Yet to be published data from clinical study combining OST-HER2 with palliative radiation in dogs with unresected, primary osteosarcoma shows clinical and radiographic arrest of the primary tumor, delayed pulmonary metastases and prolonged overall survival of greater than 500 days in 5 out of 15 dogs.

Data from new publication in the journal “Molecular Therapy” show OST-HER2 induces strong innate and cytotoxic immune responses beginning at the 1st dose of 3 dose regimen, that correlate with prevention of metastasis and long-term survival in dogs with resected primary osteosarcoma.

Data from the same study show that short-term survivors have defective immune responses to OST-HER2 that improve with the second and third administration, supporting a proposed regimen of recurrent dosing to potentially alter clinical course and repeated use after treatment failure.

OS Therapies (NYSE-A: OSTX) (“OS Therapies” or “the Company”), a clinical-stage immunotherapy and Antibody Drug Conjugate (ADC) biopharmaceutical company, today announced positive data in the prevention or delay of amputation during the treatment of primary osteosarcoma for OST-HER2 combined palliative radiation in dogs with unresected appendicular osteosarcoma. The treatment led to clinical and radiographic arrest of the primary tumor and prolonged time to metastasis in dogs without surgery or chemotherapy. The data open the potential for OST-HER2 to be used in frontline therapy in human osteosarcoma prior to initiation of chemotherapy, and potentially reduce the need for chemotherapy altogether, for the purposes of preventing or delaying limb amputation or primary tumor resection surgeries, in addition to the prevention, delay and/or control of lung metastasis.

Additionally, the Company announced the publication of positive data in the journal “Molecular Therapy” entitled “Immunological responses and clinical outcomes in dogs with osteosarcoma receiving standard therapy and a Listeria vaccine expressing HER2” demonstrated the correlation of innate and adaptive immune responses to OST-HER2, with prevention of metastasis and long term survival benefit when used in the adjuvant setting, following standard of care amputation and chemotherapy.

Treatment with OST-HER2 was found to be safe and well tolerated in both studies.
Taken together, the data support the potential of OST-HER2 to achieve progression free survival (PFS) of primary osteosarcoma, prevent or delay or metastatic disease, prolong progression free survival (PFS) in metastatic disease, and significantly improve long term survival in patients with osteosarcoma. The data on the use of OST-HER2 in unresected primary osteosarcoma in dogs is being prepared for peer-reviewed publication.

“We first published strong clinical data on the benefit of OST-HER2 in canine osteosarcoma in 2016, and that led to an initial conditional approval based on a prior manufacturing process that was suboptimal for widespread veterinary use,” said Dr. Nicola Mason, the Paul A. James and Charles A. Gilmore Endowed Professor at the University of Pennsylvania, School of Veterinary Medical. “Based upon this initial research, OS Therapies conducted a successful translational Phase 2b clinical trial in the rare pediatric indication of prevention of recurrence of fully resected, osteosarcoma lung metastases. Our newly published canine data and unpublished radation combination canine data expands the potential use of OST-HER2 into delay/prevention of metastasis and PFS following resected primary osteosarcoma and raises the intriguing possibility of combination radiation therapy and OST-HER2 in the treatment of unresectable osteosarcoma.”

The Company is preparing to submit this data to USDA, along with new data generated on its newly patented, commercially superior manufacturing process, with the aim of gaining conditional approval for the new manufacturing process for OST-HER2 in the United States to begin sales in 2025. Thereafter, the Company intends to conduct a pivotal clinical study with the aim of gaining full approval in 2026. A link to the publication is available here: Visit https://www.cell.com/molecular-therapy-family/molecular-therapy/abstract/S1525-0016(25)00113-3.

“It has been my dream since founding the Company that OST-HER2 could potentially change the standard of care in osteosarcoma, potentially limiting the need for amputation or surgical resection of the primary tumor,” said Paul Romness, CEO of OS Therapies. “With today’s data, we believe we are taking the first steps towards this given that our Comparative Oncology approach, as a result of the 96% genetic homology between human and canine osteosarcoma, leads us to believe there is significant potential for this canine data to translate into humans in the treatment of frontline and primary metastatic osteosarcoma, similarly to how it has in recurrent, fully-resected, lung metastatic osteosarcoma.”

Mr. Romness continued, “We are laser focused on getting an Accelerated Approval for OST-HER2 in recurrent, fully-resected, lung metastatic human osteosarcoma via Accelerated Approval by year-end 2025 and then using funds obtained from the sale of our pending Priority Review Voucher to expand the potential clinical uses of OST-HER2 throughout the human osteosarcoma treatment paradigm. In parallel, we believe the data from these two studies support the use of OST-HER2 in all phases of canine osteosarcoma treatment and we are hopeful to obtain conditional approval with our newly improved, patented manufacturing for OST-HER2 later this year so that we can launch the product at specialized cancer centers and patients can begin getting treatment very soon.”

OST-HER2 is being featured in the upcoming movie Shelter Me: The Cancer Pioneers. The movie offers a look into canine comparative oncology, a field that compares treatment of cancers in dogs to those in people and covers developing treatments for rare forms of cancer. A trailer for the movie is available here. The movie will be aired live nationally on PBS and will be available via streaming on PBS’ website in early May 2025.

Email Alerts

Join our email alerts to learn more about what’s happening with OS Therapies, Inc. (NYSE-A: OSTX)

Don't miss out on the latest updates and exclusive content! Be the first to receive exciting news, insightful articles, and valuable resources delivered straight to your inbox.

About OS Therapies

OS Therapies is a clinical stage oncology company focused on the identification, development, and commercialization of treatments for Osteosarcoma (OS) and other solid tumors. OST-HER2, the Company's lead asset, is an immunotherapy leveraging the immune-stimulatory effects of Listeria bacteria to initiate a strong immune response targeting the HER2 protein. OST-HER2 has received rare pediatric disease, fast-track and orphan drug designations from the US FDA. The Company has completed enrollment for a 41-patient Phase 2b clinical trial of OST-HER2 in recurrent, fully resected, lung metastatic osteosarcoma, with positive results released in the first quarter of 2025. The Company anticipates submitting a Biologics Licensing Application (BLA) to the US FDA for OST-HER2 in osteosarcoma in 2025 and, if approved, would become eligible to receive a Priority Review Voucher that it could then sell. OST-HER2 has completed a Phase 1 clinical study primarily in breast cancer patients, in addition to showing preclinical efficacy data in various models of breast cancer. OST-HER2 has been conditionally approved by the U.S. Department of Agriculture for the treatment of canines with osteosarcoma.

In addition, OS Therapies is advancing its next-generation Antibody Drug Conjugate (ADC) platform, known as tunable ADC (tADC), which features tunable, tailored antibody-linker-payload candidates. This platform leverages the Company's proprietary silicone linker technology, enabling the delivery of multiple payloads per linker. For more information, please visit www.ostherapies.com.

OS Therapies Contact Information

Jack Doll
Irpr@ostherapies.com
410.849.9067

https://x.com/OSTherapies
https://www.instagram.com/ostherapies/
https://www.facebook.com/OSTherapies/
https://www.linkedin.com/company/os-therapies/

Forward-Looking Statements

Statements in this press release about future expectations, plans and prospects, as well as any other statements regarding matters that are not historical facts, may constitute forward-looking statements within the meaning of the federal securities laws. These forward-looking statements and terms such as "anticipate," "expect," "intend," "may," "will," "should" or other comparable terms involve risks and uncertainties because they relate to events and depend on circumstances that will occur in the future. Those statements include statements regarding the intent, belief or current expectations of OS Therapies and members of its management, as well as the assumptions on which such statements are based. OS Therapies cautions readers that forward-looking statements are based on management’s expectations and assumptions as of the date of this news release and are subject to certain risks and uncertainties that could cause actual results to differ materially, including, but not limited to the approval of OST-HER2 by the US FDA and grant of a priority review voucher and other risks and uncertainties described in “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in the Company’s registration statement on Form S-1 filed with the Securities and Exchange Commission (the “SEC”) on November 12, 2024, as amended on November 27, 2024, and other subsequent documents we file with the SEC, including but not limited to our Quarterly Reports on Form 10-Q. Any forward-looking statements contained in this press release speak only as of the date hereof, and, except as required by the federal securities laws, OS Therapies specifically disclaims any obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise.