OS Therapies Inc. (NYSE American: OSTX) announced on September 21, 2026, that it completed a Type C Statistical Methods Meeting with the U.S. Food and Drug Administration regarding OST-HER2, its investigational immunotherapy for recurrent osteosarcoma.
According to the company, the FDA aligned with the updated adaptive design of a planned confirmatory Phase 3 study. OS Therapies also said the United Kingdom’s Medicines and Healthcare products Regulatory Agency will take the regulatory lead under Project Orbis, an FDA-led framework that allows participating regulators to coordinate oncology-drug reviews.
Project Orbis does not create a joint approval or guarantee a favorable regulatory decision. Each participating authority conducts its own review and independently decides whether to approve a treatment.
CEO Paul Romness said the MHRA is “taking the lead in the international OST-HER2 regulatory review process under Project Orbis.”
OST-HER2 is a Listeria-based immunotherapy designed to stimulate an immune response against HER2-expressing tumor cells. The company is developing it to prevent or delay recurrence in patients whose pulmonary metastatic osteosarcoma has been completely resected.
The completed Phase 2b study was an open-label, single-arm trial involving patients ages 12 to 39 with recently resected pulmonary recurrent osteosarcoma. On September 8, OS Therapies reported an interim three-year overall survival rate of 71.2% among OST-HER2-treated patients, compared with 45.8% in a combined published historical control group. The company reported a p-value of 0.002.
Those results were not generated through a randomized comparison with a concurrent control group. Historical-control comparisons can be affected by differences in patient selection, treatment practices and data collection. Of the 41 patients enrolled, two had not yet reached three years of follow-up when the interim analysis was announced. The company subsequently said one patient previously classified as lost to follow-up had been confirmed alive.
OS Therapies expects to submit a Conditional Marketing Authorisation Application in the United Kingdom within the coming weeks. Management is targeting the middle of the fourth quarter of 2026 to begin the Phase 3 study in the U.K., subject to requalification of existing Phase 2b drug product.
The company expects U.S. and European trial expansion after Phase 3-ready and commercial-ready drug product becomes available, which management currently projects for 2027. OS Therapies is also pursuing a separate U.S. accelerated-approval pathway and expects to complete its rolling Biologics License Application during the fourth quarter of 2026. These dates remain company targets rather than confirmed regulatory deadlines.
Financing remains a significant consideration. OS Therapies reported approximately $205,000 in cash and cash equivalents as of June 30, 2026, a six-month net loss of $19 million and operating cash use of approximately $10.1 million. Its SEC filing stated that existing cash was insufficient to fund operations and identified substantial doubt about its ability to continue as a going concern.
In August, the company raised approximately $4.7 million in net proceeds through a financing involving secured convertible notes and warrants. Up to $5 million in additional borrowing may be available, but the financing introduces debt obligations and potential shareholder dilution.
Upcoming Catalysts
- Submission of the proposed U.K. marketing application
- Potential initiation of the confirmatory Phase 3 trial
- Completion or regulatory acceptance of the U.S. BLA
- FDA decisions on pending regulatory-designation requests
- Additional three-year patient follow-up
- Manufacturing updates for Phase 3 and commercial drug product
- Further financing or partnership activity
Sources
- OS Therapies completes FDA Type C meeting — Newsfile, September 21, 2026
- OS Therapies reports interim three-year OST-HER2 data — Newsfile, September 8, 2026
- OST-HER2 Phase 2b trial record, NCT04974008 — ClinicalTrials.gov
- FDA overview of Project Orbis
- OS Therapies second-quarter 2026 results
- OS Therapies Form 10-Q for the quarter ended June 30, 2026 — SEC
Editorial Disclosure
This article is based entirely on publicly available information, including company announcements, SEC filings, the federal clinical-trial registry and FDA materials. Securities discussed or referenced include OS Therapies Inc. (NYSE American: OSTX). Biotech Stocks Daily has not received compensation from OS Therapies, its management, investor relations representatives or any third party for this specific article. Biotech Stocks Daily may have current or past paid business relationships with other companies, which do not influence the content or conclusions of this article. No staff member or principal of Biotech Stocks Daily holds a position in any security mentioned at the time of publication.
Confirmed sources include OS Therapies announcements dated September 8 and September 21, 2026, the company’s Form 10-Q for the quarter ended June 30, 2026, ClinicalTrials.gov and FDA information concerning Project Orbis. Statements concerning agency discussions, regulatory alignment, submission plans and anticipated timelines originated from OS Therapies and have not been independently confirmed through publicly posted agency meeting minutes.
OST-HER2 remains investigational and has not received marketing approval. Completion of an FDA meeting, participation in Project Orbis and receipt of regulatory designations do not establish safety or efficacy or guarantee approval. The Phase 2b study was open-label and single-arm, while the reported survival comparison used historical controls rather than a randomized concurrent control group. The planned Phase 3 study, regulatory submissions and projected timelines may be delayed or may not proceed as expected.
Financial information reflects the company’s position as of June 30, 2026, together with subsequently announced financing. OS Therapies reported limited cash, continued operating losses and substantial doubt about its ability to continue as a going concern. Its secured convertible-note financing, warrants, possible additional borrowing and authorized at-the-market offering may create debt, security-interest and dilution risks for investors.
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