OSTX News & Events

OS Therapies announced it was granted an End of Phase 2 Meeting by the United States Food & Drug Administration, FDA, to review the OST-HER2 program in the prevention or delay of recurrent, fully resected, pulmonary metastatic osteosarcoma. The Company expects the meeting to occur in the third quarter of 2025. The End of Phase 2 Meeting marks a pivotal point in the drug development process, and a significant milestone towards market access. The Company intends to seek alignment with FDA to begin a Rolling Review process for the forthcoming Biologics Licensing Application submission for OST-HER2. The Rolling Review process means that a company can submit completed sections of its Biologic License Application for review by FDA, rather than waiting until every section of the BLA is completed before the entire application can be reviewed. This can contribute to augmented interactions with FDA and potentially an expedited BLA approval timeline.

OS Therapies announced positive 1-year event free survival, overall survival and safety clinical trial data updates from the 40 patient treatment arm of its Phase 2b clinical trial of immunotherapy candidate OST-HER2 in the prevention or delay of recurrence in fully resected, lung metastatic osteosarcoma. In data presented by Principal Investigator Dr. Damon Reed at the MIB Factor Osteosarcoma Conference held in Salt Lake City, Utah on Saturday June 28, 2025 the following data updates were released: 35% of OST-HER2-treated patients achieved 1-year event free survival compared with 20% of patients from peer-reviewed publication selected by Children's Oncology Group as equivalent to osteosarcoma patient subpopulation enrolled; A total of 13 out of 40 patients were reported to have experienced severe adverse events during the trial, of which 7 patients' adverse events were treatment-associated adverse events. All of the 7 patients' TSAEs were grade 3 TSAEs; 0 patients experienced grade 4 or grade 5 TSAEs. None of the patients for whom TSAEs were reported discontinued the study. "The updated OST-HER2 data presented at MIB Factor that showed EFS data statistically significantly favoring OST-HER2 treated patients when compared with the leading peer-reviewed publications on historical event free survival outcomes in this subset of the pulmonary metastatic osteosarcoma patient population," said Dr. Robert Petit, Chief Medical & Scientific Officer of OS Therapies. "The favorable safety profile of OST-HER2 compared with standard of care is also an important quality of life factor when assessing potential new treatment options for this difficult to treat patient population."

OS Therapies announced that it received written feedback from the FDA Type D Meeting that occurred in mid-June 2025 regarding endpoints required to support an accelerated approval program marketing application for its Phase 2b trial of OST-HER2 in the prevention or delay of recurrence in fully resected, pediatric lung metastatic osteosarcoma. The company reiterates that additional data from its Phase 2b trial will be presented at the major osteosarcoma conference MIB Factor in Salt Lake City on Saturday June 28. Concurrent with this announcement, the company announced that it has submitted End of Phase 2 Meeting and Breakthrough Therapy Designation requests to FDA based on the positive Type D Meeting feedback. The End of Phase 2 Meeting is expected to occur in the third quarter of 2025. This is in alignment with the company's overall regulatory strategy and timelines.