Pharmacogenomic Evaluation of Antihypertensive Responses

Overview

There are many medications available for the treatment of high blood pressure (hypertension), but finding the right one for a specific patient can be challenging. In fact, it is estimated that only 34% of people with hypertension have their blood pressure under control. The hypothesis is that genetic differences between individuals influence their response to antihypertensive medications. This study is aimed at determining the genetic factors that may influence a person's response to either a beta-blocker or a thiazide diuretic. The hope is that through this research, we may someday be able to use an individual's genetic information to guide the selection of their blood pressure medicine, leading to better control of blood pressure, and less need for the current trial and error process.

The proposed work should help move toward the long-term goal of selection of antihypertensive drug therapy based on a patient's genetic make-up. Hypertension (HTN) is the most common chronic disease for which drugs are prescribed, and the most prevalent risk factor for heart attack, stroke, renal failure and heart failure. Responses to antihypertensive drug therapy exhibit considerable interpatient variability, contributing to poor rates of HTN control (currently 34% in the US), and frequent nonadherence and dropout from therapy. We propose to identify genetic predictors of the antihypertensive and adverse metabolic responses to two preferred and pharmacodynamically contrasting drugs, a beta-blocker (atenolol) and a thiazide diuretic (hydrochlorothiazide) given initially as monotherapy, and subsequently in combination, to 800 individuals with uncomplicated hypertension. High quality phenotype data, including both home and ambulatory measures of blood pressure (BP) response, and lipid and insulin sensitivity measures of adverse metabolic responses will be related to genetic variation through two approaches. First, testing 7 single nucleotide polymorphisms (SNPs) in each of 70 candidate genes, we will examine the influence of these genes' variation on responses to beta-blockers and diuretics (Specific Aim 1). This will include assessment of genetic associations with: antihypertensive responses to monotherapy (Aim 1a), addition of a second drug to monotherapy (Aim 1b), and combination therapy (Aim 1c); and adverse metabolic responses to mono and combination therapy (Aim 1d). This candidate gene approach will be supplemented by discovery of novel genes involved in variable BP and metabolic responses to beta-blockers and diuretics through testing of 20,000 putative functional SNPs that span the human genome (Specific Aim 2). As in Aim 1, Aim 2 will include testing for associations with antihypertensive and adverse metabolic responses to monotherapy and combination therapy. The proposed research will substantially increase our understanding of the pharmacogenetics of mono- and combination antihypertensive drug therapy. It will also lead to creation of data sets and samples that can be used by others in the field, through deposit of data to PharmGKB, and creation of immortalized cell lines from all study participants to share data and biological samples with other researchers. The proposed research is significant because genetically-targeted antihypertensive therapy could lead to dramatically higher response rates and fewer adverse effects than the usual trial-and-error approach. This would likely lead to higher rates of HTN control, less need for polypharmacy, reduced health care costs, and improved outcomes.