OS Therapies’ OST-HER2 achieves milestone in osteosarcoma treatment
OS Therapies, Inc., a clinical-stage biotechnology company, has announced data from its Phase 2b trial of OST-HER2, an innovative HER2-targeted immunotherapy. The trial focused on preventing recurrent, fully resected lung metastatic osteosarcoma, a rare and aggressive cancer. The results are significant, with OST-HER2-treated patients achieving the 12-month event-free survival (EFS) primary endpoint at a rate of 33.3%, surpassing the 20% observed in peer-reviewed historical controls. This achievement, with a p-value of 0.0158, represents a pivotal advancement in cancer immunotherapy.
A Landmark Achievement in Osteosarcoma Research
Recurrent lung metastatic osteosarcoma is an especially challenging cancer with limited treatment options. OS Therapies’ OST-HER2 employs a bioengineered form of Listeria monocytogenes to stimulate a robust immune response against HER2-expressing cancer cells. This innovative mechanism aims to prevent metastasis, delay recurrence, and extend overall survival in patients, filling a crucial gap in treatment.
In addition to the primary endpoint, secondary outcomes from the trial revealed a strong trend toward improved overall survival (OS). At the one-year mark, survival rates were 91% for OST-HER2-treated patients compared to 80% in historical controls. At two years, survival rates reached 61% versus 40% in comparable groups. Importantly, all patients who achieved the 12-month EFS endpoint remain alive in ongoing follow-ups, reinforcing the potential long-term benefits of OST-HER2.
Expert Insights: A Promising Pathway for Regulatory Approval
Chief Medical and Scientific Officer Dr. Robert Petit emphasised the significance of these findings. He noted that OST-HER2 had not only demonstrated efficacy but also a strong safety profile, making it a viable option for an underserved patient population. Similarly, OS Therapies’ Chair and CEO, Paul Romness, highlighted the alignment of the company’s regulatory strategy with updated FDA guidance for accelerated approvals. The company anticipates engaging with the FDA to secure approval for OST-HER2 without requiring additional clinical trials.
The Rare Pediatric Disease Designation: A Strategic Advantage
OST-HER2 holds a Rare Pediatric Disease Designation (RPDD) from the U.S. Food and Drug Administration, granting OS Therapies eligibility for a Priority Review Voucher (PRV) upon drug approval. These vouchers, which can be sold or transferred, have proven financially advantageous, with recent PRV sales fetching over $150 million. OS Therapies plans to leverage this opportunity, bolstered by the emerging scarcity of PRVs in the market.
A Patient-Centric Trial Design
The Phase 2b trial enrolled 39 patients aged 12 to 39, all with recurrent, fully resected lung-only metastatic osteosarcoma. Over a 48-week treatment period, patients received 16 doses of OST-HER2, followed by a four-week monitoring phase. Notably, the study observed gender differences in outcomes, with female patients achieving a 47% 12-month EFS rate compared to 20% in males.
Further subgroup analyses revealed that patients with multiple prior lung resections had higher EFS rates, indicating that OST-HER2 might be particularly effective for those with extensive surgical histories.
Market Potential and Broader Implications
The osteosarcoma treatment market was valued at $1.2 billion in 2022, with a substantial unmet need for therapies addressing metastatic disease. OS Therapies estimates that OST-HER2 could capture over $500 million of this market, given its unique positioning as an off-the-shelf immunotherapy targeting lung metastases.
The urgency for effective treatments is underscored by stark survival statistics. While patients without metastases have a three-year survival rate of 59%, those with pulmonary metastases face rates as low as 30%. These figures highlight the transformative potential of OST-HER2 for improving survival outcomes in this vulnerable population.
Innovative Science Driving Future Development
In addition to OST-HER2, OS Therapies is advancing a next-generation Antibody Drug Conjugate (ADC) platform. Known as tunable ADC (tADC), this platform allows for customised antibody-linker-payload combinations, enabling the precise delivery of multiple therapeutic agents. This proprietary technology could expand the company’s portfolio, further solidifying its position as a leader in oncology innovation.
The Road Ahead for OST-HER2
As OS Therapies prepares to navigate the regulatory pathway, the data from its Phase 2b trial underscore the promise of OST-HER2. The combination of strong efficacy, a favourable safety profile, and strategic regulatory designations positions the company for a pivotal role in the osteosarcoma treatment landscape.
Looking ahead, OS Therapies remains committed to addressing the unmet needs of patients with rare cancers. With plans to leverage its PRV upon FDA approval and expand its innovative platforms, the company is poised to make a lasting impact in oncology.
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