OS Therapies Advances OST-HER2 Toward Accelerated Approval with Elevated FDA Meeting Status

FDA elevated OS Therapies' Type D Biomarker Meeting to a Type B pre-BLA Meeting for OST-HER2 in the prevention or delay of recurrent, fully resected, pulmonary metastatic osteosarcoma. The meeting is expected to occur shortly after the Company completes submission of its clinical data package to the agency, targeted for the end of the first quarter of 2026.

The elevated meeting status signals a transition from biomarker data discussions to Accelerated Approval discussions. With the biomarker analysis complete and patent filings in process, the Company is poised to deliver data to the agency that it believes represents surrogate clinical efficacy sufficient to enable its ongoing BLA submission.

OS Therapies submitted Non-Clinical and Chemistry, Manufacturing & Controls (CMC) modules of its Biologics License Application to FDA at the end of January 2026. The Company expects clinical BLA submission after the Type D meeting in March 2026. Additional biomarker data is due in Q1 2026.

The Company is also pursuing regulatory approvals in Europe and the United Kingdom. Conditional Marketing Authorisation Application filings to the Medicines and Healthcare products Regulatory Agency and the European Medicines Agency are expected by the end of Q1 2026. A confirmatory trial is planned to start in Q3 2026.

Key opinion leaders in U.S., U.K. and European osteosarcoma are assembling to review clinical and biomarker trial data and comment on proposed confirmatory trial design. Following meetings with key opinion leaders over recent weeks, many of whom treated patients in the clinical trial, the Company believes it now has a clear path forward to establish the confirmatory randomized Phase 3 trial that is required to have commenced prior to being granted Accelerated Approval in the United States.

OST-HER2 has received FDA Orphan Drug Designation and Fast Track Designation from FDA and the European Medicines Agency. The therapy has also received Rare Pediatric Disease Designation from FDA. Under the Rare Pediatric Disease Designation program, if the Company receives Accelerated Approval in the United States, it will become eligible to receive a Priority Review Voucher that it intends to sell. The most recent publicly disclosed Priority Review Voucher transaction occurred in February 2026 at a reported value of $205 million. Another source cited potential Priority Review Voucher value at $200 million.

The Company is seeking to get Accelerated Approval for OST-HER2 in osteosarcoma in the second half of 2026. The Company anticipates receiving conditional Marketing Authorisations from the U.K.'s Medicines and Healthcare products Regulatory Agency and the European Medicines Agency for OST-HER2 in 2026.

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 primary endpoint of the study. Additional forthcoming biomarker data from the human trial is expected to further characterize immune pathway activation and its relationship to clinical outcomes.

Ayala Pharmaceuticals announced dissolution following liquidation of assets. Ayala has fully liquidated the 4.8 million shares received in the 2025 asset deal, removing that holder from the register.

OST-HER2 is an immunotherapy leveraging the immune-stimulatory effects of Listeria bacteria to initiate a strong immune response targeting the HER2 protein. 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.