OS Therapies falls 5% after reporting wider Q3 loss amid regulatory preparations

NEW YORK - On Monday, OS Therapies Inc. (NYSE:OSTX) reported a wider third quarter loss as it prepares for regulatory filings for its lead candidate OST-HER2 in osteosarcoma. The company posted a net loss of $0.21 per share in Q3 2025, compared to a loss of $0.18 per share in the same period last year.

OSTX shares fell 5.56% in pre-market trading after the clinical-stage oncology company posted its results.

The company’s operating loss increased to $6.879 million in the third quarter, up from $2.875 million in Q3 2024, primarily due to pre-payments for regulatory and pre-commercial activities related to its OST-HER2 program. OS Therapies reported $1.9 million in cash at quarter-end, with an additional $1.5 million received after the period closed.

OS Therapies highlighted promising clinical data for OST-HER2, reporting 2-year overall survival of 75% versus 40% for historical controls (p<0.0001) in patients with recurrent, fully-resected pulmonary metastatic osteosarcoma. The company has scheduled regulatory meetings with the FDA on December 11 and UK MHRA on December 8, with plans to file Biologics License Application (BLA) and Marketing Authorization Application (MAA) in January 2026.

"The next six to twelve months will be transformative for OS Therapies," said Paul Romness, Chairman and CEO. "We expect to align on the expectations for our pending BLA for OST-HER2 under the Accelerated Approval Program at our December 11, 2025 FDA Type C Meeting."

The company recently completed a $7.8 million warrant exercise that it says provides capital into late 2026 by delaying product launch to 2027. If approved by September 30, 2026, OS Therapies would remain eligible for a Priority Review Voucher based on its Rare Pediatric Disease Designation for osteosarcoma.

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