Notably, despite the observed decrease in FKBP51 levels in HD, further suppression of its activity via siRNA-mediated knockdown or pharmacological inhibition with the specific inhibitor SAFit2 significantly reduces mutant HTT (mHTT) protein levels, indicating a complex pathophysiological role for FKBP51 in HD. This evidence concerns the gene FKBP4 and Huntington disease.