IL17A and psoriasis: Also, more selective anti-IL23 agents (anti-p19) have shown efficacy and are being further developed, in contrast to agents inhibiting IL-17 downstream which have failed in clinical trials despite their clear efficacy in psoriasis (Verstockt et al. in Expert Opin Biol Ther 17(1):31–47, 2017; Verstockt et al. in Expert Opin Drug Saf 16(7):809–821, 2017).