Aqneursa (levacetylleucine)

The only approved drug for ataxia-telangiectasia and one of 2 for Niemann-Pick C (the other is Miplyffa). It is a symptomatic treatment for ataxia, taken daily and indefinitely, alongside the immunoglobulin replacement, infection management and cancer surveillance that A-T care already requires.

Levacetylleucine is a chemically modified form of the amino acid leucine. Unlike most rare disease drugs it does not act on the gene that causes either condition; IntraBio says the distinct molecular target is unknown. The proposed mechanism is that it enters metabolic pathways inside neurons and normalizes glucose metabolism, which correlates with improved activity in the cerebellum, the part of the brain that coordinates movement, and that it improves lysosomal and mitochondrial function along the way. That mechanism is why one molecule has now been approved in 2 genetically unrelated diseases that share cerebellar ataxia as a symptom. What has been shown in trials is that ataxia scores improve within 12 weeks on the drug and slip back on placebo; whether it changes the long-term course of either disease is being studied in open-label extensions and is not yet known.

In the ataxia-telangiectasia trial the most common reactions occurring in at least 5% of patients and more often than on placebo were falls, skin lacerations and urinary tract infection. Falls in a disease defined by loss of balance need care in interpretation: the trial did not attribute them to the drug, no treatment-related serious adverse events occurred, and no patient stopped because of a treatment-related reaction. In the Niemann-Pick C trial the most common reactions were abdominal pain, difficulty swallowing, upper respiratory infections and vomiting. There are no contraindications. The main label warning is embryo-fetal toxicity based on animal data, so pregnancy must be ruled out before starting.

An orphan drug already priced for Niemann-Pick C, one of the rarest diseases with an approved treatment. IntraBio has not announced a separate price for the A-T indication. Because the product is the same packets, the price patients face is set by the existing NPC list price and by what insurers agree to cover for A-T.

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For ataxia-telangiectasia, approval rested on IB1001-303 (NCT06673056), a randomized, double-blind, placebo-controlled crossover trial of 73 patients aged 4 to 50 with genetically confirmed A-T at 10 sites in 6 countries, published in The Lancet Neurology in July 2026. Each patient took levacetylleucine for 12 weeks and placebo for 12 weeks in random order. On the full 40-point SARA ataxia scale, scores improved by a mean of 1.9 points on drug versus 0.1 on placebo, a treatment effect of 1.88 points (95% CI 1.06 to 2.70; p<0.0001). On the FDA's primary measure, the 16-point functional SARA covering gait, sitting, stance and speech, the treatment difference was 0.6 points (95% CI 0.2 to 0.9). 70 of 73 patients (96%) completed. For Niemann-Pick disease type C, approval in September 2024 rested on a 60-patient crossover trial of the same design with a 0.4-point fSARA difference.

N-acetyl-L-leucine grew out of an older European drug, N-acetyl-DL-leucine, long sold for vertigo. Researchers found that the L form carried the activity and that it improved cerebellar ataxia in several rare diseases. IntraBio, based in Austin, Texas, developed the purified L form as IB1001 and won FDA approval on September 24, 2024 for the neurological manifestations of Niemann-Pick disease type C. The A-T program moved fast: the Phase 3 trial enrolled its 73 patients between March and June 2025, the supplemental application was accepted with priority review in May 2026, and the FDA approved it on September 18, 2026, 1 day ahead of its September 19 action date. It is the first drug approved for A-T anywhere in the world; an EU application for the same indication was filed in June 2026.

Until September 2026, A-T care was entirely supportive. The one other large trial, Quince Therapeutics' Phase 3 study of dexamethasone encapsulated in the patient's own red blood cells (eDSP), enrolled 105 participants, 83 of them aged 6 to 9, and missed its endpoints in January 2026, and the program was stopped. Earlier-stage work includes antisense oligonucleotides aimed at specific ATM variants and gene-based approaches. Levacetylleucine is the only treatment with a randomized trial that succeeded.