This study is exploring the recommended dosing for a new targeted therapy when given alone, or in combination with hormone therapy, in people with HR+/HER2- breast cancer and other advanced cancersA Phase 1a/1b Study Investigating the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Preliminary Antitumor Activity of the CDK4 Inhibitor BGB-43395, Alone or as Part of Combination Therapies in Patients With Metastatic HR+/HER2- Breast Cancer and Other Advanced Solid Tumors

Inclusion

• Phase 1a (Dose Escalation): Participants with histologically or cytologically confirmed advanced, metastatic, or unresectable solid tumors associated with dependency on CDK4, including HR+ breast cancer, non-small cell lung cancer, and others.
• Phase 1a: Received prior therapy for their condition (if available) and should be refractory to or intolerant of standard-of-care therapies.
• Phase 1b (Dose Expansion): Selected tumor cohorts will include HR+/HER2- breast cancer and additional tumor types.
• Phase 1b: Participants with HR+/HER2- breast cancer enrolled in regions where CDK4/6 inhibitors are approved and available must have received at least one line of therapy for advanced disease including endocrine therapy and a CDK4/6 inhibitor. Participants can have received up to 2 lines of prior cytotoxic chemotherapy for advanced disease.
• Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 1.
• Female participants with metastatic HR+/HER2- breast cancer must be postmenopausal or receiving ovarian function suppression treatment.
• Adequate organ function.