– (-)-L-threo-PDMP is an enhancer of ganglioside biosynthesis. The (-)-L-threo-PDMP (1S,2S) isomer is the active stimulatory component of DL-threo-PDMP in contrast to (+)-D-threo-PDMP , which is an inhibitor of glucosylceramide synthetase. (-)-L-threo-PDMP upregulates GM3, GD3, and GQ1b synthase levels, which are glycosyltransferases involved in ganglioside biosynthesis, and increases ganglioside levels in cells. It increases neurite outgrowth and synapse formation in vitro and improves retention of a long-term memory learned prior to forebrain ischemia in rats when administered following ischemia at a dose of 40 mg/kg per day.