Inclusion Criteria:

          -  Histologically confirmed diagnosis of one of the following: unresectable advanced or
             metastatic HCC (including fibrolamellar HCC) not amenable to a curative treatment
             approach, unresectable advanced or metastatic intrahepatic or perihilar (Klatskin) BTC
             not amenable to a curative treatment approach, extrahepatic BTC or gallbladder cancer
             infiltrating the liver or metastasized into the liver with predominant liver disease,
             not amenable to a curative treatment approach, metastasized colorectal cancer (CRC),
             pancreatic ductal adenocarcinoma (PDAC), Gastric cancer (GC), renal cell carcinoma
             (RCC), triple negative breast cancer (TNBC), cutaneous melanoma, or ocular melanoma
             with predominant liver disease not amenable to a curative treatment approach.
             Participants with other solid tumors with predominant liver disease not amenable to a
             curative treatment approach might be enrolled after Sponsor approval

          -  Measurable disease with at least one measurable locally untreated liver lesion, as
             defined by RECIST v1.1

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

          -  Adequate hematologic and major organ functions

          -  Participants for which there is no available standard therapy likely to confer
             clinical benefit, or participants who are not candidates for such available therapy

          -  Life expectancy of ≥12 weeks, approximated with Royal Marsden Hospital score 0-1 or
             Gustave Roussy Immune (GRIm) score 0-1. Participants with a Royal Marsden Hospital or
             GRIm score of ≥2 and a life expectancy of ≥12 weeks according to the investigator's
             clinical judgement may be enrolled after Medical Monitor approval has been obtained.

          -  For participants with HCC: Child-Pugh score of A6 or better

        Exclusion Criteria:

          -  History or clinical evidence of central nervous system (CNS) primary tumors or
             metastases including leptomeningeal metastases, unless they have been previously
             treated, are asymptomatic, and have had no requirement for steroids or enzyme-inducing
             anticonvulsants in the last 14 days prior to Screening

          -  Evidence of any extra-hepatic primary tumor or metastasis requiring prompt medical
             intervention

          -  Receipt of prior therapy with a TLR7/8/9 agonist and/or IFN-alpha

          -  Prior chemotherapy, antibody, or other registered or experimental cancer treatment
             within 3 weeks of study Cycle 1 Day 1. Specifically, no CPI antibody is allowed to be
             administered within 6 weeks of study Cycle 1 Day 1

          -  Receipt of investigational agent for any other indication within 3 weeks of dosing

          -  Treatment with systemic immunosuppressive medication (including, but not limited to,
             corticosteroids, cyclophosphamide, azathioprine, methotrexate, thalidomide, and
             anti-TNF-alpha agents) within 2 weeks prior to initiation of study treatment, or
             anticipation of need for systemic immunosuppressive medication during study treatment

          -  Local therapy to liver (e.g. radiofrequency ablation, percutaneuous ethanol or acetic
             acid injection, cryoablation, high-intensity focused ultrasound, transarterial
             chemoembolization, and transarterial embolization) within 3 weeks prior to initiation
             of study treatment, radioembolization within 3 months prior to initiation of study
             treatment, or non-recovery from side effects of such procedure

          -  Treatment-related toxicities from prior cancer therapy that have not resolved to </=
             Grade 1 CTC AE prior to study treatment with the exception of the following Grade 2
             toxicities:

        alopecia, peripheral neuropathy, any laboratory changes that still lie within the inclusion
        criteria defined above

          -  History of other malignancy within 2 years; exception for ductal carcinoma in situ not
             requiring chemotherapy, low grade cervical intraepithelial neoplasia (CIN),
             nonmelanoma skin cancer, low grade localized prostate cancer (Gleason score < Grade
             7), or optimally treated Stage 1 uterine cancer.

          -  Active or history of immunologic-mediated disease, including but not limited to
             myasthenia gravis, myositis, autoimmune hepatitis, systemic lupus erythematosus,
             rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, antiphospholipid
             antibody syndrome, Wegener granulomatosis, Sjogren's syndrome or Guillain-Barré
             syndrome

          -  Known active or uncontrolled bacterial, viral, fungal, mycobacterial, parasitic, or
             other infection.

          -  Ascites, pleural effusion, or pericardial effusion requiring medical intervention
             within 12 months prior to study entry.

          -  History of human immunodeficiency virus (HIV) infection

          -  Active hepatitis B virus (HBV) infection

          -  Coinfection of HBV and hepatitis C virus (HCV).