Effects of newer kidney protective agents on kidney endpoints provide implications for future clinical trials

Doubling of serum creatinine (equivalent to a 57% decline in the estimated glomerular filtration rate (eGFR)) is an accepted component of a composite kidney endpoint in clinical trials. Smaller declines in eGFR (40%, 50%) have been applied in several recently conducted clinical trials. Here, we assessed the effects of newer kidney protective agents on endpoints including smaller proportional declines in eGFR to compare relative event rates and the magnitude of observed treatment effects. We performed a post hoc analysis of 4401 patients in the CREDENCE, 4304 in the DAPA-CKD, 5734 in the FIDELIO-DKD, and 3668 in the SONAR trials, which assessed the effects of canagliflozin, dapagliflozin, finerenone and atrasentan in patients with chronic kidney disease. Effects of active therapies versus placebo on alternative composite kidney endpoints incorporating different eGFR decline thresholds (40%, 50%, or 57% eGFR reductions from baseline) with kidney failure or death due to kidney failure were compared. Cox-proportional hazards regression models were used to assess and compare treatment effects. During follow-up, event rates were higher for endpoints incorporating smaller versus larger eGFR decline thresholds. Compared to the treatment effects on kidney failure or death due to kidney failure, the magnitude of relative treatment effects was generally similar when considering composite endpoints incorporating smaller declines in eGFR. Hazard ratios for the four interventions ranged from 0.63 to 0.82 for the endpoint incorporating 40% eGFR decline and 0.59 to 0.76 for the endpoint incorporating 57% eGFR decline. Clinical trials incorporating a 40% eGFR decline in a composite endpoint would require approximately half the number of participants compared to a 57% eGFR decline with equivalent statistical power. Thus, in populations at high risk of CKD progression, the relative effects of newer kidney protective therapies appear generally similar across endpoints based on varying eGFR decline thresholds.