Mean increases from baseline in patient serum creatinine (SCr) levels have been observed in the clinical development programme for the JAK inhibitor tofacitinib. These increases predominantly occurred within the first three months, and reversed with tofacitinib withdrawal.

This phase 1, randomised, placebo-controlled, parallel-group, 2-period study assessed changes in measured glomerular filtration rate (mGFR) with tofacitinib, relative to placebo, in 148 patients with active RA. Result...