Study of RP2 Monotherapy and RP2 in Combination With Nivolumab in Patients With Solid Tumors

Inclusion Criteria: * 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 * Patients with advanced or metastatic non-neurological solid tumors, who have progressed on standard therapy or cannot tolerate standard therapy, or for which there is no standard therapy preferred to enrolment in a clinical trial * Consent to provide archival tumour biopsy samples within 6 months, or a fresh tumour biopsy is needed. Patients must also consent to provide on-treatment biopsies as per protocol * At least one measurable and injectable tumor of ≥ 1 cm in longest diameter (or shorter diameter for lymph nodes). * 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 RP2 or nivolumab * WOCBP must agree to use adequate birth control throughout their participation and for 3 months after RP2 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 RP2 alone and 7 months after nivolumab last study treatment * Have laboratory values (obtained ≤ 28 days prior to first infusion day) in accordance with the study protocol * Have an Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-1 Cohort 2a only: * Baseline ECG that does not show abnormalities according to the protocol * Baseline troponin \< 0.06 ng/mL * Baseline oxygen saturation levels that do not show abnormalities according to the protocol Cohort 2b and Part 3 only: * Patients in Cohort 2b should have histologically or cytologically confirmed diagnosis of advanced or metastatic uveal melanoma, lung cancer, breast cancer, or gastrointestinal cancers (including but not limited to colorectal cancer \[CRC\] \[microsatellite stable\], gastric cancer, gastroesophageal junction cancer, and oesophageal cancer) (n=30) * Patients with HCC and a diagnosis of hepatitis B must be off antiviral therapy for at least 4 weeks prior to enrollment. * Patients with acute or chronic hepatitis B or C must be expected to not require antiviral therapy during the RP2 treatment period. * Patients with HCC who have evidence of acute or chronic hepatitis C infection must have completed treatment for hepatitis C at least 1 month prior to study enrollment * Patients in Part 3 should have solid tumours (excluding skin cancers) that the investigator deems suitable for RP2 monotherapy, including at least 10 patients with liver metastases from prevalent tumour types (e.g. lung, breast \[including recurrent chest wall\], and gastrointestinal cancers \[colorectal, gastric, and oesophageal cancers\]) (n=15) * Patient has progressed during or after one to three prior systemic anticancer therapies for advanced or metastatic disease or during or within six months of receiving adjuvant therapy. Patients who, in the opinion of the investigator, are deemed not appropriate candidates for standard-of-care systemic anticancer therapy for advanced or metastatic disease, or who, after documented consultation with their treating physician, refuse standard-of-care systemic anticancer therapy may be eligible after discussion with the medical monitor Exclusion Criteria: * Prior treatment with an oncolytic virus 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 five half-lives or 4 weeks of first dose; whichever is shorter * 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 * Major surgery ≤ 2 weeks prior to starting study drug * Prior malignancy active with the previous 3 years; except for locally curable cancers that have apparently been cured * Female who has a positive urine pregnancy test or is breast-feeding or planning to become pregnant during study treatment and 90 days for RP2 alone or 5 months for RP2 and nivolumab after the last dose of treatment * Participation in another clinical study within 4 weeks prior to the first dose * History of myocarditis or congestive heart failure (as defined by the New York Heart Association Functional Classification III or IV), or unstable angina, serious uncontrolled cardiac arrhythmia, uncontrolled infection, or myocardial infarction within 6 months of randomization * History of allergy or sensitivity to study drug components * Has known psychiatric or substance abuse disorders that would interfere with cooperating with the requirements of the study Part 2 patients only: * Participants with history of life-threatening toxicity related to prior immune therapy except those that are likely to re-occur with standard countermeasures * Treatment with botanical preparations within 2 weeks prior to treatment * Certain autoimmune diseases, some types will be permitted * History of interstitial lung disease * Severe hypersensitivity to another monoclonal antibody * Has received radiotherapy within 2 weeks of start of study treatment * Has received a live vaccine within 28 days prior to first dose of study drug * History of non-infectious pneumonitis * History or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the study * Other serious or uncontrolled medical disorders Cohort 2b and Part 3 (only for the subset of patients with liver metastases suitable and intended for injection) * Presence of liver metastases that are estimated to invade more than one-third of the liver * Macroscopic intravascular invasion into the main portal vein, hepatic vein or vena cava * Significant bleeding event within the last 12 months that places the patient at risk for intrahepatic intratumoral injection procedure based on investigator assessment * Prior chemoembolization, radioembolization, or other locoregional liver-directed procedures to the lesion selected for intratumoral injection