By Debbie Strickland
Myriad Genetics Inc. is gearing up for an early 1998 launch of CardiaRisk, a test to identify the 20 percent of the population who are genetically at risk for severe hypertension and would benefit from a salt-restrictive diet.
The Salt Lake City company's blood test is based on the angiotensinogen (AGT) gene. In a three-year study of 1,509 patients, the 20 percent of individuals who had the AA genotype — a genetic variant at the -6 position in the AGT promoter region — produced higher levels of angiotensinogen than those with the normal GG genotype.
Angiotensinogen is converted to the peptide hormone angiotensin II which, in excessive amounts, leads to high salt retention and increased risk of hypertension and related diseases.
Study participants with the AA genotype had a higher three-year incidence of hypertension (44.6 percent) than did the GG genotype (31.5 percent). The good news for AAs is that theirs is the only group in the study which experienced a statistically significant blood pressure reduction after cutting salt intake for three years. The salt-restricted AA group's diastolic blood pressure decreased an average of 2.27 mmHg, as compared to controls with no dietary salt intervention.
GG patients who cut their salt actually experienced a 1.07 mmHg increase in average diastolic blood pressure vs. the control group.
Unless there are other risk factors, physicians typically address borderline hypertension with monitoring and lifestyle modification — including salt restriction — rather than drugs, said Myriad Spokesman William Hockett.
"With CardiaRisk, you'd find that 20 percent of borderline hypertensives would be AAs," he said. "They may well benefit from a low-salt diet and be able to maintain blood pressure control without being put on a drug."
Identification could also put those patients on alert for a host of other complications. AA genotype individuals are 3.4 times more likely to have heart attacks, 2.6 times more likely to develop coronary heart disease, and 20 times more likely to suffer preeclampsia during pregnancy.
The GG patients, meanwhile, are saved the hassle of following a low-salt diet.
In the future, CardiaRisk may provide guidance in the selection of drugs for more advanced cases of hypertension in both the AA and GG genotypes. Myriad has initiated studies to determine which pharmaceuticals work best in each group.
In the U.S. alone, some 50 million individuals have high blood pressure.
"It certainly looks like there's a massive market here," said Eric Schmidt, an analyst with UBS Securities, in New York.
CardiaRisk could generate sales of $12 million by 2001, the analyst conservatively estimates.
Based on the experience with Myriad's BRACAnalysis, sales are likely to be "relatively modest" initially, with $500,000 expected from launch through the June 30 end of Myriad's 1998 fiscal year. In 1999, sales are projected to rise to $4 million, then to $8 million in 2000.
"The [CardiaRisk] test is revolutionary in nature," Schmidt said. "But it's better to be too conservative [about sales projections] than too aggressive."
Schmidt said the test attracted a good deal of physician interest last week when data were presented at the American Heart Association's scientific meeting in Orlando, Florida. Physician comfort with genetic testing — along with reimbursement policies — will be key to sales totals.
The company is finalizing arrangements with marketing partners for CardiaRisk, expected to sell for between $300 and $400, Hockett told BioWorld Today.
At some point, sales may surpass those of BRACAnalysis — Myriad's set of three related breast cancer diagnostics and the company's first marketed product.
"It's certainly a much larger market potential than BRACAnalysis," Hockett agreed. "Twenty-five percent of the population is hypertensive. That's a very large number of individuals."
Introduced in October 1996, BRACAnalysis and related tests tallied about $500,000 in sales through June 30. Sales appear to be accelerating, however, hitting $409,000 during the quarter that ended Sept. 30.
As of that date, Myriad had $61.8 million in cash, following a net loss of $1.8 million in the quarter.
The company's shares (NASDAQ:MYGN) closed Friday at $26, down $0.50. *