Different eGFR Decline Thresholds and Renal Effects of Canagliflozin: Data from the CANVAS Program

Megumi Oshima; Bruce Neal; Tadashi Toyama; Toshiaki Ohkuma; Qiang Li; Dick de Zeeuw; Hiddo J.L. Heerspink; Kenneth W. Mahaffey; Gregory Fulcher; William Canovatchel; David R. Matthews; Vlado Perkovic

doi:10.1681/ASN.2019121312

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Visual Abstract

Significance Statement

Traditionally, clinical trials studying effects of new therapies on renal outcome use the doubling of serum creatinine (equivalent to a 57% eGFR reduction) as an end point, requiring large sample sizes. Use of lesser eGFR reductions has been proposed, but few studies have evaluated their reliability. In this post hoc study of two multicenter, randomized trials, a greater number of observed events resulted from use of 50%, 40%, and 30% eGFR reductions compared with a 57% eGFR reduction. Observed effect sizes for canagliflozin versus placebo were attenuated when lesser eGFR reductions were used, likely because of canagliflozin’s acute effect on eGFR. However, if analyses control for this acute effect, lesser eGFR decline thresholds may be preferred to identify renoprotective effects of potential therapies because much smaller sample sizes can be used.

Abstract

Background Traditionally, clinical trials evaluating effects of a new therapy with creatinine-based renal end points use doubling of serum creatinine (equivalent to a 57% eGFR reduction), requiring large sample sizes.

Methods To assess whether eGFR declines <57% could detect canagliflozin’s effects on renal outcomes, we conducted a post hoc study comparing effects of canagliflozin versus placebo on composite renal outcomes using sustained 57%, 50%, 40%, or 30% eGFR reductions in conjunction with ESKD and renal death. Because canagliflozin causes an acute reversible hemodynamic decline in eGFR, we made estimates using all eGFR values as well as estimates that excluded early measures of eGFR influenced by the acute hemodynamic effect.

Results Among the 10,142 participants, 93 (0.9%), 161 (1.6%), 352 (3.5%), and 800 (7.9%) participants recorded renal outcomes on the basis of 57%, 50%, 40%, or 30% eGFR reduction, respectively, during a mean follow-up of 188 weeks. Compared with a 57% eGFR reduction (risk ratio [RR], 0.51; 95% confidence interval [95% CI], 0.34 to 0.77), the effect sizes were progressively attenuated when using 50% (RR, 0.61; 95% CI, 0.45 to 0.83), 40% (RR, 0.70; 95% CI, 0.57 to 0.86), or 30% (RR, 0.81; 95% CI, 0.71 to 0.93) eGFR reductions. In analyses that controlled for the acute hemodynamic fall in eGFR, effect sizes were comparable, regardless of whether a 57%, 50%, 40%, or 30% eGFR reduction was used. Estimated sample sizes for studies on the basis of lesser eGFR reductions were much reduced by controlling for this early hemodynamic effect.

Conclusions Declines in eGFR <57% may provide robust estimates of canagliflozin’s effects on renal outcomes if the analysis controls for the drug’s acute hemodynamic effect.

Clinical Trial registry name and registration number: CANagliflozin cardioVascular Assessment Study (CANVAS), NCT01032629 and CANVAS-R, NCT01989754.

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