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Get filing alertsWerewolf to be acquired by Ambros in reverse merger; existing holders to own ~6.8%
Filed August 21, 2026 · Period ending August 21, 2026 · ~2 min read
Key Changes
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Werewolf enters all-stock merger with Ambros Therapeutics; existing Werewolf shareholders will own ~6.8% of combined company vs. 71.7% for Ambros holders and 21.5% for PIPE investors—massive dilution from $47.5M implied Werewolf valuation vs. $500M for Ambros.
Item 1.01 — Entry into a Material Definitive Agreement verify on EDGAR → -
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Concurrent $150M PIPE financing from RA Capital, Janus Henderson, and other healthcare investors closes immediately prior to merger; combined company to focus on Ambros' neridronate Phase 3 trial for CRPS-1, with cash runway into H1 2029.
Item 1.01 — Entry into a Material Definitive Agreement verify on EDGAR → -
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Combined company will operate as Ambros Therapeutics (ticker AMBX), headquartered in San Diego, with Ambros' current management team and board—complete leadership transition for Werewolf.
Exhibit 99.1 view on EDGAR → -
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Werewolf shareholders to receive one non-transferable CVR per share for potential future cash payments from legacy INDUKINE programs (WTX-124, WTX-330); no assurance of any CVR payments.
Item 1.01 — Entry into a Material Definitive Agreement verify on EDGAR → -
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Asymmetric termination fees: Ambros pays $20M if it pursues superior offer; Werewolf pays $1.9M under similar circumstances. Transaction expected to close Q1 2027 subject to shareholder approval and Form S-4 effectiveness.
Item 1.01 — Entry into a Material Definitive Agreement verify on EDGAR →
Summary
Werewolf Therapeutics disclosed a definitive merger agreement with Ambros Therapeutics that will leave existing Werewolf shareholders owning approximately 6.8% of the combined company—a reverse merger in all but name.
The transaction values Werewolf at $47.5 million and Ambros at $500 million, with Ambros stockholders receiving 71.7% ownership and a concurrent $150 million PIPE financing (led by RA Capital and Janus Henderson) accounting for 21.5%. The combined company will abandon Werewolf's INDUKINE platform to focus exclusively on Ambros' neridronate Phase 3 trial for CRPS-1, a rare pain disorder with no FDA-approved therapies.
Werewolf shareholders receive contingent value rights tied to potential future proceeds from the legacy assets, but these are non-transferable and carry no assurance of payment. The transaction represents a near-total dilution event for Werewolf holders, who retain less than 7% ownership and lose all board and management representation—Ambros' current CEO, CFO, and directors will lead the combined entity. The $150 million PIPE is expected to fund operations through 2028 Phase 3 topline results and into H1 2029, positioning the combined company to pursue an NDA filing if the trial succeeds. Werewolf shareholders should review the forthcoming Form S-4 proxy materials carefully, as the vote will determine whether to accept the 6.8% residual stake plus CVRs or reject the transaction. Closing is expected in Q1 2027 subject to shareholder approval from both companies and customary conditions.
Section-by-Section Diff
Event · Item 1.01 — Entry into a Material Definitive Agreement
Item 1.01 — Entry into a Material Definitive Agreement filed; see Key Changes for terms.
Added in current filing · verify on EDGAR →
On August 21, 2026, Werewolf Therapeutics, Inc., a Delaware corporation (“Werewolf”), entered into an Agreement and Plan of Merger (the “Merger Agreement”) by and among Ambros Therapeutics, Inc., a Delaware corporation (“Ambros”), Werewolf, and Wave Atlantis Merger Sub, Inc., a Delaware corporation and a direct, wholly owned subsidiary of Werewolf (“Merger Sub”). Pursuant to the Merger Agreement, and upon the terms and subject to the satisfaction of the conditions described therein, Merger Sub will be merged with and into Ambros, with Ambros surviving as a wholly owned subsidiary of Werewolf
Werewolf Therapeutics entered into a definitive merger agreement to acquire Ambros Therapeutics in an all-stock transaction structured as a reverse merger. The transaction is intended to qualify as a tax-free reorganization for U.S. federal income tax purposes. Ambros stockholders will receive Werewolf common stock based on an exchange ratio, with options to receive pre-funded warrants in certain circumstances.
Added in current filing · verify on EDGAR →
At the closing of the Merger (the “Closing” and such date, the “Closing Date”), on a pro forma basis and based upon the number of shares of Werewolf Common Stock and Merger Pre-Funded Warrants and pre-funded warrants to purchase shares of Werewolf Common Stock with an exercise price of $0.001 per share expected to be issued in connection with the Concurrent PIPE Financing (as defined below) (“PIPE Pre-Funded Warrants” and, together with the Merger Pre-Funded Warrants, the “Pre-Funded Warrants”), pre-merger equityholders of Werewolf, other than those participating in the private placement, are expected to own approximately 6.8% of the combined company, pre-merger Ambros stockholders are expected to own approximately 71.7% of the combined company and Investors (as defined below) participating in the private placement are expected to own approximately 21.5% of the combined company, in each case, calculated on a fully diluted basis, using the treasury stock method, and subject to certain assumptions, including (i) an implied valuation for Werewolf of $47.5 million, (ii) a valuation for Ambros of $500.0 million, and (iii) the relative capitalization of Werewolf and Ambros.
Upon closing, existing Werewolf shareholders will own approximately 6.8% of the combined company, Ambros stockholders will own approximately 71.7%, and PIPE investors will own approximately 21.5%. The transaction implies a $47.5 million valuation for Werewolf and a $500.0 million valuation for Ambros. This represents significant dilution for current Werewolf shareholders, who will retain less than 7% ownership.
Added in current filing · verify on EDGAR →
Concurrently with entering into the Merger Agreement, Werewolf entered into a securities purchase agreement (the “Securities Purchase Agreement”) with certain qualified institutional buyers or accredited investors (the “Investors”). Pursuant to the Securities Purchase Agreement, and subject to the terms and conditions therein, Werewolf agreed to sell, and the Investors agreed to purchase, immediately prior to the Closing of the Merger, shares of Werewolf Common Stock (the “Shares”) and, in the case of certain Investors, in lieu of shares of Werewolf Common Stock, PIPE Pre-Funded Warrants (together with the Shares, the “Securities”) for an aggregate purchase price of $150.0 million (the “Concurrent PIPE Financing”).
Werewolf entered into a securities purchase agreement for a concurrent $150.0 million private placement (PIPE) of common stock and pre-funded warrants to qualified institutional buyers and accredited investors. The PIPE financing will close immediately prior to the merger closing and is a condition to the merger. The purchase price per share will be determined prior to closing based on the allocation framework in the merger agreement.
Event · Item 3.02 — Unregistered Sales of Equity Securities
Werewolf Therapeutics disclosed unregistered sales of equity securities in a concurrent PIPE financing to qualified institutional buyers and accredited investors.
Added in current filing · verify on EDGAR →
The offering and sale of the Shares and the PIPE Pre-Funded Warrants in the Concurrent PIPE Financing will be made in reliance on the exemption from registration under Section 4(a) (2) of the Securities Act. The Investors represented that they are qualified institutional buyers or accredited investors, as such term is defined in Rule 501(a) of Regulation D under the Securities Act, and that they are acquiring the securities for investment purposes only and not with a view to any resale, distribution or other disposition of the securities in violation of the U.S. federal securities laws.
Werewolf Therapeutics sold shares and pre-funded warrants in a private placement (PIPE financing) to qualified institutional buyers and accredited investors under an exemption from SEC registration requirements. The securities were sold for investment purposes only, not for resale. The filing does not disclose the number of shares, warrant terms, or dollar amount raised.
Show 1 minor / wording change
Added in current filing · verify on EDGAR →
The securities to be issued in the Concurrent PIPE Financing will not be registered under the Securities Act or any state securities laws upon issuance and may not be offered or sold in the United States absent registration under the Securities Act or an applicable exemption from the registration requirements.
The shares and warrants issued in the PIPE financing are restricted securities that cannot be freely traded or resold without SEC registration or an applicable exemption. This creates a lock-up period for the new investors and limits near-term selling pressure, though the company may file a registration statement later to enable resales.
Event · Item 7.01 — Regulation FD Disclosure
Werewolf Therapeutics announces merger agreement with Ambros and concurrent PIPE financing, subject to shareholder approval.
Added in current filing · verify on EDGAR →
On August 21, 2026, Werewolf and Ambros issued a press release announcing the execution of the Merger Agreement and the Securities Purchase Agreement.
Werewolf Therapeutics has entered into a definitive merger agreement with Ambros and a concurrent securities purchase agreement (PIPE financing). The transaction will require shareholder approval and SEC registration via Form S-4. The combined company is expected to list on Nasdaq.
Added in current filing · verify on EDGAR →
In connection with the proposed transaction between Werewolf and Ambros, Werewolf will file relevant materials with the SEC, including the Form S-4, which will include a proxy statement relating to the proposed transaction, and a prospectus, of Werewolf (the “Proxy Statement/Prospectus”). This Current Report on Form 8-K and the exhibits filed or furnished herewith are not a substitute for the Proxy Statement/Prospectus or any other document which Werewolf may file with the SEC or send to stockholders of Werewolf or Ambros in connection with the proposed transaction. The Proxy Statement/Prospectus will be mailed to stockholders of Werewolf.
Werewolf will file a Form S-4 registration statement containing a proxy statement and prospectus for shareholder vote on the merger. Shareholders should review these materials when available, as this 8-K does not contain full transaction details or voting information.
Added in current filing · verify on EDGAR →
Important factors that could cause actual results to differ materially include, but are not limited to: (i) the satisfaction or waiver of closing conditions to the potential transaction in the anticipated timeframe or at all; (ii) the risk that the Concurrent PIPE Financing may not be completed in a timely manner or at all; (iii) the risk that the potential transaction disrupts current plans and operations or diverts management’s attention from ongoing business operations and makes it more difficult to maintain business and operational relationships; (iv) the risk that the anticipated benefits and synergies of the potential transaction will not be realized or will take longer to realize than expected; (v) the magnitude of transaction costs associated with the potential transaction and the Concurrent PIPE Financing; (vi) the occurrence of any event, change or other circumstance that could give rise to the termination of the Merger Agreement
The company identifies key risks including potential failure to close the merger or PIPE financing, operational disruption, unrealized synergies, significant transaction costs, and possible termination of the merger agreement. These standard merger risks highlight execution uncertainty.
Event · Exhibit 99.1
Werewolf Therapeutics announces merger with Ambros Therapeutics and concurrent $150M private placement to advance neridronate for CRPS-1.
Added in current filing · view on EDGAR →
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.
Werewolf Therapeutics secured commitments for an oversubscribed $150 million private placement from leading healthcare investors co-led by RA Capital Management and Janus Henderson Investors. The placement will close concurrently with the merger and is expected to fund operations through topline results from the pivotal CRPS-RISE Phase 3 trial expected in 2028 and a planned NDA submission, with cash runway into the first half of 2029.
Added in current filing · view on EDGAR →
Upon closing of the proposed transaction, the combined company will be led by current members of the Ambros Therapeutics leadership team including: • Joseph (Jay) Hagan, Chief Executive Officer • | Cris Calsada, Chief Financial Officer | • Gail Cawkwell, M.D., Ph.D., Chief Medical Officer • | Christopher Aker, General Counsel | • Kunal Kishnani, SVP of Corporate Development Members of Ambros Therapeutics’ existing board of directors will become directors of the combined company.
The combined company will be led entirely by Ambros Therapeutics' current management team, with Jay Hagan as CEO and Cris Calsada as CFO. Ambros Therapeutics' existing board members will become directors of the combined company. This represents a complete management and board transition for Werewolf Therapeutics stockholders.
Added in current filing · view on EDGAR →
The transaction is expected to close by the first quarter of 2027, subject to certain closing conditions, including the approval by the stockholders of each company, the shares of Werewolf Therapeutics common stock issuable in the transaction having been approved for listing on Nasdaq, effectiveness of the registration statement on Form S-4 (the “Form S-4”) and the satisfaction of other customary closing conditions.
The merger is expected to close by the first quarter of 2027, subject to stockholder approval from both companies, Nasdaq listing approval, effectiveness of the Form S-4 registration statement, and other customary closing conditions. The transaction has been approved by both boards of directors.
Event · Exhibit 99.2
Werewolf Therapeutics filed an 8-K disclosing a corporate presentation by Ambros Therapeutics regarding neridronate for CRPS-1.
Added in current filing · view on EDGAR →
Corporate Presentation August 2026
Werewolf Therapeutics filed an 8-K attaching a corporate presentation dated August 2026 from Ambros Therapeutics, Inc. The presentation discusses Ambros' development of neridronate, an intravenous bisphosphonate, for Complex Regional Pain Syndrome Type 1 (CRPS-1), a rare, severely painful condition with no FDA-approved therapies.
Added in current filing · view on EDGAR →
Initiated Phase 3 trial in Q1 2026 following recent FDA feedback
Ambros initiated a pivotal Phase 3 trial (CRPS-RISE) for neridronate in Q1 2026, enrolling approximately 270 patients with CRPS-1 diagnosed within 6 months and meeting precision-medicine criteria (positive triple-phase bone scan, warm subtype). The primary endpoint is change in pain intensity at Week 12. Neridronate has received FDA Breakthrough Therapy, Fast Track, and Orphan Drug Designations, and Ambros expects FDA alignment on a single pivotal study for approval.
Added in current filing · view on EDGAR →
~$104M in cash, cash equivalents, and short-term investments as of 6/30/2026
Ambros disclosed preliminary unaudited cash, cash equivalents, and short-term investments of approximately $104 million as of June 30, 2026. The presentation states this position is projected to fund the company through Phase 3 topline data readout expected in 2028. The figures are preliminary, subject to completion of closing procedures and audit review, and may differ materially from final reported results.
Added in current filing · view on EDGAR →
~65,000 newly diagnosed individuals each year in the U.S.
Ambros estimates approximately 65,000 newly diagnosed CRPS-1 patients annually in the U.S., with no FDA-approved pharmacological therapies currently available. The company plans a targeted specialty sales force focused on pain specialists and hand/foot specialists, who account for the majority of CRPS-1 diagnoses. Ambros holds U.S. commercialization rights licensed from Abiogen Pharma and expects U.S. market exclusivity through 2045 via method-of-use patents and orphan exclusivity.
Added in current filing · view on EDGAR →
Neridronate achieved the primary endpoint of ≥50% reduction in pain intensity score vs. placebo (p=0.0003) and reduced pain intensity score vs. placebo ... (p<0.0001) in Abiogen's NERIAS Phase 3 study
Ambros highlighted results from two prior Phase 3 trials conducted by Abiogen in Italy (NERIAS and NAIMES) that supported Italian approval of neridronate for CRPS. In NERIAS, neridronate achieved statistically significant reductions in pain intensity versus placebo, with durable effects observed over 12 months in long-term follow-up studies. The presentation notes neridronate is approved in Italy for CRPS, Osteogenesis Imperfecta, and Paget's Disease, with an estimated 600,000+ patients treated to date across all indications.
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