OS THERAPIES INCORPORATED Stock Price, News & Analysis

OS Therapies Incorporated (OSTX) is a clinical-stage oncology and biopharmaceutical company focused on the identification, development, and commercialization of treatments for osteosarcoma (OS) and other solid tumors. The company describes itself as the world leader in listeria-based cancer immunotherapies and trades on the NYSE American under the symbol OSTX. OS Therapies is an emerging growth company under U.S. securities regulations.

Core focus: listeria-based cancer immunotherapy

The centerpiece of OS Therapies’ pipeline is OST‑HER2, its lead asset. According to multiple company disclosures, OST‑HER2 is an immunotherapy that leverages the immune‑stimulatory effects of Listeria bacteria to initiate a strong immune response targeting the HER2 protein. OST‑HER2 (for which the World Health Organization has approved the non‑proprietary name daznelene lisbac) is being developed for the prevention or delay of recurrent, fully resected, pulmonary metastatic osteosarcoma.

OS Therapies reports that OST‑HER2 has received Rare Pediatric Disease Designation (RPDD) from the U.S. Food & Drug Administration (FDA), as well as Fast Track and Orphan Drug designations from both the U.S. FDA and the European Medicines Agency (EMA). The company has announced positive data from a Phase 2b clinical trial of OST‑HER2 in recurrent, fully resected, lung metastatic osteosarcoma, including a statistically significant benefit in the primary endpoint of 12‑month event‑free survival and reported 2‑year overall survival data as a secondary endpoint.

Regulatory strategy and rare disease positioning

OS Therapies’ public communications emphasize a regulatory strategy built around the FDA Accelerated Approval Program and conditional approvals in the United Kingdom and European Union. The company has reiterated its intention to submit a Biologics License Application (BLA) to the U.S. FDA for OST‑HER2 in osteosarcoma, supported by Phase 2b clinical data and immune activation biomarker analyses. The FDA has granted a waiver of the application fee for BLA 125867 for OST‑HER2, and EMA’s Committee for Medicinal Products for Human Use has granted Union Marketing Authorisation eligibility for OST‑HER2 in the metastatic osteosarcoma setting.

Because OST‑HER2 holds RPDD from the FDA, OS Therapies states that if the product receives Accelerated Approval by a specified date, the company would become eligible to receive a Priority Review Voucher (PRV), which it has indicated it intends to sell or monetize, subject to market conditions. Company press releases reference recent PRV sale values as context, while noting that there is no assurance of achieving comparable values.

Comparative oncology and biomarker strategy

A distinctive aspect of OS Therapies’ approach is its explicit use of Comparative Oncology, studying naturally occurring osteosarcoma in canines as a model for human disease. The company highlights data from OST‑HER2 canine studies, including upregulation of specific immune activation biomarkers associated with improved clinical outcomes in canine osteosarcoma.

In its human Phase 2b metastatic osteosarcoma trial, OS Therapies has reported that activation of immune blood biomarkers in the interferon gamma pathway distinguished long‑term survivors (two years or more) from short‑term survivors. The company describes a pre‑specified pathway analysis strategy that was developed based on immune biomarker pathway data from a 118‑patient canine metastatic osteosarcoma study. According to OS Therapies, confirmation of this pre‑specified canine biomarker pathway being upregulated in a comparable human clinical study population supports the use of these biomarkers as surrogate markers of clinical efficacy and strengthens the interpretability of survival data for regulators.

Human oncology pipeline beyond osteosarcoma

In addition to osteosarcoma, OS Therapies reports that OST‑HER2 has completed a Phase 1 clinical study primarily in breast cancer patients and has shown preclinical efficacy data in various models of breast cancer. Company communications also reference additional human oncology programs, including:

• OST‑503 in non‑small cell lung cancer in combination with Keytruda, with plans for an End of Phase 2 meeting with the FDA.
• OST‑504 in castration‑resistant prostate cancer, with a Phase 1 trial and an End of Phase 1 meeting with the FDA anticipated.

These programs position OS Therapies as a clinical‑stage cancer immunotherapy and antibody‑drug conjugate (ADC) biotechnology company working across multiple solid tumor indications, while maintaining osteosarcoma as a central focus.

Veterinary oncology and OS Animal Health

OS Therapies has created a wholly owned subsidiary, OS Animal Health (OSAH), dedicated to veterinary oncology. OSAH is focused on the development and commercialization of OST‑HER2 for canine osteosarcoma and other HER2‑positive cancers in animals. The company notes that OST‑HER2 previously received conditional approval from the U.S. Department of Agriculture (USDA) for the treatment of osteosarcoma in dogs, and OSAH intends to work on re‑establishing USDA conditional approval and commercializing OST‑HER2 in veterinary markets.

OS Therapies has announced its intent to spin off OS Animal Health into a standalone, separately financed public company listed on a U.S. national stock exchange, with OS Therapies shareholders expected to receive equity in the new entity. A Form S‑1 has been filed for OS Animal Health, and the company has described plans for OS Animal Health to focus on regulatory efforts with USDA and commercial launch preparation for canine OST‑HER2, while OS Therapies continues to pursue human oncology indications.

tADC platform and ADC/drug conjugate technology

Beyond listeria‑based immunotherapies, OS Therapies is advancing a next‑generation Antibody Drug Conjugate (ADC) and Drug Conjugate (DC) platform, referred to as its tunable ADC (tADC) platform. Company materials describe this platform as featuring tunable, tailored antibody‑linker‑payload candidates. The platform leverages proprietary Si‑Linker (also described as silicone Si‑Linker) and Conditionally Active Payload (CAP) technology designed to enable the delivery of multiple payloads per linker.

This tADC platform is positioned by OS Therapies as a separate but complementary technology base to its listeria‑based immunotherapies, supporting additional oncology drug conjugate candidates under development.

Corporate structure, listings, and capital markets activity

OS Therapies Incorporated is organized under Delaware law and identifies itself as a smaller reporting company and an emerging growth company. Its principal executive offices are in Grasonville, Maryland. The company’s common stock is listed on the NYSE American under the ticker OSTX.

The company’s SEC filings detail multiple warrant exercise inducement and exchange offers, the issuance of new warrants, and related registration statements on Form S‑1 and Form S‑3 to register the resale of common stock underlying these warrants. OS Therapies has also terminated an equity line of credit agreement with an institutional investor and has used warrant inducement transactions to raise capital. An 8‑K filed in January 2026 describes a warrant exercise inducement generating expected gross proceeds of approximately $7.5 million, with intended use of proceeds including regulatory and pre‑commercial efforts for OST‑HER2 and preparations for the OS Animal Health spinoff.

Governance and shareholder matters

OS Therapies’ definitive proxy statement and related 8‑K filings describe corporate governance actions, including:

• Annual meetings of stockholders held in a virtual format.
• Approval of amendments to increase authorized common stock and expand the share reserve under the company’s 2023 Incentive Compensation Plan.
• Adoption of bylaw amendments changing quorum requirements for stockholder meetings.
• Stockholder approval of a resolution authorizing the board to adopt a shareholder rights agreement if deemed appropriate.

These actions reflect an active capital markets and corporate governance agenda as the company advances its clinical and regulatory programs.

Investment profile

From an investor perspective, OS Therapies represents a clinical‑stage biotechnology and oncology company with a focus on rare pediatric cancer (osteosarcoma) and other solid tumors, built around listeria‑based immunotherapy and ADC/drug conjugate technologies. Its lead program OST‑HER2 has multiple regulatory designations and Phase 2b data in metastatic osteosarcoma, along with a defined regulatory path involving BLA and MAA submissions. The company also has a veterinary oncology subsidiary, OS Animal Health, with plans for a separate public listing focused on canine osteosarcoma and HER2‑positive cancers in animals.

OS Therapies’ SEC filings and press releases provide detailed information on its clinical programs, regulatory interactions with FDA, MHRA, and EMA, capital raising activities, and planned corporate transactions such as the OS Animal Health spinoff.

Frequently asked questions (FAQ)

• What does OS Therapies Incorporated do?
  OS Therapies is a clinical‑stage oncology and biopharmaceutical company focused on developing and commercializing treatments for osteosarcoma and other solid tumors. It emphasizes listeria‑based cancer immunotherapies and an ADC/drug conjugate platform, with its lead asset OST‑HER2 targeting HER2‑expressing cancers.
• What is OST‑HER2?
  OST‑HER2, also known by the WHO‑approved non‑proprietary name daznelene lisbac, is OS Therapies’ lead immunotherapy asset. It uses a HER2‑bioengineered form of Listeria monocytogenes to trigger a strong immune response against HER2‑expressing cancer cells and is being developed for the prevention or delay of recurrent, fully resected, pulmonary metastatic osteosarcoma. It has completed a Phase 2b trial in this setting and a Phase 1 trial primarily in breast cancer patients.
• What regulatory designations has OST‑HER2 received?
  Company disclosures state that OST‑HER2 has received Rare Pediatric Disease Designation from the U.S. FDA and Fast Track and Orphan Drug designations from both the U.S. FDA and the European Medicines Agency. The FDA has also granted a waiver of the application fee for the planned BLA, and EMA’s CHMP has granted Union Marketing Authorisation eligibility for OST‑HER2 in metastatic osteosarcoma.
• How does OS Therapies use Comparative Oncology?
  OS Therapies conducts and cites studies of OST‑HER2 in canine osteosarcoma as part of a Comparative Oncology strategy. Data from canine metastatic and frontline osteosarcoma studies, including immune activation biomarkers associated with improved outcomes, are used to generate and test hypotheses about surrogate biomarkers and treatment effects in human osteosarcoma trials.
• What is OS Animal Health?
  OS Animal Health (OSAH) is a wholly owned subsidiary of OS Therapies dedicated to veterinary oncology. It focuses on re‑establishing USDA conditional approval and commercializing OST‑HER2 for canine osteosarcoma and other HER2‑positive cancers in animals. OS Therapies has announced plans to spin off OSAH into a standalone public company, with OS Therapies shareholders expected to receive shares in the new entity.
• What is the tADC platform?
  OS Therapies’ tunable ADC (tADC) platform is a next‑generation antibody drug conjugate and drug conjugate technology that uses proprietary Si‑Linker and Conditionally Active Payload (CAP) technology. Company materials describe it as enabling tunable antibody‑linker‑payload candidates and the delivery of multiple payloads per linker, supporting additional oncology drug conjugate programs.
• On which exchange does OSTX trade?
  OS Therapies’ common stock trades on the NYSE American under the ticker symbol OSTX. The company has filed multiple registration statements and 8‑K reports related to its capital markets activities, including warrant inducement transactions and resale registrations.
• Is OS Therapies still in the clinical stage?
  Yes. OS Therapies describes itself in SEC filings and press releases as a clinical‑stage oncology and biopharmaceutical company. Its lead asset OST‑HER2 has completed Phase 2b and Phase 1 studies in specified indications, and the company is preparing regulatory submissions rather than reporting commercial product revenues.