The topic of chemical and biological patents is of special importance in European and German patent law. The highly technical nature of patents in this area gives rise to special problems for patent lawyers in understanding, for instance, structural alterations like polymorphism and enantiomerism, which lead to a derivative of a substance that is comprised in the prior 'art.' It is a legal question whether, and under what circumstances, such alterations are to be treated as novel, and in which cases they are part of the state of the art. Even if a substance is prior art, a new medical use of...