Efficacy and safety profile of selumetinib in symptomatic inoperable plexiform neurofibromas

Selumetinib is a MEK inhibitor, which is effective with an acceptable safety profile in reducing the volume of symptomatic inoperable plexiform neurofibromas in some clinical trials and also has been recently approved by FDA for use in children aged 2 years or older. However, no systematic review has yet been performed to provide a collective estimate of the results of all these trials.

Articles describing the use of selumetinib in patients with neurofibromatosis type-1 (NF1) with inoperable plexiform neurofibromas were searched from different electronic databases. The objectives were to provide a pooled estimate of efficacy evaluated by direct measurement and also by various functional measures, as well as the proportion of patients with adverse events. For determining pooled estimates, we included only studies with a minimum sample size of 15 with a prospective study design.

A total of eight articles with 137 patients were found and 134 patients in six uncontrolled trials were included in the quantitative review. Out of these 26 were adults (69% male; 33.2±18.4 years, range 18-60 years) and 108 were in the pediatric age group (74% boys, 10.9±2.3 years, range-2-18 years,). Total 77.86% (95% CI: 55.91-99.81%) patients had a partial response, 71.24% (95% CI: 53.62-89.93%) had a confirmed partial response, and 56.25% (95% CI: 37.53-72.49%) had a durable partial response. The average time to initial response was 7.3±2.9 cycles (range, 4 to 20), and the median time to best response was 15.4±5.8 cycles (range, 4 to 36). The average change in neurofibroma volume at best response was -28.15% (95% CI: -17.95%, -38.34%, range, -55.1% to 2.2%). Progression-free survival was observed in 93.12% of patients at the time of data cut-off. Overall, 73.26% (95% CI: 54.07%, 92.45%) patients had improvement in at least one of the functional or patient-reported outcome assessments. The most common adverse effects were grade 1 and 2 gastrointestinal symptoms (65%), an asymptomatic increase in the creatine phosphokinase level (31%), paronychia (6%), and acneiform rash (17%). A total of 17% patients required dose reduction due to these toxic effects and 10.5% (95% CI: 4.0%, 17.0%) of patients discontinued due to toxic effects.

Selumetinib can produce sustained shrinkage in the majority of patients with NF1 and symptomatic plexiform neurofibroma to provide clinically meaningful benefit in functional ability, with more robust evidence in children. The acceptable safety profile and absence of cumulative toxic effects permit long-term treatment with selumetinib.