A discussion of the Classen Immunotherapies, Inc. litigation where Classen sued a number of parties, including GlaxoSmithKline, for patent infringement. A key litigated issue before the Supreme Court was whether the US Court of Appeals for the Federal Circuit correctly limited the patent infringement safe harbor provided by Section 271(e)(1) of the Patent Act to only potentially infringing drug research activities occurring before FDA approval to market the drug.