On July 24, 2024 OS Therapies, Inc. (NYSE-A: OSTX), a clinical-stage oncology-focused immunotherapy company developing cancer vaccines and antibody drug conjugate (ADC) therapeutic candidates, reported positive data from a Phase 1 clinical trial of OST-HER2 in patients with HER2-expressing solid tumors in breast cancer and other cancers (Press release, OS Therapies, JUL 24, 2024, View Source [SID1234645073]). Additionally, the Company announced positive preclinical efficacy data for OST-HER2 in multiple models of breast cancer.
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The FDA has granted Rare Pediatric Disease Designation (RPDD), Orphan Drug Designation (ODD), and Fast Track Designation (FTD) for OST-HER2 in Osteosarcoma. OST-HER2, a biologic therapeutic candidate, is a Lm (Listeria monocytogenes) vector-based off-the-shelf immunotherapeutic vaccine designed to prevent metastasis, delay recurrence, and increase overall survival in patients with osteosarcoma and other solid tumors. The proposed OST-HER2 mechanism of action is based on innate and adaptive immune stimulating responses activated by the Lm vector. This treatment generates T cells that can eliminate or slow potential micrometastases that can grow into recurrent osteosarcoma and other solid tumors, including breast cancer. T cell responses home in on HER2 expressed by the tumor and then kill the cell, releasing additional tumor targets. There are currently no approved adjuvant treatments for recurrent osteosarcoma in the United States.
A total of twelve (12) patients with a history of HER2 positive cancer were enrolled in the Phase 1b clinical study, comprised of ten (10) patients with breast cancer, one (1) patient with esophageal cancer and one (1) patient with GE junction cancer. OST-HER2 was determined to be safe and well tolerated in patients with HER2-expressing solid tumors, including at the dose currently being used in the Company’s ongoing Phase 2b clinical trial in recurrent, resected osteosarcoma (AOST-2121, NCT04974008). The Company previously announced positive AOST-2121 interim data and is now in active discussions with the US FDA regarding a Breakthrough Therapy (BTD) designation application submitted for OST-HER2 based on the interim results. The Company is focused on approval for OST-HER2 in osteosarcoma, and thereafter plans to expand development into breast cancer and other HER2 expressing cancers such as esophageal cancer and colorectal cancer.
In addition, the Company announced positive data from multiple preclinical models of breast cancer. The key data for OST-HER2 include:
78% reduction in tumor size (3mm for OST-HER2 treated vs. 14mm for control arm) in FVB/N HER2 transgenic mouse model of breast cancer treatment at day 75
33% prevention of breast cancer in OST-HER2 treated mice vs. 0% prevention of breast cancer in FVB/N HER2 transgenic model of breast cancer prevention at week 50
20% reduction of tumor size for OST-HER2 plus HER2-targeted antibody vs. HER2-targeted antibody alone Tg tumor regression model of breast cancer at day 42
65% reduction cellular concentration of metastatic cells for OST-HER2-treated mice compared with controls in brain metastasis model of primary breast cancer