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OS Therapies' HER2 drug prevented lung cancer from returning in a 3rd of patients
Jan. 17 2025
OS Therapies’ HER2-focused immunotherapy prevented patients’ lung cancer from returning in 33% of cases, hitting the primary goal of a phase 2 trial.

The therapy, dubbed OST-HER2, uses a HER2-bioengineered form of the bacteria Listeria monocytogenes to trigger an immune response against cancer cells expressing HER2. OS Therapies had been testing the drug in a phase 2b trial in 39 patients between the ages of 12 and 39.

These individuals previously had their lung-only metastatic osteosarcoma—a type of bone cancer that spreads to the lungs—successfully removed by surgery. There are currently no approved drugs for this specific indication, the biotech noted.

The trial demonstrated that 33% of these patients not only survived but didn’t see their cancer return—an endpoint known as event-free survival (EFS)—after 12 months. The result bested the 20% EFS rate from a peer-reviewed comparable historical control data set, allowing the trial to achieve its primary endpoint, OS Therapies reported in a Jan. 15 release.

The company also saw promising results on the secondary endpoint of overall survival (OS) during an ongoing three-year follow-up with the patients. Specifically, OS after one year was 91% for individuals taking OST-HER2 compared to 80% for the historical control group, while at the two-year mark the rates were 61% and 40%, respectively.

CEO Paul Romness said the company will take the data to the FDA to try to secure an accelerated approval pathway for OST-HER2.

“The achievement of the primary endpoint in the OST-HER2 phase 2b is a tremendous success that opens the possibility, for the first time, of meaningful therapy for patients suffering from osteosarcoma with lung metastases after resection,” Romness said in the release.

OS Therapies joined the New York Stock Exchange via a $6 million IPO in August 2024. In addition to OST-HER2, the company’s pipeline includes the preclinical prospect called OST-tADC, which it has described as a next-gen ADC platform.

Since the IPO, OS Therapies has secured a place in Johnson & Johnson’s life sciences incubator JLABS.

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