Perhaps the most obvious way for AbbVie to top expectations is for Humira to hold up relatively well against biosimilar competition. There's already some reason for optimism on this front. AbbVie CEO Rick Gonzalez said in the recent quarterly update that U.S. Humira sales should fall by around 37% this year. That's at the low end of the company's previous projection of sales erosion between 35% and 55%.