Study of GS-4528 in Adults With Solid Tumors

Key Inclusion Criteria: * Documented disease: * Phase 1a dose escalation and backfill cohorts; Phase 1b dose escalation: Individuals with histologically or cytologically confirmed advanced solid tumors who have received, been intolerant to, or been ineligible for all treatment known to confer clinical benefit or have a contraindication to receive the therapy. * Phase 1a dose expansion: Individuals with histologically or cytologically confirmed select indications who have received, been intolerant to, or been ineligible for all treatment known to confer clinical benefit or have a contraindication to receive the therapy. * Eastern Cooperative Oncology Group performance status 0 or 1. * Measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 criteria. * Adequate organ function. * Individuals of childbearing potential who engage in heterosexual intercourse must agree to use method(s) of contraception. * Tissue requirements: * Phase 1a dose escalation, Phase 1a dose expansion, and Phase 1b dose escalation: Must provide pre-treatment adequate tumor tissue sample prior to enrolment. * Phase 1a backfill cohorts: Individuals must have fresh pre-treatment and on-treatment biopsy for biomarker analysis. * Life expectancy ≥ 3 months. Key Exclusion Criteria: * Positive serum pregnancy test or lactating female. * Prohibited concurrent anticancer therapy listed in the protocol. * Any anti-cancer therapy, whether investigational or approved, within protocol specified time prior to initiation of study including: major surgery (\<28 days), immunotherapy or biologic therapy (\< 28 days), chemotherapy (\< 21 days), targeted small molecule therapy (\< 14 days or \< 5 half-lives whichever is shorter), hormonal therapy or other adjunctive therapy (\< 14 days) or radiotherapy (\< 21 days). * Any prior allogeneic tissue/solid organ transplantation, including allogeneic stem cell transplantation. * Diagnosis of immunodeficiency, either primary or acquired, or systemic steroid requirement of \> 10 mg of prednisone or equivalent. * History of intolerance, hypersensitivity, or treatment discontinuation due to severe immune-related adverse events (irAEs) on prior immunotherapy. * History of autoimmune disease or active autoimmune disease that has required systemic treatment within 2 years prior to the start of study treatment. * Concurrent active second malignancy. Note: Individuals with a history of malignancy that have been completely treated, with no evidence of active cancer for 2 years prior to enrollment, or participants with surgically cured tumors with low risk of recurrence are allowed to enroll. * Have known active central nervous system (CNS) metastases and/ or carcinomatous meningitis. * Significant cardiovascular disease. * Have active serious infection requiring antibiotics. * Have active hepatitis B virus (HBV), hepatitis C virus (HCV), or human immunodeficiency virus (HIV). * History of pneumonitis, interstitial lung disease, or severe radiation pneumonitis (excluding localized radiation pneumonitis). * Symptomatic ascites or pleural effusion. * Live vaccines within 28 days of initiation of investigational product(s). Note: Other protocol defined Inclusion/Exclusion criteria may apply.