Absolute Psoriasis Area and Severity Index as a valuable marker to determine initial treatment response in psoriasis patients treated with guselkumab in routine clinical care.

Guselkumab is an anti-interleukin-23p19 monoclonal antibody approved as a first-line medication in patients with moderate-to-severe plaque-type psoriasis and second-line in active psoriatic arthritis. In the clinic, patients who have shown a lack of previous treatment efficacy and/or tolerability are often prescribed guselkumab. These patients generally have less severe psoriasis compared to clinical trial cohorts, reflected in lower Psoriasis Area and Severity Index (PASI). To evaluate treatment response in a real-world setting, we conducted a multicenter-retrospective chart review in three specialized dermatological centers. Seventy-four patients who received guselkumab treatment were included in the study and baseline characteristics were described. The mean PASI at baseline was 13.0 (± 6.7). After 12 weeks of treatment 40 patients could be followed up at the participating centers and efficacy was assessed: 72.5% of these patients achieved an absolute PASI ≤5 (55.0% ≤3; 42.5% ≤2) whereas only 57.5% of patients were able to gain a delta PASI reduction of at least 75%. Using the absolute PASI as a treatment goal rather than response rate revealed that guselkumab was highly effective in this real-world setting. In conclusion, the absolute PASI proved to be a more valuable tool to measure treatment outcome.

CYP1A1 Enzymatic Activity Influences Skin Inflammation Via Regulation of the AHR Pathway.

The AHR is an environmental sensor and transcription factor activated by a variety of man-made and natural ligands, which has recently emerged as a critical regulator of homeostasis at barrier organs such as the skin. Activation of the AHR pathway downmodulates skin inflammatory responses in animal models and psoriasis clinical samples. In this study, we identify CYP1A1 enzymatic activity as a critical regulator of beneficial AHR signaling in the context of skin inflammation. Mice constitutively expressing Cyp1a1 displayed increased CYP1A1 enzymatic activity in the skin, which resulted in exacerbated immune cell activation and skin pathology, mirroring that observed in Ahr-deficient mice. Inhibition of CYP1A1 enzymatic activity ameliorated the skin immunopathology by restoring beneficial AHR signaling. Importantly, patients with psoriasis displayed reduced activation of the AHR pathway and increased CYP1A1 enzymatic activity compared with healthy donors, suggesting that dysregulation of the AHR/CYP1A1 axis may play a role in inflammatory skin disease. Thus, modulation of CYP1A1 activity may represent a promising alternative strategy to harness the anti-inflammatory effect exerted by activation of the AHR pathway in the skin.