Chronic spontaneous urticaria (CSU), also known as chronic idiopathic urticaria, presents as hives that persist daily or almost daily for six weeks or longer without an obvious known stimulus. Drug treatment is largely dominated by anti-histamines. However, one biologic, Novartis/Roche’s Xolair, is approved for chronic idiopathic urticaria, which clinical guidelines recommend as a third-line treatment. Xolair’s dominance demonstrates that opportunity remains in the CSU market for other biologics in development. In addition, montelukast is a key drug in the CSU market and a preferred combination agent, consistent with the recommended use of leukotriene receptor antagonists as add-on treatment in the current urticaria treatment guidelines.