A Tale of Two Dasatinibs

A Tale of Two Dasatinibs

Things could be looking up for Bristol-Myers Squibb after a tumultuous year that saw the EPO Board of Appeal confirm the revocation of EP1169038, a patent protecting the successful cancer drug dasatinib (Sprycel®). This decision (T488/16) raised eyebrows in February 2017 when the Board of Appeal ruled that in the complete absence of any activity data, the patentee was unable to shift the burden of proof to show the technical effect was plausible at the time of filing and therefore refused to admit the post-filed data that could have corroborated an inventive step. You can read our original write up here.

Less widely noted however was the more promising fate of EP1610780, a later filed patent claiming the use of dasatinib in the treatment of CML (chronic myeloid leukaemia). This patent had also been opposed and revoked on the grounds of added matter and sufficiency. However, only 2 days after the “Dasatinib I” decision, the very same Board of Appeal acknowledged the sufficiency of claim 1 of the later use patent and remitted the case back to first instance proceedings to determine the outcome of inventive step (T950/13).

This is intriguing for a number of reasons and casts some light on the EPO’s position on plausibility and post-filed data.

Firstly, the text of the “Dasatinib II” patent was largely identical to that of “Dasatinib I” and still contained no experimental data. Critically, however, unlike “Dasatinib I” dasatinib was listed as a preferred compound and indeed was the only compound out of the many synthetic examples that was disclosed as suitable for treatment of CML.

The Board noted that dasatinib was clearly disclosed in the application as being suitable for CML treatment, as well as for cancers sensitive to treatment with BCR-ABL kinase inhibitors. Since it was well known in the art at the filing date that the BCR-ABL oncogene was a causative factor in CML development and BRC-ABL kinase inhibition was an effective way to treat CML, the Board considered the teaching that dasatinib was useful to treat CML equivalent to the teaching that dasatinib inhibits BRC-ABL kinase, despite the lack of experimental evidence for this in the application.

In light of this, and the functional analogy in the application to another successful BCR-ABL kinase inhibitor imatinib (Gleevec®), the Board disagreed with the Opposition Division and held that the technical concept was plausible. It was therefore allowable to admit post-published documents as evidence the invention was reproducible without undue burden at the filing date, even in the absence of data.

The use of a functional analogy to a known agent could be considered risky in terms of exposure to inventive step attacks. However, the Board took pains to distance the concepts of plausibility and obviousness from each other and state that of course a technical teaching is not rendered implausible because it was not obvious in light of the prior art.

It now falls to the Opposition Division to decide the fate of the amended claim set. A number of further points of interest have come to light after the preliminary opinion of the opposition division was released in May this year.

Firstly, the Division have indicated they will not be reconsidering plausibility and feel bound by the finding of the Board of T950/13 that the treatment of CML by dasatinib was plausible at the time of filing. Post-filed data may, therefore, be admitted to substantiate inventive step arguments.

Secondly, there is the issue of revoked “Dasatinib I”, which is cited as D1 in the remitted opposition case in view of its earlier publication date. The Division have stated this cannot be the closest prior art (despite the largely overlapping disclosures) since the division consider themselves bound by the Board of Appeal’s ruling that the earlier patent is insufficient. The division therefore indicate they will be taking this into consideration when considering obviousness.

Lastly, there were two interventions filed in the remitted proceedings, both of which have been indicated as admissible by the Division. In admitting the interventions, the Opposition Division have come to the preliminary conclusion that the arbitration proceedings instigated against the interveners by the Proprietor under Portuguese law constitute “infringement proceedings” in the sense of Article 105(1)(a) EPC.

The latest instalment of this saga appears to soften the blow of the previous decision and confirms that experimental data is indeed not essential when filing, as long as the technical effect is plausible. This may come as a relief to applicants wishing to continue the practice of early filing but still suggests withholding too much information on lead compounds is an increasingly dangerous game to play.

At the least, it may be sensible to avoid general statements and indicate specific compounds and medical indications where data is not yet available in order to give an application the best chance to clear the plausibility bar. It may also be helpful to provide a mechanism or reason why the technical effect is achieved if this is reasonably certain, although it is not fully clear if this would have been enough to sway the Board if there had not been a functional analogy to an agent known to be effective for treating the same indication.

For more information or advice, please contact Abi Heath or Nick Bassil, or your usual Kilburn & Strode advisor.

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