Edgewood Oncology has treated the first two subjects in the Phase IIa clinical trial of BTX-A51, targeting patients with metastatic breast cancer.

This marks a significant step in the development of the multi-specific kinase inhibitor, which is being investigated for its potential to treat estrogen receptor-positive/human epidermal growth factor receptor 2 negative (ER+/HER2-) metastatic breast cancer, including cases with GATA3 mutations.

The multicentre, open-label, nonrandomised, multiple dose study is designed to assess the safety, toxicity, pharmacokinetics, and preliminary efficacy of BTX-A51.

Patients with ER+/HER2- metastatic breast cancer both with and without GATA3 mutations are being enrolled at various sites, which are now open for participation.

BTX-A51 functions by inhibiting casein kinase 1 alpha (CK1α) and cyclin-dependent kinases 7 and 9 (CDK7 and CDK9). These are considered master regulators in the progression of cancer.

Edgewood Oncology chief medical officer Zung Thai said: “This represents an important milestone for both Edgewood Oncology and for patients with ER+/HER2- breast cancer, particularly those with a GATA3 mutation, who need better treatment options targeted to their underlying mutation profile.

“Moreover, while CDK4/6 inhibitors remain a cornerstone of current treatment regimens, resistance to these therapies poses a formidable challenge. 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.”

In March, the company secured $20m in Series A to advance the clinical development of its lead cancer therapy BTX-A51.

The Series A funding round was led by US-based venture fund Alta Partners. Edgewood Oncology expects the funds to finance multiple clinical trials into 2026.