OST-HER2 (AOST-2121)

August 17, 2026: OS Therapies (NYSE: OSTX) reported Q2 2026 results and outlined regulatory catalysts for OST-HER2 in fully resected, pulmonary metastatic osteosarcoma. The company is pursuing an FDA BLA under Accelerated Approval and conditional marketing applications with MHRA, EMA, and TGA.

For OST-HER2, the company highlighted statistically significant 2.5-year overall survival data of 75% vs. 47% (p=0.003), with no new deaths in the treated group between 2 and 2.5 years. It also said EMA and TGA aligned on 3-year overall survival and biomarker data as approvable conditional authorization endpoints, and that FDA/EMA/MHRA/TGA alignment was achieved on confirmatory Phase 3 trial design. EMA granted ATMP designation, enabling rolling review, and MHRA waived the Pediatric Investigation Plan requirement.

Upcoming catalysts in 2H 2026 include interim 3-year OS data in early September 2026, an FDA Type C Statistical Methods meeting in mid-September 2026, an MHRA Statistical Methods Scientific Advice meeting in September 2026, an FDA Biomarker Qualification Program meeting in September 2026, full 3-year OS data, MHRA CTN submission, BLA submission to FDA, CMAA/MAA submissions to MHRA/EMA/TGA, and planned initiation of the U.K. confirmatory Phase 3 trial.

Separately, the company announced up to $10 million in debt financing backed by U.K. VAT refunds and refundable R&D tax credits, with $5 million funded at first closing on August 10, 2026.