Safety and Pharmacokinetics Study of MK-5890 as Monotherapy and in Combination With Pembrolizumab (MK-3475) in Adults With Advanced Solid Tumors (MK-5890-001)

Participants receiving MK-5890 monotherapy who experience disease progression may be eligible
to switch to receiving MK-5890 plus pembrolizumab combination therapy for up to 35 cycles
(approximately 2 years) at the discretion of the Investigator and approval of the Sponsor.

Inclusion Criteria:

- Histologically or cytologically confirmed advanced/metastatic solid tumor by pathology
report and has received or been intolerant to all treatment known to confer clinical
benefit.

- Measureable disease by RECIST 1.1. as assessed by the local site
investigator/radiologist. Target lesions situated in a previously irradiated area are
considered measurable if progression has been demonstrated in such lesions.

- Adequate organ function.

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

- Male participants must agree to use adequate contraception during the treatment period
and for at least 120 days after the last dose of study treatment and refrain from
donating sperm during this period.

- Female participants must not be pregnant or breast feeding and agree to follow use
adequate contraception during the treatment period and for at least 120 days after the
last dose of study treatment.

- Submit an evaluable baseline tumor sample for analysis (either a newly obtained or
archival tumor sample).

Exclusion Criteria:

- History of a second malignancy, unless potentially curative treatment has been
completed with no evidence of malignancy for 2 years.

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

- Has had a severe hypersensitivity reaction to treatment with a monoclonal antibody
(mAb) and/or other components of the study treatment.

- Active infection requiring systemic treatment.

- History of interstitial lung disease.

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

- Symptomatic ascites or pleural effusion.

- Previously had a stem cell or bone marrow transplant.

- Previously had a solid organ transplant.

- Active autoimmune disease that has required systemic treatment in the past 2 years
(i.e., with use of disease-modifying agents, corticosteroids, or immunosuppressive
drugs) except vitiligo or resolved childhood asthma/atopy.

- Known human immunodeficiency virus (HIV) and/or active and acute Hepatitis B or C
infections.

- Not fully recovered from any effects of major surgery without significant detectable
infection.

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

- Had chemotherapy, definitive radiation, or biological cancer therapy within 4 weeks (2
weeks for palliative radiation) before the first dose of study treatment, or has not
recovered to Grade ≤1 or better from any AEs that were due to cancer therapeutics
administered more than 4 weeks earlier.

- Expected to require any other form of antineoplastic therapy while participating in
this study.

- On chronic systemic steroid therapy in excess of replacement doses (e.g., exceeding 10
mg/day of prednisone equivalent), or on any other form of immunosuppressive
medication.

- Regular user (including "recreational use") of any illicit drugs at the time of
signing informed consent, or has a recent history (within the last year) of substance
abuse (including alcohol), as determined by the treating investigator. Participants
who use cannabis for medicinal purposes or to treat specific symptoms will not be
excluded unless it is being abused in the opinion of the treating investigator.

- Received a live-virus vaccine within 28 days before the first dose of study treatment.

- Currently participating and receiving study treatment in a study of an investigational
agent or has participated and received study treatment in a study of an
investigational agent or has used an investigational device within 28 days before the
first dose of study treatment.