Participants will be randomized, assigned by chance, to one of five treatment groups consisting of: four groups differing in the amount of study drug given and one placebo group. The initial dose of study drug will be given intravenously, injected into a vein in the arm. Four weeks later, three subsequent doses of study drug will be given subcutaneously, through the skin, every four weeks for three doses. Patients will be followed for approximately six months after receiving their final dose.