OS Therapies files NT 10-Q, says first-quarter report will be late after slower financial close

OS Therapies Incorporated (NYSE American: OSTX) told the Securities and Exchange Commission on May 15, 2026 that it will not file its quarterly report for the period ended March 31, 2026 on time. The company filed a Form 12b-25 notification, known as an NT 10-Q, and says the Form 10-Q will follow within the five calendar days Rule 12b-25 allows. It says the delay comes from additional time needed to complete the financial statement close, and that compiling and reviewing certain information for the report has taken longer than planned. The notice checks the box stating the reasons could not be eliminated without unreasonable effort or expense.

What the notice does not say

The notice answers no to whether the company expects a significant change in results of operations from the same period last year. It does not give a reasonable estimate of any results, and it does not explain what information is still outstanding. The notice names Paul Romness, the company's Chief Executive Officer, as the contact and signed it on May 15, 2026.

The going-concern warning

The annual report for 2025, filed March 31, 2026, says the company incurred a net loss of $28.8 million during 2025 and used $14.2 million of cash in operating activities. It reports cash and cash equivalents of $269,830 as of December 31, 2025. Its independent accounting firm added an explanatory paragraph expressing substantial doubt about the company's ability to continue as a going concern for at least 12 months from the date the statements were issued. The report says the cash balance is insufficient to fund operations for that period, and that the company will need to raise substantial additional capital.

The report also describes a sales agreement under which the company may sell up to $18,000,000 of common stock through sales agents, and it discloses cash fees and warrants paid to Brookline Capital Markets, a division of Arcadia Securities, LLC, which acted as exclusive placement agent in a private placement.

The lead program

OS Therapies describes itself as a clinical-stage biopharmaceutical company focused on osteosarcoma and other solid tumors. Its lead candidate is OST-HER2, which it describes as a cancer immunotherapy that aims to produce a cellular immune response against the HER2 antigen.

The company says its Phase IIb trial enrolled 41 patients after resection of recurrent osteosarcoma, reaching full enrollment in October 2023. It says the trial met its primary endpoint with statistical significance, announced in the first quarter of 2025. In October 2025 it reported two-year overall survival data in which 75% (27 of 36 evaluable patients) of OST-HER2-treated patients reached two-year overall survival, compared with 40% in historical control patients. The comparison is to historical controls, not to a randomized group, and the sample is small: 36 evaluable patients.

Regulatory timing

The company says it submitted the non-clinical and chemistry, manufacturing and controls modules of its Biologics License Application to the U.S. Food and Drug Administration at the end of January 2026. It expects a Type B meeting with the FDA in the second quarter of 2026 and plans to submit the clinical module after that meeting. It also expects to file conditional Marketing Authorization Applications with the United Kingdom's Medicines and Healthcare products Regulatory Agency and the European Medicines Agency in the second quarter of 2026, and to release additional biomarker data in that quarter.

Those steps are all still ahead of the company. The notice itself reports no progress on them.

Who signed the annual report

Paul A. Romness signed the annual report as Chairman, President, Chief Executive Officer and Director. Christopher P. Acevedo signed as Chief Financial Officer and principal financial and accounting officer.

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