Effects of Tofacitinib on Body Composition, Bone Mineral Density and Bone Marrow Adiposity in Patients With Rheumatoid Arthritis: the TOFAT Project

Inclusion criteria

• Adult patient's ≥18 years old with moderately to severely active Rheumatoid Arthritis (RA) (ACR/EULAR criteria )
• Previously untreated with Janus Kinase (JAK) inhibitors
• With an indication for tofacitinib will be eligible.
• All patients will have to be treated with tofacitinib either alone or with methotrexate. -Healthy volunteers should be ≥18 years old.

Exclusion criteria

• • treatment with more than three anti-Tumor Necrosis Factor alpha (TNFα). Patients who were receiving anti-TNFα will be required a washout period lasting at least five-half-lives before to start tofacitinib,

• previously exposed to JAK inhibitors,
• patients who were receiving non-anti-TNFα biologics (abatacept, tocilizumab, sarilumab or rituximab) will be required a washout period lasting at least five-half-lives before to start tofacitinib
• Concomitant methotrexate (MTX) will be permitted if started ≥3 months prior to study start and at a stable dose (≤25 mg/week) for ≥4 weeks.
• history or discovery of an osteoporotic fracture AND/OR T-score≤-3 if ≥50 years AND/OR Z-score ≤-3 if <50 years during the screening phase,
• current treatment with oral corticosteroids higher than 10 mg prednisone/day,
• pathologies or treatments that could affect the bone metabolism (breast cancer with aromatase inhibitors, gastrointestinal malabsorption, stomach cancer, primary hyperparathyroidism, uncontrolled hyperthyroidism…),
• weight> 160 kg,
• patients on restrictive diets or considering such a diet during the study period,
• patients with an intense exercise program or planning to benefit from it during the study period,