Guselkumab Modulates Differentially Expressed Genes in Blood of Patients With Psoriatic Arthritis: Results from Two Phase 3, Randomized, Placebo‐Controlled Trials

OBJECTIVE: To evaluate gene expression in blood of patients with psoriatic arthritis (PsA) versus healthy controls and identify changes associated with guselkumab treatment. METHODS: Whole blood transcriptome profiling via paired‐end RNA sequencing was conducted using samples from DISCOVER‐1 and DISCOVER‐2 at baseline (n = 673) and at weeks 4 and 24 from a representative subgroup that received placebo or guselkumab (n = 227 [longitudinal PsA cohort]). Baseline samples were compared with demographically matched healthy controls (n = 21). Guselkumab‐mediated changes in gene expression were assessed in participants from the longitudinal PsA cohort who did versus did not achieve at least 20% improvement in American College of Rheumatology response criteria (ACR20) or at least 75% improvement in Psoriasis Area and Severity Index (PASI75). Differential gene expression was analyzed using edgeR. RESULTS: At baseline, 355 upregulated and 314 downregulated genes (PsA‐associated genes) were identified in patients with PsA versus healthy controls. Upregulated genes were related to neutrophil, mononuclear cell, and CD11b+ gene sets. No cell type–specific gene sets were identified among downregulated genes. Most PsA‐associated genes were modulated by guselkumab treatment. At week 24, genes downregulated by guselkumab were enriched with neutrophil, monocyte, eosinophil, and macrophage gene sets; genes upregulated by guselkumab were enriched with B cell, T cell, and natural killer cell gene sets. Reductions in expression of upregulated PsA‐associated gene sets were more pronounced in ACR20 and PASI75 responders than in nonresponders. CONCLUSION: These findings suggest a dysregulation of immune cell profiles in blood from patients in the baseline PsA cohort that approached levels in healthy controls after guselkumab treatment.