Key Inclusion Criteria:

          -  Histologically confirmed diagnosis of a locally advanced (not amenable to curative
             therapy such as surgical resection) metastatic cancer of the following histologies:
             melanoma (MEL), Merkel cell carcinoma (MCC), triple-negative breast cancer (TNBC),
             renal cell carcinoma (RCC), colorectal cancer, head and neck squamous cell carcinoma
             (HNSCC), or sarcoma.

          -  Life expectancy > 12 weeks as determined by the Investigator.

          -  Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1.

          -  Measurable disease per RECIST 1.1.

          -  Patients enrolled in Cohorts 1-10, Cohort A, Cohort B and Phase 2 Doublet must be
             refractory to all therapies known to confer clinical benefit to their disease.

          -  Fresh tumor tissue available for cellular characterization and programmed cell death
             protein 1 (PD-L1) status.

          -  Injected lesions (up to two) must be between 20 mm and 90 mm in diameter for IT
             injection; lesions must be accessible for baseline and on-treatment biopsies. Any
             liver lesion targeted for injection must not exceed 50 mm at the time of injection.

          -  Demonstrated adequate organ function within 14 days of Cycle 1 Day 1 (C1D1).

        Key Exclusion Criteria:

          -  Use of an investigational agent or an investigational device within 21 days before
             administration of first dose of study drug(s).

          -  Patients treated with prior interleukin-2 (IL-2).

          -  Patients who have been previously treated with a toll-like receptor (TLR) agonist
             (excluding topical agents) and patients who have received experimental cancer
             vaccines.

          -  Patients who have received systemic interferon (IFN)α within the previous 6 months
             prior to enrollment to the study.

          -  Other active malignancy, except non-melanomic skin cancer

          -  Evidence of clinically significant interstitial lung disease or active, noninfectious
             pneumonitis.

          -  Prior surgery or radiotherapy within 14 days of initiating study drug(s). Patients
             must have recovered from all radiation-related toxicities, not required
             corticosteroids and have not had radiation pneumonitis.

          -  Prolonged Fridericia's corrected QT interval (QTcF) > 450 ms for men and > 470 ms for
             women at Screening.

        History of unstable or deteriorating cardiac disease within the previous 6 months prior to
        screening including but not limited to the following:

          -  Unstable angina or myocardial infarction.

          -  Congestive heart failure (NYHA Class III or IV).

          -  Uncontrolled clinically significant arrhythmias.

          -  Patients with a history of any retinal disorders (e.g., retinal detachment, diabetic
             retinopathy, retinal hemorrhage, macular degeneration).

          -  Uveal melanoma will be excluded

          -  Patients with tumor that invade the superior vena cava or other major blood vessels.

        Additional general and tumor specific inclusion and exclusion criteria will apply.