Dose Determining Study of EXS74539 (REC-4539) in Participants With Select Solid Tumors

Inclusion Criteria

• Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.
• Histologically confirmed diagnosis of the following solid tumors:
• SCLC
• High grade neuroendocrine or small cell carcinomas of non-lung origin
• Non-small cell lung cancer [NSCLC]
• Prostate cancer
• Ovarian cancer
• Renal carcinoma [clear and non-clear cell]
• Head and neck squamous cell carcinoma
• Hepatic cancer
• Gastric cancer
• Triple-negative breast cancer [TNBC]
• Participant disease should have progressed, relapsed or the participants should have been intolerant to at least one prior standard systemic therapy for their respective underlying malignancy.
• Measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. Key

Exclusion Criteria

• Any medical or psychiatric condition that, in the opinion of the Investigator, could jeopardize or would compromise the participant's safety or ability to participate in the study.
• Symptomatic brain metastases, leptomeningeal metastases, or spinal cord compression due to disease. Participants with brain metastases must be clinically stable and off corticosteroids and anticonvulsants for ≥1 month prior to study treatment and not require any specific intervention for brain metastases.
• Active and clinically significant infection requiring systemic antibacterial, antiviral, or antifungal therapy <7 days of the first scheduled dose of the study treatment.
• Significant cardiac abnormalities.
• Major surgery within 28 days prior to the start of study treatment. Note: Other protocol-defined inclusion and exclusion criteria may apply.