Questions Linger on Pfizer Drug

The study's authors also told companies working on similar drugs, known as CETP inhibitors, that the Pfizer experience doesn't automatically translate into bad news for their research efforts.

"Given the potential importance" of finding new drugs to raise good cholesterol levels, "it would seem imprudent to abandon studies of CETP inhibition," especially because similar drugs don't appear to raise blood pressure.

Merck(MRK Quote) and Switzerland's Roche are developing CETP inhibitors, and they are in the process of deciding whether to move from midstage clinical testing to the third round of human tests.

Phase III testing is the most extensive and expensive clinical trial, and it represents the last clinical research before a drug is submitted to regulators.

CETP stands for cholesteryl ester transfer protein, an enzyme that affects the balance of good cholesterol and bad cholesterol. By inhibiting this enzyme, researchers believe they can tilt the balance in favor of good cholesterol.

Researchers have been looking at ways to raise good cholesterol as to augment the bad cholesterol-lowering ability of statin drugs such as Lipitor.

"Twenty years after the introduction of statins, we are still waiting for the next breakthrough," says the New England Journal of Medicine article. The lead author is cardiologist Dr. Steven Nissen of the Cleveland Clinic.