Clinical characteristics and response to biological therapies for inverse psoriasis: a real‐life comparison between the therapeutic effects of anti‐IL‐23 and anti‐IL‐17 agents

Background Inverse psoriasis (IP) is a variant of plaque psoriasis involving flexor surfaces. A clear definition of IP is still lacking. Therapy is based on topical and systemic treatments, including classic systemic drugs and biologic agents, but a well-defined therapeutic strategy is absent. Materials and methods This retrospective study investigated the general characteristics of patients with IP or vulgar psoriasis and compared the effectiveness of anti-interleukin-17 or anti-interleukin-23 agents in the same groups. Second, treatment effectiveness and the demographic characteristics of IP patients treated with IL-23 and IL-17 inhibitors were also compared. IP patients were included if they had specific psoriatic involvement of the axillary, inguinal, or submammary lines, breast folds, antecubital and popliteal pits, intergluteal fold, and perianal area. Patients with vulgar plaque psoriasis and concomitant intertriginous involvement were included in the vulgar psoriasis cohort. Results Patients with IP were prevalently female and treated with IL-17 inhibitors compared to those with vulgar psoriasis. They also had a greater risk of drug discontinuation and subsequent therapeutical switch (32.1% vs. 18.1%, P = 0.002). At later time points, those with IP showed progressively slower achievement of PASI100 and 90 compared to the cohort with vulgar psoriasis. In the IP cohort, there was greater joint involvement in patients treated with an anti-IL-17 agent (P = 0.011), who also had a lower median age of onset (P = 0.011) compared to patients treated with an anti-IL-23 agent. Patients with IP treated with an anti-IL-23 agent initiated with a lower mean PASI and showed a slower response than patients on an anti-IL-17 agent. At later time points, progressively greater effectiveness of IL-23 inhibitors was observed compared to IL-17 inhibitors. Conclusions Patients with IP responded less to biologic agents than those with vulgar psoriasis. In the IP cohort, IL-17 inhibitors had a faster onset than IL-23 inhibitors, but long-term anti-IL-23 agents seem to be associated with better outcomes.