With all the focus on the stellar launch of Regeneron's (Nasdaq: REGN) macular degeneration drug, Eylea, it's easy to forget that the biotech has a major partnership with Sanofi (NYSE: SNY) do develop a plethora of drugs.

One of those drugs, REGN727, which Sanofi calls SAR236553, is ready to hit phase 3 trials on the back of solid phase 2 data.

The drug targets a protein called PCSK9, which promotes the degradation of the LDL receptors that remove the bad cholesterol from the blood. Inhibiting PCSK9 increases the receptors, which decreases the cholesterol levels as evidenced by the 28.9% to 67.9% reduction in LDL cholesterol compared with a 10.7% reduction in patients receiving placebo.

Those are some fairly impressive numbers considering the patients have familial hypercholesterolemia, a genetic mutation that causes extremely high cholesterol levels that couldn't be controlled by statins with or without Merck's (NYSE: MRK) Zetia. Looking at the data a different way, at the top dose, 93.8% of patients were able to lower the LDL cholesterol below 100 mg/dL, a reasonable level considering the patient population, while only 13.3% of patients taking placebo reached that goal.

REGN727 looks good, but it will have competition. Amgen (Nasdaq: AMGN) is developing a similar antibody targeting PCSK9 and Alnylam Pharmaceuticals is targeting the PCSK9 by reducing the protein levels through RNAi.

Regeneron and Sanofi are ahead of the other drugs attacking PSCK9, but they'll have to deal with Isis Pharmaceuticals (Nasdaq: ISIS), which is also going after familial hypercholesterolemia patients. Sanofi, through its acquisition of Genzyme, is also part of the program. Their cholesterol reducer Kynamro, which has a different mechanism of action, was recently submitted to the Food and Drug Administration to treat the most severe familial hypercholesterolemia patients with two mutations. But the companies are also testing patients that have just one mutation like the patients Regeneron and Sanofi tested REGN727 on.

Those results should come out before phase 3 data on REGN727 is available, giving the drug an efficacy/safety target to reach if Regeneron is going to have another hit on its hands.

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