Inclusion Criteria (Parts B & C):

          -  18 years or older

          -  Histologically confirmed unresectable Stage III or Stage IV malignant melanoma, or
             other solid tumor malignancies

          -  Failed to respond to or relapsed following standard treatment, declined or was not
             eligible for standard treatment.

          -  Expected survival of at least 12 weeks.

          -  Eastern Cooperative Oncology Group performance status score of 0 or 1 is required.

          -  Evidence of adequate organ function by standard laboratory tests.

        Exclusion Criteria (Parts B & C):

          -  Evidence of progression of central nervous system (CNS) metastases or symptomatic CNS
             metastases within 35 days prior to dosing.

          -  Ocular melanoma which has not metastasized or presence of a non-solid tumor.

          -  A history of any major surgery within 4 weeks prior to dosing.

          -  Any history of antitumor therapy completed within 28 days prior to dosing.

          -  Subjects with active autoimmune disease or history of known or suspected autoimmune
             disease, with the exception of subjects with isolated vitiligo, resolved childhood
             asthma/atopy, psoriasis not requiring systemic treatment and controlled thyroid
             disorders.

          -  Clinically significant heart disease, defined as NYHA Class III or IV.

          -  Any significant systemic infection requiring IV antibiotics.

          -  Known to be human immunodeficiency virus (HIV) positive, have hepatitis B surface
             antigen (HBsAg), or hepatitis C antibodies (HCAb) unless HCV RNA undetected/negative.

          -  Treatment with any other anti-human GITR monoclonal antibody (mAb) or immunomodulatory
             therapy 42 days prior to dosing (30 days for Interleukin-2 & Interferon-α, 7 days for
             Topical Imiquimod).

          -  Adverse events from prior anti-cancer therapy that have not resolved to grade ≤1
             except for alopecia, vitiligo, or endocrinopathy managed with replacement therapy.

          -  Use of any investigational drugs within 30 days prior to dosing.

          -  Any condition that requires or is likely to require treatment with pharmacologic doses
             of systemic corticosteroids. Subjects are permitted to receive physiologic replacement
             of corticosteroid therapy (≤ 10 mg prednisone daily).