Genzyme Corp. and its partner Isis Pharmaceuticals have filed an application for FDA approval for their potential treatment for the rare genetic form of high cholesterol — Homozygous Familial Hypercholesterolemia (HoFH).

The drug candidate, if approved, would be called Kynamro, and is the second potential therapy for the disease to be filed with the FDA by a Massachusetts-based company. Aegerion Pharmaceuticals (Nasdaq: AEGR) filed an FDA application for its drug candidate, lomitapide, on March 5.

Genzyme and Isis submitted the potential treatment to European regulators last year, but delayed its planned submission to the FDA by a quarter.

As a result of the filing, Cambridge, Mass.-based Genzyme, owned by French drug maker Sanofi (NYSE: SNY), will pay Carlsbad, Calif.-based Isis a $25 million milestone payment. Both Genzyme and Aegerion had hoped to receive a shortened, six-month review process for their drug candidates, given that it is a rare disease with significant unmet medical need. However, Aegerion has received a standard, 10-month review for its potential therapy.

Genzyme also presented new data on its drug candidate, for a Phase 3 extension study including 141 patients. The trial found that patients had an average sustained reduction in LDL Cholesterol of 28 percent. Three patients withdrew from the study because of adverse events.

The most severe HoFH patients have LDL cholesterol levels that are two to four times higher than recommended levels, even when taking multiple cholesterol-lowering medications. Patients are at risk for heart attacks and strokes and often die by age 30.