Why amend an expired patent?

The maximum term of a UK patent, according to section 25 of the UK Patents Act, is 20 years from the date of filing of the application. If renewal fees continue to be paid, the last day of a patent's life will be on the day before the 20th anniversary of the date of filing. In the case of EP0736030, which was filed on 20 December 1994 and granted in 2001, the patent expired on 19 December 2014. The patent, titled "Tetrahydrofuran Antifungals" claimed the compound shown here on the right (with some optional features for X and R1).

The compound was apparently worth protecting a bit more, so a Supplementary Protection Certificate was applied for, and granted. SPC/GB06/007, granted in 2007, extended the protection by the usual five years beyond the expiry date of the patent, i.e. until 19 December 2019.

In April last year, two requests for an opinion were filed in relation to the patent and the related SPC, the requester alleging that the patent was invalid due to lack of novelty or inventive step. The requests were dealt with together, since validity of the SPC depended on validity of the patent, and resulted in opinion 09/16 & 10/16, issued on 31 May 2016. The examiner found that claims 1 to 4 of the patent were lacking novelty, but that claims 6 to 19 were novel and inventive. As is now allowed under section 73(1A-C), the comptroller initiated revocation proceedings on the patent, giving the proprietor (Merck Sharp & Dohme Corp.) until 21 December 2016 to respond. The proprietor responded, stating that they were "somewhat surprised" that the comptroller might consider revoking their patent, since it had already expired and that third parties were "unaffected by the validity, or otherwise of an expired patent", and suggesting that the only reason for amending an expired patent would be bureaucratic. They also questioned whether "otiose actions of this kind were in the mind of Parliament when S.73(1A) of the Patents Act was enacted". They did, after all this protesting, nevertheless submit amendments that limited the patent to the claims that were found to be allowable, and which also still covered the product covered by the SPC.

What I find surprising about this case is not the fact that revocation was initiated on an expired patent, but that the proprietor was apparently surprised by this possibility. An expired patent can still be used against third parties, since it could be used to claim damages for past infringements that took place while it was still alive. It can also be used to support an ongoing SPC, as in this case, so initiating revocation proceedings would be very relevant, particularly if they resulted in the SPC being knocked out as a result of the patent being found invalid. The fact that in this case the patent could be amended so that it was found to be both valid and still capable of covering the product protected by the SPC is something of a lucky break for the patent proprietor, but I don't think that this means the action was otiose at all.