 million private placement take the remaining 21.5%. The PIPE was co-led by RA Capital Management and Janus Henderson Investors. HOWL closed at $0.43 on August 21 (Polygon), down about 4% on the news, with roughly 66 million shares changing hands. The deal is expected to close by the first quarter of 2027.

Neridronate is an aminobisphosphonate that has been administered to about 600,000 patients in Italy, where it is approved for CRPS-1 under the name Neridronato. The drug concentrates at the site of injury during the “warm phase” of the condition, which is why the trial targets patients with positive triple-phase bone scans. The FDA has granted it Breakthrough Therapy, Fast Track, and Orphan Drug designations, and the agency has signaled that a single successful registrational trial could support approval. CRPS-1, formerly called reflex sympathetic dystrophy, brings an estimated 65,000 new US cases each year and has no FDA-approved therapy.

The asset driving the deal is the CRPS-RISE Phase 3 trial, a triple-blind, placebo-controlled study restricted to warm-phase CRPS-1 patients with positive triple-phase bone scans. Topline data is expected in 2028, and Ambros says the PIPE funds the company through that readout and a planned NDA, with runway into the first half of 2029.

The risk is real. The 71.7/6.8 ownership split heavily dilutes legacy Werewolf holders. Neridronate is also a bisphosphonate, a class with crowded generic economics, and the entire thesis rests on one trial with a 2028 readout.

Ambros was co-founded by Vivek Ramaswamy, the biotech entrepreneur and former presidential candidate. The reverse merger is a capital lifeline: rather than run a traditional IPO, Ambros uses Werewolf’s Nasdaq listing to go public while the $150 million PIPE supplies the funding for a trial that began dosing patients in June.

This is the latest in a 2026 wave of reverse mergers, where cash-strapped public shells give late-stage private assets a listing without a traditional IPO. For a framework on evaluating these deals, see the guide to biotech IPOs and listings.

Source: Werewolf and Ambros Therapeutics merger press release