This is a study to assess the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD) and anti-tumor activity of DS-1001b in patients with gliomas that harbor IDH1-R132 mutations.

Inclusion Criteria:

1. Has histologically confirmed glioma with an IDH1-R132 mutation
2. Has disease that has recurred or progressed following standard treatment including radiotherapy
3. Has measurable lesion(s) as per RANO criteria
4. Has Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2

Exclusion Criteria:

1. Has significant symptoms of increased intracranial pressure
2. Has another active neoplasm
3. Has active infection requiring systemic treatment
4. Has a history of severe cardiac disease
5. Has had prior treatment with any inhibitor targeting mutant IDH1
6. Has had investigational drug treatment within 4 weeks prior to the first dose of study treatment
7. Is a pregnant or lactating female

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.