FDA Approves Levacetylleucine for Ataxia-Telangiectasia

The FDA has approved levacetylleucine (Aqneursa; IntraBio) for the treatment of ataxia in adults and pediatric patients with ataxia-telangiectasia (A-T) weighing at least 15 kg.¹ The approval marks the first FDA-approved treatment indicated specifically for A-T and is based on data from the phase 3 IB1001-303 trial (NCT06673056).² Levacetylleucine previously received approval in September 2024 for neurological manifestations of Niemann-Pick disease type C.

The new indication comes after decades without a therapy approved specifically for A-T, according to the A-T Children's Project. IntraBio has also initiated a phase 3 trial evaluating levacetylleucine in CACNA1A-related disorders, a separate group of rare neurological conditions with no currently approved therapies.

"Today marks a tremendous milestone for the A-T community and IntraBio," Mallory Factor, CEO at IntraBio, said in a statement.¹ "As the first FDA-approved drug for the treatment of ataxia-telangiectasia, AQNEURSA now offers the potential to make meaningful differences in the lives of thousands of patients and their families who have lacked options to treat the diverse and debilitating array of symptoms caused by A-T."¹

Levacetylleucine efficacy in the IB1001-303 trial

The FDA approval is supported by results from IB1001-303, a randomized, double-blind, placebo-controlled crossover trial conducted at 10 sites across Germany, Slovakia, Spain, Switzerland, the United Kingdom, and the United States. The trial enrolled 73 patients with genetically confirmed A-T, ages 4 to 50 years, and 70 patients (96%) completed the study. Results were published in the July 2026 issue of The Lancet Neurology.²

On the trial's primary endpoint, the Scale for the Assessment and Rating of Ataxia (SARA), levacetylleucine produced a treatment difference of -1.9 points compared with placebo (95% CI, -2.7 to -1.1; 2-sided P <.001). The FDA separately assessed a functional SARA (fSARA) outcome, comprising gait, sitting, stance, and speech disturbance domains, which showed a mean treatment difference of -0.6 (95% CI, -0.9 to -0.2; 2-sided P <.001). Improvement was consistent across secondary endpoints and prespecified subgroups, with no evidence of heterogeneity in treatment effect between pediatric and adult populations, and benefits were evident within 12 weeks.

“The trial met its primary endpoint on the full 8-domain SARA with a treatment effect of ‑1.88 points, beyond the one-point change generally accepted as clinically meaningful. The fSARA distills the scale down to four axial domains - gait, stance, sitting and speech,” Marc C. Patterson, MD, chief medical officer at IntraBio, told NeurologyLive^®. “These domains include key activities that patients and families describe as meaningful to them including walking without help, sitting upright and unsupported, and being able to communicate and be understood. The key finding of the study was not which scale is preferred; it is that both moved in the same direction and the fSARA results were supported by consistent results demonstrated on the original SARA.”

“In both trial sequences, the benefit tracked with levacetylleucine treatment: patients who improved on levacetylleucine showed no meaningful change on placebo and lost most of the gain when switched to placebo, the pattern predicted from a pharmacologically mediated effect,” Patterson added. “The trial results are reflected in the indication for levacetylleucine in A-T; the approval is for ataxia, defined by the FDA as ‘a progressive condition resulting from degeneration of the nervous system and comprises multiple signs and symptoms, including gait ataxia, truncal ataxia, oculomotor ataxia, difficulties with balance, trouble with speech, and hand incoordination.’”

Levacetylleucine safety profile in ataxia-telangiectasia

Safety findings were consistent with levacetylleucine's established profile in NPC. No treatment-related serious adverse events or deaths occurred during the trial, and no patients discontinued treatment due to treatment-related adverse events. The most common adverse reactions occurring in at least 5% of patients and more frequently than with placebo were fall, skin laceration, and urinary tract infection.

The label carries a warning for embryo-fetal toxicity based on animal reproduction studies; prescribers are advised to verify pregnancy status before initiating treatment and to counsel patients on effective contraception during treatment and for seven days after the final dose if discontinued. Levacetylleucine inhibits P-glycoprotein (P-gp) and should not be administered concomitantly with N-acetyl-DL-leucine or N-acetyl-D-leucine, since the D-enantiomer competes for monocarboxylate transporter uptake and may reduce efficacy; patients on concomitant P-gp substrates should be monitored more frequently for adverse reactions.

IntraBio is conducting a phase 3 trial, IB1001-304, evaluating levacetylleucine in CACNA1A-related disorders, a group of rare neurological conditions affecting an estimated 30,000 individuals in the United States and 690,000 people worldwide, for which no approved therapies currently exist. The company expects to complete enrollment in the CACNA1A trial in October 2026.¹

“For decades, management of A-T was limited to supportive care. Levacetylleucine is the first treatment approved for the disease, a major milestone for the community while multidisciplinary care remains essential for people with A-T and their caregivers. This is one more tool alongside the existing plan, while the multidisciplinary framework around the patient continues unchanged,” Patterson told NeurologyLive.

“The pivotal phase 3 trial detected a treatment effect within 12 weeks. Although participants in the study responded on average within 12 weeks, clinical experience has shown that individual responses vary widely, and patients and prescribers should reach the decision to begin and continue therapy on an individual basis,” Patterson added. “While many patients will see rapid improvement in their symptoms of ataxia, others may appreciate stabilization of their progression, which may only be apparent after six to twelve months of treatment.”

"This is a historic day for the A-T community and the patients and caregivers who have coped for decades without a treatment approved specifically for A-T," Brad Margus, founder of the A-T Children's Project, said in a statement.¹ "With today's FDA decision, those impacted by A-T have a treatment option demonstrating benefit across a range of A-T symptoms, including symptoms affecting daily life for patients and their loved ones."¹

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REFERENCES
1. IntraBio announces U.S. FDA approval of AQNEURSA (levacetylleucine) for ataxia-telangiectasia. News release. IntraBio. September 18, 2026. Accessed September 18, 2026. https://www.businesswire.com/news/home/20260918198606/en/IntraBio-Announces-U.S.-FDA-Approval-of-AQNEURSA-levacetylleucine-for-Ataxia-Telangiectasia
2. Martakis K, Bremova-Ertl T, Bolton C, et al. Safety and efficacy of levacetylleucine in ataxia-telangiectasia: a phase 3, randomised, double-blind, placebo-controlled crossover trial. Lancet Neurol. 2026;25(7):633-644. doi:10.1016/S1474-4422(26)00158-4