Canada's ability to control the price of patented drug prices could be at risk after a U.S. company challenged the constitutionality of the federal regulator's ability to order a price cut for a costly treatment for a rare genetic condition. Alexion Pharmaceuticals has filed a lawsuit in Federal Court against Canada's Patented Medicine Prices Review Board that determined that the price of Soliris, which has been dubbed the world's costliest drug, is "excessive."