Phase 1a/1b First-in-Human Study of BG-C9074 Alone and in Combination With Other Anticancer Therapies in Patients With Advanced Solid Tumors

Inclusion Criteria:

1. Able to provide a signed and dated written informed consent prior to anystudy-specific procedures, sampling, or data collection.

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

3. Participants with selected histologically or cytologically confirmed advanced,metastatic, and unresectable solid tumors who have previously received standardsystemic therapy and whose cancer is not amenable to therapy with curative intent,and for whom further treatment is not available or not tolerated. Enrollment will belimited to participants with hormone receptor-positive/human epidermal growth factorreceptor 2-negative (HR+/HER2-) breast cancer, cholangiocarcinoma (CCA), endometrialcancer, squamous non-small cell lung cancer (NSCLC), triple-negative breast cancer (TNBC), or ovarian cancer. Enrollment in the Japan cohort will be limited toparticipants with HR+/HER2- breast cancer, TNBC, endometrial cancer, or ovariancancer.

4. ≥ 1 measurable lesion per Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST v1.1)

5. Able to provide an archived tumor tissue sample.

6. Adequate bone marrow and organ function.

7. Females of childbearing potential must be willing to use a highly effective methodof birth control for the duration of the study, and for ≥ 7 months after the lastdose of study drug(s).

8. Nonsterile males must be willing to use a highly effective method of birth controlfor the duration of the study treatment period and for ≥ 4 months after the lastdose of study drug(s).

Exclusion Criteria:

1. Prior treatment with a B7 homolog 4 (B7H4)-targeting antibody-drug conjugate (ADC)or an ADC with a topoisomerase 1 inhibitor (TOP1i) payload.

2. Active leptomeningeal disease or uncontrolled, untreated brain metastasis

3. Any malignancy ≤ 2 years before the first dose of study treatment(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).

4. History of interstitial lung disease, ≥ Grade 2 noninfectious pneumonitis, oxygensaturation at rest < 92%, or requirement for supplemental oxygen (includingintermittent use) at baseline.

5. Uncontrolled diabetes.

6. Infection (including tuberculosis infection) requiring systemic (oral orintravenous) antibacterial, antifungal, or antiviral therapy ≤ 14 days before thefirst dose of study treatment(s).

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