Fragile X syndrome: Lessons learned from the most translated neurodevelopmental disorder in clinical trials

Fragile X syndrome (FXS) is the leading genetic cause of autism spectrum disorder (ASD) and inherited intellectual disability (ID) worldwide. Preclinical successes in understanding the biology of FXS have led to numerous translational attempts in human clinical trials of therapeutics that target the excitatory/inhibitory neural signaling imbalances thought to underlie FXS. Despite the preclinical success story, the negative results of the human clinical trials have been deemed to be at least in part disappointing by the field. In this commentary, we contend that such negative studies results in clinical trials may actually propel the FXS field forward by serving as important lessons for designing and implementing improved future clinical trials such that can objectively assess the full range of responses to new therapeutics.