Corifollitropin alfa is a new hybrid protein of human follicle-stimulating hormone (FSH) and the C-terminal peptide of the β-subunit of human chorionic gonadotropin. Due to a slower absorption and a longer terminal half-life, corifollitropin alfa can induce multifollicular development in women undergoing controlled ovarian stimulation using gonadotropin-releasing hormone (GnRH) antagonist-assisted in vitro fertilization (IVF). In two large randomized, double-blind, phase III trials, a single subcutaneous injection of corifollitropin alfa was as effective as 7 daily injections of recombinant FSH in inducing multifollicular development when used as part of a GnRH antagonist protocol. Non-inferiority in ongoing pregnancy rates and numbers of oocytes available for IVF has been established. In another large phase III trial, non-immunogenicity of corifollitropin alfa has been demonstrated.