A Randomized, Phase 2/3 Study to Investigate the Efficacy and Safety of RP2 in Combination With Nivolumab in Immune Checkpoint Inhibitor-Naïve Adult Patients With Metastatic Uveal Melanoma

Key Inclusion Criteria: * Patients who are 18 years of age or older at the time of signed informed consent. * Patients with confirmed diagnosis of metastatic Uveal melanoma not amenable to surgical resection. * Has at least 1 measurable and injectable tumor of ≥ 1 cm in longest diameter (≥ 1.5 cm in the shortest axis for a lymph node \[LN\]) that is amenable to serial RP2 injections. * Must be willing to provide tumor biopsy samples. * LDH ≤ 2 × upper limit of normal (ULN). * Has adequate hematologic, hepatic and renal function * Prothrombin time (PT) ≤ 1.5 × ULN (or international normalization ratio \[INR\] ≤ 1.3) and partial thromboplastin time (PTT) or activated partial thromboplastin time (aPTT) ≤ 1.5 × ULN. * Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0 or 1. * Life expectancy of \> 6 months as estimated by the Investigator. Key Exclusion Criteria: * Any exposure to immune checkpoint inhibitor (ICIs) since the time of first being diagnosed with uveal melanoma. * Known acute or chronic Hepatitis B or C infection or human immunodeficiency virus (HIV) infection or any other uncontrolled infection. * Current active significant herpetic infections or prior complications of HSV-1 infection. * Any central nervous system (CNS) involvement of melanoma, including carcinomatous meningitis. * Major surgery ≤ 2 weeks prior to the first dose of study intervention. * Any bleeding, thrombotic and/or other event that places the patient at an unacceptable risk of complications of intratumoral therapy. * Active, known, or suspected autoimmune disease requiring systemic treatment. * Prior treatment with an oncolytic virus. * Requires intermittent or chronic use of systemic (oral or IV) antivirals with known antiherpetic activity (eg, acyclovir). * Systemic anticancer therapy or prior radiotherapy within 2 weeks of the first dose. * Has received Investigation agent within 4 weeks or 5 half-lives (whichever longer) prior to the first dose. * Conditions requiring treatment with immunosuppressive doses (\> 10 mg per day of prednisone or equivalent) of systemic corticosteroids other than for corticosteroid replacement therapy within 14 days after enrollment. Additional inclusion/ exclusion criteria are outlined in the study protocol