OS Therapies' investigational immunotherapy OST-HER2 has shown promising results in treating osteosarcoma, a rare but aggressive bone cancer primarily affecting children and young adults. The therapy will be featured in the upcoming PBS documentary "Shelter Me: The Cancer Pioneers," premiering April 3, 2025, which explores the field of comparative oncology.
The documentary, part of the Emmy Award-winning PBS series "Shelter Me," highlights the striking genetic similarities between human and canine osteosarcoma, with over 96% genetic homology. This connection has proven valuable for developing new treatment approaches for this challenging disease.
"Our team is dedicated to advancing a treatment for osteosarcoma and are proud to see our immunotherapy in Shelter Me: The Cancer Pioneers," stated OS Therapies' Chief Executive Officer Paul Romness. "Comparative oncology is an important area of research for us because of the striking genetic homology of over 96% between human and canine osteosarcoma."
Understanding Osteosarcoma and Current Treatment Challenges
Osteosarcoma typically develops in areas of rapid bone growth, particularly in the long bones such as the femur, tibia, and humerus. The disease has a high propensity to metastasize, especially to the lungs, which significantly complicates treatment and reduces survival rates.
Current treatment approaches involve a complex regimen of tumor resection surgery combined with aggressive chemotherapy, including methotrexate, doxorubicin, and cisplatin. These treatments require coordination among a multidisciplinary team of pediatric oncologists, surgeons, pathologists, and radiologists.
Despite these interventions, patients face significant challenges:
- Limited effectiveness for recurrent or metastatic disease
- Severe treatment-related side effects
- Chemotherapy resistance
- High recurrence rates
These limitations underscore the urgent need for innovative therapeutic approaches like OST-HER2.
OST-HER2: A Novel Immunotherapeutic Approach
OST-HER2 represents a groundbreaking approach to osteosarcoma treatment. The immunotherapy uses a bioengineered form of the bacteria Listeria monocytogenes, modified to target the HER2 protein expressed on cancer cells. This mechanism triggers a robust immune response against the cancer.
The investigational treatment has garnered significant regulatory support, including:
- Rare Pediatric Disease Designation (RPDD) from the US Food & Drug Administration
- Fast-Track designation from the FDA
- Orphan Drug designations from both the FDA and European Medicines Agency
Most importantly, OST-HER2 has demonstrated statistically significant benefits in its Phase 2b clinical trial for patients with recurrent, fully resected, lung metastatic osteosarcoma. The therapy met its primary endpoint of 12-month event-free survival (EFS).
Regulatory Pathway and Future Plans
Based on these promising results, OS Therapies anticipates submitting a Biologics Licensing Application (BLA) to the US FDA for OST-HER2 in osteosarcoma in 2025. If approved, the company would become eligible to receive a Priority Review Voucher.
The company has also scheduled a Scientific Advice Meeting (SAM) in the third quarter of 2025 to discuss the Innovative Licensing and Access Pathway (ILAP) with the United Kingdom's Medicines and Healthcare products Regulatory Agency (MHRA).
"[This] marks the beginning of the regulatory process required to bring our OST-HER2 immunotherapy to market globally," Romness explained. "As we prepare for regulatory interactions in the UK, US, Europe and other regulatory bodies worldwide, we are now focused on aligning our regulatory strategy to getting our product to patients as quickly as possible."
Approval in the UK would be particularly significant as it serves as a reference country for multiple national drug approval agencies worldwide, potentially facilitating approvals in countries including Australia, Canada, and several European nations.
Expanding Treatment Applications Through Canine Research
OS Therapies' canine osteosarcoma program has recently made significant progress in identifying biomarkers that likely drive anti-tumor activity in various contexts:
- Prevention of metastatic recurrence
- Treatment of metastases
- Primary tumor treatment for limb-sparing procedures
These findings create potential for expanding OST-HER2's applications to include treatment of unresectable lung metastases and limb-sparing procedures prior to surgical resection. The company plans to evaluate these biomarkers as potentially predictive of treatment response in humans during upcoming regulatory discussions.
The use of canine equivalent biomarkers as surrogate endpoints for rare diseases in comparative oncology has precedent, making this approach particularly valuable for osteosarcoma research.
Upcoming Data Presentations
During the Make it Better (MIB) Agents Factor Osteosarcoma Conference, scheduled for June 26-28, 2025, in Salt Lake City, Utah, key data from the Phase 2b clinical trial will be presented. This data will be compared with a newly created regulatorily compliant synthetic control group comprised of case-matched controls that will support OS Therapies' FDA submission.
The company has confirmed it has sufficient cash on hand to operate into 2026, positioning it well to advance OST-HER2 through the regulatory process and potentially to market.
Beyond Osteosarcoma: Broader Applications
While the current focus is on osteosarcoma, OST-HER2 has completed a Phase 1 clinical study primarily in breast cancer patients and has shown preclinical efficacy in various breast cancer models. This suggests potential broader applications for the technology.
Additionally, OS Therapies is advancing its next-generation Antibody Drug Conjugate (ADC) and Drug Conjugates (DC) platform, featuring tunable, tailored antibody-linker-payload candidates. This platform leverages the company's proprietary silicone Si-Linker and Conditionally Active Payload (CAP) technology, enabling the delivery of multiple payloads per linker.
The PBS documentary "Shelter Me: The Cancer Pioneers" will not only highlight OST-HER2 but also feature leading scientists from prestigious institutions including the National Cancer Institute, National Institutes of Health, the University of Pennsylvania, the University of Illinois, the University of Wisconsin, and Colorado State University. After its premiere, the documentary will be available to stream through the PBS app and on PBS.org starting in May.
