AFQ056 for Language Learning in Children With FXS

This study will enroll 100 participants with Fragile X syndrome (FXS) between the ages of 32 months and 6 years. After being informed about the study and its potential risks, patients with Fragile X Syndrome will be screened for eligibility. Participants who meet entry criteria and agree to participate will then enter a single-blind 4-month placebo lead-in during which study participants will continue therapy treatments as usual to allow for placebo effects to stabilize. At the end of the 4-month placebo lead-in, all participants will have a repeat battery of AFQ056 baseline assessments and will enter the placebo-controlled phase, where they will be randomized in a 1:1 ratio to AFQ056 or placebo. All subjects will begin at a dose of 25 mg of AFQ056 or placebo, taken orally twice per day. Over 7 weeks, they will titrate up to their maximum tolerated dose (MTD), up to 100 mg. Once they have reached their MTD, both participant groups will initiate an intensive language intervention designed to maximize the extent to which parents engage in types of verbally responsive interactions that have been well documented as facilitating language learning. The entire language intervention will be delivered to the parent in the home or at scheduled study visits through the use of a laptop computer equipped with distance video-teleconferencing software and will include coaching, homework, and feedback sessions. Subjects will be treated with their MTD in combination with the language intervention for 6 months. After 8 months of treatment in the placebo-controlled phase (including 6 months of language intervention), all participants will have final assessments and will be given the opportunity to enter the open label extension (OLE) period. In the OLE, all participants will be treated with active drug according to the same schedule as in the placebo-controlled phase with 2 months of flexible dose titration to the MTD followed by a period of stable treatment, and will continue the language intervention throughout. A post-intervention follow-up visit will be conducted one month after the final assessment visit of the trial. Researchers will compare overall weighted communication score in the AFQ056 and placebo groups, after 6 months of treatment in combination with an intensive standardized parent-implemented language learning intervention. This is meant to serve as a marker of drug effect on neural plasticity, the core problem in the disorder. Further assessments will also be compared between groups to determine changes in language, cognitive, and adaptive functioning.