This is an open-label study to evaluate the safety, tolerability, and pharmacokinetics of DS-1123a in Japanese subjects with advanced solid tumors.

Inclusion Criteria:

• Advanced solid tumor that is refractory to standard treatment, or for which no standard treatment is available.
• Eastern Cooperative Oncology Group performance status (PS) of 0 or 1.

Exclusion Criteria:

• Have any of the following concomitant disease or had the history of having following disease within 6 months before enrollment:

  • Cardiac failure (NYHA ≥ ClassIII), myocardial infarction, cerebral infarction, unstable angina, arrhythmia requiring treatment, coronary-artery/peripheral artery bypass surgery, cerebrovascular disease, pulmonary thromboembolism, deep-vein thrombosis or clinically severe thromboembolic event, or clinically severe pulmonary disease (eg, interstitial pneumonia, pulmonary fibrosis, radiation pneumonia, drug induced pneumonia),

• Severe or uncontrolled concomitant disease.

• Clinically active brain metastases defined as symptomatic or requiring treatment.

De-identified individual participant data (IPD) and applicable supporting clinical trial documents may be available upon request at https://vivli.org/. In cases where clinical trial data and supporting documents are provided pursuant to our company policies and procedures, Daiichi Sankyo will continue to protect the privacy of our clinical trial participants. Details on data sharing criteria and the procedure for requesting access can be found at this web address: https://vivli.org/ourmember/daiichi-sankyo/

Studies for which the medicine and indication have received European Union (EU) and United States (US), and/or Japan (JP) marketing approval on or after 01 January 2014 or by the US or EU or JP Health Authorities when regulatory submissions in all regions are not planned and after the primary study results have been accepted for publication.

Formal request from qualified scientific and medical researchers on IPD and clinical study documents from clinical trials supporting products submitted and licensed in the United States, the European Union and/or Japan from 01 January 2014 and beyond for the purpose of conducting legitimate research. This must be consistent with the principle of safeguarding study participants' privacy and consistent with provision of informed consent.