OS Therapies, Inc. (NYSE-A: OSTX) has entered into agreements for the commercial manufacture of OST-HER2, its lead immunotherapy candidate. This move supports the anticipated submission of a Biologics Licensing Application (BLA) to the U.S. Food and Drug Administration (FDA) for accelerated or conditional approval. The company is currently compiling data from its recently concluded Phase 2b trial of OST-HER2 in the prevention of recurrent lung metastatic osteosarcoma, preparing for a Type B or Type C meeting with the FDA.
Clinical Trial Results and Regulatory Pathway
The Phase 2b clinical trial of OST-HER2 in recurrent, fully resected, lung metastatic osteosarcoma has shown positive results, which were released in the first quarter of 2025. The company anticipates that the FDA meeting will pave the way for the BLA submission in 2025. OST-HER2 has already been granted rare pediatric disease, fast-track, and orphan drug designations by the FDA, underscoring the unmet need in treating osteosarcoma.
OST-HER2: An Immunotherapeutic Approach
OST-HER2 leverages the immune-stimulatory effects of Listeria bacteria to stimulate a robust immune response targeting the HER2 protein. This off-the-shelf immunotherapy is designed to activate the immune system to target HER2-positive cancer cells. The completed Phase 2b trial enrolled 41 patients. Furthermore, OST-HER2 has been conditionally approved by the U.S. Department of Agriculture for treating osteosarcoma in canines.
Tunable Antibody-Drug Conjugate (ADC) Platform
In addition to OST-HER2, OS Therapies is advancing its next-generation Antibody Drug Conjugate (ADC) platform, known as tunable ADC (tADC). This platform features tunable, tailored antibody-linker-payload candidates, utilizing the company's proprietary silicone linker technology to deliver multiple payloads per linker. This platform aims to provide tailored cancer treatments with improved efficacy and reduced side effects.
Patent Protection and Market Opportunity
OS Therapies has received a Notice of Allowance from the United States Patent & Trademark Office (USPTO) for a patent covering the manufacturing methods required for the OST-HER2 commercial product. The USPTO granted a Patent Term Adjustment of 572 days, providing market exclusivity for the OST-HER2 commercial drug product into 2040. The company believes the market opportunity for OST-HER2 in the prevention of lung metastases in osteosarcoma is over $500 million.
Financial Position
OS Therapies completed a $7.1 million financing in January 2025 and has sufficient capital into mid-2026. The company intends to focus on gaining FDA BLA approval for OST-HER2 in osteosarcoma in late 2025 and may sell the Priority Review Voucher (PRV) it would receive from the FDA BLA approval prior to the September 30, 2026 PRV deadline.
