This case, a pharmaceutical patent fight between AstraZeneca and Apotex, includes language from the court that explicitly warns against the practice of evergreening, whereby pharmaceutical companies seek to extend the life of patent protection by adding new patents of marginal significance.
Geist quoted from the Canadian Supreme Court:
Given the evident (and entirely understandable) commercial strategy of the innovative drug companies to evergreen their products by adding bells and whistles to a pioneering product even after the original patent for that pioneering product has expired, the decision of the Federal Court of Appeal would reward evergreening even if the generic manufacturer (and thus the public) does not thereby derive any benefit from the subsequently listed patents.
In an earlier post, IPBiz noted the misuse of the evergreen concept in an article entitled Biotechnology's Prescription for Patent Reform which appeared in 5 J. Marshall Rev. Intell. Prop. L. 317 (2006):
After 1995, USPTO rules indicate that a patent will expire 20 years after the date of the earliest priority filing. Thus, continuation practice does NOT enable a patent applicant to keep an application alive in the PTO indefinitely.
**Separately, as Chiron v. Genentech (among others) illustrated, a patent applicant, in a continuation application, must have written description and enablement support for any later filed claims. See also discussion in 88 JPTOS 743.