Emulation of the SUMMIT Heart Failure Trial in Healthcare Claims Data

This is a non-randomized, non-interventional study that is part of the Randomized Controlled Trials Duplicated Using Prospective Longitudinal Insurance Claims: Applying Techniques of Epidemiology (RCT DUPLICATE) initiative (www.rctduplicate.org) of the Brigham and Women's Hospital, Harvard Medical School. It is intended to emulate, as closely as is possible in healthcare insurance claims data, the SUMMIT trial described below. Although many features of the trial cannot be directly replicated in healthcare claims, key design features, including outcomes, exposures, and inclusion/exclusion criteria, were selected to proxy those features from the trial. In addition to closely emulating the trial population, this study also evaluates outcomes in a broader, less restrictive cohort to enhance generalizability to patients typically encountered in routine clinical practice. Randomization cannot be achieved in healthcare claims data but was proxied through a statistical balancing of measured covariates according to standard practice. Investigators assume that the RCT provides guidance on the reference standard treatment effect estimate. However, failure to replicate RCT findings is not necessarily indicative of the inadequacy of the healthcare claims data for emulation for a range of possible reasons, as the end points examined in the database study were partly only of exploratory nature in the trial. Moreover, divergence from these end points do not provide information on the validity of the original RCT finding. The SUMMIT trial is a superiority trial that included an evaluation of the effect of tirzepatide, a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist (RA), vs placebo on all-cause mortality or worsening heart failure events among individuals with heart failure with preserved ejection fraction. The database study designed to emulate the type 2 diabetes mellitus (T2DM) subgroup of the SUMMIT trial will be a new-user active-comparative study, conducted using 2 national United States claims databases, where we compare the effect of tirzepatide vs sitagliptin, a dipeptidyl peptidase-4 inhibitor (DPP4i) on the composite end point of all-cause mortality or heart failure hospitalization. While the SUMMIT trial was conducted in participants with and without T2DM, both subgroups showed similar effect estimates in their results. Furthermore, while the trial compared tirzepatide vs placebo, we chose to use sitagliptin as an active-comparator proxy for placebo in the T2DM subgroup. Sitagliptin was specifically chosen because a major randomized controlled trial on cardiovascular outcomes demonstrated that the drug does not affect the cardiovascular outcomes under investigation. Furthermore, clinical guidelines during the study period recommended both drug classes under investigation as second- or third-line options for glucose lowering and were similarly costly.