Short-term anti-proteinuric effect of tacrolimus is not related to preservation of the glomerular filtration rate in IgA nephropathy: A 5-year follow-up study

Abstract

Background: The immunosuppressive drug tacrolimus has the short-term effect of reducing proteinuria in patients with immunoglobulin A nephropathy (IgAN). Our study investigated the effects on proteinuria and kidney function after discontinuation of tacrolimus.

Methods: Patients with biopsy-proven IgAN were included in the study and randomly divided into two treatment groups. There was a corresponding control group for each treatment group. The first group included patients treated with tacrolimus (Tac vs non-Tac group) and the second group included patients with a renin angiotensin system blocker (RASi vs non-RASi group). The Tac group received treatment for up to 16 weeks, with the administration of tacrolimus being ceased at the final visit (trial phase). We tracked the patients at 12, 24, 52, and 240 weeks (observational phase). The primary outcomes examined were the percentage change (from the trial phase to the observational phase) of time-averaged proteinuria (TA-proteinuria; g/g creatinine [cr]) and the estimated glomerular filtration rate (eGFR). Time-averaged proteinuria was defined as the average of urine protein to creatinine ratio (UPCR), measured every 3 months during both the trial and observational phases of the study.

Results: A significant reduction in UPCR was observed in the Tac group compared to non-Tac group at the 4 and 8 week visits during the trial phase (p = 0.023 and p = 0.003, respectively). However, the difference between the Tac group and non-Tac group was not evident in the other review periods, estimated by linear mixed effect model. The percentage change in TA-proteinuria was greater in the Tac group than that in the corresponding control group (116 ± 96% vs. 63 ± 239%, p = 0.004). Therefore, during the observational phase, TA-proteinuria was not significantly different between the Tac group and the non-Tac group (1.150 ± 0.733 g/g cr vs. 1.455 ± 2.017 g/g cr, p = 0.775). The levels of eGFR throughout the observational phase were not significantly different between the two groups. Furthermore, the mean rate of eGFR change throughout both phases of the study was -6.4 ± 5.9 mL/min/1.73 m2/year in the non-Tac group and -5.4 ± 7.9 mL/min/1.73 m2/year in the Tac group (p = 0.988).

Conclusion: The anti-proteinuric effect of tacrolimus was promptly reversed 3 months after discontinuing the drug. The use of tacrolimus for a short period of time for patients with IgAN temporarily reduces proteinuria, but the data showed no long-term efficacy regarding proteinuria reduction and improvement of renal function.

Fig 1. Study algorithm.

One patient in the non-Tac group withdrew at the 8-week visit because of the addition of a prohibited drug in another department, one patient in the Tac group withdrew at day 1 after enrollment because of pregnancy and had taken only 2 mg of tacrolimus, and another patient in the Tac group withdrew at the 4-week visit because of general weakness and myalgia related to medication.

Fig 2. The changes in UPCR (A, C) and eGFR (B, D) during the follow-up period after cessation of the clinical study.

From left to right, each box-plot represents the follow-up periods of 0-weeks, 4-weeks, 8-weeks, 12-weeks and 16-weeks of the trial phase, and 12-weeks, 24-weeks, 52-weeks, and the final visit by October 2016 of the observational phase. A. The p-value for tests of between two groups was 0.130. B. The p-value for tests of between-subjects effects was 0.543. C. The p-value for tests of between-subjects effects was 0.830. D. The p-value for tests of between-subjects effects was 0.488. Tac: Tacrolimus, RASi: renin-angiotensin-aldosterone system inhibitor, UPCR: urine protein to creatinine ratio, eGFR: estimated glomerular filtration rate by the equation of CKD-EPI. The p-value estimated by linear mixed effect model.

Fig 3. The difference in outcome parameters between groups.

Outcome parameters represent the followings; O1, decrease of time-averaged proteinuria from trial phase and to the observational phase; O2, remission of UPCR <0.2 g/g cr during observational phase; O3, rapid decline of eGFR ≥5 mL/min/1.73 m² during observational phase; O4, composite outcome of increase in serum cr level (≥50% from baseline) noted during observational phase or deterioration of renal function to end stage renal disease. Outcome parameters were compared by Chi-square test or Fisher’s exact test according to the number of each cell in the tacrolimus group (A) and RASi group (B).