A phase 3 study investigated the safety and efficacy of levacetylleucine in the treatment of ataxia-telangiectasia. It was a randomised, double-blind, placebo-controlled crossover trial. The results showed a significant and clinically meaningful improvement in patient functioning. Levacetylleucine was also safe and well-tolerated. This indicates a favourable benefit-risk profile for the treatment of this condition. An ongoing open-label extension phase of this trial is currently underway. This phase will investigate the potential long-term, neuroprotective, and disease-modifying effects of the drug.