OS Therapies Reports First Quarter 2025 Financial Results and Provides Business Update

OS Therapies Inc. (NYSE-A: OSTX) (“OS Therapies” or “the Company”), a clinical-stage cancer immunotherapy and antibody drug conjugate biotechnology company, today reported first quarter 2025 financial results ended March 31, 2025 and provided a business update.

“The first quarter of 2025 was a crucial execution quarter for OS Therapies, as we announced positive data from our OST-HER2 Phase 2b clinical trial in the prevention of recurrent, fully resected, lung metastatic pediatric osteosarcoma and will be leveraging this data to seek Accelerated Approval from the FDA and other regulatory authorities,” said Paul Romness, MHP, Chairman & CEO of OS Therapies. “Additionally, we consolidated ownership of the listeria immunotherapy platform, adding three clinical stage and eight preclinical assets to our pipeline. We extended the exclusivity protection for its commercial runway into 2040 with the issuance of a new manufacturing patent. Additionally, we have secured research coverage from Wall Street analysts who have shown significant interest in the revival of the listeria immunotherapy platform. We have started important interactions with the FDA with a view towards an Accelerated Approval, with the Osteosarcoma community supporting in the ongoing FDA process. We believe we are well positioned to bring the first new treatment for osteosarcoma to market in over 40 years.”

“As outlined in communications surrounding our 2024 Annual Report on Form 10-K, the first quarter saw some significant one-time expenses related to closing out the treatment phase of the Phase 2b trial, as well as start-up costs for regulatory preparations ahead of our submission,” said Chris Acevedo, Chief Financial Officer of OS Therapies. “Those one-time expenses are now largely behind us, and we have dramatically reduced our burn rate, positioning us to operate into mid-2026.”

First Quarter 2025 Corporate Highlights:

• Reported positive data for our Phase 2b clinical trial of OST-HER2 in the prevention of recurrent, fully resected, lung metastatic osteosarcoma, a rare pediatric indication
• Announced agreement to acquire three clinical stage, eight preclinical stage and all intellectual property surrounding the listeria cancer immunotherapy platform from Ayala Pharmaceuticals
• Initiated manufacturing protocols to support the commercial launch of OST-HER2
• Received a Notice of Allowance from the US Patent & Trademark Office related to the pending issuance of a patent protecting a new commercial manufacturing process for the listeria cancer immunotherapy platform into 2040
• Formed subsidiary OS Drug Conjugates (OSDC) to create a focused business development opportunity for the Company’s proprietary pH-sensitive tunable Antibody Drug Conjugates and tunable Drug Conjugates platform
• Secured a Scientific Advice Meeting with the UK Medicines and Healthcare products Regulatory Agency to discuss seeking approval in the UK for OST-HER2 in the prevention of recurrent, fully resected, lung metastatic osteosarcoma
• Received the keynote presentation at the osteosarcoma community’s leading conference MIB Factor for June 28, 2025 in Salt Lake City, Utah

Second Quarter 2025 Progress to Date and Future Milestones