Purity >98%. PDMP is a ceramide analog first prepared in a search for inhibitors of glucosylceramide synthase. PDMP has two adjacent chiral centers (C1 and C2) allowing for the formation of four possible isomers. PDMP contains all four of these stereoisomers. Treatment of cultured cells with PDMP reduces the synthesis of sphingosine and its derivatives, increases cellular ceramide, and induces cell cycle arrest. The ability to inhibit glucosylceramide synthase has been found to reside in the D-threo (1R,2R) enantiomer. Other activities, such as alkaline ceramidase inhibition and cytotoxicity, may involve interactions between PDMP isomers and/or direct activities of the other three isomeric PDMP compounds. By inhibiting Beta-1,4-galactosyltransferase 6, PDMP can also prevent the synthesis of lactosylceramide, a known promotor of neuroinflammation in mice during chronic experimental autoimmune encephalomyelitis, a model of multiple sclerosis.