Neurological effects of encapsulated dexamethasone sodium phosphate in children aged 6-9 years with ataxia telangiectasia (NEAT): a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial.

Abstract

BACKGROUND: Ataxia telangiectasia is a rare, multisystem disorder with progressive cerebellar neurodegeneration and no approved treatments. The efficacy of corticosteroids, including erythrocyte encapsulated dexamethasone sodium phosphate (eDSP), which have been studied for two decades in this disease, has not yet been proven in randomised trials. We aimed to investigate the safety and efficacy of eDSP in children aged 6-9 years with ataxia telangiectasia. METHODS: NEAT was a multicentre, randomised, double-blind, placebo-controlled phase 3 study, conducted at 20 sites across nine countries (Denmark, Germany, Italy, Norway, Poland, Spain, Switzerland, UK, and USA). Eligible participants were children aged 6 years or older weighing at least 15 kg, with a genetic diagnosis of ataxia telangiectasia and presence of neurological symptoms. Participants were randomly assigned (1:1) to the eDSP or placebo group via an independent interactive web response system and were stratified by age (6-9 years or ≥10 years), sex, and region (USA vs other countries). All participants, investigators, sponsors, and raters were masked to treatment assignments. eDSP was given intravenously every 21-30 days for six doses. All randomly assigned participants were included in the intention-to-treat (ITT) and safety populations; the primary and secondary efficacy analyses were conducted in participants aged 6-9 years in the ITT population. The primary efficacy endpoint was the change in Rescored Modified International Cooperative Ataxia Rating Scale (RmICARS) score between baseline and month 6, and a mixed-model-repeated-measures analysis was used. The trial was registered at ClinicalTrials.gov, NCT06193200, and is completed. FINDINGS: Between June 24, 2024, and Dec 17, 2025, we screened 125 participants for eligibility, of whom 105 (84%) were randomly assigned to the eDSP group (n=51 [49%]) or the placebo group (n=54 [51%]) and received at least one dose of treatment. The mean age was 8·5 years (SD 1·9) in the eDSP group and 8·6 years (2·3) in the placebo group (overall age range 6-17 years). In the eDSP group, 24 (47%) of 51 participants were girls and 27 (53%) were boys and, in the placebo group, 26 (48%) of 54 were girls and 28 (52%) were boys. Of ITT participants aged 6-9 years, 38 (95%) of 40 in the eDSP group and 41 (95%) of 43 in the placebo group completed the study. Compared with the placebo group, no significant differences were identified in change in RmICARS score from baseline to 6 months in participants aged 6-9 years: least squares mean difference -1·30 (95% CI -2·77 to 0·18; p=0·085). Adverse events were reported in 47 (92%) of 51 participants in the eDSP group and in 50 (93%) of 54 participants in the placebo group. The most common treatment-emergent adverse events were vomiting, pyrexia, pruritus, nasopharyngitis, cough, headache, and fatigue. There were no reports of treatment-related serious adverse events or deaths. Safety laboratory parameters did not identify adverse effects on growth, metabolism, bone mineral density, or endocrine function in any of the treatment groups. INTERPRETATION: The primary efficacy endpoint was not achieved, because the effect of eDSP on neurological symptoms did not reach statistical significance. The favourable safety profile of eDSP, previously described in a large study of children with ataxia telangiectasia, was confirmed in this trial. The eDSP programme, comprising two randomised studies and treating the largest cohort of patients with ataxia telangiectasia to date, underscores the need for rigorously designed trials of sufficient duration to detect sustained clinical benefit. FUNDING: Quince Therapeutics.