Summary
This is a phase I, First-in-Human (FIH), open-label study to evaluate the safety,
tolerability, pharmacokinetic (PK) profile, and preliminary efficacy of RGT-419B administered
orally as monotherapy OR in combination with Hormonal Therapy in subjects with HR+, HER2-
locally advanced and unresectable (Stage III) or metastatic (Stage IV) breast cancer whose
disease has progressed during prior therapy with an approved CDK4/6i plus hormonal therapy.