This is a Phase 1b open-label study to evaluate the safety and clinical activity of zimberelimab (AB122) in biomarker-selected participants with advanced solid tumors.

The activity of zimberelimab every 3 weeks (Q3W) will be evaluated in molecularly defined patient populations as described by the StrataNGS test (to be performed outside of this study protocol). Participants with any advanced tumor type will be stratified evenly by tumor biomarker status as follows: TMB-H or Strata Immune Signature positive. Each cohort may enroll approximately 40 participants. Following completion of and/or discontinuation from investigational product and follow-up, all participants will be followed for survival.

Inclusion Criteria:

• Capable of giving signed informed consent.
• Male or female participants ≥ 18 years of age at the time of screening.
• Negative serum pregnancy test at screening and negative serum or urine pregnancy test every 3 months during the treatment period (women of childbearing potential only).
• Pathologically confirmed tumor that is metastatic, advanced, or recurrent with progression for which no alternative known to improve survival or curative therapy exists. Tumors must be TMB-H or Strata Immune Signature positive.
• Must have at least 1 measurable lesion per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1. The measurable lesion must be outside of a radiation field if the participant received prior radiation.
• Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1.
• Prior chemotherapy or certain immune therapies or biologic agents must have been completed at least 4 weeks (28 days) before investigational product administration and all AEs have either returned to baseline or stabilized.
• Previously treated brain or meningeal metastases with no evidence of progression by magnetic resonance imaging (MRI) for at least 4 weeks (28 days) prior to the first dose.
• Immunosuppressive doses of systemic medications, such as corticosteroids or absorbed topical corticosteroids (doses > 10 mg/day prednisone or equivalent) must be discontinued at least 2 weeks (14 days) before investigational product administration. Physiologic doses of corticosteroids < 10 mg/day of prednisone or its equivalent may be permitted
• Prior surgery that required general anesthesia or other major surgery as defined by the Investigator must be completed at least 4 weeks before investigational product administration
• Negative tests for hepatitis B surface antigen, hepatitis C virus antibody (or hepatitis C qualitative ribonucleic acid [RNA; qualitative]), and human immunodeficiency virus (HIV)-1 and HIV-2 antibody at screening
• Adequate organ and marrow function

Exclusion Criteria:

• Use of any live attenuated vaccines against infectious diseases within 4 weeks (28 days) of initiation of investigational product.
• Underlying medical conditions that, in the Investigator's or Sponsor's opinion, will make the administration of investigational product hazardous or obscure the interpretation of toxicity determination or Adverse events (AEs).
• History of myocardial infarction within 6 months or history of arterial thromboembolic event within 3 months of the first dose of investigational agent.
• Has known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial.
• Is pregnant or breastfeeding or expecting to conceive or father children within the projected duration of the study, starting with the pre-screening or screening visit through 90 days after the last dose of investigational product.
• Any active or documented history of autoimmune disease or history of a syndrome that required systemic steroids or immunosuppressive medications.
• Any acute gastrointestinal symptoms at the time of screening or admission.
• Prior malignancy active within the previous year except for locally curable cancers that have been apparently cured.
• Prior treatment with an anti-PD-L1 or anti-PD-1 as monotherapy or in combination.
• Prior treatment with temozolomide.
• Use of other investigational drugs (drugs not marketed for any indication) within 28 days or at least 5 half-lives (whichever is longer) before investigational product administration.

Arcus will provide access to individual de-identified participant data and related study documents (e.g., protocol, Statistical Analysis Plan [SAP], Clinical Study Report [CSR]) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions.

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