Updated INDIGO Results and Clinical Insights

Six months after initial data cleaning, the 20-month follow-up provided more robust PFS estimates. The updated analysis could not estimate median PFS for the vorasidenib arm, suggesting substantially longer disease control than initially projected.

A significant secondary finding emerged regarding seizure control. Despite enrolling patients with controlled seizures, approximately one-third experienced breakthrough seizures during the study period. The vorasidenib arm demonstrated statistically significant seizure reduction compared to placebo, with the effect predominantly driven by oligodendroglioma patients who have higher baseline seizure rates.

The seizure control benefit likely results from either direct anti-epileptogenic effects of 2-hydroxyglutarate reduction or indirect effects through decreased tumor burden, similar to radiation therapy's seizure control mechanisms in IDH-mutant gliomas.

Neurocognitive function and quality of life assessments remained stable throughout treatment in both arms, suggesting that watchful waiting doesn't harm function and that vorasidenib treatment doesn't impair cognitive performance.

Response rates remained modest at 10% to 11% during the first 20 months, consistent with expectations for gradual tumor changes rather than dramatic shrinkage. The benefit appeared to be sustained disease stabilization rather than rapid tumor regression.

Updated data presented at ASCO 2026 now shows estimated PFS reaching 44 months with continued censoring between 34 to 46 months, suggesting the benefit could extend even further. Only 28% of vorasidenib-treated patients have required subsequent radiation or chemotherapy, indicating durable disease control for the majority.