AB0837 ITCH AS THE MAJOR MEDIATOR OF THE EFFECT OF TOFACITINIB ON HEALTH-RELATED QUALITY OF LIFE IN PsA: A MEDIATION ANALYSIS
Authors: P. C. Taylor, A. G. Bushmakin, J. C. Cappelleri, P. Young, R. Germino, J. F. Merola, G. Yosipovitch
Journal: Annals of the Rheumatic Diseases (2020)

Background: PsA is a chronic, systemic inflammatory disease with signs and symptoms across multiple domains, including cutaneous manifestations, which can impact health-related quality of life (HQoL). Tofacitinib is an oral Janus kinase inhibitor for the treatment of PsA. In two Phase 3 randomised studies, patients (pts) with active PsA treated with tofacitinib experienced greater improvements in various dermatologic endpoints, compared with placebo. As pruritus is a bothersome symptom of skin disease in pts with PsA, we sought to determine how tofacitinib affects HQoL via clinical improvements in skin symptoms including itch. Objectives: To determine the relationships between tofacitinib treatment, dermatologic symptoms and pt-reported HQoL related to skin disease in PsA. Methods: Analyses used data (mean scores from Months 1 and 3) from two Phase 3 studies (OPAL Broaden [ NCT01877668 ]; OPAL Beyond [ NCT01882439 ]) of pts with active PsA treated with tofacitinib 5 mg twice daily or placebo; pts were tumour necrosis factor inhibitor (TNFi)-naïve or had previous inadequate response (IR) to ≥1 TNFi. All pts were treated continuously with a single conventional synthetic DMARD. Mediation modelling, a statistical method used to assess mechanisms underlying observed relationships between different variables via other explanatory variables (mediators), was applied. The mediation model included: treatment, as the independent (explanatory) binary variable (tofacitinib 5 mg BID vs placebo); HQoL, measured by Dermatology Life Quality Index (DLQI), as the dependent (outcome) variable; and two mediators, pt-reported Itch Severity Index (ISI) and Physician’s Global Assessment of Psoriasis (PGA-PsO) (a latent variable represented by erythema, induration and scaling). The initial model designated the treatment effect on DLQI mediated via ISI and PGA-PsO as an indirect effect, and treatment effects not attributable to ISI or PGA-PsO as a direct effect (Figure 1). Results: Data were collected from 468 pts, pooled from both studies. In the initial model (pooled data), the effect of tofacitinib treatment on DLQI was largely mediated by itch (measured by ISI) and PGA-PsO (indirect effect) (p&lt;0.0001); the effect of treatment attributable to factors other than ISI and PGA-PsO (direct effect) was not statistically significant (p=0.66). Results were consistent for pooled and individual study data. Because the direct effect was small and not statistically significant, the model was re-specified to exclude the direct effect of tofacitinib treatment on DLQI. In the revised model (pooled data), 17.7% of the indirect effect was attributable to PGA-PsO (p=0.0006) and 82.3% was attributable to itch (assessed by ISI) (p&lt;0.0001) (Figure 2). Analyses of individual studies using the revised model gave results generally consistent with pooled data. Conclusion: Dermatology-focused mediation modelling showed that a majority of the effect (~80%) of tofacitinib treatment on DLQI is mediated by improvements in itch, with ~20% mediated via improvements in PGA-PsO. Acknowledgments: Study sponsored by Pfizer Inc. Medical writing support was provided by Eric Comeau of CMC Connect and funded by Pfizer Inc. Disclosure of Interests: Peter C. Taylor Grant/research support from: Celgene, Eli Lilly and Company, Galapagos, and Gilead, Consultant of: AbbVie, Biogen, Eli Lilly and Company, Fresenius, Galapagos, Gilead, GlaxoSmithKline, Janssen, Nordic Pharma, Pfizer Roche, and UCB, Andrew G Bushmakin Shareholder of: Pfizer Inc, Employee of: Pfizer Inc, Joseph C Cappelleri Shareholder of: Pfizer Inc, Employee of: Pfizer Inc, Pamela Young Shareholder of: Pfizer Inc, Employee of: Pfizer Inc, Rebecca Germino Shareholder of: Pfizer Inc, Employee of: Pfizer Inc, Joseph F. Merola Consultant of: Merck, AbbVie, Dermavant, Eli Lilly, Novartis, Janssen, UCB Pharma, Celgene, Sanofi, Regeneron, Arena, Sun Pharma, Biogen, Pfizer, EMD Sorono, Avotres and LEO Pharma, Gil Yosipovitch Grant/research support from: Galderma, Kiniksa, Leo, Menlo, Novartis, Pfizer, Sanofi Regeneron, Consultant of: Eli Lilly, Galderma, Kiniksa, Leo, Menlo Therapeutics, Novartis, Pfizer Inc, Sanofi Regeneron, Trevi, Sienna