Study to Evaluate Safety, Pharmacokinetics and Therapeutic Activity of RO6874281 as a Combination Therapy in Participants With Unresectable Advanced and/or Metastatic Renal Cell Carcinoma (RCC)

Inclusion criteria:

* Unresectable advanced and/or metastatic RCC with component of clear cell histology and/or component of sarcomatoid histology that has not been previously treated with any systemic therapy, including treatment in the adjuvant setting
* During dose escalation only, an additional population with unresectable advanced and/or metastatic 2nd line RCC patients is allowed
* At least one tumor lesion with location accessible to biopsy per clinical judgment of the treating physician
* Consent to provide an archival tumor tissue sample (if available) and to undergo baseline and on treatment tumor biopsies for pharmacodynamic biomarker analysis
* Measurable disease, as defined by RECIST v1.1. At least one lesion accessible for biopsy
* Participants with unilateral pleural effusion are eligible if they fulfill both of the following: (a) New York Heart Association (NYHA) Class 1; (b) Global initiative for obstructive lung disease (GOLD) test level 1 (forced expiratory volume in 1 second \[FEV1\]/ forced vital capacity \[FVC\] less than \[\<\] 0.7 and FEV1 greater than or equal to \[\>=\] 80 percent \[%\] predicted after inhaled bronchodilator)

Adequate hematological function: neutrophil count of ≥1.5 ≥109 cells/L, platelet count of ≥100,000/≥L, Hb ≥9 g/dL (5.6 mmol/L), lymphocytes ≥0.8 ≥109 cells/L.

Exclusion Criteria:

* Symptomatic or untreated central nervous system (CNS) metastases
* Participants with asymptomatic CNS metastases with previous or concomitant brain deficiencies, as defined in the protocol
* Participants with confirmed bilateral pleural effusion
* Episode of significant cardiovascular/cerebrovascular acute disease within 6 months prior to Cycle 1 Day 1
* Active or uncontrolled infections
* Human immunodeficiency virus (HIV) or active Hepatitis A, B, C, D and E virus (HAV, HBV, HCV, HDV and HEV) infection.
* Major surgery or significant traumatic injury \<28 days prior to Cycle 1 Day 1 (excluding fine needle biopsies) or anticipation of the need for major surgery during study treatment
* Serious, non-healing wound; active ulcer; or untreated bone fracture
* Proteinuria as demonstrated by a urine protein to creatinine ratio (UPCR) of \>=1.0 at screening
* History of, active or suspicion of autoimmune disease
* Concurrent use of high dose of systemic steroids. The use of inhaled, topical and ophthalmic steroids is allowed.