Study of Preladenant (MK-3814) Alone and With Pembrolizumab (MK-3475) in Participants With Advanced Solid Tumors (MK-3814A-062)

Inclusion Criteria:

* Has a histologically- or pathologically-documented, locally-advanced or metastatic solid tumor for which standard therapy, either does not exist or has been proven ineffective, intolerable or refused by the participant. Each participant must have received at least one and up to five prior lines of cancer treatment regimens, excluding neo-adjuvant, adjuvant, maintenance treatment and surgery
* Has provided a tumor tissue sample (archival or newly obtained core or excisional biopsy of a tumor lesion)
* Has measurable disease per RECIST 1.1
* Has an Eastern Cooperative Oncology Group (ECOG) performance status 0-1
* Females must not be pregnant
* Female and male participants of reproductive potential must agree to use adequate contraception starting from the first dose of study therapy, throughout the study period, and for up to 120 days after the last dose of study therapy

Exclusion Criteria:

* Has disease that is suitable for local treatment administered with curative intent
* Has received previous treatment with an immunomodulatory agent (e.g, anti- Programmed Cell Death Receptor 1/ Programmed Cell Death Receptor Ligand 1 or anti-cytotoxic T-lymphocyte-associated antigen-4) and was discontinued from treatment due to a Grade 3 or higher immune-related adverse event
* Has received previous treatment with an adenosine A2a receptor antagonist (e.g. CPI-444, HTL1071, PBF-509)
* Has had chemotherapy, definitive radiation, or biological cancer therapy within 4 weeks of the first dose of study therapy, or has not recovered to Common Toxicity Criteria for Adverse Events (CTCAE) grade 1 or better from any adverse event
* Is currently participating or has participated in a study with an investigational agent or using an investigational device within 28 days of the first dose of study therapy
* Is currently taking or has taken drugs that interfere with Cytochrome P450 (CYP)3A4 or CYP2C8 or grapefruit and star fruit in diet within 14 days of the first dose of study therapy
* Is currently taking or has taken proton pump inhibitors within 5 days of the first dose of study therapy
* Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy or any other form of immunosuppressive therapy within 7 days of the first dose of study therapy
* Is expected to require any other form of systemic or localized antineoplastic therapy while on study
* Has a history of a second malignancy, unless potentially curative treatment has been completed, with no evidence of malignancy for 5 years
* Has clinically active central nervous system metastases and/or carcinomatous meningitis
* History of a severe hypersensitivity reaction to treatment with the monoclonal antibody/components of the study drug
* Has an active infection requiring therapy
* History of interstitial lung disease
* History of (non-infectious) pneumonitis that required steroids or current pneumonitis
* History of active tuberculosis
* Has an active autoimmune disease that has required systemic treatment in the past 2 years
* Has received a live-virus vaccine within 30 days of the first dose of study therapy
* Has known Human Immunodeficiency Virus (HIV) (HIV 1 or 2 antibodies) and/or known active and acute Hepatitis B or C infections
* Has known psychiatric or substance abuse disorders that would interfere with the ability to cooperate with the requirements of the study
* Is pregnant or breastfeeding, or expecting to conceive or father children within the projected duration of the study
* Has not fully recovered from any effects of major surgery without significant detectable infection
* Has had surgery that required general anesthesia within 2 weeks of the first dose of study therapy
* Has had surgery that required regional/epidural anesthesia within 72 hours of the first dose of study therapy