Key Inclusion Criteria:

          -  Male or female ≥ 18 years of age

          -  Solid tumor cancer with at least one injectable cutaneous, subcutaneous or nodal tumor
             OR at least one injectable liver metastasis that can be visualized and injected under
             radiologic guidance

          -  Have advanced or metastatic solid tumors who are refractory to, ineligible for,
             relapsed from and/or intolerant of standard of care treatment or must have a disease
             for which no standard of care exists

          -  Be fully recovered from major surgery and from the acute toxic effects of prior
             chemotherapy radiotherapy, or immunotherapy

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

          -  Must have adequate hematologic function in accordance with the study protocol

          -  Must have adequate hepatic function in accordance with the study protocol

          -  Must have adequate renal function in accordance with the study protocol

          -  Female subjects of reproductive potential must have a negative serum pregnancy test
             during Screening and a serum or urine pregnancy test must be re-confirmed as negative
             no more than 72 hours before starting study treatment. Females of reproductive
             potential as well as fertile men with partners who are female of reproductive
             potential must agree to abstain from sexual intercourse or to use 2 effective forms of
             contraception (including at least 1 barrier form) from the time of giving informed
             consent, during the study, and for 6 months (both females and males) following the
             last dose of study drug(s)

          -  Life expectancy of ≥ 3 months

        Expansion:

        •Evaluable or measurable disease, according to Response Evaluation Criteria in Solid Tumors
        (RECIST) v1.1 criteria

        Key Exclusion Criteria:

          -  Subjects on current antiviral treatment for herpes virus infections

          -  Requires chronic or intermittent treatment with systemic antivirals

          -  Any systemic anti-cancer treatment (including investigational agents) within 4 weeks
             prior to the first dose of study drug

          -  Has received prior radiotherapy within 2 weeks of start of study treatment

          -  Myelosuppressive chemotherapy within 4 weeks of study treatment

          -  Prior checkpoint inhibitor therapy administered within 4 weeks of study treatment

          -  Is currently participating in or has participated in a study of an investigational
             agent or has used an investigational device within 4 weeks prior to the first dose of
             study treatment.

          -  Has not fully recovered from any effects of major surgery or not free of significant
             detectable infection

          -  Other active malignancy within the previous 3 years of first dose of study treatment

          -  Has known active Central Nervous System (CNS) metastases and/or carcinomatous
             meningitis

          -  Have had significant active cardiac disease within 6 months prior to the start of
             study treatment

          -  Has an active autoimmune disease that has required systemic treatment in past 2 years

          -  Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy

          -  Has received a live vaccine within 30 days prior to the first dose of study drug

          -  Are pregnant or breastfeeding