Factors impacting progression from oligoarticular to polyarticular PsA: Data from the FOREMOST study

Laura Coates¹, Philip J. Mease², Joseph Merola³, Lourdes Perez Chada⁴, Dafna D. Gladman⁵, Alen Zabotti⁶, Ulrich Mrowietz⁷, mitsumasa kishimoto⁸, Cynthia Deignan⁹, Siddharth Chaudhari¹⁰, Lichen Teng¹¹ and Laure Gossec¹², ¹Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, England, United Kingdom, ²Department of Rheumatology, Providence-Swedish Medical Center and University of Washington, Seattle, WA, ³UT Southwestern Medical Center, Dallas, TX, ⁴Harvard Medical School, Wayland, MA, ⁵Schroeder Arthritis Institute, Krembil Research Institute, Toronto Western Hospital, Division of Rheumatology, Toronto, ON, Canada, ⁶Division of Rheumatology, Department of Medicine (DMED), Academic Hospital "Santa Maria della Misericordia", ASUFC, University of Udine, Udine, Italy, Udine, Italy, ⁷Department of Dermatology, University Medical Center Schleswig-Holstein, Kiel, Germany, ⁸Kyorin University School of Medicine, Tokyo, Japan, ⁹Amgen, Inc., Agoura Hills, CA, ¹⁰Amgen Inc., Thousand Oaks, CA, ¹¹Amgen Inc., Thousand Oaks, ¹²Sorbonne Universite and Pitie-Salpetriere Hospital, Paris, France

Meeting: ACR Convergence 2025

Keywords: Inflammation, prevention, prognostic factors, Psoriatic arthritis, Randomized Trial

Session Information

Date: Sunday, October 26, 2025

Title: (0554–0592) Spondyloarthritis Including Psoriatic Arthritis – Treatment Poster I

Session Type: Poster Session A

Session Time: 10:30AM-12:30PM

Background/Purpose: FOREMOST (NCT03747939)1 offers novel insights on early oligoarticular (oligo, ≤4 active joints) PsA. Our aim was to analyse progression to polyarticular (poly; >4 active joints) disease and predictors of progression in FOREMOST.

Methods: FOREMOST is a randomized trial of 308 patients with early (duration ≤5 years) oligo PsA and limited joint involvement ( >1 to ≤4 swollen and >1 to ≤4 tender joints; 66–68 joints assessed) who received apremilast (APR) (n=203) or placebo (PBO) (n=105) for 24 weeks, with a primary outcome at 16 weeks1. Standard of care (SoC) NSAIDs and/or conventional synthetic (cs) DMARDs were permitted if taken at a stable dose through Week 24. Progression to poly disease was defined as changing from ≤4 active (swollen and/or tender) joints at baseline to >4 active joints at Week 16. In a post hoc, multivariable regression analysis, we assessed predictors of progression in the overall FOREMOST population and the placebo (PBO)±SOC group (as a surrogate for natural history). Variables of interest were selected on clinical relevance (Table 1) and backward selection used to identify statistically significant predictors of progression (p< 0.05 threshold); based on clinical relevance, body mass index (BMI) and enthesitis (Leeds index, LDI) were forced to remain in the model. Missing joint data were imputed using last observation carried forward.

Results: In FOREMOST, most patients had ≤4 active joints at baseline (overall, 268/308 [87%]; APR, 176/203 [87%]; PBO±SOC, 92/105 [88%]) and baseline characteristics were similar between APR and PBO±SOC1. In the overall population, APR was associated with statistically significant lower odds of progression vs PBO±SOC (Odds Ratio [OR] [95% CI], 0.42 [0.22, 0.77]; Fig 2a; adjustment for other covariates). After adjusting for treatment, being female (vs male), not receiving (vs receiving) csDMARDs during the study, and enthesitis (SPARCC >0; vs no enthesitis) were associated with statistically significantly higher odds of progression; patients with dactylitis (LDI >0) showed a non-significant trend towards higher odds of progression vs patients without dactylitis. In the PBO±SOC group, being female, being csDMARD-naive (vs prior csDMARD use), dactylitis (LDI > 0; vs no dactylitis), and not having nail psoriasis (vs having nail psoriasis) were associated with statistically significant higher odds of progression (Fig 2b).

Conclusion: Our data provides novel insights into factors driving progression from oligo to poly PsA, with female sex, enthesitis and dactylitis found to increase the risk of progression. These data may help clinicians identify patients with poor prognosis who require close monitoring and more intensive treatment. Among patients in FOREMOST receiving PBO, prior csDMARD use decreased the likelihood of progression more than three-fold. Compared with PBO±SOC, APR more than halved the likelihood of progression. These findings highlight the importance of early intervention in oligo PsA and the benefit of APR in delaying/preventing progression to poly disease. Our results should be validated using other PsA cohorts.1. Gossec, L., et al. Ann Rheum Dis, 2024. 83(11): p. 1480-1488.

Disclosures: L. Coates: AbbVie, 2, 5, 6, Amgen, 2, 5, 6, Biogen, 6, BMS, 2, Boehringer Ingelheim, 2, Celgene, 2, 5, 6, Domain, 2, Eli Lilly and Company, 2, 5, 6, Galapagos, 2, 6, Gilead, 2, 5, 6, GSK, 6, Janssen, 2, 5, 6, Medac, 6, MoonLake Immunotherapeutics, 2, Novartis, 2, 5, 6, Pfizer, 2, 5, 6, UCB, 2, 5, 6; P. Mease: AbbVie, 2, 5, 6, Acelyrin, 2, 5, Amgen, 2, 5, 6, BMS, 2, 5, Century, 2, Cullinan, 2, Eli Lilly and Company, 2, 5, 6, Inmagene, 2, J&J Innovative Medicine, 2, 5, 6, MoonLake Immunotherapeutics, 2, Novartis, 2, 5, 6, Pfizer, 2, 5, 6, Sana, 5, Spyre, 5, Takeda, 2, UCB, 2, 5, 6; J. Merola: AbbVie/Abbott, 2, 12, Investigator, Amgen, 2, 12, Investigator, Arena, 2, Avotres, 2, Biogen, 2, 12, Investigator, Bristol-Myers Squibb(BMS), 2, 12, Investigator, Celgene, 2, Dermavant, 2, 12, Investigator, Eli Lilly, 2, 12, Investigator, EMD Serono, 2, Janssen, 2, 12, Investigator, Leo Pharma, 2, 12, Investigator, Merck/MSD, 2, Novartis, 2, 12, Investigator, Pfizer, 2, 12, Investigator, Regeneron, 2, 12, Investigator, Sanofi, 2, 12, Investigator, Sun Pharma, 2, 12, Investigator, UCB, 2, 12, Investigator; L. Perez Chada: Bristol-Myers Squibb(BMS), 2, 6, Takeda, 2; D. Gladman: AbbVie, 2, 5, Amgen, 2, 5, AstraZeneca, 2, BMS, 2, 5, Eli Lilly, 2, 5, Janssen, 5, Johnson & Johnson, 2, Novartis, 2, 5, Pfizer, 2, 5, Roche, 2, UCB, 2, 5; A. Zabotti: AbbVie/Abbott, 2, 5, Amgen, 2, 5, Eli Lilly, 2, 5, Johnson & Johnson, 2, 5, 6, Novartis, 2, 5, UCB, 2, 5; U. Mrowietz: AbbVie, 1, 5, 6, Aditxt, 1, Almirall, 1, Amgen, 1, Biogen, 1, Boehringer-Ingelheim, 1, Bristol-Myers Squibb(BMS), 1, Eli Lilly, 1, Immunic Therapeutics, 1, Janssen-Cilag, 1, LEO Pharma, 1, Merck/MSD, 1, Novartis, 1, Phi-Stone, 1, selectION, 1, Sharp & Dohme, 1, 5, 6, UCB, 1, UNION therapeutics, 1, 5, 6; m. kishimoto: AbbVie, 2, 6, Amgen, 2, 6, Asahi-Kasei Pharma, 2, 6, Astellas, 2, 6, Ayumi, 2, 6, BMS, 2, 6, Celgene, 2, 6, Chugai, 2, 6, Daiichi-Sankyo, 2, 6, Eisai, 2, 6, Eli Lilly, 2, 6, Gilead, 2, 6, Johnson & Johnson, 2, 6, Kyowa Kirin, 2, 6, Novartis, 2, 6, Ono Pharma, 2, 6, Takeda, 2, 6, Tanabe-Mitsubishi, 2, 6, UCB, 2, 6; C. Deignan: Amgen Inc., 3, 11; S. Chaudhari: Amgen Inc., 3, 11; L. Teng: Amgen Inc., 3, 11; L. Gossec: AbbVie, 2, 5, Amgen, 2, Biogen, 5, BMS, 2, Celltrion, 2, Eli Lilly, 2, 5, Janssen, 2, MSD, 2, Novartis, 2, 5, Pfizer, 2, UCB, 2, 5.

To cite this abstract in AMA style:

Coates L, Mease P, Merola J, Perez Chada L, Gladman D, Zabotti A, Mrowietz U, kishimoto m, Deignan C, Chaudhari S, Teng L, Gossec L. Factors impacting progression from oligoarticular to polyarticular PsA: Data from the FOREMOST study [abstract]. Arthritis Rheumatol. 2025; 77 (suppl 9). https://acrabstracts.org/abstract/factors-impacting-progression-from-oligoarticular-to-polyarticular-psa-data-from-the-foremost-study/. Accessed .

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