Answer ... A patent is unenforceable if:

• it is found to be invalid;
• the term of the patent has expired; or
• the maintenance fees have not been paid.

A patent may be found invalid, and therefore unenforceable, for various reasons set out in the Patent Act, including anticipation, obviousness, patent-ineligible subject matter and reasons related to disclosure.

If a patent owner fails to pay a maintenance fee and does not remedy the default, the patent will be deemed to have expired as of the due date of the maintenance fee and is unenforceable.

There are also various exceptions and defences to infringement, including prior use, development for government approval, third-party rights, laches and experimentation.

Answer ... Canada has no doctrine of inequitable conduct. However, there are circumstances in which conduct of the patent owner may affect the validity, and therefore the enforceability, of a patent.

Per the Patent Act, a patent may be void if:

• any material allegation in the petition of the applicant in respect of the patent is untrue; or
• the specification and drawings contain more or less than is necessary for obtaining the end for which they purport to be made, and the omission or addition was wilfully made for the purpose of misleading.

Furthermore, in any action or proceeding regarding a patent, a written communication between the applicant and the Canadian Intellectual Property Office may be admitted into evidence to rebut any representation made by the patent owner in the action or proceeding as to the construction of a claim of the patent.

Answer ... The Patent Act requires that an applicant reply in good faith to any requisition made by an examiner in connection with examination of a patent application. Canadian courts have held that ‘good faith’ means replying with complete, honest and impartial disclosure (Lundbeck v Ratiopharm, 2009 FC 1102).

Furthermore, a patent may be void if:

• any material allegation in the petition of the applicant in respect of the patent is untrue; or
• the specification and drawings contain more or less than is necessary for obtaining the end for which they purport to be made, and the omission or addition was wilfully made for the purpose of misleading.

Additionally, if a patent owner makes an untrue material allegation in a request for reversal of expiration of a patent which expired due to failure to pay a maintenance fee, then the patent may be declared expired as of the missed deadline to pay the maintenance fee.