First-in-human Study of DS-1062a for Advanced Solid Tumors

The dosage strength will change during the study but all participants will receive the same
study drug. So the study is not a true 2-arm study, it is a 2-part study.

In both parts, subjects with pathologically documented unresectable advanced NSCLC who have
been refractory to or relapsed from standard treatment or for which no standard treatment is
available, will be enrolled. Additional solid tumors might be evaluated, if the study
treatment demonstrates acceptable safety, tolerability and efficacy in NSCLC patients. After
the primary analysis, the main (registered) study will be considered complete, but data will
be collected from participants who continue receiving study drug.

Inclusion Criteria:

- Has a pathologically documented unresectable advanced NSCLC disease not amenable to
curative therapy

- Has relapsed from or is refractory to standard treatment or for which no standard
treatment is available

- Consents to provide tumor tissue sample for the measurement of recent TROP2 levels by
immunohistochemistry, which means archived sample following last treatment or
pre-DS1062a treatment biopsy (there is no minimum TROP2 expression level required for
inclusion)

- Is aged ≥20 years old in Japan or ≥18 years old in other countries

- Has an Eastern Cooperative Oncology Group performance status 0-1

- Has a left ventricular ejection fraction (LVEF) ≥50% by either an ECHO or MUGA within
28 days before registration

- Has measurable disease based on RECIST version1.1

- Has adequate organ function within 7 days before enrollment

- Has an adequate treatment washout period prior to enrollment

- If of reproductive potential, agrees to use a highly effective from of contraception
or avoid intercourse during and upon completion of the study and for at least 4 months
after the last dose of study drug, and agrees not to retrieve, freeze or donate sperm
or ova starting at Screening and throughout the study period, and at least 4 months
after the final study drug administration

- After being fully informed about their illness and the investigative nature of the
protocol (including foreseeable risks and possible toxicities), is willing and able
comply with the protocol and to provide written, ethics committee-approved informed
consent form before performance of any study-specific procedures or examinations

- Has a life expectancy of ≥3 months

- If the study Sponsor decides to evaluate additional solid tumors, subjects must
satisfy following criteria to be included in the study: Has a pathologically
documented advanced solid tumor.

Exclusion Criteria:

- 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 history of myocardial infarction or unstable angina within 6 months before
enrollment

- Has a medical history of symptomatic congestive heart failure (New York Heart
Association classes II-IV) or a serious cardiac arrhythmia requiring treatment Has a
corrected QT by Fridericia's formula (QTcF), of >470 ms based on a triplicate 12-lead
ECG

- Has clinically significant lung disease or is suspected to have such diseases by
imaging at Screening

- Has clinically significant corneal disease

- Has an uncontrolled infection requiring IV antibiotics, antivirals, or antifungals

- Has active human immunodeficiency virus infection that is uncontrolled (increasing
plasma HIV RNA viral load) with medication, or has an active hepatitis B or C
infection

- Has clinically active brain metastases, defined as untreated and symptomatic, or
requiring therapy with steroids or anticonvulsants to control associated symptoms
(participants with treated brain metastases that are no longer symptomatic and who
require no treatment with steroids may be included in the study if they have recovered
from the acute toxic effect of radiotherapy)

- Is lactating or pregnant as confirmed by pregnancy tests performed within 7 days
before enrollment

- Has unresolved toxicities from previous anticancer therapy

- Has a concomitant medical condition that would increase the risk of toxicity, in the
opinion of the Investigator

- Has known hypersensitivity to either the drug substances or inactive ingredients in
the drug product

- 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