There is a balm in Gilead: Idenix's patent infringed but invalid

Authors: Darren Smyth and Robert Barker (EIP)

Idenix Pharmaceutical, Inc. v Gilead Sciences, Inc. & Others [2014] EWHC 3916 (Pat), Patents Court, England and Wales, 1 December 2014

Journal of Intellectual Property Law & Practice (2015) doi: 10.1093/jiplp/jpv044, First published online: March 8, 2015

Idenix unsuccessfully argued that a cited document constituting novelty-only prior art is not entitled to its priority date due to a procedural defect rather than its substantive disclosure.

Legal context

According to Article 54(3) of the European Patent Convention (EPC), a European patent application that has a priority date before the date of filing of a subsequent patent application, but is published on or after the subsequent patent application's filing date (or effective priority date if priority is claimed), can be cited as prior art against the novelty, but not inventive step, of the subsequent patent application.

When contemplating prior art patent applications under Article 54(3), two aspects must be considered in assessing the validity of the application's claim to priority: the substantive disclosure of the application and priority document, and the procedural rights of the applicant.

With respect to the substantive disclosure of the application, in order to be entitled to priority the subject matter of the application must be present in the priority document. Further, regarding the procedural aspect of claiming priority, the applicant claiming priority must be either the applicant of the priority document or the successor in title to the priority applicant. Many practitioners are used to considering the substantive aspects of the priority claims of the prior art, but it is unusual for the procedural validity of a priority claim to be attacked.


The patent in suit (EP 1523489) claimed pharmaceutical compositions for the treatment of viruses belonging to the Flaviviridae family. Idenix asserted that Gilead infringed the patent by the keeping and disposal of sofosbuvir (marketed as Sovaldi), a drug for use in the treatment of Hepatitis C (which belongs to the Flaviviridae family).

Gilead denied infringement and filed a counterclaim for revocation of the patent on the grounds that the claimed subject matter (i) lacked novelty over a PCT application owned by Gilead (PCT/US2004/012472, ‘the Pharmasset PCT’), (ii) lacked inventive step, (iii) was insufficiently disclosed, and (iv) contained added matter over the application as filed.

The Pharmasset PCT was a novelty-only citation, and even then only if it was entitled to its claimed priority; the Idenix filing date fell between the priority date and the filing date of the Pharmasset PCT. Idenix did not dispute the substantive entitlement to priority of the Pharmasset PCT from the priority application (US Provisional Patent Application 60/474,368 – ‘US 368’), but alleged that the Pharmasset PCT applicant was not entitled to claim priority from US 368 at the time of filing. Furthermore, Idenix did not contest that, if the Pharmasset PCT priority claim was found to be valid, all but two of the claims would lack novelty.

When the Pharmasset PCT was filed there were two Pharmasset legal entities: Pharmasset Ltd, a company incorporated in Barbados (‘Pharmasset Barbados’), and Pharmasset Inc., a company incorporated in the state of Georgia, USA (‘Pharmasset Georgia’). US 368 was filed in the name of the inventor, Mr Clark, who worked for Pharmasset Georgia, but the Pharmasset PCT was filed in the name of Pharmasset Barbados.

Gilead convinced Mr Justice Arnold that, according to contracts governed by US Federal and Georgia State law, the Pharmasset PCT was entitled to priority from US 368 in the UK, as discussed in the analysis below. Consequently, the patent was found to lack novelty over the Pharmasset PCT. Irrespective of the PCT's right to priority, the claimed subject matter was also found to lack an inventive step as it did not make any technical contribution to the art, and was insufficiently disclosed, as the patent did not enable the claimed inventions to be performed without undue burden.

Turning to the accusation of infringement, Gilead's product sofosbuvir was found to fall inside the granted claims' scope, but this was of little consequence given the finding of invalidity.

An interesting point (although ultimately irrelevant to the outcome) arose during construction of the term ‘phosphate’. Gilead cited Actavis v Lilly [2014] EWHC 1511 (Pat), another decision of Arnold J, when arguing that, as the claim had been amended during prosecution, the term ‘phosphate’ should be construed narrowly. The judge disagreed:
I had held in Actavis v Lilly at [112] that, in principle, a limitation made to a claim to avoid an objection of lack of clarity could be relied on as aid to construction. I adhere to that view, but with the benefit of the arguments of the present case I would add that such an amendment is less likely to be a useful aid to construction than a limitation to avoid an objection of lack of support, which was the primary focus of my discussion in Actavis v Lilly.

Gilead provided three routes by which Pharmasset Barbados was Mr Clark's successor in title. The main argument Gilead relied upon was that the contract of employment signed by Mr Clark stated that his rights to the invention vested in Pharmasset Georgia, and a separate agreement between the two Pharmasset entities further assigned these rights to Pharmasset Barbados.

This assertion presented by Gilead was complicated by the fact that there were no records of a signed copy of the agreement between the two Pharmasset entities. Idenix presented strong arguments that this agreement was never signed, and that therefore Pharmasset Barbados was not the successor in title to the invention. However, on balance, Arnold J decided that the agreement had been signed on the basis that, among other reasons, it was unlikely that such an important document had not been signed.

Arnold J held that the effect of the two contracts was to vest Pharmasset Barbados with the entitlement to priority. Accordingly, the Pharmasset PCT was found to be entitled to claim priority from US 368.

Gilead was able to prove a succession in title, but only because it had access to documentation that would not usually be available to the public; the priority claim was held valid, and the claimed subject matter to consequently lack novelty. However, it is somewhat unsatisfactory that the decision regarding novelty was entirely dependent on these private records. Had the prior art in question been owned by a third party, the various agreements and contracts presented in this trial would have been inaccessible: in such a case, would the outcome have been different? This must call into question whether the procedural validity of a priority claim of a prior art document should be a relevant consideration. There is an argument that for prior art under 54(3) EPC, only the substantive disclosure should be at issue.

Practical significance

The priority entitlement issue in this case arose in part due to executed assignments being misplaced. These should be treasured in case a priority claim is ever disputed, either when enforcing rights as a patentee, or when relying on the priority claim in an invalidity attack on another party. However, there is no obvious resolution to the issue regarding how to prove the validity of a third party's priority claim, as these privately held assignments would probably be impossible to access.

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