Osteosarcoma Now has been following the development of OST-HER2, one of the most advanced investigational therapies currently being developed specifically for osteosarcoma.
Over the past three years, we have reported on the progression of the PhaseThe different stages of clinical trials that must be done to investigate a new drug. Phase 1 is the first stage while phase 4 is the final stage. 2b clinical trial, encouraging survival data, regulatory designations and the company’s preparations for submission to the U.S. Food and Drug Administration (FDA). Today, we are bringing you another important update as OST-HER2 continues its journey towards potential approval.
While OST-HER2 has not yet been approved, the latest announcement represents another significant milestone in the regulatory process and follows encouraging long-term clinical trial results that continue to generate optimism within the osteosarcoma community.
The latest development
OS Therapies has announced that the FDA’s Center for Drug Evaluation and Research (CDER) has accepted a new meeting request to review the company’s patent-pending pharmacodynamic biomarker data for OST-HER2.
The meeting forms part of the FDA’s BEST (BiomarkerA molecule in the body that can indicate a specific condition or process in the body., EndpointS and other Tools) Program, which evaluates biomarkers that may help demonstrate whether a treatment is producing its intended biological effect.
Alongside this, the company will also meet with the FDA’s Center for Biologics Evaluation and Research (CBER) to discuss updated overall survival data, statistical analyses and plans for its Biologics License Application (BLA).
Although these meetings do not mean the treatment has been approved, they are an important part of the regulatory pathway and demonstrate that discussions with the FDA continue as the company prepares for a potential submission under the Accelerated Approval pathway.
Why is this significant?
Unlike previous updates, this announcement is not about new clinical trial results. Instead, it focuses on how the FDA will evaluate the evidence supporting OST-HER2.
One of the key areas under discussion is the company’s biomarker programme.
Biomarkers are measurable indicators within the body that help researchers understand whether a treatment is producing its intended biological effect. In the case of OST-HER2, these biomarkers are designed to demonstrate that the therapy is successfully stimulating an immune response against osteosarcoma cells.
If the FDA determines that these biomarkers provide meaningful supporting evidence, they could strengthen the overall evidence package submitted alongside the clinical trial results.
What have the clinical trials shown so far?
The excitement surrounding OST-HER2 is not based solely on its innovative approach. It is also driven by encouraging results from its Phase 2b clinical trial involving patients with fully resected pulmonary metastatic osteosarcoma.
Earlier analyses demonstrated that the study achieved its primary endpoint, showing a statistically significant improvement in 12-month Event-Free Survival (EFS) compared with historical controls. This suggested that patients treated with OST-HER2 remained free from recurrence for longer than would typically be expected.
More recently, OS Therapies announced updated 2.5-year Overall Survival (OS) results. According to the company, 75% of patients treated with OST-HER2 were alive at 2.5 years, compared with 47% of patients in a pooled historical control group. Importantly, no additional patient deaths were reported in the treatment group between the two-year and 2.5-year analyses, suggesting that the survival benefit has continued to mature over time.
While these results are highly encouraging, it is important to recognise that they come from a Phase 2b study and not a large randomised Phase III clinical trial. The data will continue to be evaluated by regulators, and longer-term follow-up remains an important part of understanding the full benefit of the treatment.
Why does this bring hope?
For decades, treatment options for osteosarcoma have changed very little, particularly for patients whose disease has spread to the lungs or returned following treatment.
OST-HER2 represents a different approach. Rather than using conventional chemotherapy, it is an investigational immunotherapy designed to stimulate the body’s immune system to recognise and destroy any microscopic osteosarcoma cells that may remain after surgery. The goal is to reduce the risk of recurrence and improve long-term survival.
The combination of positive clinical outcomes, maturing survival data and continued engagement with the FDA means OST-HER2 has become one of the most closely watched investigational therapies in osteosarcoma research.
Although it is still too early to know whether the treatment will ultimately receive regulatory approval, each positive milestone provides cautious optimism that meaningful progress is being made. For patients, families and clinicians who have waited many years for new treatment options, every successful step through the clinical and regulatory process offers renewed hope for the future.
Continuing to follow the journey
Drug development is a long and complex process, often taking many years from the laboratory to potential approval. We understand the frustration this can cause patients and their loved ones.
Since first reporting on OST-HER2 in 2023, we have remained committed to following its progress and explaining what each milestone means for the osteosarcoma community.
We will continue to monitor the development of OST-HER2, sharing updates as further clinical data emerge and as regulatory decisions are made.
As always, our aim is to provide balanced, evidence-based information that helps patients, families, clinicians and researchers stay informed about the latest advances in osteosarcoma research.
OST-HER2 remains an investigational therapy and has not yet been approved for routine clinical use. This article is intended for informational purposes only and should not be interpreted as medical advice.