CA-2025-001040 - [2025] EWCA Civ 903

Lord Justice Arnold:

Introduction

This appeal requires this Court once again to consider the concept of plausibility when determining the validity of a patent. It has many similarities with Sandoz Ltd v Bristol-Myers Squibb Holdings Ireland Unlimited Company [2023] EWCA Civ 472, [2023] RPC 12 (“Sandoz v BMS”), although there are differences. One of the main differences is that the appeal also requires the Court to consider the concept of arbitrary selection from the prior art.

The Defendant (“AstraZeneca”) was the proprietor of European Patent (UK) No. 1 506 211 entitled “C-aryl glucoside SGLT2 inhibitors and method” (“the Patent”), which expired on 14 May 2023, and is the proprietor of UK Supplementary Protection Certificates Nos. SPC/GB13/021 and SPC/GB14/050 (“the SPCs”) based on the Patent, which expire on 13 and 14 May 2028. The claims of the Patent relate to a compound called dapagliflozin, marketed by AstraZeneca under the trade mark Forxiga pursuant to a marketing authorisation granted on 14 November 2012, which is used to treat diabetes. The Claimants contend that the Patent was invalid, and therefore the SPCs are invalid. There is no challenge to the claimed priority date of 20 May 2002. AstraZeneca acquired the Patent from Bristol-Myers Squibb (“BMS”) in 2014.

Dapagliflozin is an inhibitor of the sodium-dependent glucose co-transporter protein SGLT2. SGLT2 is responsible for the re-uptake of glucose in the proximal tubule of the kidney back into the bloodstream. SGLT2 inhibitors are understood to reduce blood glucose levels by preventing glucose reabsorption into the blood, thereby facilitating excretion into the urine.

The Claimants contend that the Patent was invalid for lack of inventive step and/or insufficiency. In summary they plead that:

the Patent did not make it plausible that dapagliflozin is an SGLT2 inhibitor, a selective SGLT2 inhibitor or useful for treatment of diabetes; and

the Patent did not make a technical contribution over International Patent Application No. WO 01/27128 A1 (“WO 128”) filed by BMS and published on 19 April 2001, but rather merely made an arbitrary selection of dapagliflozin from the class of compounds disclosed in WO 128 without disclosing any advantage for dapagliflozin compared to that class.

WO 128 discloses a class of compounds defined by an extremely broad Markush formula, Formula I, that are said to be SGLT2 inhibitors. It also describes a narrower (but very broad) class defined by Formula IA and a still narrower (but broad) class defined by Formula IB. It is common ground that dapagliflozin falls within the class defined by Formula IB and differs in only one respect from a member of that class described in Example 12 of WO 128.

Originally the Claimants also contended that it was obvious (in the conventional sense) to arrive at dapagliflozin as an SGLT2 inhibitor from the disclosure of WO 128, but that allegation was not pursued in their closing submissions at trial.

After a seven day trial Dr Michael Tappin KC sitting as a Deputy High Court Judge held that the Patent was invalid on both grounds pursued by the Claimants for the reasons given in an impressive judgment running to 282 paragraphs dated 28 April 2025 [2025] EWHC 1012 (Pat). AstraZeneca appeals with permission granted by the judge on eight grounds. I expedited the hearing of the appeal because the market for dapagliflozin is a large one and the Claimants (and a number of other generic pharmaceutical companies) are currently restrained by interim injunctions and undertakings from launching generic dapagliflozin products.

It is worth noting that Dr Tappin KC was particularly well-qualified to hear this case, since he not only has a degree in chemistry and a doctorate in biochemistry, but also had the experience gained from appearing as counsel in (among many other cases) Sandoz v BMS.