OS Therapies eyes global osteosarcoma vaccine approvals after Phase IIb win
OS will now seek approval for OST-HER2’s in the indication throughout the UK, US and EU. OS Therapies’ cancer vaccine, OST-HER2, has offered improvements to overall survival (OS) in a Phase II trial in METS osteosarcoma.
OS Therapies’ cancer vaccine, OST-HER2, has been shown to significantly improve overall survival (OS) in patients with recurrent, fully resected, pulmonary metastatic osteosarcoma after two years. This effect was observed in a Phase IIb trial (NCT04974008), which saw 75% of patients given the immunotherapy were alive at the two-year mark. This is a statistically significant improvement over the 40% observed in the historical control group.
Additionally, 100% of those demonstrating event-free survival (EFS) after 12 months achieved OS at the two-year mark. This trend was also seen to a lesser degree in patients who did not experience EFS at 12 months, with 59% of individuals remaining alive after two years.
This follows a positive topline readout for the OST-HER2 trial back in January, which saw 33% of patients achieve 12-month EFS compared with 20% seen in historical control groups.
These outcomes will be welcome news for OS Therapeutics, which shelled out $8m to Ayala Pharmaceuticals for the full global rights to OST-HER2 and two other cancer therapies in January 2025. This followed a licensing deal the biotech struck up with the cancer vaccine’s creator, Advaxis, which went on to merge with Ayala in 2022.
In a bid to get the drug to market, OS Therapies’ CMO, Robert Petit, noted that the company will file for approval in the US, UK and EU. “We remain on track to file a conditional Marketing Authorisation Application (MAA) to Medicines and Healthcare products Regulatory Agency (MHRA) in December 2025, a Biologics Licensing Application (BLA) under the Accelerated Approval Program to the FDA in January 2026, and an MAA to the EMA in the first quarter of 2026,” Petit clarified.
If OST-HER2 were to get the US Food and Drug Administration (FDA) green light, it would become the first targeted treatment available for metastatic osteosarcoma. While a range of targeted therapies such as tyrosine kinase inhibitors (TKIs) are sometimes prescribed off-label for osteosarcoma, there are currently no approved treatments in the indication.
This means that patients have to rely on chemotherapy and radiotherapy, which demonstrate modest outcomes and come with debilitating side effects. This has led to poor prognoses in this patient faction, with a research paper published by the National Institutes of Health (NIH) estimating that the five-year OS rate for this indication is just 20 to 40%.
However, Dr Peter Anderson, paediatric oncology at Cleveland Children’s Clinic and scientific advisor to OS Therapies, noted that the data in this Phase IIb study is “encouraging” for the sector. “OST-HER2 is safe and well tolerated, and new treatments are needed for metastatic osteosarcoma,” Anderson stated. “I am hopeful that this immunotherapy will become a treatment options for patients in the near future,” he added.
There are currently at least three therapies being explored in Phase III studies in osteosarcoma, according to GlobalData’s Pharma Intelligence Center. GlobalData is the parent company of Clinical Trials Arena. This includes Bayer’s Stivarga (regorafenib), Lee’s Pharmaceutical Holdings’ socazolimab and Taiho Pharmaceutical’s TAS-115.
