BGB-43395 Alone or as Part of Combination Therapies in Participants With Breast Cancer and Other Advanced Solid Tumors

Brief Summary

This is a dose escalation and dose expansion study to compare how well BGB-43395, a cyclin-dependent kinase 4 (CDK4) inhibitor, works as monotherapy or in combination with either fulvestrant or letrozole in participants with hormone receptor positive (HR+) and human epidermal growth factor 2 negative (HER2-) breast cancer (BC) and other advanced solid tumors. The main purpose of this study is to explore the recommended dosing for BGB-43395.

Intervention / Treatment 

  • Drug: BGB-43395
  • Drug: Fulvestrant
  • Drug: Letrozole

Inclusion Criteria

  • Phase 1a (Dose Escalation) and 1b (Dose Expansion): Participants with histologically or cytologically confirmed advanced, metastatic, or unresectable solid tumors associated with dependency on CDK4, including HR+ breast cancer, ovarian cancer, endometrial 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. In regions where approved and available, participants with HR+ breast cancer must have received at least 2 prior lines of treatment including endocrine therapy and a CDK4/6 inhibitor.
  • Phase 1b: 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.
  • Stable 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 without symptomatic visceral disease.

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