A Study of MK-6598 as Monotherapy and in Combination With Pembrolizumab (MK-3475) in Advanced Solid Tumors (MK-6598-001)

Inclusion Criteria:

• Has a histologically- or cytologically-confirmed advanced/metastatic solid tumor bypathology report and has received, or been intolerant to, all treatment known toconfer clinical benefit.

• Has measurable disease by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1as assessed by the local site investigator/radiology.

• Has one or more discrete malignant lesions that are amenable to a minimum of 2separate biopsies.

• Has a baseline tumor sample that can be submitted for analysis.

• Human immunodeficiency virus (HIV)-infected participants must have well controlledHIV on antiretroviral therapy (ART).

• A participant assigned male sex at birth who receives MK-6598 must agree to usecontraception and should refrain from donating sperm during the specified period(s)of at least 102 days after study interventions.

• A participant assigned female sex at birth is eligible to participate if notpregnant or breastfeeding and at least 1 of the following: not a participant ofchildbearing potential (POCBP) or a POCBP who agrees to follow the contraceptiveguidance during the treatment period and for up to 120 days after studyintervention.

Exclusion Criteria:

• Received prior systemic anticancer therapy including investigational agents within 4weeks before the first dose of study intervention or has not recovered to CTCAEVersion 5.0 Grade 1 or better from any AEs that were due to cancer therapeuticsadministered more than 4 weeks earlier (this includes participants with previousimmunomodulatory therapy with residual immune-related AEs).

• Known additional malignancy that is progressing or has required active treatmentwithin 2 years.

• Clinically active central nervous system (CNS) metastases and/or carcinomatousmeningitis.

• A severe hypersensitivity (≥Grade 3) reaction to treatment with a monoclonalantibody/components of the study intervention.

• Active infection requiring therapy.

• History of interstitial lung disease.

• History of (noninfectious) pneumonitis that required steroids or currentpneumonitis.

• Active autoimmune disease that has required systemic treatment in the past 2 years.Replacement therapy (eg, thyroxine, insulin, or physiologic corticosteroid) isallowed.

• Has known hepatitis B or C infections or known to be positive for hepatitis Bsurface antigen (HBsAg)/hepatitis B virus (HBV) deoxyribonucleic acid (DNA) orhepatitis C antibody or ribonucleic acid (RNA).

• Has a history or current evidence of any condition, therapy, laboratory abnormality,or other circumstance that might confound the results of the study or interfere withthe participant's participation for the full duration of the study, such that it isnot in the best interest of the participant to participate, in the opinion of thetreating investigator.

• Received prior radiotherapy within 2 weeks of start of study intervention, hasradiation-related toxicities requiring corticosteroids, or had a history ofradiation pneumonitis.

• Has received a live or live-attenuated vaccine within 30 days before the first doseof study intervention. Administration of killed vaccines are allowed.

• Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent orwith an agent directed to another stimulatory or co-inhibitory T-cell receptor (eg,cytotoxic T-lymphocyte-associated protein 4 [CTLA-4], OX 40, CD137), and wasdiscontinued from that treatment due to a ≥Grade 3 immune-related AE (irAE).

• Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily of prednisone equivalent) or any other form ofimmunosuppressive therapy within 7 days before the start of study treatment.

• Has had an allogeneic tissue/solid organ transplant in the last 5 years or hasevidence of graft-versus-host disease.