Difficult to treat (D2T) rheumatoid arthritis (RA) is considered a clinical setting that physicians already label as very complicated to address from a therapeutic point of view for various reasons [1]. In particular, the Committee that developed the definition of D2T established that, to label a patient as D2T, >2 conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) and ≥2 biologic (b) or targeted synthetic (ts) DMARDs with different mode of action should have failed, together with another clinical or radiological item among: -at least moderate disease activity (according to validated composite measures including joint counts, e.g.
