BTX-9341 + fulvestrant

BTX-9341 + fulvestrant is an investigational combination therapy under clinical evaluation for advanced and/or metastatic hormone receptor-positive (HR+), HER2-negative (HER2-) breast cancer. BTX-9341 is a first-in-class, oral small molecule degrader that targets cyclin-dependent kinase 4 (CDK4) and cyclin-dependent kinase 6 (CDK6), leading to their catalytic degradation. This results in robust inhibition of Cyclin E and CDK2 transcription, cell cycle arrest, and anti-tumor activity. Fulvestrant is a selective estrogen receptor degrader (SERD) that antagonizes the estrogen receptor pathway. Preclinical studies have shown that the combination of BTX-9341 with fulvestrant produces synergistic anti-proliferative effects in HR+ breast cancer models, including those resistant to prior CDK4/6 inhibitor therapies[2][6][8]. The combination aims to overcome resistance mechanisms seen with current standard-of-care treatments.