Effect of everolimus on renal function in patients with tuberous sclerosis complex: evidence from EXIST-1 and EXIST-2

Abstract

Background: A reduction in renal angiomyolipoma volume observed with everolimus (EVE) treatment in patients with tuberous sclerosis complex (TSC) has been postulated to translate to clinical benefit by reducing the risk of renal hemorrhage and chronic renal failure.

Methods: The long-term effects of EVE on renal function (∼4 years of treatment) were examined in patients treated with EVE in the Phase 3 EXIST-1 and EXIST-2 studies. Patients in EXIST-1 had TSC and subependymal giant cell astrocytoma (SEGA), and patients in EXIST-2 had renal angiomyolipoma and a definite diagnosis of TSC or sporadic lymphangioleiomyomatosis. EVE was administered at 4.5 mg/m2/day, with adjustment to achieve target trough levels of 5-15 ng/mL in EXIST-1 and at 10 mg/day in EXIST-2. Estimated glomerular filtration rate (eGFR) and creatinine levels were assessed at baseline, at Weeks 2, 4, 6, 8, 12 and 18, then every 3 months thereafter. Proteinuria was graded according to National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0.

Results: A total of 111 patients from EXIST-1 and 112 patients from EXIST-2 were included in this analysis. Respective mean ages at EVE initiation were 10.5 [standard deviation (SD) 6.45] and 33.2 (SD 10.29) years, and 3.6% and 37.5% of patients had undergone prior renal intervention. Mean baseline eGFR was 115 and 88 mL/min/1.73 m2 in EXIST-1 and EXIST-2, respectively. Overall, mean eGFR remained stable over time in both studies, with an decline in renal function mostly confined to some patients with severely compromised renal function before treatment. Patients with prior renal intervention exhibited low eGFR values throughout the study. The incidence of proteinuria increased after initiating treatment with EVE and was mostly Grade 1/2 in severity, with Grade 3 proteinuria reported in only two patients. Measurements of proteinuria were limited by the use of urine dipstick tests.

Conclusions: The use of EVE does not appear to be nephrotoxic in patients with SEGA or renal angiomyolipoma associated with TSC and may preserve renal function in most patients.ClinicalTrials.gov identifiers NCT00789828 and NCT00790400.

Keywords: mTOR inhibition; renal function; tuberous sclerosis.

© The Author(s) 2018. Published by Oxford University Press on behalf of ERA-EDTA.

Figures

FIGURE 1

Mean eGFR over time in the EXIST-1 and EXIST-2 studies. The MDRD formula [33] was used to estimate GFR for patients ≥18 years of age and the ‘bedside’ Schwartz formula [34] was used to estimate GFR in patients

FIGURE 2

Boxplots of the change in eGFR based on treatment and baseline CKD stage during the double-blind phases of (A) EXIST-1 and (B) EXIST-2. The MDRD formula [33] was used to estimate GFR for patients ≥18 years of age and the ‘bedside’ Schwartz formula [34] was used to estimate GFR in patients <18 years of age.

FIGURE 3

Mean percentage change from baseline in eGFR with SD. The MDRD formula [33] was used to estimate GFR for patients ≥18 years of age and the ‘bedside’ Schwartz formula [34] was used to estimate GFR in patients

FIGURE 4

eGFR over time according to previous angiomyolipoma-related renal intervention in EXIST-2 patients. GFR was estimated using the MDRD formula [33]. aIncludes embolization, thermoablation and angiomyolipoma-related surgery other than nephrectomy. bIncludes partial and complete nephrectomy.