The new drugs in development by top pharmaceutical makers and up-and-coming biotechs are injectable medications that block a protein called PCSK9.

They have shown promise in early clinical trials for slashing "bad" LDL cholesterol further than widely used statins can alone. Their biggest advocates say PCSK9 blockers have the potential to be the next multibillion-dollar class of heart drugs.

Regeneron Pharmaceuticals Inc last year disclosed that its product slashed levels of LDL cholesterol up to 65 percent beyond reductions seen alone with statins - pills like Pfizer Inc's Lipitor and AstraZeneca Plc's Crestor that are today's standard treatments.

The company on Monday will unveil full trial results, including safety findings - giving a fuller picture of its potential and how widely it might be prescribed if approved.

Wall Street has followed the drug, called REGN 727, as well as rival products from Amgen Inc, Merck & Co and other drugmakers that are nipping at its heels. But relatively few doctors know much about the emerging new class of treatments.

"I can't believe the cardiologists won't be in awe of the LDL reductions" seen for Regeneron's drug, said Mani Mohindru, an analyst with Think Equity. She speculated the medicine, being developed in partnership with French drugmaker Sanofi, could generate huge sales if it succeeds in larger trials and remains free of serious safety concerns.

Regeneron is best known for its drug Eylea, approved to treat a leading cause of blindness called macular degeneration. Company shares have more than doubled to the $115 range since the injectable medicine, which competes with Roche Holding AG's Lucentis, was approved by U.S. regulators in November.

Mohindru said Regeneron shares could jump another $5 or more, to new lifetime highs, after the REGN 727 study is presented on Monday in Chicago.

"It will be a significant event because a lot of cardiologists haven't seen this data," she said. "And Wall Street still doesn't appreciate how wide a use the drug could have. It's not in Regeneron's stock in a big way, so there's upside here."

Amgen on Sunday will present data from a study of its anti-PCSK9 medicine, called AMG145. Although it is an early-stage trial involving relatively few patients, compelling effectiveness and safety data might allow it to steal some of the Regeneron product's thunder.

"PCSK9 is one of the most exciting targets in cardiovascular drug development today," Michael Severino, Amgen's chief medical officer, said in an interview.

WHEN STATINS AREN'T ENOUGH

Severino said a large number of patients - some studies suggest 40 to 50 percent - fail to reach their cholesterol-lowering goals despite being on statins, and that PCSK9 inhibitors could give them the needed extra push. Moreover, the drugs could help a much smaller group of patients who cannot tolerate statins, he said.

An estimated 9 million Americans are deemed at high or very high risk of heart-related problems, and could benefit most from PCSK9 drugs added to statins. And at least another 1 million could use them instead of statins.

"For 30 years there really hasn't been another drug therapy of important magnitude added to the benefit of statins," said Dr. Jefferey Borer, head of cardiology for SUNY-Downstate Medical Center in New York. "Most doctors don't know about this approach, so I think there will be a tremendous amount of interest at the meeting and people will begin to talk about it."

But Borer cautioned that more safety data is needed for anti-PCSK9 drugs because so many people may use them. "We need many large trials."

Regeneron plans to begin a number of large late-stage trials of REGN 727 by mid-2012. Amgen, meanwhile, is gearing up for a series of mid-stage studies of its product that will involve almost 2,000 patients.

"The initial market opportunity might be the sickest patients, maybe those who have had a heart attack or are at risk of another heart attack," said Deutsche Bank analyst Robyn Karnauskas, who added that segment represents about 3 million people in the United States.

"Nobody knows their sales potential," she said, but speculated the class of drugs could fetch $8 billion to $25 billion a year, depending on pricing and how widely they are prescribed.

Hundreds of other studies will be presented at the four-day heart meeting that begins on Saturday, tracing the effectiveness of medicines, medical devices and medical procedures. Researchers will present findings on when it is most beneficial to use a coronary computed tomography angiogram on people who come to the emergency room with chest pain, and a study that examines the benefits of lowering LDL cholesterol earlier in life. Researchers will also present two-year data on Edwards Lifesciences Corp's aortic heart valve that can be implanted using a catheter, rather than through traditional open heart surgery. Data from the first year of the study was the highlight of last year's meeting, showing the device was effective but greatly increased the risk of stroke. Another study likely to draw interest from cardiologists and endocrinologists alike is a trial that compared blood sugar, cholesterol, blood pressure and other measures of obese patients who underwent two types of bariatric surgery with those whose blood sugar was managed with drugs.

(Editing by Michele Gershberg and Matthew Lewis)

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