• Provision of informed consent prior to any study specific procedures.

• Must be ≥ 18 years.

• Body weight \> 30 kg.

• For Cohort A: Patients must have histologically or cytologically confirmed diffuse astrocytic and oligodendroglial tumors by World Health Organization 2016 classification which are IDH mutant. They must have not received more than 2 regimens of systemic therapy after initial relapse.

• For Cohort B: Patients must have histologically or cytologically confirmed adenocarcinoma of the biliary tract which are IDH mutant. They must have not received more than 2 regimens of systemic therapy for advanced disease.

• Patients must have normal organ and bone marrow function measured within 28 days prior to administration of study treatment

• Eastern Cooperative Oncology Group (ECOG) performance status 0-1.

• Patients must have a life expectancy ≥ 16 weeks.

• All participants must agree to use methods to prevent pregnancy as agreed upon between the participant and the study doctor from the signing of the informed consent form and continue throughout the period of taking study treatments and for 3 months after the last doses of study drugs.

• Patients are willing and able to comply with the protocol for the duration of the study including undergoing treatment and scheduled visits and examinations.

• Patients in Cohorts A and B must have measurable disease

• Patients with glioma or central nervous system (CNS) metastases must be asymptomatic and at least 28 days after the most recent CNS treatment and is clinically stable, and at least 14 days on stable doses of corticosteroids and/or anti-seizure medications.