Efficacy of dupilumab in chronic prurigo and chronic idiopathic pruritus: a systematic review of current evidence and analysis of response predictors

Dupilumab has demonstrated a great reduction in chronic pruritus that is the hallmark of atopic dermatitis (AD). Underscoring relevant pathogenesis similarities emerging from AD, chronic idiopathic pruritus (CIP) and chronic prurigo (CP), several authors suggested the beneficial role of dupilumab in these conditions. The evidence on this subject is limited with no precise data available. In this study, we carried out a systematic literature review in order to evaluate the efficacy of dupilumab on both pruritus and skin manifestations in the two largest retrospective cohorts of patients with CP and CIP and tried to identify potential response predictors. Electronic searches were conducted on 4 databases. Our primary outcome was the improvement in pruritus measured by a reduction in the patient's reported numerical rating scale of itch (NRSI) by >4. Secondary outcomes included the proportion of patients with a complete response at the end of treatment, reduction in the number of lesions by the Investigator Global Assessment (IGA), improvement in numerical rating scale of sleep (NRSS), improvement in quality of life measured by the Dermatology Life Quality Index (DLQI), time until patient perceived any improvement (Time-First) and time until the patient-reported absence of pruritus (Time-Final). Descriptive statistics were calculated for each demographic and clinical variable. Univariate logistic regression analyses were conducted to explore the association between response to dupilumab and potential predictive factors. We included 25 articles in the analysis, counting a total of 153 patients. Based on CP patients' cohort (n = 132), the mean NRSI at baseline was 8.79 ± 0.86 and the NRSI final was 2.32 ± 1.27. The mean time to first improvement was 5.18 ± 3.13 weeks, while the time to complete improvement of pruritus (Time-final) was 13.6 ± 12.0 weeks. Ninety patients out of 109 (83%) noticed an improvement in pruritus before 4 weeks of dupilumab therapy. At the end of treatment, 18 patients out of 126 (14%) had a complete remission of pruritus and 110 patients out of 123 (89%) had a reduction of NRSI >4. The reduction in NRSI was significantly greater in patients improving before 4 weeks of treatment (6.57 ± 1.71) compared with patients improving in more than 4 weeks (5.49 ± 1.39, P < 0.001). Patients with history of AD and those who have been previously treated with cyclosporine or methotrexate had a significantly lower reduction in NRSI (e.g. 6.05 ± 1.34 vs. 7.08 ± 1.90, P < 0.01 for nonassociated AD patients). Based on CIP patient's cohort (n = 21), the mean NRSI at baseline was 8.33 ± 0.80 and the NRSI final was 0.95 ± 0.59. The mean time to first improvement was 2 ± 0 weeks, while the time to complete improvement (Time-final) was 14.6 ± 10 weeks. At the end of treatment, 3 patients out of 21 (14%) had a complete remission of pruritus and 100% of patients had a reduction of NRSI >4. No serious treatment-emergent adverse events were reported. The most common adverse event was mild conjunctivitis (13 cases). We highlight the importance of one early sign of improvement as a predictor of the future response to dupilumab: the improvement before 4 weeks of treatment that leads significantly to a greater final reduction in NRSI. Furthermore, patients with the presence or history of atopy appear to be less responsive to dupilumab than nonatopic patients and develop more side effects, in particular conjunctivitis.