Two recent clinical trials provide evidence that interleukin-17 (IL-17) and its receptor are viable targets to treat psoriasis.

In one of these phase 2, randomized, double-blind trials, Kim Papp et al. (N. Engl. J. Med. 366, 1181–1189) tested different doses of brodalumab, a monoclonal antibody against the IL-17 receptor A, or placebo in 198 patients with psoriasis. In a separate trial, Craig Leonardi et al. (N. Engl. J. Med. 366, 1190–1199) treated 142 people with psoriasis with placebo or different doses of ixekizumab, a monoclonal antibody that directly targets IL-17.

After 12 weeks of treatment, both teams reported that the antibody-treated patients showed statistically significant improvements on the psoriasis area-and-severity index, a scale commonly used to quantify disease progression. Moreover, the safety profile of both antibodies was satisfactory.

Antibodies against other cytokines such as IL-12 and IL-23 are effective against psoriasis, acting at least in part by reducing the production of IL-17 and the generation of T helper type 17 immune responses. The clinical development of IL-17–targeting molecules may nevertheless be advantageous in terms of selectivity, as inhibiting the IL-12/IL-23 axis can also affect T helper type 1 responses, which are important in fighting infection. Phase 3 clinical trials will be necessary to establish the long-term safety and efficacy of brodalumab and ixekizumab.