Psoriasis (Ps) is a chronic inflammatory disease with an important genetic component. It shares pathophysiological mechanisms with other autoimmune diseases such as psoriatic arthritis (PsA), rheumatoid arthritis (RA) and Crohn's disease (CD). These conditions can be treated using biological drugs such as infliximab, adalimumab and etanercept, which selectively block the proinflammatory cytokine tumor necrosis factor (TNF)-α. Although these agents have greatly improved the prognosis of Ps, PsA, RA and CD, they do not cure the disease and are expensive; in addition, significant proportions of patients do not respond or develop serious adverse effects. Therefore, it is important to investigate biomarkers, such as gene polymorphisms, that can predict which patients will respond best to a specific drug. Some polymorphisms in genes TNF, TNF receptor superfamily 1B (TNFR1B) and TNFα-induced protein 3 gene (TNFAIP3) have been associated with response to anti-TNF therapy in patients with Ps. The present article reviews other polymorphisms that could also play a role in prediction of response to these treatments.

Psoriasis improves when IL-17 is blocked. Anti-TNF drugs reduce the IL-17 signaling pathway, and anti-IL-17 drugs are being developed to treat moderate-to-severe psoriasis. We analyzed three SNPs in IL-17A (rs2275913 and rs10484879) and IL-17F (rs763780) to look for an association with psoriasis and/or with response to anti-TNF drugs or ustekinumab. We included 197 healthy controls and 194 patients with moderate-to-severe psoriasis. The results of the univariate analysis showed an association between rs10484879 and psoriasis, although this relationship disappeared after adjustment for HLA-C (rs12191877). We also found an association between rs763780 (IL-17F) and response to ustekinumab (n = 70) and infliximab (n = 37) at 3 and 6 months and an association between rs763780 and the response to adalimumab at 6 months (n = 67).

Anti-tumor necrosis factor (anti-TNF) drugs are effective against psoriasis, although 20-30% of patients are nonresponders. Few pharmacogenomic studies have been performed to predict the response to anti-TNF drugs in psoriasis. We studied 173 polymorphisms to establish an association with the response to anti-TNF drugs in patients with moderate-to-severe plaque psoriasis (N=144). We evaluated the response using PASI75 at 3, 6 and 12 months. The results of the multivariate analysis showed an association between polymorphisms in PGLYR4, ZNF816A, CTNNA2, IL12B, MAP3K1 and HLA-C genes and the response at 3 months. Besides, the results for polymorphisms in IL12B and MAP3K1 were replicated at 6 months. We also obtained significant results for IL12B polymorphism at 1 year. Moreover, polymorphisms in FCGR2A, HTR2A and CDKAL1 were significant at 6 months. This is the first study to show an association with these polymorphisms. However, these biomarkers should be validated in large-scale studies before implementation in clinical practice.