Low-dose rapamycin (sirolimus) effects in autosomal dominant polycystic kidney disease: an open-label randomized controlled pilot study

Abstract

Background and objectives: The two largest studies of mammalian target of rapamycin inhibitor treatment of autosomal dominant polycystic kidney disease (ADPKD) demonstrated no clear benefit on the primary endpoint of total kidney volume (TKV) or on eGFR. The present study evaluated two levels of rapamycin on the 12-month change in (125)I-iothalamate GFR (iGFR) as the primary endpoint and TKV secondarily.

Design, setting, participants, & measurements: In a 12-month open-label pilot study, 30 adult patients with ADPKD were randomly assigned to low-dose (LD) rapamycin (rapamycin trough blood level, 2-5 ng/ml) (LD group, n=10), standard-dose (STD) rapamycin trough level (>5-8 ng/ml) (STD group, n=10), or standard care (SC group, n=10). They were evaluated with iGFR and noncontrast computed tomography.

Results: Change in iGFR at 12 months was significantly higher in the LD group (7.7±12.5 ml/min per 1.73 m(2); n=9) than in the SC group (-11.2 ± 9.1 ml/min per 1.73 m(2); n=9) (LD versus SC: P<0.01). Change in iGFR at 12 months in the STD group (1.6 ± 12.1 ml/min per 1.73 m(2); n=8) was not significantly greater than that in the SC group (P=0.07), but it was in the combined treatment groups (LD+STD versus SC: P<0.01). Neither eGFR calculated by the CKD-Epidemiology Collaboration equation nor TKV (secondary endpoint) changed significantly from baseline to 12 months in any of the groups. On the basis of results of the mixed model, during the study, patients in the LD group had significantly lower trough blood levels of rapamycin (mean range ± SD, 2.40 ± 0.64 to 2.90 ± 1.20 ng/ml) compared with those in the STD group (3.93 ± 2.27 to 5.77 ± 1.06 ng/ml) (P<0.01).

Conclusion: Patients with ADPKD receiving LD rapamycin demonstrated a significant increase in iGFR compared with those receiving standard care, without a significant effect on TKV after 12 months.

Keywords: ADPKD; iothalamate GFR; rapamycin.

Figure 1.

Individual absolute ¹²⁵I-iothalamate GFR (iGFR) changes at 12 months with low-dose (LD) or standard-dose (STD) rapamycin or without rapamycin. iGFR change at 12 months (mean±SD): LD, 7.7±12.5; STD, 1.6±12.1; and standard care (SC), −11.2±9.1 ml/min per 1.73 m². LD versus SC: P<0.01; STD versus SC: P=0.07; LD+STD versus SC: P<0.01; LD versus STD: P=0.52. P values based on Tukey-adjusted t tests for multiple comparisons. Median (—) and 25th and 75th percentile changes in iGFR: LD, 2.0 (−1.0, 18.0) ml/min per 1.73 m², respectively; STD, (2.5 (−7.0, 6.5) ml/min per 1.73 m², respectively; and SC, −11.0 (−18.0, −1.0) ml/min per 1.73 m², respectively. Twenty-one of these 26 patients had an initial iGFR≥60 ml/min per 1.73 m² and 5 (*) did not.