The primary purpose of the study is to evaluate the safety, tolerability, and efficacy of DS-3939a in combination with other anticancer agents or as a monotherapy in participants with solid tumors.
Sign and date the Main Trial informed consent form (ICF), prior to the start of any trial-specific procedures.
Adults greater than or equal to (≥)18 years of age at the time the Main Trial ICF is signed (follow local regulatory requirements if the legal age of consent for trial participation is >18 years old).
Histologically documented Stage IIIB, IIIC disease who is not candidate for surgical resection or definitive chemoradiation, or Stage IV NSQ NSCLC.
Has a left ventricular ejection fraction (LVEF) ≥50 percent (%) by either an echocardiogram (ECHO) or multigated acquisition scan (MUGA) within 28 days of the first trial intervention.
Prior systemic anticancer therapy targeting MUC1 or TA-MUC1.
Prior systemic anticancer therapy with topoisomerase 1 inhibitor or topoisomerase 1 inhibitor-based antibody-drug conjugate (ADCs) (e.g., datopotamab deruxtexan and Sacituzumab govitecan).
Has spinal cord compression or clinically active central nervous system (CNS) metastases.
Has multiple primary malignancies.
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Treatment groupsSee each treatment group below.