In this first-in-human, muticenter, non-randomized, open-label, standard 3+3 dose escalation Phase I study encompasses 5 parts (Part 1-5). The purpose of this FIH study is to evaluate the safety and tolerability profile of CBA-1205.

To evaluate safety and efficacy of CBA-1205 in the following five parts in a stepwise manner:

Part 1

• In Part 1, safety and tolerability in patients with Solid Tumor where no standard treatment is available, or who are intolerable or non-responder to the standard treatment will be evaluated. Initial dose for Part 2 will be determined.

Part 2

• In Part 2, safety and tolerability in patients with advanced and/or recurrent Hepatocellular Carcinoma which are unresectable, or who are intolerable or non-responder to the standard treatment will be evaluated. Recommended dose in this population will be determined.

Part 3

• In Part 3, safety and efficacy at the recommended dose in patients with advanced and/or recurrent Hepatocellular Carcinoma which are unresectable, or who are intolerable or non-responder to the standard treatment will be evaluated.

Part 4

• In Part 4, safety and efficacy in patients with Malignant Melanoma who are refractory or intolerant to standard therapy.

Part 5

• In Part 5, safety, tolerability and the recommended dose of the study drug in patients with Pediatric Cancer where no standard treatment is available, or who are intolerable or non-responder to the standard treatment will be evaluated.

PK analysis

Inclusion Criteria:(Part 1-4)

• Patients who provide voluntary written informed consent to participate in the study
• Patients with an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of≤1
• Patients with preserved renal function as evidenced by laboratory data obtained within 7 days before enrollment (creatinine: ≤ ULN ×1.5)
• Patients who meet the following laboratory criteria of bone marrow function as evidenced by laboratory data obtained within 7 days before enrollment: Neutrophil count;≥1500/μL, Platelet count; ≥75000/μL, Hemoglobin;≥9.0 g/dL.
• Patients having Solid Tumors with no standard therapy available or refractory or intolerable to standard therapy (Part2, 3)
• Patients with Child-Pugh A or B (Part2, 3)
• Patients with Malignant Melanoma who are refractory or intolerant to standard therapy (Part 4)

Inclusion Criteria:(Part 5)

• Patients who provide voluntary written informed consent to participate in the study from both the subject (if aged 16 years or older) and their legal representatives
• Japanese patients aged 2 years or older and under 20 years at the time of informed consent
• Patients with a Lansky Performance Status (LPS) of ≥70 (for patients aged 15 years or younger) or a Karnofsky Performance Status (KPS) of ≥70 (for patients aged 16 years or older)
• Patients with preserved renal function as evidenced by laboratory data obtained within 7 days before enrollment (eGFR ≥60 mL/min/1.73 m²)
• Pediatric patients with cancers with no standard therapy available or refractory or intolerable to the standard therapy

Exclusion criteria: (Part1-5)

• Patients who have undergone major surgery within 28 days before enrollment
• Patients who have received anticancer treatment with surgical therapy, radiation therapy, and/or drug therapy within 14 days before enrollment
• Patients who have received anticancer treatment with immune checkpoint inhibitor, etc. within 28 days before enrollment
• Patients with Grade 2 or higher concurrent disease or prior therapy-related toxicity
• Patients who have received any other investigational product within 28 days before enrollment
• Patients with current or previous inadequately controlled or clinically significant cardiac disease
• Patients who, in the opinion of the investigator or subinvestigator, is not appropriate