Inclusion Criteria:

          -  Subjects with metastatic or locally advanced, incurable non-small-cell lung cancer
             (NSCLC [adenocarcinoma, adenosquamous, or squamous]), head and neck squamous cell
             carcinoma (HNSCC), urothelial cancer, or malignant melanoma who have exhausted or
             declined available standard therapy.

          -  Subjects progressing on previous treatment with a checkpoint inhibitor targeting
             thePD-1/PD-L1 pathway, alone or in combination with chemotherapy after previously
             having achieved stable disease or better and stayed on such therapy for ≥12 weeks.

          -  Primary or metastatic lesion suitable for biopsy and willingness to undergo repeat
             biopsies as appropriate.

          -  Willing and able to provide intravenous access for the administration of the study
             drug and for blood sampling/testing.

        Exclusion Criteria:

          -  Subjects with NSCLC tumors with genetic alteration or mutation, for which FDA-approved
             targeted therapy is available.

          -  Treatment with systemic anticancer treatments, investigational products, or major
             surgery within 4 weeks before first dose of study drug or 5 half-lives, whichever is
             shorter. Subjects should have recovered from previous treatment toxicity (except hair
             loss and peripheral neuropathy).

          -  History of uncontrolled brain metastasis.

          -  Subject has received extended field radiotherapy ≤4 weeks before the start of
             treatment (≤2 weeks for limited field radiation to alleviate symptoms), and who has
             not recovered from related side effects of such therapy (except for hair loss).

          -  Subjects who have previously experienced an immune-related adverse event (irAE) to
             pembrolizumab, for which permanent discontinuation is required. Subjects without a
             formal contraindication due to previous irAE are not eligible if the AE has not
             resolved or requires steroids (>10 mg prednisone-equivalent per day) for ongoing
             management.

          -  Subjects with active severe infection requiring oral antibiotics.

          -  Clinical evidence of an active second invasive malignancy with the exception of stable
             prostate cancer on watchful waiting.

          -  Uncontrolled or significant cardiovascular disease.

          -  History of autoimmune disease requiring systemic immunosuppressive therapy (daily
             prednisone equivalent doses >10 mg/day).

          -  HIV patients can be enrolled if the infection is adequately controlled.

          -  Known bleeding disorder or coagulopathy. Subjects on stable anticoagulant therapy are
             allowed.

          -  Known or suspected allergy to study treatment or related products.

          -  Women who are pregnant or breastfeeding, or trying to become pregnant.

          -  Patients with chronic viral hepatitis.

        Other protocol-defined inclusion/exclusion criteria may apply.