Potential applications of pharmacogenomics to heart failure therapies

Dose Response of β-Blockers in Adrenergic Receptor Polymorphism Genotypes

Background In heart failure (HF) with reduced ejection fraction, 2 clinical trials, the BEST (β-Blocker Evaluation of Survival Trial) and HF-ACTION (Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training), have reported an effectiveness interaction between the ADRB1 (β-1 adrenergic receptor) Arg389Gly polymorphism and β-blockers (BBs). HF-ACTION additionally reported a dose-related interaction of unclear origin. If confirmed and pharmacogenetically resolved, these findings may have important implications for HF with reduced ejection fraction precision therapy. We used uniform methodology to investigate BB dose-ADRB1 Arg389Gly polymorphism interaction with major clinical end points in BEST/bucindolol and HF-ACTION/other BB databases. Methods This was a retrospective analysis of prospectively designed DNA substudies from BEST (N=1040) and HF-ACTION (N=957). Subjects were genotyped for ADRB1 Arg389Gly and ADRA2C (α2C adrenergic receptor) Ins322-325Del. BB dose was defined as either no/low dose or high dose, according to total daily dose of either bucindolol (BEST subjects) or other BB (HF-ACTION subjects) standardized to carvedilol equivalents. The main outcome of interest was all-cause mortality, and CV mortality/HF hospitalization was a secondary outcome. Results Subjects in each trial had less all-cause mortality with high- versus no/low-dose BB if they had ADRB1 Arg389Arg (BEST: hazard ratio [HR]=0.40, P=0.002; HF-ACTION: HR=0.45, P=0.005) but not Arg389Gly genotype (both P>0.2). Among gene-dose groups, there was a differential favorable treatment effect of 46% for high-dose bucindolol with ADRB1 Arg389Arg versus Gly carrier genotype (HR, 0.54; P=0.018), but not for no/low-dose bucindolol. In contrast, HF-ACTION Arg389Arg genotype subjects taking no/low-dose BB had greater all-cause mortality compared with 389Gly carriers (HR, 1.83; P=0.015), whereas all-cause mortality did not vary by genotype among subjects taking high-dose BB (HR, 0.84; P=0.55). Conclusions The enhanced HF with reduced ejection fraction efficacy of bucindolol in the ADRB1 Arg389Arg versus 389Gly carrier genotypes occurs at high dose. Other BBs taken at low dose have reduced efficacy for Arg389Arg genotype subjects compared with 389Gly carriers, suggesting a greater relative treatment effect at high dose. These data support guideline recommendations to use high, clinical trial target doses of all BBs to treat HF with reduced ejection fraction.

Pharmacogenomics of Bucindolol in Atrial Fibrillation and Heart Failure

PURPOSE OF REVIEW

We explore the pharmacogenomics of the beta-blocker bucindolol by discussing relevant beta-1 adrenergic receptor (ADRB1) polymorphisms and recent beta-blocker studies. Through this, we will understand how bucindolol may help patients with atrial fibrillation and heart failure with reduced ejection fraction (AF-HFrEF), which carries poor prognosis.

RECENT FINDINGS

Retrospective study of the Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training trial revealed the interaction between the optimal beta-blocker dose and the ADRB1 Arg389 genotype for HFrEF clinical outcomes. Further, a combinatorial genotype analysis in the Beta-Blocker Evaluation of Survival Trial showed that the Arg389Arg genotype, but not the Gly carrier, was associated with 40% lower mortality risk with bucindolol. Finally, the AF-HFrEF subgroup with the ADRB1 Arg389Arg genotype had greater heart rate reduction and suggestion for mortality benefit. Therapeutic response to beta-blockers varies by beta-blocker mechanism, ADRB1 Arg389 genotype, and clinical setting (AF, HFrEF, AF-HFrEF). The ongoing trial A Genotype-Directed Comparative Effectiveness Trial of Bucindolol and Toprol-XL for Prevention of Symptomatic Atrial Fibrillation/Atrial Flutter in Patients with Heart Failure prospectively identifies AF-HFrEF patients with favorable genotype for bucindolol to prevent AF recurrence.

Mode of Death After Acute Heart Failure Hospitalization - A Clue to Possible Mechanisms

Heart failure continues to be a leading cause of hospitalization worldwide, and acute heart failure (AHF) carries significant risk for short-term morbidity and mortality. Despite many trials of potential new therapies for AHF, there have been very few advances over the recent decades. In this review, we will examine mortality during and after AHF hospitalization, with an emphasis on available data on mode of death (MOD). We will also review data on the timing of different MOD after AHF and the effect of specific therapies, as well as what is known about the contribution of specific pathophysiological mechanisms. Finally, we discuss the potential utility of further study of MOD data for AHF and its application to drug development, risk stratification, and therapeutic tailoring to improve short- and long-term outcomes in AHF.