The selectivity of Janus kinase inhibitors (JAKis) is still a matter debate, as no JAKi specific for only one (JAK) isoform. Currently approved JAKis in rheumatoid arthritis (RA) all inhibit JAK1, which an effective therapeutic target RA. Although selective JAK1 inhibition seems not to decrease drug efficacy, may modify the safety profile this class. Indeed, balance benefit and risk inhibiting ...