HTT and Huntington disease: Its derivative PBT2 has also been shown to reduce Aβ levels and improve cognition in several Phase Ib/IIa trials.[11] In Huntington disease (HD), copper accumulation promotes the aggregation of Huntingtin proteins and interacts with histidine residues at the N-terminal end of the protein.[4] Copper may contribute to the pathogenesis of HD by inhibiting lactate dehydrogenase, a key enzyme involved in lactate metabolism.[12] Copper chelators (clioquinol or tetrathiomolybdate) attenuate cognitive deficits and behavioral abnormalities in the R6/2 HD mouse model.[13]