Remember Effient? The blood thinner that was once Eli Lilly and Co.’s greatest post-Zyprexa hope and then, after a slow launch, was dismissed as an abject failure? Well, it’s turning out to defy both predictions.

Indianapolis-based Lilly and its development partner on the drug, Japan-based Daiichi Sankyo Inc., posted $72 million in sales of Effient during the second quarter, up from $56 million in the first quarter and $47 million in the fourth quarter of 2010.

Effient’s accelerating sales is good news for Lilly, which desperately needs new revenue to replace revenue that will be lost to generics when its $5-billion-a-year Zyprexa sees its U.S. and European patents expire in October.

And while Lilly's and Daiichi’s marketing directors say they can keep Effient sales growing at the 28-percent clip they did in the second quarter, analysts at best think Effient will reach $1 billion by 2016, one year before its patent expires.

“Cardiologists, but particularly interventional cardiologists, are gaining confidence around the product,” said Vince Truax, Lilly’s marketing manager for Effient.  “We’ve got three-quarters of interventional cardiologists writing Effient [prescriptions] right now.”

Effient is used, in combination with aspirin, to prevent blood clots in patients who have had a heart attack, stroke or severe chest pain and have been treated with angioplasty. It’s often first prescribed in hospitals, when heart attack patients are rushed to the emergency room.

Given those circumstances, Lilly and Daiichi found that cardiologists wanted to be absolutely sure how Effient would work in patients before using it regularly. Physicians already have a well-established product in Plavix that they can use in heart patients.

“As we talk to more interventional cardiologists and run it through the market, they’re seeing clarity of where to use the product,” Truax said.

That clarity has focused on two specific groups of patients. The first are those who are having a heart attack and have a heart rhythm that is elevated at a specific point on an electrocardiogram. The second group are do not have the elevated rhythm, but do have chest pain or are having a heart attack, and are also at risk of diabetes.

It’s in these two subgroups of patients where Effient is gaining most traction, Truax said.

“This is a launch in a very narrow set of a patient type. It’s still a significant market. In that context, we feel good about the performance,” Truax said.

Analysts, though, had hoped Effient would be able to broaden out for use in many groups of heart patients. That broader use is what drove Plavix to generate the second-highest amount of sales of any drug in the world for its makers, New York-based Bristol-Myers Squibb Co. and France-based Sanofi Aventis SA.

Because Plavix’s U.S. patent expires in November (and already has expired in many European markets), analysts said Effient would have to establish a big market presence early in order to have a chance against cheaper generics. That hasn’t happened.

Now, to complicate matters further, the U.S. Food and Drug Administration last week approved Brilinta, a drug made by United Kingdom-based AstraZeneca plc, for the broad uses Plavix is approved for.

The combination of competitive threats has led most analysts to predict Effient as a middling performer from now until its patent life ends.

“Effient’s launch has been disappointing in the U.S.,” wrote Deutsche Bank analyst Barbara Ryan in a July 22 note. “It has also been launched in most major European markets, but faces additional competitive pressures there from widely available generic Plavix products and from the recently approved Plavix alternative from AZN [Brilinta].”