For years, Jazz Pharmaceuticals ' ( JAZZ 2.04% ) success has been almost entirely dependent on that of Xyrem, a narcolepsy drug responsible for more than 70% of the company's revenue. The company's good fortune is likely to come to an end: Recently, Harmony Biosciences, Avadel Pharmaceuticals ( AVDL 0.83% ), and Axsome Therapeutics ( AXSM 1.36% ) have all developed (or are about to develop) branded competitors that will take market share away from Xyrem before its patent expires.