Subject Inclusion Criteria

        In order to be eligible for participation in this trial, the subject must:

          1. Have one of the following diagnoses/conditions:

               1. Renal cell carcinoma - previously treated and progressive disease, locally
                  advanced or metastatic

               2. Urothelial cell carcinoma - previously treated and progressive disease, locally
                  advanced or metastatic

               3. Prostate cell carcinoma - progressive disease, locally advanced or metastatic
                  disease (enrolling only at IUSCC and its affiliates). Patients with
                  hormone-sensitive disease where ADT in combination with either docetaxel or
                  abiraterone is indicated will not be eligible (i.e. patients with high burden
                  disease).

          2. Be willing and able to provide written informed consent for the trial.

          3. Be 18 years of age or older on day of signing informed consent.

          4. Have measurable disease based on RECIST 1.1. for patients with solid malignancies or
             evaluable disease as assessed by bone scan and/or PET scan. Patients with advanced or
             metastatic prostate cancer can have either androgen-sensitive or castration-resistant
             disease.

          5. Have a performance status of 0-2 on the ECOG Performance Scale.

          6. Demonstrate adequate organ function. All screening labs should be performed within 10
             days of treatment initiation.

          7. Female subject of childbearing potential should have a negative urine or serum
             pregnancy test within 72 hours prior to receiving the first dose of study medication.
             If the urine test is positive or cannot be confirmed as negative, a serum pregnancy
             test will be required.

          8. Subjects of childbearing potential should be willing to use 2 methods of contraception
             for the course of the study through 120 days after the last dose of study medication.
             Acceptable methods of birth control include: abstinence, partner with previous
             vasectomy, placement of an intrauterine device (IUD), condom with spermicidal
             foam/gel/film/cream/suppository, diaphragm or cervical vault cap, or hormonal birth
             control (pills or injections). NOTE: Females are considered of childbearing potential
             unless they are surgically sterile (they have undergone a hysterectomy, bilateral
             tubal ligation, or bilateral oophorectomy) or they are postmenopausal (a woman who is
             ≥45 years of age and has not had menses for greater than 1 year).

          9. Male subjects without a previous vasectomy should agree to use an adequate method of
             contraception (i.e. abstinence, condom with spermicidal foam/gel/film/cream) starting
             with the first dose of study therapy through 120 days after the last dose of study
             therapy.

         10. Subjects with urothelial carcinoma must have received a prior platinum-based regimen
             in the metastatic setting or have signed consent for this study within 12 months of
             receiving a platinum-based regimen in the perioperative setting (neoadjuvant or
             adjuvant).

         11. Subjects with a history of diabetes mellitus must have HgbA1c level of <8.5% upon
             study entry.

        Subject Exclusion Criteria

        The subject must be excluded from participating in the trial if the subject:

          1. Is currently participating and receiving study therapy or has participated in a study
             of an investigational agent and received study therapy or used an investigational
             device within 4 weeks of the first dose of treatment.

          2. Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any
             other form of immunosuppressive therapy within 7 days prior to the first dose of trial
             treatment.

          3. Has active TB (Bacillus Tuberculosis)

          4. Hypersensitivity to pembrolizumab or any of its excipients.

          5. Has had a prior anti-cancer monoclonal antibody (mAb) within 4 weeks prior to Cycle 1
             Day 1 or who has not recovered (i.e. ≤ Grade 1 or at baseline) from adverse events due
             to agents administered more than 4 weeks earlier.

          6. Has had prior chemotherapy, targeted small molecule therapy, or radiation therapy
             within 2 weeks prior to Cycle 1 Day 1 or who has not recovered (i.e. ≤ Grade 1 or at
             baseline) from adverse events due to a previously administered agent.

               -  Note: Subjects with ≤ Grade 2 neuropathy are an exception to this criterion and
                  may qualify for the study.

               -  Note: If subject received major surgery, they must have recovered adequately from
                  the toxicity and/or complications from the intervention prior to starting
                  therapy.

          7. Has a known additional malignancy that is progressing or requires active treatment.
             Exceptions include basal cell carcinoma of the skin or squamous cell carcinoma of the
             skin that has undergone potentially curative therapy or in situ cervical cancer.

          8. Has known active central nervous system (CNS) metastases and/or carcinomatous
             meningitis. Subjects with previously treated brain metastases may participate provided
             they are stable (without evidence of progression by imaging for at least four weeks
             prior to the first dose of trial treatment and any neurologic symptoms have returned
             to baseline), have no evidence of new or enlarging brain metastases, and are not using
             steroids for at least 7 days prior to trial treatment. This exception does not include
             carcinomatous meningitis which is excluded regardless of clinical stability.

          9. Has 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). Replacement therapy (e.g. thyroxine, insulin, or physiologic corticosteroid
             replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a
             form of systemic treatment.

         10. Has known history of, or any evidence of active, non-infectious pneumonitis.

         11. Has an active infection requiring systemic therapy.

         12. Has a history or current evidence of any condition, therapy, or laboratory abnormality
             that might confound the results of the trial, interfere with the subject's
             participation for the full duration of the trial, or is not in the best interest of
             the subject to participate, in the opinion of the treating investigator.

         13. Has known psychiatric or substance abuse disorders that would interfere with
             cooperation with the requirements of the trial.

         14. Is pregnant or breastfeeding, or expecting to conceive or father children within the
             projected duration of the trial, starting with the pre-screening or screening visit
             through 120 days after the last dose of trial treatment.

         15. Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent (only
             during Dose Expansion Phase Cohort A).

         16. Has a known history of Human Immunodeficiency Virus (HIV) (HIV 1/2 antibodies).

         17. Has known active Hepatitis B (e.g. HBsAg reactive) or Hepatitis C (e.g. HCV RNA
             [qualitative] is detected).

         18. Has received a live vaccine within 30 days of planned start of study therapy.