Obesity and Early Biologic Failure in Psoriasis: An Italian Multicentre Retrospective Cohort Study

Introduction Obesity may reduce biologic effectiveness in psoriasis, but its effect on specific reasons for treatment discontinuation is less well defined. We evaluated the association between obesity and biologic drug survival, with particular attention to primary failure and therapeutic class. Methods This retrospective multicentre cohort study included patients with plaque psoriasis treated with biologics at five Italian dermatology centres. Analyses were conducted at the treatment-line level using Kaplan-Meier methods and Cox proportional hazards models. Obesity was defined as body mass index (BMI) ≥ 30 kg/m2. BMI was also examined continuously and using a natural cubic spline. Logistic regression and Cox models with standard errors clustered by patient were used as sensitivity analyses. Results Overall, 573 patients contributed 770 treatment lines; 193 of 562 patients with available BMI data (34.3%) were obese. Primary failure occurred in 17.0% of treatment lines from patients with obesity and 5.8% of treatment lines from patients without obesity (log-rank p < 0.001). In the adjusted Cox model, obesity was associated with a higher risk of primary failure (hazard ratio [HR] 2.75, 95% confidence interval [CI] 1.59–4.77). Each 5 kg/m2 increase in BMI was associated with a 37% higher risk (HR 1.37, 95% CI 1.14–1.65), with evidence of non-linearity (likelihood ratio p = 0.0018). Compared with tumour necrosis factor-α inhibitors, interleukin (IL)-17 inhibitors (HR 0.49, 95% CI 0.24–0.97) and IL-23 pathway inhibitors (HR 0.47, 95% CI 0.24–0.93) showed lower primary failure risks. Obesity was not associated with secondary failure or safety-related discontinuation. Conclusion Obesity was associated mainly with early biologic failure in psoriasis. The association was most evident with tumour necrosis factor-α inhibitors.