Study of GS-4528 in Adults With Solid Tumors

Key Inclusion Criteria:

* Documented disease:

1. 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.
2. 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.
3. Eastern Cooperative Oncology Group performance status 0 or 1.
4. Measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 criteria.
5. Adequate organ function.
6. Individuals of childbearing potential who engage in heterosexual intercourse must agree to use method(s) of contraception.
7. Tissue requirements:

1. Phase 1a dose escalation, Phase 1a dose expansion, and Phase 1b dose escalation: Must provide pre-treatment adequate tumor tissue sample prior to enrolment.
2. Phase 1a backfill cohorts: Individuals must have fresh pre-treatment and on-treatment biopsy for biomarker analysis.
3. Life expectancy ≥ 3 months.

Key Exclusion Criteria:

1. Positive serum pregnancy test or lactating female.
2. Prohibited concurrent anticancer therapy listed in the protocol.
3. 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).
4. Any prior allogeneic tissue/solid organ transplantation, including allogeneic stem cell transplantation.
5. Diagnosis of immunodeficiency, either primary or acquired, or systemic steroid requirement of > 10 mg of prednisone or equivalent.
6. History of intolerance, hypersensitivity, or treatment discontinuation due to severe immune-related adverse events (irAEs) on prior immunotherapy.
7. History of autoimmune disease or active autoimmune disease that has required systemic treatment within 2 years prior to the start of study treatment.
8. 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.
9. Have known active central nervous system (CNS) metastases and/ or carcinomatous meningitis.
10. Significant cardiovascular disease.
11. Have active serious infection requiring antibiotics.
12. Have active hepatitis B virus (HBV), hepatitis C virus (HCV), or human immunodeficiency virus (HIV).
13. History of pneumonitis, interstitial lung disease, or severe radiation pneumonitis (excluding localized radiation pneumonitis).
14. Symptomatic ascites or pleural effusion.
15. Live vaccines within 28 days of initiation of investigational product(s).

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