Placental transfer of tofacitinib in the ex vivo dual-side human placenta perfusion model

Tofacitinib is a small molecule Janus kinase (JAK) inhibitor, introduced to the European market in 2017, for the treatment of rheumatoid arthritis, psoriatic arthritis and ulcerative colitis. In the treatment of women with autoimmune diseases, pregnancy is a relevant issue, as such diseases typically affect women in their reproductive years. Currently, there is limited data on the use of tofacitinib during pregnancy. To estimate the extent of placental transfer in the absence of clinical data, we conducted ex vivo dual-side perfused human placental cotyledon perfusions. Term placentas were perfused for 180 min with tofacitinib (100 nM, added to the maternal circuit) in a closed-closed configuration. At the end of the perfusions, drug concentrations in the maternal and fetal reservoirs were near equilibrium, at 35.6 ± 5.5 and 24.8 ± 4.7 nM, respectively. Transfer of tofacitinib was similar to that observed for the passive diffusion marker antipyrine (100 µg/mL, added to the maternal reservoir). Final antipyrine maternal and fetal concentrations amounted to 36.9 ± 3.0 and 36.7 ± 1.3 µg/mL, respectively. In conclusion, in the ex vivo perfused placenta tofacitinib traverses the placental barrier rapidly and extensively. This suggests that substantial fetal tofacitinib exposure will take place after maternal drug dosing.