With C20-analogs 53-57 in hand, attention turned towards determining their cellular efficacy and overall potency in a human PBMCs assay measuring the secretion of IL-17A. IL-17A is a major effector cytokine in the pathogenesis of psoriasis, and antibodies targeting IL-17A or its receptors have shown to be highly efficacious in psoriasis patients (e.g. calcipotriol (7) potently inhibits the secretion of IL-17A). In the assay event, human PBMCs were supplemented with IL-23 to stimulate the Th17 pathway and incubated with T-cell receptor crosslinking antibodies anti-CD3/antiCD28 for 3 days to stimulate the secretion of IL-17A.