A retrospective analysis of the safety of tacrolimus use and its optimal cut-off concentration during pregnancy in women with systemic lupus erythematosus: study from two Japanese tertiary referral centers.

Background: Tacrolimus is one of the major treatment options for systemic lupus erythematosus (SLE) and is considered to be a pregnancy-compatible medication. Since little is known about tacrolimus safety during pregnancy complicated by SLE, this study was designed.

Methods: We included SLE pregnant patients who were followed up at two Japanese tertiary referral centers. We performed multivariate logistic regression analysis to assess each adverse pregnancy outcome (APO) risk. Moreover, we assessed the influence of tacrolimus on the APO ratio in pregnant patients with lupus nephritis, and the impact of combined tacrolimus-aspirin therapy on the APO ratio relative to patients exclusively administered tacrolimus.

Results: Of the 124 pregnancies, 29 were exposed to tacrolimus. Multivariate analysis showed no statistical difference in APO ratio. (overall APO: adjusted odds ratio [aOR], 0.69; 95% confidence interval [CI], 0.23-2.03; p = 0.50; maternal APO: aOR, 1.17; 95% CI, 0.36-3.83; p = 0.80; neonatal APO: aOR, 1.10; 95% CI, 0.38-3.21; p = 0.86; PROMISSE APO: aOR, 0.50; 95% CI, 0.14-1.74; p = 0.27). Blood pressure and estimated glomerular filtration rate (eGFR) during pregnancy and after delivery did not differ between the two groups. Receiver operating characteristic (ROC) curve showed that tacrolimus concentration > 2.6 ng/ml was related to reduced preterm birth rate. (AUC = 0.85, 95% CI: 0.61-1.00, sensitivity: 93% and specificity: 75%). Regarding effect of tacrolimus on lupus nephritis during pregnancy, tacrolimus showed no increased risk of APO, blood pressure or eGFR during pregnancy and after delivery. (overall APO: OR, 1.00; 95% CI, 0.25-4.08; p = 0.98; maternal APO: OR 1.60, 95% CI, 0.39-6.64; p = 0.51; neonatal APO: OR, 0.71; 95% CI, 0.17-3.03; p = 0.65, PROMISSE APO: OR, 0.50; 95% CI, 0.08-3.22; p = 0.47). Tacrolimus-aspirin combination therapy showed a protective tendency against hypertensive disorders during pregnancy, preeclampsia and low birth weight.

Conclusions: Tacrolimus use during pregnancy with SLE and lupus nephritis showed no significant influence on APO, blood pressure, or renal function; therefore tacrolimus may be suitable for controlling lupus activity during pregnancy. In addition, when using tacrolimus during pregnancy, we should aim its trough concentration ≥ 2.6 ng/ml while paying careful attention to possible maternal side effects of tacrolimus.

Trial Registration: Retrospectively registered.