IntraBio Inc. has secured a regulatory milestone that patients with ataxia-telangiectasia have never previously had: an approved medicine specifically treating the progressive loss of coordination that defines much of the neurological burden of the disease. The United States Food and Drug Administration approved AQNEURSA, or levacetylleucine, on September 18 for treatment of ataxia in adults and children with ataxia-telangiectasia weighing at least 15 kilograms. The decision makes AQNEURSA the first approved treatment for ataxia associated with A-T and gives the medicine a second U.S. indication after its 2024 approval for neurological manifestations of Niemann-Pick disease type C.
The pivotal evidence is unusually clear for an ultra-rare neurological disease. In a randomized, double-blind, placebo-controlled crossover Phase 3 trial involving 73 genetically confirmed patients, levacetylleucine produced a mean 1.92-point improvement from baseline on the Scale for the Assessment and Rating of Ataxia compared with a 0.14-point improvement during placebo treatment. The modeled treatment effect was 1.88 points in favour of levacetylleucine, with a 95% confidence interval of 1.06 to 2.70 points and a p-value below 0.0001. No treatment-related serious adverse events or deaths were reported in the trial.
Yet the significance of the approval should be defined carefully. AQNEURSA treats ataxia; it is not a cure for ataxia-telangiectasia, nor has the FDA concluded that it prevents the cancers, immunodeficiency, lung disease or other systemic complications caused by ATM mutations. The next scientific question is therefore considerably larger than whether levacetylleucine can make neurological function measurably better over 12 weeks. It is whether continued treatment can preserve function for years in a disease that progressively damages multiple organ systems.
Why is ataxia-telangiectasia much more than a movement disorder?
Ataxia-telangiectasia is caused by biallelic pathogenic variants in the ATM gene, which encodes a protein involved in coordinating cellular responses to DNA double-strand breaks, oxidative stress and other forms of genomic damage. Loss of normal ATM function produces a complex disorder involving progressive cerebellar degeneration, impaired coordination, abnormal eye movements, immunodeficiency, respiratory disease and markedly increased cancer susceptibility. Neurological symptoms typically emerge during childhood, often beginning with an abnormal gait or difficulty maintaining balance.
That multisystem biology is essential when interpreting AQNEURSA. The FDA indication specifically covers ataxia, one of the disease’s most visible and disabling manifestations, but the underlying ATM defect continues to affect DNA repair and immune function. A recent Johns Hopkins cohort analysis found primary cancers in 84 of 508 people with A-T, or 16.5%, with cumulative cancer incidence reaching 29% by age 35 and hematologic malignancies accounting for most observed cancers.
Older natural-history studies also illustrate the severity of the disease, although outcomes have improved as supportive care has advanced. A systematic review found neurological problems were the most common presenting manifestations and confirmed that malignancy, pulmonary disease and infections remain major contributors to premature mortality. The rarity and heterogeneity of A-T mean historical survival estimates vary substantially and should not be treated as precise forecasts for an individual patient.
AQNEURSA therefore addresses a clinically meaningful part of the disease rather than the entire syndrome. That distinction does not diminish the approval; it defines where physicians and families should look for benefit and where multidisciplinary care remains indispensable.
What does a 1.88-point improvement on an ataxia scale mean in everyday life?
The Phase 3 study enrolled 73 patients aged four to 50 across research centres in the United States and Europe. Patients were randomized to receive levacetylleucine followed by placebo or placebo followed by levacetylleucine, with each treatment period lasting 12 weeks. Because every participant could contribute observations under both treatment conditions, the crossover design allowed investigators to compare neurological performance within the same rare patient population while reducing some of the variability that makes ultra-rare disease trials difficult.
The primary analysis reported a mean change of minus 1.92 points on the full SARA during levacetylleucine treatment compared with minus 0.14 points during placebo. Lower scores indicate better neurological function. The investigators concluded that the difference represented a statistically significant and clinically meaningful improvement.
Interpreting that number requires more care than saying patients simply became 1.88 points “better.” Ataxia scales combine several functional domains, and the practical impact of a change can differ depending on a patient’s baseline impairment. An improvement affecting gait or standing may matter differently from a similar numerical change driven by another domain.
The FDA’s own summary uses the functional Scale for Assessment and Rating of Ataxia, or fSARA, to describe the regulatory evidence. That modified measure evaluates gait, sitting, stance and speech disturbance, with higher scores indicating worse neurological status. The agency said patients scored better while receiving AQNEURSA than while receiving placebo and demonstrated significant neurological improvement.
For families facing a progressive disease, the practical question will now shift toward durability. A measurable improvement over three months is valuable, but preserving mobility, speech or independence over several years would represent a much larger clinical consequence.
Why was a crossover trial particularly useful in such a rare disease?
Ataxia-telangiectasia is estimated to affect roughly one in 40,000 to one in 100,000 people worldwide, making conventional large parallel-group Phase 3 trials extraordinarily difficult. Recruiting hundreds or thousands of genetically confirmed patients is unrealistic, particularly when patients vary substantially in age, severity and disease progression.
A crossover study partially solves that problem because patients receive both active treatment and placebo during different periods. Each participant therefore contributes more information than they would in a conventional design where they remain permanently assigned to one treatment.
That approach also introduces interpretive questions. Investigators need to consider whether the effect of treatment persists after switching and whether the washout or sequencing of treatment periods influences results. In the AQNEURSA Phase 3 programme, the statistical analysis accounted for the crossover structure, and 70 of the 73 randomized patients completed the trial according to the FDA.
For rare neurological disorders, this kind of design can offer a compromise between methodological rigor and practical recruitment limits. The trial was still randomized, double-blinded and placebo controlled, but it extracted more comparative information from a population of only 73 people.
Does AQNEURSA modify the disease or mainly improve neurological function?
This may be the most important unanswered question after approval.
The Phase 3 study demonstrates treatment-related improvement in ataxia over relatively short controlled periods. The investigators described levacetylleucine as having a favourable benefit-risk profile and noted that the ongoing open-label extension is intended to investigate potential longer-term neuroprotective and disease-modifying effects. That language is important because those effects remain under investigation rather than established by the FDA approval.
IntraBio proposes that levacetylleucine acts on cellular metabolic pathways involving mitochondrial and lysosomal function, membrane potential and cellular signalling. The company has pursued the same molecule across neurological disorders with different genetic causes, suggesting it believes the drug acts on downstream cellular dysfunction shared across diseases rather than correcting one specific mutation.
That may explain why AQNEURSA can now carry indications in both Niemann-Pick disease type C and ataxia-telangiectasia, two genetically distinct disorders that nevertheless produce progressive neurological dysfunction.
But symptomatic improvement and disease modification are not identical concepts. A medicine could improve neuronal function while treatment continues without materially altering the long-term rate of neuronal loss. Demonstrating true disease modification would require longer follow-up showing that treated patients decline more slowly than expected, retain abilities longer or diverge meaningfully from natural history over time.
The ongoing extension data will therefore be particularly important. If improvements persist or neurological decline remains slower after years of treatment, AQNEURSA’s significance could expand substantially beyond a symptomatic ataxia medicine.
What does AQNEURSA leave untreated in ataxia-telangiectasia?
The approval does not remove the need for intensive multidisciplinary care. People with A-T commonly require neurological assessment, respiratory management, nutritional support, physical and speech therapy, immunology care and surveillance for malignancies. Radiation sensitivity can also complicate diagnostic imaging and cancer treatment because ATM deficiency makes cells unusually vulnerable to ionising radiation.
AQNEURSA has not been shown to correct the underlying ATM mutation. The FDA announcement does not claim that the medicine restores immune function, prevents pulmonary disease or lowers cancer incidence. Those remain separate clinical problems requiring ongoing monitoring and treatment.
This creates an important expectation-management issue as the first approved therapy reaches patients. “First treatment” can easily be interpreted outside specialist medicine as equivalent to a comprehensive treatment of A-T. The actual indication is narrower and more defensible: AQNEURSA treats ataxia associated with the disorder.
That nevertheless could have meaningful downstream effects. Better mobility and coordination may influence independence, fall risk, communication, caregiver workload and participation in daily activities. Those real-world benefits will become easier to evaluate as commercially treated populations accumulate.
How manageable does AQNEURSA’s safety profile look?
The Phase 3 publication reported 54 adverse events among 29 patients receiving levacetylleucine compared with 75 events among 25 patients during placebo exposure. No treatment-related serious adverse events or deaths occurred.
The FDA identifies falls, skin lacerations and urinary tract infections as the most common adverse reactions reported in patients with A-T. The medicine has no listed contraindications, although animal data indicate potential fetal harm. The agency also warns against simultaneous use with N-acetyl-DL-leucine and advises closer monitoring when AQNEURSA is administered with P-glycoprotein substrates.
Oral administration may be commercially and clinically advantageous compared with more invasive neurological therapies. Levacetylleucine is supplied for oral suspension and dosing is adjusted by body weight, making it feasible for chronic outpatient use rather than requiring infusion-centre infrastructure.
Because A-T is lifelong, however, long-term tolerability matters more than a short controlled safety period. Even relatively mild adverse effects can affect adherence when medication must be taken continuously for years.
Why does this second indication matter strategically for IntraBio?
AQNEURSA was first approved by the FDA in September 2024 for neurological manifestations of Niemann-Pick disease type C in adults and pediatric patients weighing at least 15 kilograms. The European Commission subsequently authorized levacetylleucine for NPC in adults and children aged six years and older who meet the European weight requirement.
The A-T approval demonstrates that IntraBio may be able to build multiple rare-neurology indications around one active molecule rather than depending on a single ultra-small patient population. That is commercially important because each individual disorder may contain only hundreds or thousands of treatable patients.
The development strategy is already extending further. IntraBio is advancing a Phase 3 programme evaluating N-acetyl-L-leucine in CACNA1A-related disorders including spinocerebellar ataxia type 6, episodic ataxia type 2 and familial hemiplegic migraine type 1. ClinicalTrials.gov lists an estimated 60-patient randomized, placebo-controlled crossover study with completion planned after 2027.
Success there would strengthen the idea that levacetylleucine is not merely an NPC drug successfully repurposed once, but a broader neurological platform capable of addressing impaired cellular function across genetically distinct disorders.
Failure would place more weight on the possibility that efficacy depends on specific disease biology rather than a widely applicable cellular mechanism.
Could one molecule become a rare-neurology platform without becoming a catch-all therapy?
There is a long history of drugs showing encouraging signals across small neurological populations only to produce inconsistent results as development expands. Rare diseases are particularly vulnerable to that risk because trials are small, patient populations heterogeneous and endpoints sometimes difficult to validate.
IntraBio’s strongest evidence therefore remains indication specific. AQNEURSA has now passed randomized controlled testing and regulatory review in A-T rather than relying on extrapolation from NPC.
The Phase 3 effect also needs to be interpreted according to what the trial measured. It supports neurological benefit over the controlled period. It does not prove that the molecule can correct every downstream consequence of ATM dysfunction.
That distinction may actually strengthen the platform strategy. A company does not need one medicine to cure several disorders to create value. It needs reproducible, clinically meaningful effects on important manifestations in carefully selected diseases.
What should clinicians and families watch after the FDA approval?
Long-term extension data are now the most important scientific milestone. Physicians need to understand whether early neurological improvement persists, increases, plateaus or disappears with continued therapy.
Real-world functional outcomes will matter as well. Measures such as falls, mobility, speech, daily activities, need for assistance and progression toward wheelchair dependence can help translate trial-scale changes into outcomes meaningful to families.
International regulatory expansion is another milestone. IntraBio has been pursuing an extension of AQNEURSA’s European authorization to include ataxia-telangiectasia, potentially creating a second major market if European regulators reach a favourable conclusion.
Finally, the broader clinical-development programme will show whether levacetylleucine can support more indications. CACNA1A disorders provide the next important test of whether the biological strategy travels beyond the two diseases in which AQNEURSA has already reached regulators.
The September 18 approval nevertheless changes the treatment landscape immediately. For the first time, physicians treating ataxia-telangiectasia have an FDA-approved medicine specifically directed at the disorder’s progressive ataxia rather than relying entirely on supportive interventions.
The harder question begins after approval. A-T is a lifelong disease involving neurodegeneration, immune dysfunction, pulmonary complications and cancer susceptibility. AQNEURSA has demonstrated that neurological function can improve over a 12-week controlled period. Establishing whether that improvement translates into years of preserved function is what would transform the approval from the first treatment for ataxia into something even more consequential for the natural history of the disease.
