A Study to Investigate the Effects and Safety of SPG601 for the Treatment of Fragile X Syndrome in Male Participants

This is a Phase 2b/3, randomized, double-blind, placebo-controlled, study designed to evaluate the efficacy, safety and tolerability of multiple dose regimens of SPG601 in male participants with FXS. The study consists of two parts, Phase 2b, dose-regimen finding, 4-arm parallel design: Eligible participants will be randomized to receive SPG601 or matched placebo. Participants will receive study intervention over 4 weeks and will be followed up for 4 weeks after last dose of study intervention. Phase 3, 2-arm parallel design: Eligible participants will be randomized 1:1 to receive SPG601 or matched placebo. The dose of SPG601 administered in the Phase 3 will be defined based on analysis of Phase 2b. Participants will receive study intervention over 12 weeks and will be followed up for 4 weeks after last dose of study intervention.