WP1066 is a well-known inhibitor of the JAK/STAT3 signaling pathway. By a screen of known small molecule inhibitors of various enzymes and protein factors, we identified WP1066 as a ceramide glucosyltransferase inhibitor. Ceramide glucosyltransferase catalyzes the first glycosylation step during glycosphingolipid synthesis. We found that WP1066 inhibited the activity of ceramide glucosyltransferase with an IC50 of 7.2 mu M, and that its action was independent of JAK/STAT3 pathway blockade. Moreover, the modes of inhibition of ceramide glucosyltransferase were uncompetitive with respect to both C-6-NBD-cermide and UDP-glucose. (C) 2017 Elsevier Inc. All rights reserved.