Vorasidenib in IDH1-mutant or IDH2-mutant low-grade glioma (INDIGO): secondary and exploratory endpoints from a randomised, double-blind, placebo-controlled, phase 3 trial.
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BACKGROUND: In a phase 3 trial, vorasidenib, an oral brain-penetrant inhibitor of mutant isocitrate dehydrogenase 1 and 2 (IDH1/2), resulted in improved progression-free survival (primary endpoint) and time to next intervention (key secondary endpoint) at second interim analysis, resulting in study unblinding. We report 6 months of additional double-blind data, from second interim analysis (Sept 6, 2022) to unblinding (March 7, 2023), and the effect of vorasidenib on volumetric tumour growth rate, health-related quality of life (HRQOL), neurocognitive function, and seizure control. METHODS: INDIGO was a randomised, double-blind, placebo-controlled, phase 3 trial done in 92 hospitals in Canada, France, Germany, Israel, Italy, Japan, the Netherlands, Spain, Switzerland, the UK, and the USA. Patients aged 12 years or older with residual or recurrent grade 2 IDH1/2-mutant diffuse glioma, a Karnofsky performance-status score of 80 or higher, at least one previous surgery, and no other previous anticancer treatment were eligible. Patients were randomly assigned (1:1; stratified according to locally determined chromosome 1p/19q codeletion status and baseline tumour size) to oral vorasidenib (40 mg) or placebo once a day in continuous 28-day cycles until disease progression or unacceptable toxicity. Progression-free survival per masked independent review committee was the primary endpoint, and time to next intervention was the key secondary endpoint. Prespecified secondary endpoints included tumour growth rate (6-monthly change in tumour volume) and HRQOL (Functional Assessment of Cancer Therapy-Brain [FACT-Br]). Prespecified exploratory endpoints included neurocognitive function (cognitive performance instruments) and seizure activity (self-reported). The full analysis set was used for all efficacy analyses and included all randomly assigned patients, and the safety analysis set was used for all safety analyses and included all patients who received one or more doses of vorasidenib or placebo. The trial is registered with ClinicalTrials.gov, NCT04164901. Recruitment is complete and the trial is ongoing. FINDINGS: Between Jan 9, 2020, and Feb 22, 2022, 331 patients were enrolled and randomly assigned to vorasidenib (n=168) or placebo (n=163). 187 (56%) patients were male, 144 (44%) were female, and 257 (78%) were White. Median follow-up was 20·1 months (IQR 15·9 to 23·8). With an additional 6 months of follow-up, median progression-free survival (not reached [95% CI 22·1 to not estimated] vs 11·4 months [95% CI 11·1 to 13·9]; hazard ratio [HR] 0·35 [95% CI 0·25 to 0·49]) and time to next intervention (not estimated [not estimated to not estimated] vs 20·1 months [17·5 to 27·1]; HR 0·25 [0·16 to 0·40]) remained substantially improved with vorasidenib versus placebo. Tumour growth rate was -1·3% (95% CI -3·2 to 0·7) with vorasidenib and 14·4% (95% CI 12·0 to 16·8) with placebo (difference 15·9% [95% CI 12·6 to 19·3]). Mean FACT-Br total scores were similar between the vorasidenib and placebo groups (158·2 [SD 26·4] and 158·8 [23·3]) at baseline and remained high (154·2 [29·8] and 153·2 [29·4]) by the end of treatment. There was no difference between vorasidenib or placebo in neurocognitive functions of verbal learning, executive function, attention, working memory, and psychomotor function from baseline through to end of treatment. The vorasidenib group had lower rates of seizures than the placebo group (18·2 seizures per person-year [95% CI 8·4 to 39·5] vs 51·2 seizures per person-year [22·9 to 114·8]). The most common grade 3 or worse treatment-emergent adverse events (TEAEs) in the vorasidenib and placebo groups, respectively, were increased alanine aminotransferase (17 [10%] and two [1%]), increased aspartate aminotransferase (eight [5%] and none), seizures (seven [4%] and five [3%]), and increased γ-glutamyltransferase (five [3%] and two [1%]). Serious TEAEs occurred in 20 (12%) patients in the vorasidenib group and ten (6%) in the placebo group; the most common were seizures. There were no treatment-related deaths. INTERPRETATION: Vorasidenib reduced tumour growth rate and improved seizure control compared with placebo, with no observed negative effects on HRQOL or neurocognition. Additional follow-up supported the robustness of progression-free survival and time to next intervention in patients with grade 2 IDH1/2-mutant diffuse glioma. These findings support the use of vorasidenib in patients with grade 2 IDH1/2-mutant gliomas who only had surgical intervention and are not in immediate need of radiotherapy or chemotherapy. FUNDING: Servier.