SPC for Darunavir - protection by Markush formula

Litigation concerning Supplementary Protection Certificates (SPCs) frequently involves referrals to the Court of Justice of the EU (CJEU), as reported here.  It is therefore refreshing that the UK High Court has just issued a decision in Sandoz v Searle without requesting further guidance from the CJEU.

At issue was the validity of SPC/GB07/038 for a product described in the SPC as "Darunavir or the pharmaceutically acceptable salt, ester or prodrug thereof". The key question in this case was whether the anti-retroviral Darunavir is ‘protected by a basic patent in force’, as required by Article 3 (a) of the SPC Regulation.  

The claims of the basic patent define a group of compounds by reference to a Markush formula (a formula which consists of a specified backbone that may have various different substituents ). Darunavir is a specific compound that falls within the scope of this formula.  However, Darunavir is neither explicitly recited in the claims, nor explicitly mentioned elsewhere in the patent. 

The CJEU has previously established that it is necessary for the product to be "specified" or "identified" in the wording of the claims, but this test has been criticised as being unclear.  In particular, Mr Justice Arnold questioned (in Novartis Pharmaceuticals UK Ltd v MedImmune Ltd) whether this test would be met by a claim reciting a Markush formula which covers a large number of compounds, one of which is the product in respect of which an SPC is sought.

More recent guidance by the CJEU (Eli Lilly v Human Genome Sciences) sets out that it is not necessary for the active ingredient to be identified in the claim by means of a structural formula: it is sufficient for the active ingredient to be covered by a functional description provided that the claims "relate, implicitly but necessarily and specifically, to the active ingredient”.

In view of this guidance, Mr Justice Arnold now felt able to answer his own question, finding that it is sufficient for the claim to specify the product by means of a Markush formula which covers it. 

Mr Justice Arnold has previously suggested that there should be an additional requirement that the product embodies the inventive advance/ technical contribution of the claim (Teva UK Limited & others v Gilead Sciences Inc).  Perhaps unsurprisingly, in the present case he was able to arrive at a conclusion that would not have been altered by the application of this proposed additional test.  

This ruling suggests that an SPC may validly be based on a claim that protects the relevant product only by virtue of a Markush formula, which is a welcome development for innovative drug developers.  It is important to bear in mind, however, that this decision may be appealed, and that the referral to the CJEU mentioned above is still pending. Follow us to keep up-to-date with developments in this area.  

Barbara Rigby
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