Gaboxadol in angelman syndrome: A double-blind, parallel-group, randomized placebo-controlled phase 3 study.

PURPOSE: To evaluate efficacy and safety of gaboxadol for treatment of children with Angelman syndrome (AS). METHOD: In this international, double-blind, phase 3 trial, we randomized children 4-12 years old with a molecular diagnosis of AS and a Clinical Global Impression (CGI)-severity score ≥3 to either daily administration of weight-based gaboxadol or matching placebo for 12 weeks. The primary endpoint was the CGI-Improvement-AS (CGI-I-AS) score at week 12. Secondary endpoints included the proportion of participants with CGI-I-AS response of ≤3 (i.e., at least "minimal improvement") and ≤2 (i.e., at least "much improvement") at week 12. Safety and tolerability were monitored throughout the study. Weight based dosing of study drug ranged from 0.125 mg/kg to 0.24 mg/kg depending on weight range. RESULTS: Between August 2019 and November 2020, 104 participants were enrolled: participants 4-12 years old were randomly (1:1) assigned to gaboxadol (n = 47) or placebo (n = 50), and 7 other participants 2─3 years old who received gaboxadol and were assessed for safety only. All gaboxadol-treated participants and 48 of 50 placebo-treated participants completed treatment. There was no significant difference in CGI-I-AS between groups: at week 12, mean CGI-I-AS score was 3.3 (SD, 1.00) and 3.2 (SD, 1.05) in the gaboxadol and placebo groups, respectively, yielding a least squares mean difference of zero (p = 0.83). There were no between-group significant differences with respect to CGI-I-AS responses. Gaboxadol was well tolerated in all age groups of this study. CONCLUSIONS: There was no significant difference in CGI-I-AS between gaboxadol and placebo after 12 weeks of study treatment in pediatric AS participants. CLINICALTRIALS: GOV: NCT04106557.

A Double-Blind, Randomized, Placebo-Controlled Clinical Study of Trofinetide in the Treatment of Fragile X Syndrome.

BACKGROUND: We analyze the safety and tolerability of trofinetide and provide a preliminary evaluation of its efficacy in adolescent and adult males with fragile X syndrome. METHODS: This study was an exploratory, phase 2, multicenter, double-blind, placebo-controlled, parallel group study of the safety and tolerability of orally administered trofinetide in 72 adolescent and adult males with fragile X syndrome. Subjects were randomly assigned in a 1:1:1 ratio to 35 or 70 mg/kg twice daily trofinetide or placebo for 28 days. Safety assessments included adverse events, clinical laboratory tests, vital signs, electrocardiograms, physical examinations, and concomitant medications. Efficacy measurements were categorized into four efficacy domains, which related to clinically relevant phenotypic dimensions of impairment associated with fragile X syndrome. RESULTS: Both 35 and 70 mg/kg dose levels of trofinetide were well tolerated and appeared to be generally safe. Trofinetide at the 70 mg/kg dose level demonstrated efficacy compared with placebo based on prespecified criteria. On the basis of a permutation test, the probability of a false-positive outcome for the achieved prespecified success was 0.045. In the group analysis, improvement from treatment baseline was demonstrated on three fragile X syndrome-specific outcome measures. CONCLUSIONS: Trofinetide was well tolerated in adolescent and adult males with fragile X syndrome. Despite the relatively short duration of the study, a consistent signal of efficacy at the higher dose was observed in both caregiver and clinician assessments, based on a novel analytical model incorporating evaluation of multiple key symptom areas of fragile X syndrome. This finding suggests a potential for trofinetide treatment to provide clinically meaningful improvement in core fragile X syndrome symptoms.