FDA Approves First Drug for Ataxia in Rare A-T

FDA approved IntraBio’s AQNEURSA (levacetylleucine) on 19 September 2026 to treat ataxia in adult and pediatric patients with ataxia-telangiectasia, a rare and fatal neurodegenerative disorder with no previously approved treatment for the symptom. The approval, granted under Priority Review, is the drug’s second indication: AQNEURSA was first approved in 2024 for Niemann-Pick disease type C. The new label rests on a 73-patient placebo-controlled crossover trial that met its primary endpoint with a statistically significant, clinically meaningful result.

What ataxia-telangiectasia is, and why the symptom mattered

Ataxia-telangiectasia is a rare, inherited neurodegenerative disorder caused by mutations in the ATM gene. It typically presents in early childhood with progressive loss of muscle control and coordination — ataxia — alongside small dilated blood vessels (telangiectasia), immune deficiencies, and a substantially elevated risk of cancer. The disease is progressive and fatal, and until this approval, physicians had no FDA-approved medicine to address the ataxia itself; management relied on supportive and symptomatic care. A therapy shown to measurably improve motor coordination fills a gap that had no pharmacological answer.

The trial: a crossover design in a very small population

Rare-disease trials rarely have the luxury of large parallel-group cohorts, and IB1001-303 shows the workaround: a two-period crossover in 73 patients, where each participant received both levacetylleucine and placebo in sequence, with a 12-week treatment period each. That design lets every patient serve as their own control, extracting a statistically meaningful signal from a population too small to power a conventional trial. The primary endpoint — change on the Scale for the Assessment and Rating of Ataxia (SARA), the standard clinical measure of ataxia severity — showed a -1.88-point difference favoring levacetylleucine over placebo (-1.92 vs. -0.14), reaching statistical significance at p<0.001. Secondary endpoints moved the same direction: the International Cooperative Ataxia Rating Scale (ICARS) improved by -4.22 points on drug versus -1.69 on placebo (p=0.003), and the Investigator's Clinical Global Impression of Improvement scored -0.6 versus -0.2 (p=0.02). IntraBio reported no drug-related serious adverse events, consistent with levacetylleucine's existing safety record from its Niemann-Pick disease type C approval.

A second indication, not a new drug

AQNEURSA's regulatory path illustrates a strategy increasingly common among rare-disease sponsors: develop one molecule across multiple genetically distinct but mechanistically related disorders. Levacetylleucine, the active ingredient, was first approved in 2024 to treat neurological symptoms of Niemann-Pick disease type C, a different lysosomal storage disorder. IntraBio's supplemental NDA for A-T leveraged an already-established safety database and manufacturing record, which likely contributed to a Priority Review clearing in roughly four months from FDA's May 2026 acceptance to the September approval — a compressed timeline relative to a ground-up new molecular entity review. For RA teams managing rare-disease portfolios, the case is a template: an approved active ingredient with a plausible mechanism in a second orphan indication can move through supplemental filings faster than starting a new NDA.

Frequently asked questions

What did FDA approve on 19 September 2026?

A supplemental New Drug Application for AQNEURSA (levacetylleucine) oral suspension, from IntraBio Inc., adding ataxia in adult and pediatric patients weighing at least 15 kg with ataxia-telangiectasia (A-T) to the drug's label. It is the first FDA-approved treatment for ataxia in A-T.

Was AQNEURSA already approved for something else?

Yes. FDA first approved AQNEURSA in 2024 for Niemann-Pick disease type C, a different rare neurodegenerative disorder. The 19 September action is a second, separate indication added by supplemental NDA, not a new drug approval.

What evidence supported the approval?

IB1001-303, a randomized, double-blind, placebo-controlled, two-period crossover trial (NCT06673056) in 73 patients with A-T aged 4 and older, each treatment period lasting 12 weeks. Levacetylleucine produced a statistically significant, clinically meaningful improvement on the Scale for the Assessment and Rating of Ataxia (SARA) compared with placebo, with consistent results on secondary endpoints and no new safety signals.

What review pathway did the application use?

FDA accepted the sNDA and granted Priority Review in May 2026; the application also carried Orphan Drug designation. A-T is a rare, ATM-gene neurodegenerative disorder with no previously approved treatment for its ataxia symptoms.