Inclusion Criteria:

          -  The patient must have advanced cutaneous melanoma or acral melanoma; no more than 5
             patients with acral melanoma may enroll in this cohort (Cohort 1). Or, the patient
             must have unresectable and/or metastatic mucosal melanoma (Cohort 2).

          -  Patient must have received previous treatment as follows: a) patient has received
             anti-PD-[L]1 therapy ± anti-CTLA-4 therapy, and ≤1 other prior regimen of systemic
             anti-neoplastic therapy; b) patient should have experienced objective response (PR or
             CR) or SD as BOR to anti-PD-[L]1 therapy; c) patients with BRAF mutations may or may
             not have received prior targeted therapy.

          -  Patients must have disease that is measurable based on RECIST 1.1., that has not
             recently been irradiated or used to collect a biopsy.

          -  Patient is willing to undergo a pretreatment tumor biopsy or provide qualifying
             archival tumor tissue.

          -  Patient has an Eastern Cooperative Oncology Group (ECOG) status of 0 or 1 and an
             estimated life expectancy of ≥3 months.

          -  Additional criteria may apply.

        Exclusion Criteria:

          -  Patient has uveal melanoma.

          -  Patient has received prior IL-2-based or IL-15-based cytokine therapy.

          -  Patient requires systemic corticosteroids (>10 mg of prednisone daily, or equivalent)
             however, replacement doses, topical, ophthalmologic, and inhalational steroids are
             permitted.

          -  Patient has undergone prior solid organ and/or non-autologous hematopoietic stem cell
             or bone marrow transplant.

          -  Patient is currently pregnant, breastfeeding, or is planning to become pregnant or to
             begin breastfeeding during the study period or within 30 days after last study drug
             administration.

          -  Patients with active or symptomatic central nervous system metastases unless the
             metastases have been treated by surgery and/or radiation therapy and/or gamma knife,
             the subject has been tapered to a dose of 10 mg of prednisone (or equivalent) or less
             of corticosteroids for at least 2 weeks before the first dose, and the subject is
             neurologically stable. Patients with leptomeningeal disease are excluded.

          -  Patient has known or suspected hypersensitivity to any components of nemvaleukin.

          -  Patients with an uncontrollable bleeding disorder.

          -  Patient has QT interval corrected by the Fridericia Correction Formula values of >470
             msec (in females) or >450 msec (in males); patient who is known to have congenital
             prolonged QT syndromes; or patient who is on medications known to cause prolonged QT
             interval on ECG.

          -  Patient has developed Grade ≥3 immune-related AEs (irAEs) while on prior
             immunotherapy, (eg, pneumonitis, nephritis, and neuropathy).

          -  Additional criteria may apply.