A Study of RO7821657 in Participants With Solid Tumors

• Life expectancy estimated by the Investigator to be ≥12 weeks.
• Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) 0-1.
• Presence of measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) v1.1; previously irradiated lesions are considered measurable if progression has been demonstrated in such lesions after the irradiation.
• Availability of archival tumor tissue or tissue obtained from a fresh biopsy at screening if formalin-fixed paraffin-embedded [FFPE]-preserved archival tissue is not available. The archival tumor tissue should come from a core biopsy, a punch biopsy, an excisional biopsy, or a surgical specimen. Lymph node biopsy, bone biopsy (unless from soft tissue), or fine needle aspiration are unacceptable for submission. Lesions that are intended to be biopsied should not be counted as target lesions.
• Adequate cardiovascular function:

New York Heart Association (NYHA) Heart Failure Class ≤ 1.

• Agreement to adhere to the contraception requirements.

• Participants with active Central Nervous System (CNS) metastases.
• Any unresolved toxicities from prior therapy, i.e., radiotherapy, chemotherapy, targeted or checkpoint inhibitor therapy or surgical procedure, greater than CTCAE Grade 1 at the time of starting study treatment, except for alopecia and Grade 2 neuropathy.

a) Stable endocrine AEs managed with hormone replacement are permitted, including hypothyroidism on stable thyroid hormone replacement.

• History of interstitial pulmonary disease, drug-induced pneumonitis, or evidence of active pneumonitis on screening computed tomography (CT) scan.
• Participants with pulmonary miliary metastatic pattern (innumerable small lesions) or pulmonary lymphangitic carcinomatosis.
• Active autoimmune disease that has required systemic treatment (except replacement treatment) within the last 2 years or any disease requiring immunosuppressive therapy while on study.