The Food and Drug Administration yesterday approved BiDil, a drug specifically intended for use by African-Americans with congestive heart failure.
The agency called the approval a step toward "the promise of personalized medicine." Studies showed that blacks benefited from the drug while the overall population did not.
"The good news is they couldn't vote against [BiDil] because it's effective. ... The drug seems to work," said Lawrence C. Brody, a geneticist at the National Human Genome Research Institute, part of the National Institutes of Health.
The clinical trials were convincing, he said, because BiDil produced striking improvement among patients who were already receiving state-of-the-art treatment for their heart failure.
Yet he and other geneticists have argued that racial self-identification is a crude measure of an individual's genetic heritage, calling into question a black person's likely response to a drug identified for African-Americans' use.
"It may be that if this [BiDil's effectiveness] is a race-specific response, it is unlikely to be due to any genetics because people of African origin are extremely diverse," Brody said.
Genetic variation across the African continent has been shown to be more diverse than anywhere else on Earth. It's possible BiDil works because of an environmental factor common to blacks, such as diet or stress.
Neither the company nor the FDA's advisers could say why the drug appeared to work better in self-identified African-Americans in the most recent clinical trials, yet seemed not to work in earlier trials among non-African Americans.
"In the future, we hope to discover characteristics that identify people of any race who might be helped by BiDil," said Dr. Robert Temple, FDA associate director of medical policy.
FDA spokeswoman Suzanne N. Trevino said the BiDil label will state that studies have shown the drug is effective in self-identified African-Americans but have not shown similar efficacy among other groups.
"Doctors," she said, "are free to prescribe it to their patients if they believe it would help their condition," called "off-label" use.
The Associated Press contributed to this article.