African-American heart failure patients taking

NitroMed's

(NTMD)

drug BiDil had a 43% improvement in survival compared to similar patients taking a placebo, according to statistically significant results from a phase III study reported Monday.

On two other measures of clinical benefit -- time to first hospitalization for heart failure and quality of life -- BiDil also proved superior to placebo with statistically significant results.

The BiDil data presented Monday at the American Heart Association Scientific Sessions were

highly anticipated. In July, NitroMed shares soared when the company halted the late-stage clinical study of BiDil after an independent monitoring board said the drug provided a statistically significant survival benefit. The benefit was so compelling, the monitoring board said, it would have been unethical to keep the drug away from patients taking a placebo.

Until Monday, investors had been guessing the exact magnitude of the survival benefit conveyed by BiDil. The reported 43% reduction in all-cause mortality generally exceeded expectations, which were in the range of a 30%-40% survival benefit.

NitroMed shares rose $1.95, or 8%, to $25.68 in Friday's regular session, partly on anticipation of strong BiDil results, but also because an embargoed

New England Journal of Medicine

article describing the actual data from the BiDil study was

leaked to select investors.

BiDil is not a novel, groundbreaking drug. It's actually a combination of two generic products, isosorbide dinitrate and hydralazine, neither of which are approved for heart failure. Previous studies of BiDil failed to show any benefit in a general population of heart failure patients, but NitroMed reanalyzed the data and discovered that the drug seemed to help African-Americans. This led the company to conduct another phase III trial, the African American Heart Failure Trial, or A-HeFT, enrolling 1,000 African-Americans in 170 sites across the U.S.

The actual primary endpoint of the A-HeFT study was a composite score of mortality, time until first hospitalization for heart failure and quality of life. BiDil patients scored better than placebo patients and the result was statistically significant.

Each component of the primary endpoint was also individually analyzed. In addition to the aforementioned 43% survival benefit, BiDil patients had a 33% relative reduction in time to first hospitalization for heart failure and higher quality of life scores, according to the study results.

Adam Feuerstein writes regularly for RealMoney.com. In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet.com. He also doesn't invest in hedge funds or other private investment partnerships. He invites you to send your feedback to

adam.feuerstein@thestreet.com.