OS Therapies completes purchase of Advaxis immunotherapy assets from Ayala

OS Therapies Incorporated has completed its acquisition of the listeria-based cancer immunotherapy assets of Advaxis Immunotherapies from Ayala Pharmaceuticals, according to a press release filed as an exhibit to a Form 8-K on April 15, 2025. The release is dated April 9, 2025, the day the company announced the closing. It does not state the purchase price, the form of payment or any other deal terms.

Three clinical programs and eight preclinical candidates

The three clinical-stage programs are OST-AXAL, OST-503 and OST-PSA. OST-AXAL, for human papillomavirus-associated cancers, has completed the first of two Phase 3 trials, known as AIM2CERV. The release does not report that trial's results. OST-503, for non-small cell lung cancer and glioblastoma, reported positive Phase 2 data in lung cancer. The release gives no patient numbers or endpoints for that study, so the description of the data as positive rests on the company's own word. OST-PSA targets prostate cancer, and the release gives no clinical status for it.

The eight preclinical candidates are described as targeting more than 30 cancers, but the release does not name them. The company says new manufacturing-based intellectual property protects the platform and its candidates into 2040.

Chief Executive Paul Romness said the deal consolidated "all of the intellectual property for the listeria cancer immunotherapy platform into OS Therapies." The company also says it is now positioned as the world leader in listeria-based cancer immunotherapies. That is a claim the company makes about itself, and the release cites no market ranking to support it.

The lead asset is not approved

The lead asset is OST-HER2, which the company is developing to prevent recurrence in fully resected, lung metastatic osteosarcoma. The release says the company intends to submit a request for accelerated approval to the U.S. Food and Drug Administration in the third quarter of 2025, and it had targeted approval for year-end 2025. No approval has been granted, and the release does not describe any FDA feedback on the request.

The company says OST-HER2 produced positive data in a Phase 2b trial. The release does not give that trial's size, results or endpoints. OST-HER2 has Rare Pediatric Disease Designation. If it is approved, the company would become eligible for a Priority Review Voucher, which the release values at $150 million. A voucher is only granted on approval, so that value depends on an outcome the company has not yet reached.

The annual report filed March 31, 2025, describes OS Therapies as a clinical-stage company focused on osteosarcoma and other solid tumors. The filing cites published studies saying that recurrence or metastasis happens in about half of osteosarcoma patients within 12 to 18 months after initial remission. It also says the company plans to extend OST-HER2 into breast, esophageal and lung cancers, and to use its OST-Tunable Drug Conjugate platform against ovarian, lung and pancreatic cancers.

Money and the open questions

The release does not report cash, operating losses or debt. The business section of that annual report does not give those figures either. The release does not say how OS Therapies paid for the Advaxis assets, so readers cannot tell from the filings whether the purchase used cash, shares or a combination. For a company whose lead asset still needs approval, that gap matters.

The company says it will move the OST-HER2 request forward in the third quarter of 2025 and then explore the platform's potential more widely. It does not give a date for any further trial results, and the release does not name a partner or a financing for the work.

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