Relationship Among Treatment, Pruritus, Investigator’s Static Global Assessment, and Quality of Life in Patients with Atopic Dermatitis

Introduction: The Investigator’s Static Global Assessment (ISGA) is a 5-point rating scale that is recommended by the US Food and Drug Administration for assessing the severity of atopic dermatitis (AD), and ISGA success is a widely used endpoint in AD clinical studies. In this study, we seek to interpret the relationship of ISGA with treatment, pruritus, and quality of life (QoL) by conducting post hoc analyses of pooled data from two phase 3 crisaborole studies. Methods: Patients aged ≥ 2 years with baseline ISGA of 2 (mild) or 3 (moderate) were randomly assigned 2:1 to receive crisaborole or vehicle for 28 days. Disease severity, pruritus severity, and QoL were assessed with the ISGA, Severity of Pruritus Scale (SPS), and Dermatology Life Quality Index (DLQI; patients aged ≥ 16 years), or Children’s Dermatology Life Quality Index (CDLQI; patients aged 2–15 years), respectively. The effect of treatment on ISGA and the relationship between ISGA and QoL were analyzed using a longitudinal repeated-measures model. The interrelationship between treatment, disease severity, pruritus, and QoL was analyzed with a mediation model. Results: Overall, 1522 patients (crisaborole, n = 1016; vehicle, n = 506) were included. Estimated longitudinal profiles indicated changes in ISGA by day 8 were large for crisaborole (effect size [ES]: − 0.68) and small for vehicle (ES: − 0.34). There was a direct relationship between ISGA and DLQI and CDLQI severity bands in the longitudinal repeated-measures model. For both QoL mediation models, treatment effects on QoL were mediated indirectly by reduction in pruritus (DLQI, 42.4%; CDLQI, 58.1%) and disease severity (DLQI, 12.2%; CDLQI, 33.1%). Conclusions: These post hoc analyses suggest that ISGA success is a clinically meaningful endpoint associated with reduction in the severity of pruritus and improvement in QoL.