Study of MK-3475 in Patients With Microsatellite Unstable (MSI) Tumors (Cohorts A, B and C)

Inclusion Criteria:

   - Cohort A only: Patients with microsatellite instability (MSI) positive colorectal
   cancer

   - Cohort B only: Patients with MSI negative colorectal cancer

   - Cohort C only: Patients with MSI positive non-colorectal cancer -

   - Have measurable disease

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

   - Adequate organ function as defined by study-specified laboratory tests

   - Must use acceptable form of birth control through the study and for 28 days after
   final dose of study drug

   - Signed informed consent form

   - Willing and able to comply with study procedures

   - Agree to have a biopsy of participants' cancer

   - Patients with colon cancer must have received at least two prior cancer therapy
   regimens.

   - Patients with other cancer types must have received at least one prior cancer therapy

   - Progressive disease

Exclusion Criteria:

   - Patients with uncontrolled intercurrent illness, including but not limited to ongoing
   or active infection, systematic congestive heart failure, unstable angina pectoris,
   cardiac arrhythmia or psychiatric condition that would limit compliance with study
   requirements.

   - Patients who have had chemotherapy or biological cancer therapy within 2 weeks prior
   to the first dose of study drug

   - Patients who have had radiation within 2 weeks prior to the first dose of study drug

   - Patients who have undergone major surgery within 4 weeks of dosing of investigational
   agent

   - Patients who have received another investigational product or investigational device
   within 4 weeks prior to receiving study drug

   - Patients who have received any of the following concomitant therapy: Interleukin-2
   (IL-2), interferon, or other non-study immunotherapy regimens, immunosuppressive
   agents, other investigational therapies or chronic use of systemic corticosteroids
   within one week prior to first dose of study drug

   - Patients who have received a live vaccine within 4 weeks prior to or after any dose of
   MK-3475 (exception: inactivated flu vaccines)

   - Patients who have received growth factors, including but not limited to
   granulocyte-colony stimulating factor (G-CSF), granulocyte macrophage-colony
   stimulating factor (GM-CSF), erythropoietin, etc. within 2 weeks of study drug
   administration

   - Patient who have had prior treatment with anti-PD-1 (anti-programmed cell death
   protein 1), anti-PD-L1, anti-PD-L2, anti-CD137, anti-OX-40, anti-CD40, or anti-CTLA-4
   antibodies

   - Patients with history of any autoimmune disease:inflammatory bowel disease, (including
   ulcerative colitis and Crohn's Disease), rheumatoid arthritis, systemic progressive
   sclerosis (scleroderma), systemic lupus erythematosus (SLE) autoimmune vasculitis,
   central nervous system (CNS) or motor neuropathy considered to be of autoimmune
   origin.

   - Patients who have known history of infection with HIV, hepatitis B, or hepatitis C

   - Patients with evidence of interstitial lung disease

   - Systemically active steroid use

   - Patients on home oxygen

   - Patients with oxygen saturation of <92% on room air by pulse oximetry

   - Pregnant or lactating

   - Conditions, including alcohol or drug dependence, or intercurrent illness that would
   affect the patient's ability to comply with study visits and procedures

   - Patient with known active central nervous system metastases and/or carcinomatous
   meningitis.

   - Patients with primary brain tumors.

   - Requires any other form of systemic or localized antineoplastic therapy while on study

   - Has any tissue or organ allograft

   - Patients with history of allogeneic hematopoeitic stem cell transplant