Progression from oligoarticular to polyarticular psoriatic arthritis and apremilast as a disease modifier: novel insights from FOREMOST

Objectives: Data regarding progression from oligoarticular to polyarticular psoriatic arthritis (PsA) are sparse. Using FOREMOST, we identify progression predictors and evaluate apremilast’s treatment effect in early PsA. Methods: FOREMOST (NCT03747939) randomized N = 308 patients with early (mean duration, 9.9 months) PsA and limited joint involvement (>1 to ≤4 swollen and >1 to ≤4 tender joints; not confirmed by imaging) to apremilast or placebo for 24 weeks, followed by open-label apremilast through week 48. Multivariable logistic regression modelled predictors of progression from oligoarticular (≤4 active [swollen and/or tender] joints) to polyarticular (>4 active joints) PsA at week 16 and the effect of apremilast. Disease progression, disease activity, clinical signs/symptoms and tolerability were summarized through week 48 for N = 291 patients receiving ≥1 apremilast dose (from randomization or switched from placebo). Results: Most (268/308 [87.0%]) patients had oligoarticular PsA at baseline; 25.1% (59/235) progressed to polyarticular PsA by week 16 (data as observed). Apremilast reduced odds of progression vs placebo by 58% (odds ratio [OR; 95% CI]: 0.42 [0.22, 0.77]). In placebo-treated patients, being female, being csDMARD-naïve, and having dactylitis significantly increased odds of progression (OR: 3.35 [1.20, 9.34], 3.42 [1.18, 9.93], and 9.26 [1.32, 65.09], respectively). Apremilast treatment for up to 48 weeks maintained low rates of disease progression and improvements in disease activity/clinical signs and symptoms, with no new safety signals. Conclusion: Initiating apremilast treatment during the early, oligoarticular phase of PsA reduced disease activity and delayed progression to polyarticular disease, with benefits maintained with up to 48 weeks of treatment. Trial registration: ClinicalTrials.gov; NCT03747939.