It's widely accepted that people from certain ethnic backgrounds
are more prone to certain medical conditions. There's
a higher than average rate of nasopharangeal cancer in
Chinese people while East Asians and Hispanics are predisposed
to melasma. This is due to a number of factors —
genetics, diet, environment, socio-economics. But never
before have meds been designed with a specific race in
mind. The ground-breaking African-American Heart Failure
Trial (A-HeFT), published in the November 11 issue of
the New England Journal of Medicine, could change
all that.
HEART
STOPPING RESULTS
A-HeFT tested a fixed-dose combination of isosorbide
dinitrate and hydralazine, two generic blood pressure
meds available for years. The American biotech firm,
NitroMed, sponsored the trial after patenting the formulation
— called 'BiDil.' Decades ago, the combination
was tested in multi-racial trials without much success.
But after reanalyzing that data, NitroMed suspected
they'd found a benefit for blacks. Coincidentally, other
data began to emerge showing that many blacks don't
respond to ACE inhibitors — a standard treatment
in heart failure.
Headed by Dr Anne L Taylor of the
University of Minnesota, A-HeFT randomized 1,050 men
and women with advanced heart failure to either BiDil
or placebo added to their regular meds. All patients
identified themselves as black. Within a year, patients
taking BiDil had a whopping 43% reduction in death and
33% reduction in hospital time — enough to stop
the study early on humanitarian grounds.
What's behind these results? The
answer may have something to do with nitric oxide, which
relaxes blood vessels, lowers blood pressure and increases
heart muscle efficiency. Many blacks don't seem to absorb
nitric oxide well. And in fact, blacks have much higher
heart failure rates than whites, being 2.5 times more
likely than whites to die of it between the ages of
45 and 65. The A-HeFT researchers concluded that their
combo concoction may improve the ability of black heart
failure patients to utilize nitric oxide.
NOT
SO FAST
So, is this good news for the nearly 700,000 black Canadians?
The answer is, maybe — but there are caveats. First,
the study relied on the murkily self-defined category
of race as a surrogate for a specific genetic type,
despite the conceptual vagueness and lack of data matching
race to genetic or physiological differences. Second,
limiting a drug trial to a single racial group may ignore
those outside the group who could also benefit. (A-HeFT
didn't test any other races than blacks.) Also, once
a pharmaceutical company gets a patent, there's no incentive
to spend more money to figure out the genetic or physiological
story.
Dr David Alter, professor of medicine
at the University of Toronto and a researcher at the
Institute of Clinical and Evaluative Sciences, says
a little healthy skepticism wouldn't be remiss. "Group
responses to treatment may be based on social, cultural,
economic, environmental or other factors, not just genetics,"
he notes. "For example, we've been seeing subgroup effects
— based on things like gender, age or comorbidities
— for years."
Getting a patent on race-specific
grounds was an attractive marketing incentive for NitroMed.
It prevents approval of a generic fixed-dose formulation
until 2020 instead of just 2007, which would have been
the case otherwise. Nevertheless, once doctors figure
out dosages, they can offer the generics to patients
for about 50 cents a day.
Dr Alter says that here in Canada
there is less of an emphasis on race in medicine than
in the US. " The emphasis here is more on socioeconomic
issues, and health disparities based on them," he says.
However, he agrees that using phenotype as an inclusion
criterion may sometimes have merit — but urges
caution. "What we must finally do," he says, "is drill
down to the genetics and tease out why some patients
respond and some don't."
For more on heart failure treatments,
see "Pantyhose-like
device offers support to failing hearts".
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