Study of DS-7300a in Participants With Advanced Solid Malignant Tumors
Study of DS-7300a in Participants With Advanced Solid Malignant Tumors
This study is in one single group of participants with advanced solid tumors who have not
 been cured by other treatments. It is the first time the drug will be used in humans, and
 will be in two parts.

 The primary purpose of the parts are:

 -  Dose Escalation Part: To evaluate the safety and tolerability and to determine the
 maximum tolerated dose and the recommended dose for expansion of DS-7300a.

 -  Dose Expansion Part: To investigate the safety, tolerability and antitumor activity of
 DS-7300a.

 This study is expected to last approximately 3.5 years from the time the first participant is
 enrolled to the time the last participant is off the study.

 The number of treatment cycles is not fixed in this study. Participants who continue to
 benefit from the study treatment may continue, unless:

 -  they withdraw

 -  their disease gets worse

 -  they experience unacceptable side effects.
Inclusion Criteria:

 -  Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0 or 1.

 -  Has at least 1 measurable lesion according to Response Evaluation Criteria in Solid
 Tumors (RECIST) Version 1.1.

 -  Has adequate cardiac, hematopoietic, renal and hepatic functions

 -  Has an adequate treatment washout period prior to start of study treatment

 Additional Inclusion Criteria for Part 1 (Dose Escalation)

 -  Has a pathologically documented advanced/unresectable or metastatic head and neck
 squamous cell carcinoma, esophageal squamous cell carcinoma, squamous and
 adenocarcinoma non-small cell lung cancer (NSCLC), bladder cancer, sarcoma,
 endometrial cancer, melanoma, prostate cancer, breast cancer that is refractory to or
 intolerable with standard treatment, or for which no standard treatment is available.

 Additional Inclusion Criteria for Part 2 (Dose Expansion)

 -  Has a pathologically documented advanced/unresectable or metastatic head and neck
 squamous cell carcinoma, esophageal squamous cell carcinoma, squamous-NSCLC that is
 refractory to or intolerable with standard treatment, or for which no standard
 treatment is available. Additional or alternative indications may be added to
 expansion cohorts based on preliminary signals of activity in dose escalation via a
 protocol amendment.

 Exclusion Criteria:

 -  Has prior treatment with B7-H3 targeted agent.

 -  Has prior treatment with an antibody drug conjugate that consists of an exatecan
 derivative that is a topoisomerase I inhibitor (e.g., trastuzumab deruxtecan).

 -  Has multiple primary malignancies, except adequately resected non-melanoma skin
 cancer, curatively treated in situ disease, or other solid tumors curatively treated,
 with no evidence of disease for ≥3 years.

 -  Has a medical history of myocardial infarction, symptomatic congestive heart failure
 (CHF) (New York Heart Association classes II-IV), unstable angina or serious cardiac
 arrhythmia.

 -  Has an uncontrolled infection requiring systemic therapy.

 -  Has clinically significant pulmonary compromise or requirement for supplemental
 oxygen.

 -  Has substance abuse or any other medical conditions that would increase the safety
 risk to the subject or interfere with participation of the subject or evaluation of
 the clinical study in the opinion of the Investigator.