Three recent Canadian Federal Court and Federal Court of Appeal decisions make reference to fundamentals of the patent system and all involve questions of validity of claims that are directed to either (i) a specific form of a known chemical molecule having distinct biological properties (so-called enantiomers, mirror images of the same molecule where each enantiomer can have significantly different biological activity); or (ii) a particular medical use of a known chemical compound [Janssen-Ortho v Novopharm (2007), Pfizer v Ranbaxy (2008); and Eli Lilly v Apotex (2008)].