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Edgewood Oncology Advances BTX-A51 to Phase IIa Trial in Certain Breast Cancer Patients

NEW YORK – Edgewood Oncology on Tuesday said it has started treating patients in a Phase IIa trial of BTX-A51 in estrogen receptor (ER)-positive HER2-negative metastatic breast cancer with and without GATA3 mutations.

The trial initially evaluated the safety and dosage of BTX-A51, a multi-specific kinase inhibitor of CK1α, CDK7, and CDK9, in solid tumors. In this expansion phase of the study, researchers will evaluate BTX-A51's safety and preliminary efficacy in patients with ER-positive, HER2-negative breast cancer and explore whether there is a differential treatment benefit based on whether patients have GATA3-mutated tumors.

GATA3 mutations occur in about 15 percent of breast cancer cases, according to Edgewood, and are associated with poorer progression-free and overall survival on hormone therapy. Because these patients typically have p53 wild-type tumors that overexpress MDM2 to suppress p53 function, Edgewood is exploring BTX-A51 as a potential treatment for this subpopulation because it can reduce MDM2 expression, which, in turn, stabilizes the p53 protein and allows it to function normally to mediate cell death.

Edgewood Chief Medical Officer Zung Thai said in a statement that this subgroup of patients with GATA3 mutations lacks biomarker-targeted treatment options.

"Moreover, while CDK4/6 inhibitors remain a cornerstone of current treatment regimens, resistance to these therapies poses a formidable challenge," Thai continued. "By targeting CDK7 and CDK9, key regulators of cell cycle progression, BTX-A51 not only aims to circumvent this resistance but also to transform the treatment landscape.”

Edgewood, based in Brookline, Massachusetts, is also exploring BTX-A51 as a treatment for acute myeloid leukemia in a Phase I trial and studying it preclinically in liposarcoma. Earlier this year, the firm raised $20 million in Series A funding to support trials of the drug.