OS Therapies reported statistically significant improvement in the 12-month event-free survival (EFS) primary endpoint of its Phase 2b trial of OST-HER2 in recurrent, fully resected, lung metastatic osteosarcoma. The company disclosed upregulation of key immune activation biomarkers that correlated with durable responses, strengthening its upcoming Biologics License Application (BLA) under the U.S. FDA’s Accelerated Approval Program. Management reiterated the January 15, 2026 release date for the full biomarker dataset, which will underpin the BLA submission. Following the announcement, OSTX shares declined by 8.3% on Thursday as investors weighed the timing of regulatory feedback and potential for a Priority Review Voucher upon approval.

OS Therapies’ wholly-owned unit OS Animal Health (OSAH) has filed a Form S-1 with the SEC to list on NYSE American or Nasdaq Capital Markets in the first half of 2026. OSTX shareholders are slated to receive one OSAH share for every ten OSTX shares held at the to-be-determined record date. OSAH will concentrate on re-establishing USDA conditional approval and commercializing OST-HER2 for canine osteosarcoma and other HER2-positive cancers in animals. The veterinary oncology market, valued at $1.58 billion in 2024 and projected to reach $4.77 billion by 2034, offers a large opportunity: the canine cancer segment accounted for over 86.09% of 2024 revenues and is expected to grow at a 12.56% compound annual rate through 2030. Leadership aims to leverage prior OST-HER2 canine trial data—highlighted in a 2x Emmy-nominated, Anthem Award–winning PBS documentary—to expedite market reentry and revenue generation.