Federal Court finds Expert Blinding to be One Factor in Assessing Weight Given to Expert Evidence

Federal Court finds Expert Blinding to be One Factor in Assessing Weight Given to Expert Evidence

Gilead Sciences, Inc v Canada (Health), 2016 FC 857

When using expert witnesses in patent litigation, blinding them to the legal framework may be viewed favourably, however, it is only one of perhaps several factors that will be considered when assessing the weight given to their evidence.

In this case, the Federal Court (“FC”) granted Gilead Sciences, Inc.’s (“Gilead”) application for an order prohibiting the Minister of Health from issuing a Notice of Compliance to Apotex Inc. (“Apotex”) in respect of its Notice of Allegation until the expiry of Gilead’s Canadian Patent No. 2,261,619 (“the ‘619 Patent”). [137]

The ‘619 Patent covers VIREAD®, a prodrug used in the treatment and prophylaxis of HIV. [5] The asserted claim in the ‘619 Patent is Claim 32, which describes the chemical compound tenofovir disoproxil (“TD”) and its salts, tautomers and solvates. [6] Apotex alleged invalidity on the grounds of anticipation, invalid selection as a selection patent, obviousness, and inutility. [6]

Expert Blinding: One of Several Factors Considered

A preliminary issue assessed by the FC was the weight to be given to expert evidence. Gilead provided the legal framework to its experts early, including the legal test for anticipation, obviousness, and utility, whereas Apotex did not do so before the experts had drawn their own conclusions on issues, thereby “blinding” them. [55] Apotex submitted that the court has recognized expert blinding as a preferred method for gathering evidence and asked that greater weight be given to its experts. [56] The FC found that blinding of a witness is one of perhaps several factors that influences weight given, but it is not a matter that goes to admissibility. [56] The FC further stated that blinding is a question of relevance, reliability and weight, and is not a doctrinal matter. [59] Throughout the decision, the FC noted the greater experience and knowledge of Gilead’s experts and two false statements made by Apotex’ witnesses as factors that affected weight given. [68, 79, 106, 130]

Validity: Invalidity Allegations Unjustified

In assessing anticipation, the FC accepted Gilead’s expert evidence that the disclosure in the prior art, EP0481214 (“the ‘214 Application”), provided no clear direction to follow that would inevitably lead the person of skill in the art (“POSITA”) to TD. [83]

In analyzing the allegations of an invalid selection patent, the FC found that even if the ‘214 Application included TD (which it found it did not), TD presented special advantages over the other members of the claimed genus that were not disclosed, making it a valid selection patent. [91]

Upon reading the ‘619 Patent through the eyes of the unimaginative POSITA, the FC was unable to find that it was uninventive and either self-evident or obvious-to-try. [104] Rather, the FC found that it required an inventive spark as the prodrug literature suggested there would be instability in the ‘619 Patent. [105, 112]

In assessing utility, the FC determined the promise of the patent to be “efficient oral delivery of the parent compound through its prodrug, which has a specific carbonate moiety, yielding bis(POC)PMPA or tenofovir disoproxil.” [124] The FC found that in vivo testing was not required to prove utility, and that in vitro laboratory results demonstrated a clear bioavailability improvement over the parent drug alone. [129, 132, 135]