Study of MK-2118 Administered as Intratumoral Injection as Monotherapy and in Combination With Pembrolizumab (MK-3475) or by Subcutaneous Injection in Combination With Pembrolizumab in the Treatment of Adults With Advanced/Metastatic Solid Tumors or Lymphomas (MK-2118-001)

Participants will receive either MK-2118 monotherapy or MK-2118 in combination with
pembrolizumab for up to 35 cycles (approximately 2 years).

All participants will undergo an at least 24-hour observation period following the first dose
administration of MK-2118 on Cycle 1, Day 1.

Inclusion Criteria:

Arms 1 and 2 Participants:

- Has any histologically or cytologically confirmed advanced/metastatic solid tumor by
pathology report and has received, or have been intolerant to all treatment known to
confer clinical benefit. Solid tumors and lymphomas of any type are eligible for
enrollment. For cutaneous T-cell lymphoma (CTCL), histopathological diagnosis should
be confirmed in a skin biopsy representative of disease.

- Have Stage III or Stage IV disease that is not surgically resectable. Stage IIB
(T3N0M0B0-1) CTCL participants are eligible.

Arm 3 Participants:

-Has metastatic liver and/or liver lesion involvement that does not exceed one third of the
total liver volume in participants to be treated by liver IT injection. Hepatocellular
carcinoma participants are excluded from eligibility of IT liver injection.

All Participants:

- Stage III or Stage IV disease that is not surgically resectable.

- Has ≥1 injectable lesion that is amenable to injection and biopsy via visual
inspection for a cutaneous lesion, or via ultrasound guidance for a subcutaneous
lesion.

- Has ≥1 discrete, distant noninjected lesion that is amenable to biopsy via visual
inspection or amenable to biopsy via image guidance.

- Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.

- Demonstrates adequate organ function.

- If of childbearing potential, must agree to use adequate contraception during the
treatment period and for at least 120 days after the last dose of study treatment.

- Human Immunodeficiency Virus (HIV) -infected participants must meet these additional
criteria:

1. Have HIV-1 infection documented by laboratory test.

2. Have well-controlled HIV on anti-retroviral therapy (ART), defined as: 1) must
have a CD4+ T-cell count >350 cells/mm^3 at time of screening; 2) must have
achieved and maintained virologic suppression defined as confirmed HIV
ribonucleic acid (RNA) level <50 or below the lower limit of quantification
(LLOQ) using the locally available assay at the time of screening and for ≥12
weeks prior to screening; and 3) must have been on a stable regimen, without
changes in drugs or dose modification, for ≥4 weeks prior to study entry (Day 1).

Exclusion Criteria:

- History of a second malignancy, unless potentially curative treatment has been
completed, with no evidence of malignancy for 2 years (except for successful
definitive resection of basal cell carcinoma of the skin, superficial bladder cancer,
or in situ cervical cancer).

- Clinically active central nervous system metastases and/or carcinomatous meningitis.

- Severe hypersensitivity reaction to treatment with a monoclonal antibody (mAb).

- Active autoimmune disease that has required systemic treatment in the past 2 years.

- History of vasculitis.

- Active infection requiring therapy.

- History of (noninfectious) pneumonitis that required steroids or current pneumonitis.

- Undergone prior allogeneic hematopoietic stem cell transplantation within the last 5
years.

- Known Hepatitis B or C infection.

- Pregnant or breastfeeding, or expecting to conceive or father children within the
projected duration of the study.

- Not fully recovered from any effects of major surgery, and is free of significant
detectable infection.

- HIV-infected participants with history of Kaposi's sarcoma and/or multicentric
Castleman's disease.

- HIV-infected participants who have had an HIV-related opportunistic infection within 6
months.

- Had chemotherapy, definitive radiation, or biological cancer therapy within 4 weeks (2
weeks for palliative radiation) prior to the first dose of study treatment, or has not
recovered to baseline or Common Terminology Criteria for Adverse Events (CTCAE) Grade
1 from the AEs due to cancer therapeutics administered >4 weeks earlier.

- Been treated within 2 weeks of Cycle 1 Day1 with any of the following: strong/moderate
Cytochrome P450 2C9 (CYP2C9) inhibitors, such as: amiodarone, felbamate, fluconazole,
miconazole, piperine, oxandrolone, fluorouracil and its derivatives (combination drug
tegafur/gimeracil/oteracil [TS-1], Uftoral [UFT], tegafur, carmofur, doxifluridine,
capecitabine), sulfaphenazole, cyclosporine, bucurol, tienilic acid; UGT1A3 inhibitors
(including ritonavir, quinidine, probenecid, and valproic acid); or strong carbonyl
reductase (CBR) inhibitors (including quercetin, menadione, glycyrrhetinic acid, and
flufenamic acid).

- Currently participating and receiving study therapy or has participated in a study of
an investigational agent and has received study therapy or has used an investigational
device within 28 days of administration of MK-2118.

- Expected to require any other form of antineoplastic therapy while on study.

- On chronic systemic steroid therapy in excess of replacement doses (prednisone ≤10
mg/day is acceptable), or on any other form of immunosuppressive medication. For CTCL,
continued use of either prednisone ≤10 mg/day or continued use of topical steroids is
acceptable.

- Received a live vaccine within 28 days prior to first dose.

- Been treated with a stimulator of interferon genes (STING) agonist (eg, MK-1454,
ADU-S100 [synthetic cyclic dinucleotide (CDN)]).

- Has a history of re-irradiation for SCCHN at the projected injection site.

- Has a tumor(s) in direct contact or encases a major blood vessel and has ulceration
and/or fungation onto the skin surface at the projected injection site.