Vorasidenib Maintenance for IDH Mutant Astrocytoma

Diffuse gliomas are the most common primary brain tumors in adults and are associated with high morbidity and mortality. Approximately 25% of diffuse gliomas harbour mutations in the isocitrate dehydrogenase (IDH) 1 or 2 genes. Among IDH-mutated gliomas, IDH-mutant astrocytoma is the most common diagnosis and occurs mainly in adults in their thirties or forties. Most cases correspond to CNS5 WHO grade 2 and 3, while grade 4 tumors are rare. The prognosis of grade 2 and 3 tumors is significantly better (median overall survival times up to 10 years) than that of grade 4 tumors (median overall survival times around 3-7 years).

According to international guidelines and based on randomized clinical trials, treatment options for IDH-mutated astrocytoma after maximum safe neurosurgical resection include active surveillance or radiotherapy followed by chemotherapy with procarbazine, lomustine and vincristine (PCV) or temozolomide. An active surveillance strategy, however, can be recommended for patients with oligodendroglioma grade 2 or astrocytoma grade 2 with particularly favourable prognostic factors, such as absence of neurological deficits and limited tumor burden. Despite this multimodal treatment, IDH-mutant astrocytomas recur and ultimately lead to patient death, with median progression-free survival times around 7 years and overall survival times of approximately 9-11 years. Novel treatment strategies are needed to extend the survival of these patients.

Recently, the international randomized placebo-controlled phase III INDIGO trial has shown considerable efficacy on progression free survival of the mutant IDH inhibitor vorasidenib in patients with IDH-mutant diffuse grade 2 gliomas that were considered candidates for an active surveillance strategy by the treating physician. Vorasidenib (AG881) is an orally available brain-penetrant dual inhibitor of mutant IDH1 and IDH2 proteins. INDIGO enrolled patients with residual or recurrent non-enhancing grade 2 IDH-mutant glioma who had not received prior radiotherapy or chemotherapy. Participants received either vorasidenib (40 mg once daily) or a matched placebo, given continuously in 28-day cycles. From January 2020 through February 2022, a total of 331 participants were randomly assigned to receive vorasidenib (168 participants) or placebo (163 participants ). The image-based progression-free survival was significantly longer for participants in the vorasidenib group than in the placebo group: 27.7 months (95% CI, 17.0 to non-estimable) vs 11.1 months (95% CI, 11.0-13.7), with a hazard-ratio for disease progression or death of 0.39 (95% CI, 0.27-0.56, p<0.001). Additionally, time to next intervention was significantly delayed in the vorasidenib group as compared to the placebo group with a hazard ratio of 0.26 (95% CI, 0.15-0.43, p<0.001). Adverse events leading to treatment interruption occurred in 3.6% of the vorasidenib group and 1.2% of the placebo group. An increased alanine amino transferase level of grade 3 or higher occurred in 9.6% of participants receiving vorasidenib and in none of the participants receiving placebo. Overall, based on the INDIGO trial data, registrational approval by the FDA was granted in August 2024 and EMA approval is expected. Vorasidenib is likely to enter routine clinical practice for patients with IDH-mutant gliomas that do not require immediate chemoradiotherapy.

In the current trial, the investigator will evaluate whether adding vorasidenib as maintenance therapy after completion of standard chemoradiotherapy in patients with astrocytoma, IDH-mutant, CNS5 WHO Grade 2 or 3 prolongs progression-free survival compared to placebo. This trial will also explore the effect of vorasidenib maintenance treatment on overall survival, response rate, time to next intervention, toxicity, health-related quality of life, neurological symptoms, and neurocognitive function. Additionally, this trial will enable translational research through the analysis of tissue samples, liquid biopsies (blood samples), and neuroimaging data.

Overall, VIGOR aims to establish a new standard of care for IDH-mutated, CNS5 WHO Grade 2 or 3 astrocytoma by incorporating maintenance targeted therapy with vorasidenib into the current standard of care chemoradiotherapy.