Auditory N1 event-related potential amplitude is predictive of serum concentration of BPN14770 in fragile x syndrome.

Fragile X syndrome (FXS) is a rare neurodevelopmental disorder caused by a CGG repeat expansion ≥ 200 repeats in 5' untranslated region of the FMR1 gene, leading to intellectual disability and cognitive difficulties, including in the domain of communication. A recent phase 2a clinical trial testing BPN14770, a phosphodiesterase 4D inhibitor, showed improved cognition in 30 adult males with FXS on drug relative to placebo. The initial study found significant improvements in clinical measures assessing cognition, language, and daily functioning in addition to marginal improvements in electroencephalography (EEG) results for the amplitude of the N1 event-related potential (ERP) component. EEG results suggest BPN14770 improved neural hyperexcitability in FXS. The current study investigated the relationship between BPN14770 pharmacokinetics (PK) and the amplitude of the N1 ERP component from the initial data. Consistent with the original group-level finding in period 1 of the study, participants who received BPN14770 in the period 1 showed a significant correlation between N1 amplitude and serum concentration of BPN14770. These findings strengthen the validity of the original result, indicating that BPN14770 improves cognitive performance by modulating neural hyperexcitability. This study represents the first report of significant correlation between a reliably abnormal EEG marker and serum concentration of a novel pharmaceutical in FXS.

Inhibition of phosphodiesterase-4D in adults with fragile X syndrome: a randomized, placebo-controlled, phase 2 clinical trial.

The goal of this study was to determine whether a phosphodiesterase-4D (PDE4D) allosteric inhibitor (BPN14770) would improve cognitive function and behavioral outcomes in patients with fragile X syndrome (FXS). This phase 2 trial was a 24-week randomized, placebo-controlled, two-way crossover study in 30 adult male patients (age 18-41 years) with FXS. Participants received oral doses of BPN14770 25 mg twice daily or placebo. Primary outcomes were prespecified as safety and tolerability with secondary efficacy outcomes of cognitive performance, caregiver rating scales and physician rating scales (ClinicalTrials.gov identifier: NCT03569631 ). The study met the primary outcome measure since BPN14770 was well tolerated with no meaningful differences between the active and placebo treatment arms. The study also met key secondary efficacy measures of cognition and daily function. Cognitive benefit was demonstrated using the National Institutes of Health Toolbox Cognition Battery assessments of Oral Reading Recognition (least squares mean difference +2.81, P = 0.0157), Picture Vocabulary (+5.81, P = 0.0342) and Cognition Crystallized Composite score (+5.31, P = 0.0018). Benefit as assessed by visual analog caregiver rating scales was judged to be clinically meaningful for language (+14.04, P = 0.0051) and daily functioning (+14.53, P = 0.0017). Results from this study using direct, computer-based assessment of cognitive performance by adult males with FXS indicate significant cognitive improvement in domains related to language with corresponding improvement in caregiver scales rating language and daily functioning.