Sustained Inhibition of Structural Damage Progression and Improvements in Disease Activity With Guselkumab in Biologic‐Naïve Participants with Active and Erosive Psoriatic Arthritis: Results Through Week 48 of the Phase 3b Randomized, Double‐Blind, Placebo‐Controlled APEX Study

Objective In APEX, guselkumab, which binds to the IL‐23p19 subunit and CD64 on IL‐23‐producing cells, demonstrated significant joint efficacy and inhibition of structural damage progression in participants with active and erosive PsA through Week (W)24; W48 findings are reported herein. Methods The APEX modified full analysis set included 1020 biologic‐naïve adults with active PsA (≥3 tender joints; ≥3 swollen joints; CRP ≥0.3mg/dL; ≥2 erosive joints) randomized to guselkumab every (Q)4W (N=273), guselkumab at W0,4 then Q8W (N=371), or placebo followed by guselkumab Q4W beginning at W24 (N=376). Outcomes through W48 included ACR20/50/70 response rates (using multiple/nonresponder imputation); least squares mean (LSM) change in PsA‐modified van der Heijde‐Sharp score (vdH‐S); achievement of clinically meaningful improvement (CMI; ≥0.35‐point) in HAQ‐DI, ≥90% improvement in Psoriasis Area and Severity Index (PASI90), and minimal disease activity (MDA). Results Through W48, 93% (950/1020) of participants completed study intervention. Guselkumab Q4W and Q8W through W48 demonstrated durable ACR20/50/70 response rates (71‐74%/51‐56%/31‐35%), and low rates of structural damage progression (vdH‐S LSM change: 0.60‐0.78); 60‐64% of participants reported HAQ‐DI CMI, 74‐80% achieved PASI90, 36‐41% achieved MDA. Following transition to guselkumab, structural damage progression among placebo‐randomized participants diminished (vdH‐S LSM change W0‐24: 0.96; W24‐48: 0.41) and clinical response rates increased through W48. Adverse event rates were consistent with placebo and guselkumab through W24 and stable through W48 of guselkumab. Conclusion APEX W48 findings further support guselkumab use for durable and comprehensive treatment of diverse PsA manifestations. Inhibition of cumulative joint damage with guselkumab may optimize outcomes.