Inclusion Criteria:

          -  For Phase I the subject has histological or cytological evidence of a solid tumor. For
             Phase II the subject must have 1 of the specified adult solid tumor types defined in
             the protocol

          -  Subject must have at least one target lesion based on RECIST

          -  Subject has an Eastern Cooperative Oncology Group Performance Status (ECOG PS) score
             of 0 or 1

          -  Subjects must have adequate liver function

          -  Subjects must have adequate kidney function

          -  Subjects must be recovered from the effects of any prior chemotherapy, immunotherapy,
             other prior systemic anticancer therapy, radiotherapy or surgery

          -  Subjects who have received radiation therapy must wait at least 4 weeks after their
             last radiation treatment before enrollment into the study

          -  Females of childbearing potential must have a negative pregnancy test within 7 days of
             the start of treatment and on Day 1 before the first dose is administered

          -  Subject will agree to follow contraceptive requirements defined in the protocol

          -  Additional criteria may apply

        Exclusion Criteria:

          -  Subject is currently pregnant, planning to become pregnant, or breastfeeding

          -  Subjects with an active infection or with a fever ≥ 38.5°C within 3 days of the first
             scheduled day of dosing for Cycle 1

          -  Subjects with active or symptomatic central nervous system metastases are excluded.
             Subjects with central nervous system metastases are eligible for the study if the
             metastases have been treated by surgery and/or radiation therapy, the subject is off
             corticosteroids for at least 2 weeks, and the subject is neurologically stable

          -  Subjects with known hypersensitivity to any components of ALKS 4230 or to
             pembrolizumab or any of its excipients

          -  Subjects who require pharmacologic doses of systemic corticosteroids are excluded;
             replacement doses, topical, ophthalmologic, and inhalational steroids are permitted

          -  Subjects who developed autoimmune disorders while on prior immunotherapy, including
             pneumonitis, nephritis, and/or neuropathy

          -  Subjects with any other concurrent uncontrolled illness, including mental illness or
             substance abuse, which may interfere with the ability of the subjects to cooperate and
             participate in the study

          -  The subject is known to be positive for human immunodeficiency virus (HIV), hepatitis
             B or C, or active tuberculosis, or has a known history of tuberculosis

          -  Additional criteria may apply