20/11/2023
In a UK Patents Court case decided earlier this year, Gilead Sciences v NuCana, Gilead sought revocation of the UK designations of two of NuCana’s European patents, EP 2955190B1 and EP 3904365B1, from the same family. These patents covered NuCana’s anti-cancer drug acelarin. NuCana counterclaimed that their patents were infringed by Gilead’s anti-viral products containing the compound sofosbuvir.
The subject matter of the two patents in suit related to nucleoside analogues that interfere with cell replication. It had been difficult to get nucleoside analogues into cells, so prodrugs, called ProTides, were developed by NuCana. The patent claims covered ProTides as defined by a Markush formula. The judge, Meade J, considered that sofosbuvir fell within the Markush formula and so would infringe the patents if they were valid. However, the patents were found invalid on a number of grounds.
Firstly, the patents were deemed invalid on the ground of added matter. NuCana’s proposed amendments to the Markush formula constituted deletion from multiple lists. The new set of compounds encompassed by the amended Markush formula was considered to be significantly different such that “the skilled person would not think that there had been a mere reduction still leaving the same generic class differing only in size”. It is therefore worth bearing in mind when drafting pharmaceutical patents that the broadest Markush formula may not be the best option.
Plausibility was also considered. Meade J was bound by the ab initio plausibility test set out in Warner Lambert, but given that Enlarged Board of Appeal decision G2/21 at the European Patent Office was pending, the judge also considered an ab initio implausibility approach in the event G2/21 led to a change in case law. Regardless of the approach taken, it was considered that the skilled team would not think that it was plausible that all compounds encompassed by the Markush formula would have meaningful cytotoxic activity.
Meade J also considered that there was undue burden insufficiency: no person genuinely representative of the ordinary skilled person was shown to be successful in the synthesis of so-called “2MU2FD” intermediates, which fell under the scope of the claim.
However, the biggest take away messages from this case were in relation to the interplay between UK and EPO proceedings. EP 2955190B1 was under appeal at the EPO (case T795/21) following an opposition decision to maintain the patent in amended form. At the time of the UK hearing, the EPO’s Technical Board of Appeal (TBA) had issued a preliminary opinion, but the hearing and issuance of their final decision were yet to take place. Meade J considered the TBA preliminary opinion, but commented that it was not binding, and nor would the final decision be binding. Meade J did not consider that it was necessary to wait for the final decision of the TBA. He pointed out that any differences in the conclusions would likely be attributable to the different evidence received, with UK proceedings allowing for cross-examination, which does not feature in EPO proceedings. Out of interest, it is noted that the TBA subsequently also revoked EP 2955190B1, but on the grounds of lack of inventive step and added matter relating to different claim sets. EP 3904365B1 was not opposed at the EPO.
Gilead and NuCana were obligated to inform the court on the progress of the EPO proceedings. However, it was hinted that if they had informed the court that the EPO hearing and decision was imminent, the UK proceedings may have been stayed if considered practical to do so.
Also, in relation to the interplay between UK and EPO proceedings, this case cautions against using the same expert witness in EPO and UK proceedings. One of NuCana’s experts was used as a witness in both UK and EP proceedings, and this was criticised by Meade J. If the same witness is used, careful consideration of how the expert is instructed is required so that they are not led in a certain direction that results in them taking a different approach to that of the skilled person.
Gilead Sciences v NuCana therefore teaches that consideration of the impact of EPO proceedings on UK proceedings (and vice versa) is required.
This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.
