By Bill Berkrot
Jan 23 (Reuters) - A cholesterol fighter developed by Amgen Inc from a highly promising new class of medicines significantly lowered levels of "bad" LDL cholesterol in a late stage trial in patients unable to tolerate statin drugs, the company said on Thursday.
The results marked the third successful Phase III test of the drug evolocumab reported by Amgen in recent months - this one in a patient population among the most in need of alternative therapies.
An estimated five to 20 percent of heart patients are intolerant of statin medications for lowering cholesterol due to side effects such as muscle weakness or fatigue, Amgen said.
Evolocumab belongs to a class of medicine called PCSK9 inhibitors that work by blocking a protein that reduces the liver's ability to remove LDL cholesterol from the blood.
Based on dramatic LDL lowering demonstrated by Amgen and other companies in earlier studies, PCSK9 inhibitors could be the most important new heart drugs to come along in several years with multibillion-dollar sales potential.
The injected medicines are likely to be used in high risk heart patients unable to lower their LDL levels sufficiently with high doses of widely used statin drugs, such as Pfizer's Lipitor, and in those unable to take statins.
Many patients remain at high risk of heart attack and stroke "despite the use of all available therapies," Amgen research and development chief Sean Harper said in a telephone interview.
"The ability to treat those individuals with a completely distinct mechanism and see this very large effect size of dropping LDL cholesterol by roughly 50 percent, that's a pretty big deal for those patients," Harper said.
The company expects during the current quarter to have results of its final two Phase III studies - one in patients already taking high doses of statins and one in patients genetically predisposed to dangerously high cholesterol levels.
Amgen will provide details of its latest 307-patient Phase III study, called GAUSS-2, which compared evolocumab to Merck & Co's Zetia (ezetimibe), at an upcoming medical meeting.
However, the world's largest biotech company said the percentage of cholesterol lowering was consistent with those observed in a similar, smaller Phase II trial. In that study, evolocumab led to 51 percent reduction in LDL levels and 63 percent when combined with Zetia versus a 15 percent reduction seen with Zetia alone.
"It's very unusual to have a therapeutic that addresses one of the underlying factors that drive the greatest mortality risk that exists in Western countries, and increasingly in developing countries - cardiovascular disease driven by atherosclerosis," Harper said.
The company anticipates that some of its global filings seeking approval of the drug will occur this year.
"We don't come across therapeutics like this very often in this industry," Harper said. "It is very exciting, and as we get each data set our confidence slowly builds that we have the efficacy and the safety profile that will make this an important medicine."
Regeneron Pharmaceuticals Inc, in partnership with Sanofi, is also in Phase III testing of a rival drug. Pfizer is developing its own PCSK9 inhibitor.
Amgen shares were down about 0.6 percent at $123.55 on Nasdaq, roughly in line with declines in the broader market.