We applied for US and Canadian Utility Patents. Our US patent issued. After the US patent issued, during prosecution, the Canadian patent examiner sent back an office action and cited prior art that we did not cite in the US application. What do we do now.
Information that comes to your attention before the grant of your U.S. patent must be brought to the attention of the USPTO even if it is after the notice of allowance and payment of the issue fee. After grant there is no obligation to do anything with this new reference. However, if you feel it weakens the patent, you might request an ex parte reexamination. This will allow the new reference to be considered, and arguments and amendments to be made. You may end up with a narrowed but stronger patent.