Inclusion Criteria:  Male or female participant must be at least 18 years of age inclusive (or complies with country-specific regulatory requirements, at least 20 years of age in Japan), at the time of signing the informed consent. Participants with histologically or cytologically confirmed advanced (locoregionally recurrent, not amenable to curative therapy) or metastatic solid tumors who have no standard therapies with a proven clinical benefit, or who are intolerant to or unwilling to receive these therapies for any reasons. Measurable disease by RECIST 1.1. (Part A only) Participants should have 1 of the following tumor types: malignant melanoma (MEL), head and neck squamous cell carcinoma (HNSCC), renal cell carcinoma (RCC), urothelial carcinoma (UC), non-small cell lung cancer (NSCLC), or triple-negative breast cancer (TNBC), esophageal cancer (EC; esophageal squamous cell carcinoma and adenocarcinoma), or gastric cancer (GC; gastric and gastroesophageal junction adenocarcinoma). (Part B only) Participants should have 1 of specific histologically or cytologically confirmed tumor types selected by the sponsor after completion of Part A-1. (Part C only) Participants should have 1 of specific histologically or cytologically confirmed tumor types selected by the sponsor after completion of Part A-2. Participants should be willing and able to provide permission to access archival formalin-fixed paraffin-embedded (FFPE) tumor tissues (as block or unstained slides) for this study. Participants should be willing and able to provide both pre-treatment and on-treatment paired tumor biopsy samples. (At selected sites only) Participants should be willing and able to provide both pre-treatment and on-treatment paired tumor biopsy samples. Fresh tissue samples are required as these will be used for the proof of mechanism analysis. Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0 or 1. An estimated life expectancy of at least 12 weeks. Adequate hematologic and organ function as confirmed by laboratory values. QT interval corrected with the Fridericia formula (QTcF) ≤ 480 milliseconds in 12-lead electrocardiogram (ECG) at Screening.  Exclusion Criteria:  Presence or history of autoimmune diseases or immune-mediated diseases that require chronic use of systemic corticosteroids (> 10 mg of prednisone equivalent per day), immunosuppressive agents, or disease-modifying agents. Active clinically significant bacterial, viral or fungal infection, or any major episode of infection requiring hospitalization or treatment with parenteral antiinfectives within 4 weeks before the first dose of study intervention. Uncontrolled or clinically significant cardiovascular disease defined as New York Heart Association (NYHA) classification III or IV. A positive test for hepatitis B surface antigen (HBsAg) and/or hepatitis C virus (HCV) antibody (a confirmatory HCV RNA test if HCV antibody was positive). A positive serological test for human immunodeficiency virus (HIV) infection. Known history of any other relevant congenital or acquired immunodeficiency. Known history of severe allergy, hypersensitivity, anaphylaxis, or any serious adverse reaction to any component of study intervention or formulation components and/or any other monoclonal antibodies. Women who are pregnant or breastfeeding or trying to become pregnant. Clinical evidence of uncontrolled brain metastasis. Clinical evidence of any active second invasive malignancy (except stable prostate cancer on watchful waiting). (Parts A-2 and C only): Participants who developed an immune-related adverse event (irAE) during prior pembrolizumab treatment that required a delay in the scheduled administration for more than 4 weeks due to any grade of irAEs or led to permanent discontinuation of pembrolizumab. Also, participants whose previous irAE due to pembrolizumab has not resolved to ≤ Grade 1 and/or still requires corticosteroids (> 10 mg of prednisone-equivalent per day). Prior treatment with systemic anticancer drugs (including any investigational medicinal products) within 28 days or 5 half-lives (whichever is shorter) before the first dose of study intervention. Prior major surgery within 28 days before the first dose of study intervention. Prior extended field radiotherapy within 28 days before the first dose of study intervention (within 14 days for limited field radiation for palliation). Participants who have not recovered from any previous treatment toxicities to ≤ Grade 1 or baseline (except alopecia and peripheral neuropathy) before the first dose of study intervention. Prior treatment with anti-CCR8 antibody for any indication. Receipt of a live, attenuated vaccine within 28 days before the first dose of study intervention.