APEX phase IIIb trial Week 24 results: Inhibition of structural damage progression in PsA with guselkumab

Psoriatic arthritis (PsA) is a chronic, heterogenous, inflammatory disease resulting in structural damage that affects patient HRQoL. Guselkumab is a dual-acting mAb indicated for moderate-to-severe plaque psoriasis and active PsA. Early findings from DISCOVER-2 (NCT03158285) have demonstrated less radiographic progression with guselkumab vs placebo.

During the European Alliance of Associations for Rheumatology (EULAR) 2025 Congress, Philip Mease presented findings through Week 24 (W24) from the phase IIIb APEX trial (NCT04882098) assessing the efficacy and safety of guselkumab vs placebo in the inhibition of structural damage progression in PsA.¹

Patients who were biologic-naïve and had active PsA for ≥6 months, along with ≥2 erosive joints on hand/foot radiographs were included (N = 1,020). Eligible patients were randomized to receive guselkumab 100 mg SC Q4W (n = 273), guselkumab 100 mg SC Q8W (n = 371), or placebo (n = 376). The primary endpoint was ACR20 response at W24. Key secondary endpoints included mean change in total PsA-modified vdH-S score at W24.

Key learnings

The primary endpoint was met; guselkumab Q4W and Q8W demonstrated a higher ACR20 response rate vs placebo at W24 (66.6% vs 68.3% vs 47.0%; p < 0.001). Guselkumab vs placebo also achieved higher ACR50 and ACR70 response rates (p < 0.001 each).

Guselkumab Q4W and Q8W had a lower total PsA-modified vdH-S score vs placebo (0.55 vs 0.54 vs 1.35, respectively; p = 0.002). Guselkumab demonstrated a lower erosion score (p = 0.002) and JSN score (p = 0.025) vs placebo. 

At W24, a higher proportion of patients in the guselkumab group demonstrated a change in PsA-modified vdH-S score ≤0.5 (p = 0.007), PASI 90 (p < 0.001), and HAQ-DI (p < 0.001) vs the placebo group.

Guselkumab did not demonstrate any new safety signals. AEs (38.2% vs 42.5% vs 37.3%) and SAEs (1.8% vs 3.1% vs 2.6%) were comparable between the guselkumab Q4W, guselkumab Q8W, and placebo groups, respectively.