Alnylam, Medicines Co cholesterol drug effective for 6 months-study

PCSK9 is a protein that prevents LDL being removed from the blood. ALN-PCSsc also targets PCSK9 but via a different mechanism called RNA interference, or RNAi.

While Repatha and Praluent block PCSK9 from doing its job in the blood, Alnylam's drug prevents production of PCSK9 at the source in the liver.

Doses of 300 milligrams, 500 mg and 800 mg led to sustained reduction of PCSK9 of 80 pct or greater. At Six months, the effect began to wane with LDL down by 47 percent.

Lower LDL is associated with reducing heart attacks and death. Huge ongoing trials will determine if the new PCSK9 drugs have that affect, as widely used statins such as Lipitor do.

Alnylam and Medicines Co envision twice a year injections of their drug, likening it to a flu shot, which could enhance patient compliance.

The recently approved drugs that list for more than $14,000 a year, vastly more expensive than older cholesterol treatments, must be injected every other week.

Pharmacy benefit managers Express Scripts and CVS Health have said they will tightly control which patients they will agree to pay for for treatment with the expensive new medicines.

Alnylam believes its drug will have an advantage with payers, which may be wishful thinking.

"We think payers will like it because they don't mind paying for medicines if patients will actually take it," Vaishnaw said.

The companies expect to move forward with the 300 mg dose in Phase II trials involving 400 to 500 patients beginning this year. Larger trials that would be used to seek approval are planned for 2017. (Reporting by Bill Berkrot; Editing by Chizu Nomiyama)