Testing for a genetic variation could predict the likelihood that a patient will respond well to certain statins. But some researchers say it's too soon to use the variation to determine treatment.

Researchers from Celera reported yesterday in the Journal of the American College of Cardiology that a single substitution in the sequence of a gene called KIF6 makes people both more susceptible to heart attacks and more responsive to certain drugs that lower cholesterol. Though there is no known biological explanation linking the variation to heart disease, the study found that it increases the risk of heart attacks and strokes by 55 percent.

Celera, the company best known for sequencing the human genome, examined 35 single-nucleotide polymorphisms (SNPs) in 30,000 patients. Of those, "KIF6 is by far the most significant," says Thomas J. White, chief scientific officer at Celera. In fact, nearly 60 percent of the study population was found to carry the KIF6 variant. (According to the study, these findings take into account other factors, such as smoking, high blood pressure, and cholesterol levels.)

The researchers also found that carriers of the KIF6 variant responded better to the cholesterol-lowering drugs pravastatin (Pravachol) and atorvastatin (Lipitor). For example, among patients with the genetic variation, those who took pravastatin were 37 percent less likely to experience a heart attack than those who took the placebo. Those without the genetic variation who took the drug were only 14 percent less likely to experience a heart attack than those who took the placebo. Statins are big sellers for the pharmaceutical industry. In 2006, Lipitor, the world's best-selling drug, brought in $13 billion in global sales.

"This is one of the first studies to show an interaction with therapy" and genotype, says Marc Sabatine, professor of medicine at Harvard Medical School and a coauthor on one of the papers. "That is very exciting to see."

Surprisingly, the researchers found that KIF6 doesn't appear to work by lowering levels of LDL or "bad" cholesterol, the standard by which drugs used to prevent heart attacks are normally measured. White says that KIF6 may instead act by stabilizing "vulnerable plaques," which are particularly prone to triggering heart attacks.

Celera is developing a diagnostic that would test for the KIF6 variant and expects to launch it in a few months.

But some experts caution that it may be premature to introduce such diagnostic tests before there is further confirmation of KIF6's role in heart disease.