OS Therapies Aligns with FDA and Accepts Project Orbis Invitation

OS Therapies, Inc., a leading developer of gene-edited, Listeria-based cancer immunotherapies, has achieved a significant milestone in its pursuit of regulatory approval for its lead product, OST-HER2, in the treatment of metastatic osteosarcoma. The company has aligned with the U.S. Food and Drug Administration (FDA) on the adaptive design for a Phase 3 clinical trial, which is expected to commence in the fourth quarter of 2026. This alignment was achieved after a successful Scientific Advice Meeting with the FDA, MHRA, and EMA.

In a move to further streamline the regulatory process, OS Therapies has accepted an invitation from the MHRA to become the sponsor for Project Orbis, an international initiative aimed at harmonizing regulatory reviews for cancer treatments. Project Orbis, launched by the FDA, seeks to facilitate the approval of promising therapies by partnering with regulatory agencies from other countries. By participating in this program, OS Therapies aims to expedite the approval process in the U.K., U.S., and Europe.

The company's lead product, OST-HER2, has already received Orphan Drug Designation (ODD), Fast Track Designation (FTD), and Rare Pediatric Disease Designation (RPDD) from the FDA, as well as ODD, FTD, and Advanced Therapy Medicinal Product (ATMP) designations from the European Medicines Agency (EMA). These designations are intended to accelerate the development and approval of innovative treatments for rare diseases.

OST-HER2 is an immunotherapy that leverages the immune-stimulatory effects of Listeria bacteria to target the HER2 protein. The product is designed to target two mutated extracellular epitopes and one mutated intracellular epitope of the HER2 oncogene, requiring only one of these three epitopes to be present in a tumor (or micro-metastasis) to trigger the desired immune response. Positive data from a Phase 2b clinical trial have demonstrated significant benefits in the prevention or delay of recurrence in fully resected, pulmonary metastatic osteosarcoma.

OS Therapies is also advancing its next-generation Antibody Drug Conjugate (ADC) and Drug Conjugates (DC), known as tunable ADC (tADC), which features tunable, tailored antibody-linker-payload candidates. This platform leverages the company's proprietary silicon Si-Linker and Conditionally Active Payload (CAP) technology, enabling the delivery of multiple payloads per linker.

The company is currently seeking a Biologics License Application (BLA) from the FDA for OST-HER2 in osteosarcoma and anticipates receiving Conditional Marketing Authorization Applications (CMAA) from the U.K.'s Medicines and Healthcare products Regulatory Agency (MHRA) and the EMA in the fourth quarter of 2026. Additionally, the company has completed the resubmission of a Regenerative Medicine Advanced Therapy (RMAT) request and has accepted a Commissioner's National Priority Review Voucher (CNPV) letter of intent from the FDA.

With the recent alignment with the FDA and the acceptance of the Project Orbis invitation, OS Therapies is well-positioned to move forward with its regulatory filings and clinical trials. The company's CEO, Paul Romness, expressed optimism about the progress, stating, "With alignment in hand with the FDA on the most recent updates to the proposed adaptive design for the Phase 3 trial, we have overcome a key hurdle to initiating the Phase 3 in the U.K. and beyond. 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."

The company's commitment to advancing treatments for osteosarcoma and other solid tumors is evident in its ongoing research and development efforts. OS Therapies continues to explore innovative approaches to immunotherapy, with the goal of providing patients with faster access to promising therapies.