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11.13.06, 8:35 AM ET

A new cholesterol-lowering shot being developed by tiny Isis Pharmaceuticals of Carlsbad, Calif., may be more powerful than existing pills like Lipitor, Zocor and Crestor. The drug's potential is likely to garner interest from investors, because cholesterol treatments are the drug industry's top sellers.

In midstage trials, the results of which were presented Sunday night at the annual meeting of American Heart Association, the medicine cut patients' levels of LDL, the bad cholesterol, by 60%. If those results hold up in later studies, that would make Isis' (nasdaq: ISIS - news - people ) chemical, still known by the code number 301012, more powerful than the two most powerful cholesterol cutters on the market: Crestor, from AstraZeneca (nyse: AZN - news - people ), and Vytorin, from Merck (nyse: MRK - news - people ) and Schering-Plough (nyse: SGP - news - people ).

Better yet, a second study shows that 301012, a weekly injection, works well when given on top of the popular pills called statins that are used to treat high cholesterol. In patients who had high cholesterol levels despite taking 20 milligrams or more a day of Lipitor, from Pfizer (nyse: PFE - news - people ), or Zocor, from Merck, 301012 cut LDL levels in half.

John Kastelein, the University of Amsterdam researcher who conducted the studies with Isis, says that if physicians eventually get to add 301012 to their arsenal, it will be possible to get "virtually anyone" to the aggressively low cholesterol goals that have been set by government-organized committees. The drug's potential, he says, "is incredible."

There is still a long way to go before millions of patients take 301012 to prevent heart attacks--although the drug could be on the market to help some exceptionally sick people in just a few years. For one thing, it will take years to establish that the shot is as safe as the pills that are routinely popped by people who are at risk for heart attacks. The data presented last night was shown as part of an invited speech by an Isis scientist, and so it didn't go through the same review process as most studies presented at the AHA meeting.

Another problem: Existing cholesterol drugs are pills. Right now, patients getting 301012 in clinical trials receive a weekly shot. Kastelein says it's possible the drug might work if given once every two weeks or even once a month. Evan Stein, director of the Metabolic and Atherosclerosis Research Center in Cincinnati, points out that patients now self-inject drugs for diseases like rheumatoid arthritis and diabetes. "As long as the drug is effective and safe, it should do well," says Stein, who has worked with Isis on clinical trials of the drug.

One market for the shot will be the 5% or more of patients who cannot take statins like Lipitor or Crestor because of their muscle-damaging side effects. It is also possible that some patients would prefer the once-a-month shot to a daily tablet. (See: " Cholesterol Comeback.")

But the nearest-term potential for the drug will be in patients who have a rare genetic disease in which both copies of a gene that controls getting cholesterol out of the body are defective. These people's cholesterol goes down when they get existing drugs, but not enough, and sometimes it must be taken out with filtration machines. Because of this dire need and the small number of people who have the disease, approval could happen with just a few patients.

Mark Wedel, chief medical officer at Isis, says that a plan with the FDA has already been finalized. Data for these very sick people could come by the end of this year or the beginning of 2007.

Next up would be studies in the larger population who have both copies of the gene. At the same time, Isis will be testing the drug in people who have garden-variety high cholesterol in the hopes of achieving a mass-market blockbuster.

Wall Street is starting to take notice of the potential. When Forbes.com looked at Isis in February, excitement over 301012 caused the company's stock to hit a new 52-week high. Since then, shares have doubled, to $10.40. Last week, analysts from three firms--Cowen & Co. (nasdaq: COWN - news - people ), A.G. Edwards (nyse: AGE - news - people ), and Leerink Swann--initiated coverage of the company, telling investors that Isis stock should outperform the market.

Over the past few years, Isis has been buffeted by repeated clinical failures. This time, though, the enthusiasm of doctors and stock analysts seems as if it might be justified.