Levacetylleucine sNDA for ataxia-telangiectasia receives FDA Priority Review

The FDA has accepted IntraBio’s supplemental new drug application (sNDA) for levacetylleucine (AQNEURSA) for ataxia-telangiectasia (A-T) in adult and pediatric patients and granted the application Priority Review, according to a May 19 company announcement. The agency assigned a Prescription Drug User Fee Act target action date of September 19, 2026.¹

“Today’s announcement represents a profound step forward — not just for IntraBio, but for the thousands of patients and families living with Ataxia-Telangiectasia who have waited far too long for a treatment option,” said Mallory Factor, president and CEO of IntraBio.¹ If approved, levacetylleucine would become the first FDA-approved treatment specifically indicated for A-T, a rare inherited neurodegenerative disorder with onset typically in early childhood.

The sNDA is supported by data from IB1001-303, described by the company as a pivotal phase 3 randomized, double-blind, placebo-controlled crossover trial in pediatric and adult patients with A-T. IntraBio reported that the trial met its primary endpoint and all key secondary endpoints with high statistical significance, with improvements in neurologic signs, symptoms, and function. The release did not provide numerical efficacy results, endpoint definitions, sample size, or subgroup analyses.¹

Safety findings reported in the announcement were limited. The company stated that levacetylleucine was generally safe and well-tolerated in the trial and that no drug-related serious adverse events were observed.¹ Full evaluation of the application will require FDA review of the complete clinical data set, including durability of response, treatment effects across age and disease-severity groups, and adverse event rates relative to placebo.

A-T is caused by pathogenic variants affecting DNA damage response pathways and is characterized by progressive cerebellar ataxia, oculomotor abnormalities, dysarthria, telangiectasias, immunodeficiency, pulmonary complications, and increased malignancy risk.² Published reviews estimate prevalence at approximately 1 in 40,000 to 1 in 100,000 live births, consistent with the company’s description.^1,2 Neurologic symptoms often begin in early childhood, and many patients lose independent ambulation as the disease progresses.²

Current management is supportive and multidisciplinary, including neurologic, immunologic, pulmonary, rehabilitation, nutritional, and oncology surveillance strategies.² No disease-modifying therapy has been approved by the FDA for A-T, leaving symptomatic care and complication prevention as the main clinical approach. For pediatric clinicians, a potential pharmacologic option would be most relevant if it demonstrates measurable functional benefit and an acceptable safety profile in children over time.

Levacetylleucine is the L-enantiomer of N-acetyl-leucine and is already approved in the United States for the treatment of neurologic manifestations of Niemann-Pick disease type C (NPC) in adults and pediatric patients weighing at least 15 kg.³ The mechanism by which levacetylleucine exerts its therapeutic effect in NPC is not fully established in prescribing information.3 In the European Union, AQNEURSA is authorized for neurologic manifestations of NPC in adults and children aged 6 years and older weighing at least 20 kg, either with miglustat or as monotherapy in patients who cannot tolerate miglustat.

The US prescribing information for the currently approved NPC indication includes warnings on embryo-fetal toxicity based on animal reproduction data. It advises confirming pregnancy status before treatment in females of reproductive potential and using effective contraception during therapy and for 7 days after discontinuation.³ Common adverse reactions listed for the approved indication include abdominal pain, dysphagia, upper respiratory tract infections, and vomiting. The label also advises avoiding concomitant use with N-acetyl-DL-leucine or N-acetyl-D-leucine and monitoring for adverse reactions related to P-glycoprotein substrates when used concomitantly.³

The regulatory review now shifts the focus from topline trial results to FDA assessment of the complete sNDA package. Key clinical questions include the magnitude of functional improvement, its persistence in a progressive disorder, applicability to younger children and patients with advanced disease, and how safety compares with the known profile in NPC.

References

1. IntraBio Inc. FDA accepts sNDA and grants Priority Review to AQNEURSA for Ataxia-Telangiectasia. BusinessWire. Published May 19, 2026. Accessed May 19, 2026. https://www.businesswire.com/news/home/20260519802425/en/FDA-Accepts-sNDA-and-Grants-Priority-Review-to-AQNEURSA-for-Ataxia-Telangiectasia
2. Rothblum-Oviatt C, Wright J, Lefton-Greif MA, McGrath-Morrow SA, Crawford TO, Lederman HM. Ataxia telangiectasia: a review. Orphanet J Rare Dis. 2016;11:159. doi:10.1186/s13023-016-0543-7
3. IntraBio Inc. AQNEURSA (levacetylleucine) prescribing information. IntraBio Inc. Updated September 2024 Accessed May 19, 2026. https://www.aqneursa.com/wp-content/aqneursa-prescribing-information.pdf