FMR1 and fragile X syndrome: However, clinical trials of GSK3β inhibition as a potential FXS treatment show only minor improvements (Berry-Kravis et al., 2008; Liu and Smith, 2014; Telias, 2019), possibly because FMRP regulation of Wnt signaling for neural differentiation happens during early development, which was bypassed in these trials (Telias et al., 2015).