A Dose Escalation and Expansion Study of Lomvastomig, a PD-1/TIM-3 Bispecific Antibody, in Participants With Advanced and/or Metastatic Solid Tumors

Inclusion Criteria:

General Inclusion Criteria:

* Part A: Patient must have histologically or cytologically confirmed advanced and/or metastatic solid tumor malignancies for which standard curative or palliative measures do not exist, are no longer effective, or are not acceptable to the patient
* Eastern Cooperative Oncology Group Performance Status 0-1
* Measurable disease as defined by Response Evaluation Criteria in Solid Tumors (RECIST v1.1)
* Fresh biopsies may be required
* Negative HIV, hepatitis B, or hepatitis C test result
* Women of childbearing potential and male participants must agree to remain abstinent or use contraceptive methods as defined by the protocol

Additional Specific Inclusion Criteria for Participants with Melanoma:

* Histologically confirmed, unresectable stage III or stage IV melanoma
* Previously treated with approved anti-programmed death-ligand 1 (PD-L1)/anti-programmed death-1 (PD-1) agents with or without approved anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) therapy and up to one additional treatment regimen

Additional Specific Inclusion Criteria for Participants with Non-small Cell Lung Cancer (NSCLC) who Previously Received Treatment for Metastatic Disease:

* Histologically confirmed advanced NSCLC
* Previously treated with approved PD-L1/PD-1 inhibitors and platinum-based chemotherapy
* Not more than 2 prior lines of treatment for metastatic disease are allowed prior to enrolling to the study
* Participants must have experienced initial clinical benefit (stable disease or better) from most recent checkpoint inhibitor (CPI) therapy
* Tumor PD-L1 expression as determined by immunohistochemistry assay of archival tumor tissue or tissue obtained at screening

Additional Specific Inclusion Criteria for Participants with Non-small Cell Lung Cancer (NSCLC) who Previously Did Not Receive Treatment for Metastatic Disease:

* Histologically confirmed advanced NSCLC
* Tumor PD-L1 expression as determined by immunohistochemistry assay of archival tumor tissue or tissue obtained at screening

Additional Specific Inclusion Criteria for Participants with Small Cell Lung Cancer (SCLC):

* Histologically confirmed SCLC
* Participants may have had prior chemotherapy, radiation therapy, or declined approved therapies for SCLC

Additional Specific Inclusion Criteria for Participants with Esophageal Squamous Cell Carcinoma (ESCC):

* Participants whose major lesion was histologically confirmed as squamous cell carcinoma or adenosquamous cell carcinoma of the esophagus
* Patients who have previously received not more than 1 prior line of treatment for metastatic disease prior to enrolling to the study

Exclusion Criteria:

General Exclusion Criteria:

* Pregnancy, lactation, or breastfeeding
* Known hypersensitivity to any of the components of RO7121661
* Active or untreated central nervous system (CNS) metastases
* An active second malignancy
* Evidence of concomitant diseases, metabolic dysfunction, physical examination findings, or clinical laboratory findings giving reasonable suspicion of a disease or condition that contraindicates the use of an investigational drug or that may affect the interpretation of the results or render the participant at high risk from treatment complications
* Known active or uncontrolled bacterial, viral, fungal, mycobacterial, parasitic, or other infection
* Treatment with oral or IV antibiotics within 2 weeks prior to Cycle 1 Day 1
* Active or history of autoimmune disease or immune deficiency
* Prior treatment with adoptive cell therapies, such as CAR-T therapies
* Concurrent therapy with any other investigational drug \<28 days or 5 half-lives of the drug, whichever is shorter, prior to the first RO7247669 administration
* Regular immunosuppressive therapy
* Radiotherapy within the last 4 weeks before start of study drug treatment, with the exception of limited palliative radiotherapy
* Prior treatment with a T-cell immunoglobulin and mucin domain-3 (TIM-3) inhibitor

Additional Specific Exclusion Criteria for Participants with NSCLC who Previously Received Treatment for Metastatic Disease:

\- Patients with the following mutations, rearrangements, translocations are not eligible: epidermal growth factor receptor (EGFR); anaplastic lymphoma kinase (ALK); ROS proto-oncogene 1 (ROS1), BRAFV600E, and neurotrophic receptor tyrosine kinase (NTRK)

Additional Specific Exclusion Criteria for Participants with NSCLC who Did Not Previously Receive Treatment for Metastatic Disease:

* Prior therapy for metastatic disease
* Adjuvant anti-PD-1 or anti-PD-L1 therapy

Additional Specific Exclusion Criteria for Participants with Small-Cell Lung Cancer (SCLC):

\- Prior therapy with any immune CPIs (such as anti-PD-L1/PD-1, CTLA-4)

Additional Specific Exclusion Criteria for Participants with Esophageal Squamous Cell Carcinoma (ESCC):

\- Prior therapy with any immunomodulatory agents