ANA-arthritis: clinical and biomarker characterization of a population for basket trials.

ABSTRACT

OBJECTIVES: ANA-associated RMDs (ANA-RMDs-SLE, pSS, scleroderma, inflammatory myositis, mixed connective tissue disease (MCTD) and undifferentiated connective tissue disease) are a disease spectrum with overlapping clinical and immunological features. Musculoskeletal inflammation is common and impactful across ANA-RMDs. We evaluated musculoskeletal inflammation (ANA-arthritis) prevalence in a multi-disease ANA-RMD study, assessed its clinical impact across ANA-RMD diagnoses, proposed new basket groupings of patients and evaluated immunological profiles in legacy and new basket contexts. METHODS: An observational study enrolled ANA-RMD patients. Demographic variables, comorbidities, therapies, disease activity instruments (BILAG, SLEDAI, ESSDAI, physician-VAS), patient-reported outcomes (SF36, FACIT-Fatigue, EQ5D, ICECAP-A, WPAI, patient-VAS) and biomarker profile (6 gene expression scores, flow cytometry, autoantibody profile) were analysed. Reclustering utilized Gaussian Mixture Modelling (GMM). Clinical and immune features of new and legacy clusters were compared. RESULTS: Inflammatory MSK symptoms were prevalent across ANA-RMDs, in 213/294 patients. In ANA-arthritis patients, most variables did not differ between diagnoses, excluding EQ5D-5L index and mobility domains (lower in MCTD/pSS, both p< 0.05). Fibromyalgia and osteoarthritis prevalence were similar across diagnoses. Therapy use differed significantly, biologic use being greatest in SLE (p< 0.05).GMM yielded two multi-disease clusters; High-MSK disease activity (n = 89) and Low-MSK disease activity (n = 124). High-MSK disease activity contained all patients with active joint swelling and had significantly higher prednisolone usage, PGA and Sm/RNP/SmRNP/Chromatin positivity, Tetherin-MFI and Interferon Score-A activity; with numerically lower fibromyalgia and osteoarthritis prevalence. CONCLUSION: We define ANA-Arthritis, a more clinically and immunologically homogeneous population than existing RMDs for trials, and a more prevalent population for therapies in the clinic.