Synthesis and Biological Activity of a Novel Inhibitor of Dihydroceramide Desaturase

A novel mechanism‐based dihydroceramide desaturase inhibitor (XM462) in which the substrate C5 methylene group is replaced by a sulfur atom is reported. Dihydroceramide desaturase inhibition occurred both in vitro and in cultured cells with IC50 values of 8.2 and 0.78 μM, respectively, at a substrate concentration of 10 μM. In vitro experiments showed that XM462 produced a mixed‐type inhibition (Ki=2 μM, α=0.83). LC‐MS analyses showed that accumulation of endogenous dihydroceramides occurred in cells upon treatment with XM462 in serum‐free medium, whereas ceramides built up in controls. In addition, XM462 was found to be metabolised to its 1‐glucosyl and 1‐phosphocholine derivatives, and to the products of N‐deacylation and reacylation with palmitoyl and stearoyl groups. In Jurkat A3 cells cultured in serum‐free medium, viability, as the percentage of trypan blue unstained cells in total cells, was reduced upon XM462 treatment (5 μM, 24 h), but not in controls. The interest of this compound is discussed. Rational design considering both mechanistic aspects of enzymatic desaturation and structural features of reported fatty acyl‐CoA desaturase inhibitors led to the dihydroceramide desaturase inhibitor XM462. The design, synthesis, and biological activity of this compound both in vitro and in Jurkat A3 human leukemia cells are reported.