OS Therapies Announces Positive Biomarker Data from Phase 2b Clinical Trial of OST-HER2 in the Prevention or Delay of Recurrent, Fully Resected, Pulmonary Metastatic Osteosarcoma
Rhea-AI Summary
OS Therapies (NYSE American: OSTX) reported positive biomarker results from its Phase 2b OST-HER2 trial in fully resected, pulmonary metastatic osteosarcoma. Activation of interferon gamma pathway blood biomarkers correlated with overall survival, distinguishing patients with >=2-year survival from those 1 year. The biomarker strategy was pre-specified based on a 118-patient canine study published February 2025, supporting translational Comparative Oncology. The company is drafting a BLA and targets UK approval by end-Q2 2026, US by end-Q3 2026, and Europe by end-2026. OST-HER2 holds FDA ODD, FDA/EMA Fast Track, and FDA RPDD; PRV eligibility exists if Accelerated Approval occurs before Sept 30, 2026.
Positive
- Interferon gamma biomarkers predicted survival (>=2 years vs <1 year)
- Pre-specified biomarker strategy derived from 118-patient canine study
- Targeted regulatory timelines: UK end-Q2 2026; US end-Q3 2026
- OST-HER2 holds FDA ODD, FDA/EMA Fast Track, and FDA RPDD
Negative
- Regulatory approval dates are company targets, not guarantees
- PRV eligibility conditional on Accelerated Approval before Sept 30, 2026
- BLA and marketing authorizations remain pending and incomplete
News Market Reaction
On the day this news was published, OSTX declined 5.81%, reflecting a notable negative market reaction. Argus tracked a peak move of +4.9% during that session. Argus tracked a trough of -14.0% from its starting point during tracking. Our momentum scanner triggered 9 alerts that day, indicating moderate trading interest and price volatility. This price movement removed approximately $3M from the company's valuation, bringing the market cap to $55M at that time. Trading volume was very high at 3.2x the daily average, suggesting heavy selling pressure.
Data tracked by StockTitan Argus on the day of publication.
Key Figures
Market Reality Check
Peers on Argus
OSTX was up 0.65% pre-news with mixed biotech peers: BYSI up 7.74%, IMMX up 10.22%, while ACET and ATHE were down 0.48% and 3.74%, pointing to stock-specific factors rather than a uniform sector rotation.
Historical Context
| Date | Event | Sentiment | Move | Catalyst |
|---|---|---|---|---|
| Jan 14 | Subsidiary S-1 filing | Positive | +0.7% | Planned OS Animal Health IPO and share distribution to OSTX holders. |
| Jan 12 | Warrant financing | Positive | -7.1% | Warrant inducement raising $7.53M for runway and filings. |
| Jan 05 | Corporate outlook | Positive | +7.5% | Outlined 1H 2026 BLA/MAA timelines and key data readouts. |
| Dec 15 | FDA Type C meeting | Positive | -7.7% | FDA confirmed single-arm data could support Accelerated Approval. |
| Dec 09 | UK MHRA pre-MAA | Positive | +0.0% | MHRA alignment on CMC and biomarker surrogate endpoint strategy. |
Recent history shows mixed reactions: OSTX has often sold off or been flat on seemingly positive regulatory and clinical updates, with more divergences than alignments.
Over the last few months, OS Therapies has advanced both its lead OST-HER2 osteosarcoma program and corporate structure. A warrant inducement financing on Jan 12, 2026 raised $7.53M for regulatory and commercial preparations and an OS Animal Health spinoff plan. An S-1 for OS Animal Health on Jan 14, 2026 outlined share distribution to OSTX holders. Earlier, a Type C FDA meeting on Dec 15, 2025 and a successful UK MHRA pre-MAA meeting on Dec 9, 2025 confirmed that single-arm Phase 2b data and biomarker correlations could support accelerated or conditional approvals, setting the stage for today’s biomarker-focused announcement.
Regulatory & Risk Context
OS Therapies has an effective S-3 shelf filed on Aug 8, 2025, allowing it to offer up to $100,000,000 in securities, plus an at-the-market program for up to $18,000,000 of common stock. Two prospectus supplements (424B5 and 424B7) were filed in Aug 2025 and Sep 2025, indicating the shelf has already been used and could provide further financing capacity alongside potential dilution.
Market Pulse Summary
The stock moved -5.8% in the session following this news. A negative reaction despite positive biomarker data would fit prior instances where favorable regulatory updates did not translate into sustained gains. Investors may focus on financing overhang from the shelf and past warrant activity, or on execution and timing risks around multiple planned BLA and MAA submissions. The pattern of divergence on good news could make the timeline to regulatory decisions and any additional capital raises key factors in how sentiment evolved.
Key Terms
interferon gamma medical
biomarkers medical
comparative oncology medical
biologics license application (bla) regulatory
marketing authorisation application regulatory
orphan disease designation regulatory
fast track designation regulatory
priority review voucher regulatory
AI-generated analysis. Not financial advice.
- Activation of immune blood biomarkers from interferon gamma pathway distinguished long term survivors (>=2 years) from short-term survivors (<1year)
- Pre-specified pathway analysis strategy developed as a result of immune biomarker pathway data generated from 118-patient canine metastatic osteosarcoma study published in February 2025 demonstrates translational power of Comparative Oncology to identify surrogate markers of clinical efficacy
New York, New York--(Newsfile Corp. - January 15, 2026) - OS Therapies Inc. (NYSE American: OSTX) ("OS Therapies" or "the Company"), the world leader in listeria-based cancer immunotherapies, today announced positive biomarker data from its Phase 2b clinical trial of OST-HER2 in the prevention or delay of recurrent, fully resected, pulmonary metastatic osteosarcoma (the "Human Metastatic Osteosarcoma Trial"). Activation of immune blood biomarkers in the interferon gamma pathway was predictive of overall survival, distinguishing long term survivors (>=2 years) from short-term survivors (<1year). The Company's pre-specified pathway analysis strategy that was developed as a result of immune biomarker pathway data generated from 118-patient canine metastatic osteosarcoma study published in February 2025 (the "Canine Metastatic Osteosarcoma Trial") demonstrates the translational power of Comparative Oncology in identifying surrogate markers of clinical efficacy for human osteosarcoma clinical development programs.
"Leveraging the power of Comparative Oncology, we were able to train and test potentially predictive biomarkers from the Canine Metastatic Osteosarcoma Trial in order to form a hypothesis to test in a pre-specified way in the Human Metastatic Osteosarcoma Trial," said Paul Romness, MHP, Chairman & CEO of OS Therapies. "We believe the confirmation of this pre-specified pathway analysis in humans adds significant resolution to our clinical data, increasing the clinical interpretability of the 2-year overall survival data for regulatory agencies. The confirmation of a pre-specified canine biomarker pathway being upregulated in a comparable human clinical study population leveraged canine biomarker data to a generate hypothesis that was tested in a pre-specified way and confirmed as a surrogate marker of clinical efficacy. This biomarker data strengthens our pending Biologics License Application (BLA) submission."
The Company is focused on completing the drafting of its planned BLA submission along with its pending Marketing Authorisation Application submissions in the U.K. and Europe. The Company is targeting gaining regulatory approval for OST-HER2 in the United Kingdom by the end of the second quarter of 2026, the United States by the end of the third quarter of 2026 and Europe by year end 2026."
OST-HER2 has received FDA Orphan Disease Designation (ODD) and Fast Track Designation from FDA & EMA and has received Rare Pediatric Disease Designation (RPDD) from FDA. Under the RPDD program, if the Company receives Accelerated Approval prior to September 30, 2026, it will become eligible to receive a Priority Review Voucher (PRV) that it intends to sell. The most recent PRV sale, valued at
About OS Therapies
OS Therapies is a clinical stage oncology company focused on the identification, development, and commercialization of treatments for Osteosarcoma (OS) and other solid tumors. The Company is the world leader in listeria-based cancer immunotherapies. OST-HER2, the Company's lead asset, is an immunotherapy leveraging the immune-stimulatory effects of Listeria bacteria to initiate a strong immune response targeting the HER2 protein. OST-HER2 has received Rare Pediatric Disease Designation (RPDD) from the U.S. Food & Drug Administration and Fast-Track and Orphan Drug designations from the U.S. FDA and European Medicines Agency. The Company reported positive data in its Phase 2b clinical trial of OST-HER2 in recurrent, fully resected, lung metastatic osteosarcoma, demonstrating statistically significant benefit in the 12-month event free survival (EFS) primary endpoint of the study. The Company anticipates submitting a Biologics Licensing Application (BLA) to the U.S. FDA for OST-HER2 in osteosarcoma in 2026 and, if approved, would become eligible to receive a Priority Review Voucher that it could then sell. OST-HER2 has completed a Phase 1 clinical study primarily in breast cancer patients, in addition to showing preclinical efficacy data in various models of breast cancer. OST-HER2 has been conditionally approved by the U.S. Department of Agriculture for the treatment of canines with osteosarcoma.
In addition, OS Therapies is advancing its next-generation Antibody Drug Conjugate (ADC) and Drug Conjugates (DC), known as tunable ADC (tADC), which features tunable, tailored antibody-linker-payload candidates. This platform leverages the Company's proprietary silicone Si-Linker and Conditionally Active Payload (CAP) technology, enabling the delivery of multiple payloads per linker. For more information, please visit www.ostherapies.com.
Forward-Looking Statements
Statements in this press release about future expectations, plans and prospects, as well as any other statements regarding matters that are not historical facts, may constitute forward-looking statements within the meaning of the federal securities laws. These forward-looking statements and terms such as "anticipate," "expect," "intend," "may," "will," "should" or other comparable terms involve risks and uncertainties because they relate to events and depend on circumstances that will occur in the future. Those statements include statements regarding the intent, belief or current expectations of OS Therapies and members of its management, as well as the assumptions on which such statements are based. OS Therapies cautions readers that forward-looking statements are based on management's expectations and assumptions as of the date of this press release and are subject to certain risks and uncertainties that could cause actual results to differ materially, including, but not limited to the approval of OST-HER2 by the U.S. FDA and other risks and uncertainties described in "Risk Factors" in the Company's most recent Annual Report on Form 10-K, most recent Quarterly Report on Form 10-Q and other subsequent documents the Company files with the Securities and Exchange Commission. Any forward-looking statements contained in this press release speak only as of the date hereof, and, except as required by the federal securities laws, OS Therapies specifically disclaims any obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise.
OS Therapies Contact Information:
Investor Relations
Harrison Seidner, PhD
WaterSeid Partners
OSTX@waterseid.com
Public Relations
Stephanie Chen
Elev8 New Media
media@ostherapies.com
https://x.com/OSTherapies
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https://www.linkedin.com/company/os-therapies/
To view the source version of this press release, please visit https://www.newsfilecorp.com/release/280482
FAQ
What did OS Therapies announce about OST-HER2 biomarker data on January 15, 2026?
How does the February 2025 118-patient canine study relate to OSTX human data?
What regulatory timelines did OS Therapies (OSTX) provide for OST-HER2 approvals?
Is OST-HER2 eligible for a Priority Review Voucher (PRV) and what is its condition?
What regulatory designations does OST-HER2 hold as of January 15, 2026?
