Safety and Efficacy of Vicriviroc (MK-7690) in Combination With Pembrolizumab (MK-3475) in Participants With Advanced/Metastatic Microsatellite Stable (MSS) Colorectal Cancer (CRC) (MK-7690-046)

Inclusion Criteria:

• Have a histologically proven locally advanced unresectable or metastatic CRC.

• Have locally confirmed MSS CRC.

• Have been previously treated with standard therapies, which must includefluoropyrimidine, oxaliplatin, and irinotecan, and have received, been intolerantto, or been ineligible for all treatment known to confer clinical benefit.

• Have measurable disease per RECIST 1.1 as assessed by the local siteinvestigator/radiology.

• Have provided archival tumor tissue sample or newly obtained core or excisionalbiopsy of a tumor lesion not previously irradiated.

• Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1within 7 days of starting study intervention.

• Male participants must agree to use contraception and refrain from donating spermfor at least 120 days after the last dose of study intervention.

• Female participants must be not pregnant and not breastfeeding. Further, a femaleparticipant must either not be a woman of childbearing potential (WOCBP) or, if aWOCBP, agree to use contraception during the treatment period and for at least 120days after the last dose of study intervention.

• Have adequate organ function.

Exclusion Criteria:

• Have a known additional malignancy that is progressing or has required activetreatment within the past 2 years. Participants with basal cell carcinoma of theskin, squamous cell carcinoma of the skin, or carcinoma in situ (e.g., breastcarcinoma, cervical cancer in situ) that have undergone potentially curative therapyare not excluded.

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

• Have severe hypersensitivity reaction to treatment with any monoclonal antibody orcomponents of the study interventions.

• Have an active autoimmune disease requiring systemic treatment in the past 2 years,except vitiligo or resolved childhood asthma/atopy.

• Have a history of vasculitis.

• Have an active infection requiring systemic therapy.

• Have symptomatic ascites or pleural effusion.

• Have interstitial lung disease requiring oral or IV glucocorticoids.

• Have a history of pneumonitis (noninfectious) that required steroids, or has currentpneumonitis.

• Have a known history of human immunodeficiency virus (HIV) infection.

• Have a known history of hepatitis B or known active hepatitis C virus infection.

• Have a known history of active tuberculosis (TB; Bacillus tuberculosis).

• Have a history or current evidence of any condition, therapy, or laboratoryabnormality that might confound the results of the study, interfere with theparticipant's participation for the full duration of the study, make administrationof the study interventions hazardous, or make it difficult to monitor adverseevents.

• Have a known psychiatric or substance abuse disorder that would interfere with theparticipant's ability to cooperate with study requirements.

• Are pregnant or breastfeeding or expecting to conceive or father children within theprojected duration of the study, starting with the Screening Visit through 120 daysafter the last dose of study intervention.

• Are a WOCBP who has a positive urine pregnancy test within 72 hours beforerandomization or treatment allocation.

• Have undergone major surgery and have not recovered adequately from any toxicityand/or complications from the intervention before starting study intervention.

• Have a seizure disorder requiring ongoing antiseizure therapy or with any conditionthat, in the judgment of the investigator, is likely to increase the risk of seizure (e.g., CNS malignancy or toxoplasmosis).

• Have known gastrointestinal (GI) disease such as esophageal, gastric, or duodenalulceration or inflammatory bowel disease, or history of GI surgery.

• Are using any drug (therapeutic or recreational), or withdrawal thereof, that posesan increased risk of convulsions.

• Have had an allogeneic tissue/solid organ transplant.

• Have received prior therapy with vicriviroc or other CCR5 antagonist (e.g.,maraviroc) or have received prior therapy with an anti-PD-1, anti-PD-L1, or antiPD-L2 agent.

• Have been treated with an agent directed to another stimulatory or co-inhibitoryT-cell receptor (e.g., cytotoxic T-lymphocyte-associated protein 4 [CTLA-4], OX 40,CD137).

• Have received prior systemic anticancer therapy, including investigational agents,or has used an investigational device within 28 days before the first dose of studyintervention.

• Have received prior radiotherapy (not to target lesions) within 2 weeks of start ofstudy intervention.

• Are expected to require any other form of antineoplastic therapy while on study.

• Have a diagnosis of immunodeficiency, is receiving chronic systemic steroid therapyin excess of replacement doses (prednisone ≤10 mg/day is acceptable), or is takingany other form of immunosuppressive medication within 7 days before the first doseof the study intervention.

• Have received a live-virus vaccine within 30 days before the first dose of the studyintervention.

• Are currently participating in or have participated in a study of an investigationalagent, or have used an investigational device within 28 days before the first doseof study intervention.