Testing Addition of an Anti-cancer Drug, Vorasidenib to Temozolomide, After Radiation for Advanced Brain Cancer

The primary and secondary objectives of the study: PRIMARY OBJECTIVE: I. To determine if vorasidenib citrate (vorasidenib) and adjuvant temozolomide following radiation therapy improves progression-free survival (PFS) per blinded independent review in patients with newly-diagnosed IDH-mutant astrocytoma (World Health Organization \[WHO\] grade 3) compared to placebo given with adjuvant temozolomide following radiation therapy. SECONDARY OBJECTIVES: I. To evaluate the safety and tolerability of vorasidenib versus (vs.) placebo in combination with temozolomide, following radiation therapy. II. To evaluate PFS associated with vorasidenib vs. placebo in combination with temozolomide following radiation therapy, defined by local institutional review. III. To evaluate the efficacy of vorasidenib vs. placebo in combination with adjuvant temozolomide, following radiation therapy, based on overall survival (OS). IV. To evaluate the efficacy of vorasidenib vs. placebo in combination with temozolomide, following radiation therapy, based on objective response rate (ORR), complete response (CR) + partial response (PR), time to response, time to CR+PR, duration of response, and duration of CR+PR, with response assessed per the blinded independent review using the Response Assessment in Neuro-Oncology (RANO) 2.0 criteria in patients with measurable tumor at baseline. V. To evaluate the efficacy of vorasidenib vs. placebo in combination with temozolomide, following radiation therapy, based on ORR, CR+PR, time to response, time to CR+PR, duration of response, and duration of CR+PR, with response assessed per local institutional review or investigator using the RANO 2.0 criteria. VI. To evaluate the efficacy of vorasidenib vs. placebo in combination with temozolomide, following radiation therapy, based on time to next intervention. VII. To evaluate vorasidenib vs. placebo in combination with temozolomide, following radiation, with respect to health-related quality of life (HRQoL) as assessed by the Functional Assessment of Cancer Therapy-Brain (FACT-Br) and symptom burden as assessed by the MD Anderson Symptom Inventory-Brain Tumor (MDASI-BT). EXPLORATORY OBJECTIVES: I. To correlate tumor genotype with PFS. II. To evaluate the effect of the addition of vorasidenib to adjuvant temozolomide on seizure control. OUTLINE: Patients are randomized 1:1 to 1 of 2 arms. ARM I (CONTROL): Patients receive intensity-modulated radiation therapy (IMRT)/volume modulated arc therapy (VMAT) or pencil beam scanning (PBS) or intensity-modulated proton therapy (IMPT) once daily (QD) on Monday-Friday for 33 fractions. Starting 4 weeks after radiotherapy, patients receive temozolomide orally (PO) QD on days 1-5 and placebo PO QD on days 1-28 of each cycle. Cycles of combination treatment repeat every 28 days for up to 12 months and placebo alone repeats every 28 days in the absence of disease progression or unacceptable toxicity. Additionally, patients undergo blood sample collection and magnetic resonance imaging (MRI) throughout the study. ARM II (EXPERIMENTAL): Patients receive IMRT/VMAT or PBS or IMPT QD on Monday-Friday for 33 fractions. Starting 4 weeks after radiotherapy, patients receive temozolomide PO QD on days 1-5 and vorasidenib PO QD on days 1-28 of each cycle. Cycles of combination treatment repeat every 28 days for up to 12 months and vorasidenib alone repeats every 28 days in the absence of disease progression or unacceptable toxicity. Additionally, patients undergo blood sample collection and MRI throughout the study. After completion of study treatment, patients are followed up every 3 months for the first 2 years, every 4 months for the next 2 years, and then every 6 months for up to 10 years.