After Pfizer's (NYSE:PFE) $800 million bomb with torcetrapib last December, there was a possibility that all drugs that inhibited the same target protein -- cholesteryl ester transfer protein (CETP) -- might suffer the same fate. Merck (NYSE:MRK) seems to have alleviated some of that fear yesterday with the release of its newest phase 2 data.

The second-highest doses of the drug MK-859 lowered "bad" LDL cholesterol by 40%, while increasing the patient's "good" HDL cholesterol by a very impressive 139%. When the highest dose of MRK-859 was combined with Lipitor, the LDL cholesterol dropped even more -- to 68% of the starting level.

Most importantly, Merck didn't see the rise in blood pressure that occurs with Pfizer's torcetrapib. Investors should be cautiously optimistic about the results, but only a much larger and longer phase 3 trial will tell for certain that there are no side effects big enough to derail this blockbuster.

Merck is taking a multifaceted approach to finding a blockbuster that increases HDL levels. The only drug on the market that substantially increases HDL, niacin, has the bad side effect of turning patients flush. The company is waiting on an FDA decision over its CORDAPTIVE drug, which is a combination of its extended-release niacin and a flushing pathway inhibitor. If MK-859 is ever approved, it would compete with CORDAPTIVE, as well as with Abbott Laboratories' (NYSE:ABT) extended-release niacin drug, Niaspan.

With Zocor already facing generic competition, Merck is trying to expand its cholesterol-fighting dynasty beyond Zetia and Vytorin (since it has to share profits for both with Schering-Plough (NYSE:SGP)). MK-859 seems like just the molecule, but it's going to be a few years before we know for sure.

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