BGB-43395 Alone or as Part of Combination Therapies in Chinese Participants With HR+/HER2- Breast Cancer and Other Advanced Solid Tumors

Inclusion Criteria:

• Phase 1a (Dose Escalation): Participants with histologically or cytologicallyconfirmed locally advanced or metastatic solid tumors associated with CDK4dependency, including HR+/HER2- breast cancer. Participants must have received priorstandard-of-care therapies for their disease, unless the therapy is not available ornot tolerated, or is determined not appropriate based on the investigator'sjudgment.

• Phase 1b (Dose Expansion): Participants with selected solid tumors including locallyadvanced or metastatic HR+/HER2- breast cancer.

• Female participants with metastatic HR+/HER2- breast cancer will be required to haveovarian function suppression using gonadotropin-releasing hormone (GnRH) agonistssuch as goserelin or be postmenopausal.

• Male participants with HR+/HER2- breast cancer will be required to have gonadalsuppression using GnRH agonists when being treated with letrozole or fulvestrant.

• Patients must have ≥1 measurable lesion per RECIST v1.1.

• Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 1.

• Adequate organ function without symptomatic visceral disease.

Exclusion Criteria:

• Prior therapy selectively targeting CDK4 (prior CDK4/6 inhibitor therapy ispermitted).

• Known leptomeningeal disease or uncontrolled untreated brain metastasis.

• Any malignancy ≤ 3 years before the first dose of study drug(s) except for thespecific cancer under investigation in this study and any locally recurring cancerthat has been treated with curative intent (eg, resected basal or squamous cell skincancer, superficial bladder cancer, or carcinoma in situ of the cervix or breast).

• Uncontrolled diabetes.

• Infection requiring systemic antibacterial, antifungal, or antiviral therapy ≤ 28days before the first dose of study drug(s), or symptomatic COVID-19 infection.Patients receiving prophylactic antibiotics (eg, for prevention of urinary tractinfection, chronic obstructive pulmonary disease, or for dental extraction) areeligible. Patients who have recovered from symptomatic COVID-19 infection can berescreened for this study.

• Untreated chronic hepatitis B or active hepatitis C infection.

Note: Other protocol defined Inclusion/Exclusion criteria may apply.