A causal mediation analysis of the pooled FIDELITY trial data (n = 12,143) demonstrates that the cardiovascular benefit of finerenone in patients with type 2 diabetes and chronic kidney disease is largely driven by early reductions in urine albumin-to-creatinine ratio (UACR) and systolic blood pressure. Within four months, UACR and systolic blood pressure changes accounted for 39% and 21% of the long-term cardiovascular risk reduction, respectively, while shifts in body weight and serum potassium did not mediate outcomes. These findings highlight UACR and blood pressure as complementary early markers to monitor cardiovascular efficacy when initiating finerenone therapy.
We performed causal mediation analysis using individual patient data from FIDELITY (pooled FIDELIO-DKD and FIGARO-DKD; n = 12,143). Mediators were change from baseline to month 4 in log urine albumin-to-creatinine ratio (UACR), systolic blood pressure (SBP), body weight, and serum potassium. The outcome was time from month 4 to first cardiovascular event (cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, or heart failure hospitalization). Outcome models used parametric accelerated failure time regression with Weibull distribution. Joint mediation by UACR and SBP was estimated by bootstrapping.
At month 4, finerenone reduced UACR by 32.2% (95% CI 30.3 to 34.2), SBP by 3.6 mmHg (3.1 to 4.1), and body weight by 0.23 kg (0.13 to 0.32), and increased serum potassium by 0.19 mEq/L (0.17 to 0.20). Although all four biomarkers changed significantly, only UACR and SBP mediated cardiovascular outcomes: UACR mediated 39% (95% CI 7 to 71) and SBP mediated 21% (3 to 40); body weight and potassium did not. Jointly, UACR and SBP mediated 50% (95% CI 21 to 100) of the cardiovascular benefit.
In T2D and CKD, early reductions in UACR and SBP jointly account for half of finerenone's long-term cardiovascular benefit. Body weight and potassium changes do not mediate the benefit, supporting UACR and SBP as complementary indicators of cardiovascular efficacy.
