Glomerular filtration rate (GFR)-based endpoints, either as time-to-event endpoints or as mean rate of decline in GFR (slope), are possible endpoints in randomized controlled trials (RCTs) evaluating treatments for progression of chronic kidney disease (CKD). We have previously demonstrated robust trial-level associations between treatment effects on GFR decline with treatment effect on the clinical endpoint of kidney failure with replacement therapy (KFRT)1,2. As such treatment effects on GFR decline are increasingly adopted for use in RCTs3-5.