The injectable drug works by blocking PCSK9, a naturally occurring protein that coaxes the body to hold onto "bad" LDL cholesterol. In small earlier trials, REGN727 slashed LDL levels by 40 to 70 percent without any serious side effects.

That is comparable to the largest LDL reductions typically seen with standard oral treatments called statins that include Pfizer Inc's Lipitor and AstraZeneca Plc's Crestor.

Some analysts believe REGN727 could generate annual multi-billion dollar sales if it is proven safe and effective in the trials and is approved. The medicine would be geared to patients that cannot tolerate statins and to millions of others who do not get their LDL levels down to target levels with statins.

"The studies could allow us to have a global launch in 2016, but our goal is for the first launch by the fourth quarter of 2015," Jay Edelberg, head of Sanofi's development program for REGN727, said in an interview.

Other drugmakers, including Merck & Co and Amgen Inc, are racing to develop their own PCSK9 inhibitors, spurred in part by stellar results seen in earlier small mid-stage trials of REGN727.

Edelberg said patients in large Phase III studies would receive injections of REGN727 every two weeks. Most will take it in combination with statins. It will also be tested in separate trials among patients who cannot tolerate statins, as well as among patients with gene mutations that make them and family members highly prone to high cholesterol and heart disease.

"Only a few hundred patients have been enrolled, but we hope to roll out all the studies this year," he said.

Edleberg said one of the Phase III trials will test the safety of REGN727 over an extended period and that another especially long study will evaluate the drug's potential to reduce the incidence of heart attacks and other cardiovascular problems.

Some 24 million patients in the United States take statins, the majority of which fail to drive down LDL to target levels, Edelberg said.

(Reporting By Ransdell Pierson in New York; editing by Andre Grenon)

• A Permanent Economic Emergency