Study of GS-4528 in Adults With Solid Tumors

The goals of this clinical study are to identify if GS-4528 alone or in combination with anti-programmed cell death protein 1 (PD-1) (Anti-PD-1) Monoclonal Antibody is safe and tolerable in people with solid tumors and to identify the recommended dose of GS-4528 for further development that is safe to give to people alone or in combination with Anti-PD-1 Monoclonal Antibody.

The primary objectives of this study are:

* To assess the safety and tolerability of GS-4528 as monotherapy and in combination with Anti-PD-1 Monoclonal Antibody in participants with advanced solid tumors.
* To identify the maximum tolerated dose (MTD)/maximum administered dose (MAD) and/or the recommended Phase 2 dose (RP2D) of GS-4528 as monotherapy and in combination with Anti-PD-1 Monoclonal Antibody in participants with advanced solid tumors.


Eligibility Criteria:
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.