Introduction. Kidney transplant recipients with proteinuria have an increased risk of graft failure. We studied the effects of the vitamin D receptor activator paricalcitol in kidney transplant recipients with residual proteinuria after optimization of the renin-angiotensin-aldosteron system (RAAS) blockade.
Patients and Methods. In this single-centre, placebo-controlled, double-blind trial, we enrolled kidney transplant recipients with urinary protein-to-creatinine ratio (UPCR) ≥20 mg/mmol despite optimization of the RAAS blockade during the run-in-phase. Patients were randomly assigned to receive 24 weeks’ treatment with 2 µg/day paricalcitol or placebo. Primary endpoint was the percent change in geometric mean UPCR, and secondary endpoints included the percent change in geometric mean urinary albumin-to-creatinine ratio (UACR) and 24-hour proteinuria from baseline to last measurement during treatment. Analysis was by intention-to-treat. This trial is registered with ClinicalTrials.gov, number NCT01436747.
Results. In 2012, 190 of 572 prevalent kidney transplant recipients (33%) had UPCR ≥20 mg/mmol. Of the 168 patients who undergo randomization, 83 were allocated to paricalcitol, and 85 to placebo; all patients received at least one dose of study drug and had UPCR data at baseline and at least one time-point during treatment. Change in UPCR was -38% (from 74 to 46 mg/mmol; 95% CI -45% to -31%) in the paricalcitol group and 21% (from 55 to 63 mg/mmol; 95% CI 9% to 36%) in the placebo group (P<0.001). Change in UACR and 24-hour proteinuria was -47% (95% CI -54% to -38%) and -35% (95% CI -42% to -28%) in the paricalcitol group, and 11% (95% CI -5% to 29%) and 19% (95% CI 8% to 30%) in the placebo group, respectively. Incidence of mild hypercalcemia was higher in the paricalcitol group. A reduction of the study drug dose lead to normal serum calcium levels in all patients.
Conclusion. In kidney transplant recipients, addition of 2 µg/day paricalcitol lowers residual proteinuria, and could be used as an effective approach to lower graft failure risk.
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