Inclusion Criteria:

          -  Must be willing and able to participate and comply with all trial requirements and
             able to provide signed and dated informed consent prior to initiation of any trial
             procedures

          -  Male or Female ≥ 18 years of age

          -  Have an Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-1.

          -  Have at least one injectable tumor

          -  Have laboratory values (obtained ≤ 28 days prior to first infusion day) in accordance
             with the study protocol

          -  Women of child-bearing potential (WOCBP) must have a negative urine pregnancy test at
             screening and a negative urine pregnancy test prior to administration of each dose of
             RP1 or nivolumab

          -  WOCBP must agree to use adequate birth control throughout their participation and for
             3 months after RP1 alone and 5 months after nivolumab last study treatment

          -  Males with partners of child-bearing potential must agree to use adequate birth
             control throughout their participation and for 3 months for RP1 alone and 7 months
             after nivolumab last study treatment

        For Subjects in the Combination Treatment

          -  Baseline ECG that does not show abnormalities according to the protocol

          -  Baseline oxygen saturation levels that do not show abnormalities according to the
             protocol

          -  Have provided a former tumor pathology specimen or be willing to supply a new tumor
             sample from a biopsy

        For Subjects in Phase 2 only

          -  Have a predicted life expectancy of ≥ 3 months

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

          -  Subjects with melanoma: has Stage IIIb to IV (skin, eye or mucosal) for whom anti PD-1
             therapy is indicated or who have previously received an anti-PD-1 therapy, or have
             refused, become intolerant to or have no further therapy options available

          -  Subjects with MSI-H tumors: has diagnosis of MSI-H tumor (according to protocol
             definition) for whom anti PD-1 therapy is indicated, or have refused, become
             intolerant to or have no further therapy options available

          -  Subject with dMMR tumors: has diagnosis of dMMR tumor (according to protocol
             definition) for whom anti PD-1 therapy is indicated, or have refused, become
             intolerant to or have no further therapy options available

          -  Subject with NMSC: has diagnosis of locally advanced or metastatic NMSC that are not
             considered treatable by surgery including basal cell carcinoma, cutaneous squamous
             cell carcinoma, basosquamous carcinoma, Merkel cell carcinoma and other non-melanoma
             skin cancers (per protocol) for whom anti PD-1 therapy is indicated, or have refused,
             become intolerant to or have no further therapy options available Subjects with
             bladder cancer: diagnosis of locally advanced or metastatic bladder cancer for whom
             anti PD-1 therapy is indicated, or have refused, become intolerant to or have no
             further therapy options available

        Exclusion Criteria:

          -  Prior treatment with an oncolytic therapy

          -  History of viral infections according to the protocol

          -  Systemic infection requiring IV antibiotics within 14 days prior to dosing

          -  Prior complications with herpes infections

          -  Chronic use of anti-virals

          -  Systemic therapies for cancer within 4 weeks of first dose (some others may be
             accepted with shorter time periods)

          -  Conditions that require certain doses of steroids (some doses and types will be
             permitted)

          -  Known active brain metastases - previously treated brain metastases may be permitted

          -  Prior certain other diagnosis of cancer

          -  Is participating in another clinical study or has participated in the past 4 weeks
             prior to the first dose

        Combination Phase Subjects

          -  Certain autoimmune diseases, some types will be permitted

          -  Allergy or sensitivity to study drug components

          -  History of interstitial lung disease

          -  History of non-infectious pnuemonitis

          -  Other serious or uncontrolled medical disorders