The Company aligned with the FDA on the use of the proposed adaptive design agreed upon with the U.K.'s Medicines and Healthcare products Regulatory Agency (MHRA) and the European Medicines Agency (EMA) for the pending Phase 3 clinical trial that is expected to commence in the fourth quarter of 2026. The Company expects to hold its previously disclosed invited Type B Pre-BLA meeting with FDA in the fourth quarter of 2026 following the submission of the clinical section, inclusive of 3-year overall survival data, thereby completing the ongoing BLA filing that was initiated in January 2026.

Concurrent with this announcement, OS Therapies announced that it has accepted a request from MHRA to become the Company's representative to Project Orbis following the recent successful Statistical Methods Scientific Advice Meeting (SAM). Project Orbis is an innovative reciprocal global initiative designed to facilitate international regulatory collaboration in the field of oncology. Launched by the FDA, this program seeks to streamline the process of drug approval for cancer treatments by partnering with regulatory agencies from other countries. The goal of Project Orbis is to provide patients with faster access to promising therapies through simultaneous submission and review of oncology products across multiple nations. By sharing critical insights and harmonizing standards, participating countries aim to enhance the development of effective cancer treatments and improve patient outcomes worldwide. FDA's Center for Biologics Evaluation and Research (CBER) recently re-opened Project Orbis.

"With alignment in hand with FDA on the most recent updates to the proposed adaptive design for the Phase 3 trial design reviewed with MHRA and EMA, we have overcome the key hurdle to initiating the Phase 3 in the U.K. and beyond." said Paul Romness, MPH, Chairman & CEO of OS Therapies. "More importantly, now that MHRA has stepped up and volunteered to take the international lead with Project Orbis, we expect to be able to move expeditiously through the regulatory process in the U.K., U.S. and Europe."

OST-HER2 has received Orphan Drug Designation (ODD), Fast Track Designation (FTD) and Rare Pediatric Disease Designation (RPDD) from the FDA, and ODD, FTD and ATMP from the EMA. Under the RPDD program, if the Company is granted a BLA in the United States, it will become eligible to receive a Priority Review Voucher (PRV) that it intends to sell. The most recent PRV sale occurred in August 2026 for $220 million. However, there can be no assurance that the Company would realize a comparable value, if any, in connection with any future PRV sale. OS Therapies has completed resubmission of a Regenerative Medicine Advanced Therapy (RMAT) request and the Company's Commissioner's National Priority Review Voucher (CNPV) letter of intent has been accepted by FDA. OS Therapies is seeking to obtain a BLA under the Accelerated Approval Program in the U.S. and Conditional Marketing Authorization Applications (CMAAs) in Europe, the U.K. and Australia for OST-HER2 in metastatic osteosarcoma in the fourth quarter of 2026.