Background: The relationship between the benefits of empagliflozin in heart failure with reduced ejection fraction (HFrEF) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) has not been reported., Objectives: The authors sought to evaluate the relationship between NT-proBNP and empagliflozin effects in EMPEROR-Reduced (Empagliflozin Outcome Trial in Patients With Chronic Heart Failure With Reduced Ejection Fraction)., Methods: Patients with HFrEF were randomly assigned to placebo or empagliflozin 10 mg daily. NT-proBNP was measured at baseline, 4 weeks, 12 weeks, 52 weeks, and 100 weeks. Patients were divided into quartiles of baseline NT-proBNP., Results: Incidence rates for each study outcome were 4- to 6-fold higher among those in the highest versus lowest NT-proBNP quartiles (≥3,480 vs <1,115 pg/mL). Study participants with higher NT-proBNP had 2- to 3-fold total hospitalizations higher than the lowest NT-proBNP quartile. Empagliflozin reduced risk for major cardiorenal events without heterogeneity across NT-proBNP quartiles (primary endpoint P interaction = 0.94; renal composite endpoint P interaction = 0.71). Empagliflozin treatment significantly reduced NT-proBNP at all timepoints examined; by 52 weeks, the adjusted mean difference from placebo was 13% (P < 0.001). An NT-proBNP in the lowest quartile (<1,115 pg/mL) 12 weeks after randomization was associated with lower risk for subsequent cardiovascular death or heart failure hospitalization regardless of baseline concentration. Treatment with empagliflozin resulted in 27% higher adjusted odds of an NT-proBNP concentration of <1,115 pg/mL by 12 weeks compared with placebo (P = 0.01)., Conclusions: In EMPEROR-Reduced, higher baseline NT-proBNP concentrations were associated with greater risk for adverse heart failure or renal outcomes, but empagliflozin reduced risk regardless of baseline NT-proBNP concentration. The NT-proBNP concentration after treatment with empagliflozin better informs subsequent prognosis than pretreatment concentrations. (Empagliflozin Outcome Trial in Patients With Chronic Heart Failure With Reduced Ejection Fraction [EMPEROR-Reduced]; NCT03057977)., Competing Interests: Funding Support and Author Disclosures The EMPEROR-Reduced trial was supported by Boehringer Ingelheim and Eli Lilly and Company. Dr Januzzi is supported in part by the Hutter Family Professorship at Harvard Medical School; is a Trustee of the American College of Cardiology; is a board member of Imbria Pharmaceuticals; has received grant support from Applied Therapeutics, Innolife, Novartis Pharmaceuticals, and Abbott Diagnostics; has received consulting income from Abbott, Janssen, Novartis, and Roche Diagnostics; and participates in Clinical Endpoint Committees/Data Safety Monitoring Boards for Abbott, AbbVie, Amgen, Bayer, CVRx, Janssen, MyoKardia, and Takeda. Dr Zannad has recently received Steering Committee or Advisory Board fees from Amgen, AstraZeneca, Bayer, Boehringer Ingelheim, Boston Scientific, Cardior, CVRx, Janssen, LivaNova, Merck, Mundipharma, Novartis, Novo Nordisk, and Vifor Fresenius. Dr Anker has received fees from Abbott, Bayer, Boehringer Ingelheim, Cardiac Dimension, Cordio, Impulse Dynamics, Novartis, Occlutech, Servier, and Vifor Pharma; and has received grant support from Abbott and Vifor Pharma. Dr Butler is a consultant for Abbott, Adrenomed, Amgen, Array, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol Myers Squibb, CVRx, G3 Pharmaceutical, Impulse Dynamics, Innolife, Janssen, LivaNova, Luitpold, Medtronic, Merck, Novartis, Novo Nordisk, Relypsa, Roche, V-Wave Limited, and Vifor. Dr Filippatos has lectured for and/or has Committee Member contributions in trials sponsored by Medtronic, Vifor, Servier, Novartis, Bayer, Amgen, and Boehringer Ingelheim. Dr Pocock is a consultant for Boehringer Ingelheim. Dr Ferreira is a consultant for Boehringer Ingelheim. Dr Sattar has consulted for Amgen, AstraZeneca, Boehringer Ingelheim, Eli Lilly, Merck Sharp and Dohme, Novo Nordisk, Novartis, Sanofi, and Pfizer; and has received grant support from Boehringer Ingelheim. Drs Vedin and Schnee, Mr Cotton, and Ms Iwata are employees of Boehringer Ingelheim Pharmaceuticals. Dr Packer has received personal fees from Boehringer Ingelheim during the conduct of the study; and has received personal fees from AbbVie, Akcea, Amarin, AstraZeneca, Amgen, Boehringer Ingelheim, Daiichi Sankyo, Johnson & Johnson, Lilly, Novartis, ParatusRx, Pfizer, Relypsa, Sanofi, Synthetic Biologics, and Theravance outside the submitted work. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)