Association between serum interleukin-17A and clinical response to tofacitinib and etanercept in moderate to severe psoriasis

BackgroundPsoriasis is a systemic inflammatory disease with a pathophysiology involving interleukin (IL)-17. Tofacitinib is an oral Janus kinase inhibitor. Etanercept is a tumour necrosis factor- inhibitor used in the treatment of psoriasis. Neither agent inhibits IL-17 directly. AimTo evaluate correlations between circulating IL-17A and clinical efficacy in patients with psoriasis treated with tofacitinib or etanercept. MethodsSerum concentrations of IL-17A homodimer and IL-17A/F heterodimer were determined by immunoassays at weeks 0, 4 and 12 in patients with moderate to severe psoriasis treated with placebo (n = 60), tofacitinib 5 mg twice daily (n = 184), tofacitinib 10 mg twice daily (n = 190), or etanercept 50 mg subcutaneously twice weekly (n = 190). Disease severity was assessed using the Psoriasis Area and Severity Index (PASI) and clinical response was defined as patients achieving 75% improvement from baseline PASI (PASI75). ResultsSerum levels of IL-17A homodimer at week 0 showed moderate correlation with PASI, with a Spearman correlation coefficient of 0.43. Furthermore, serum levels of IL-17A homodimer showed a clear correlation with clinical response, with a decrease of 57.1% in patients achieving PASI75 at week 12, but only 15.9% decrease in nonresponders. PASI75 responders had lower median concentrations of IL-17A (range across treatments: 0.24-0.27 pg/mL) at week 12 vs. nonresponders (0.37-0.62 pg/mL), regardless of the treatment. Serum IL-17A/F heterodimer showed similar decreases at week 12 in responders and nonresponders. ConclusionsBaseline serum IL-17A correlates moderately with psoriasis severity. Reduction in circulating IL-17A is required for disease remission regardless of therapeutic agent.