It’s a fact: Methotrexate patent invalid for obviousness

In Medexus v Accord, the Federal Court concluded that a patent covering the use of methotrexate to treat inflammatory autoimmune diseases was obvious.

Methotrexate has been used as a medication since the 1950s, first to treat cancer and later to treat inflammatory autoimmune diseases. The plaintiffs sell pre-filled syringes of methotrexate under the brand name Metoject for the treatment of IADs. Accord obtained regulatory approval for its pre-filled methotrexate syringes on the basis of a comparison to Metoject. The plaintiffs sued Accord for infringement of Canadian patent 2,659,662.

Inadmissible “fact” witness testimony

The plaintiffs called the authors of a prior art article as fact witnesses at trial. Accord brought a motion to exclude their testimony on the basis that their evidence was irrelevant and would be tantamount to expert opinion tendered under the guise of fact evidence. Justice Pallotta dismissed the motion, heard the authors’ evidence, and took the issue of admissibility under reserve.

Justice Pallotta ultimately concluded that the authors’ evidence was inadmissible. The authors discussed their article, including what statements in the article meant. Justice Pallotta concluded that the authors’ testimony was unnecessary to the extent that it repeated what was in the article and that it was irrelevant to the extent that elaborated on the article because that information would not inform how the skilled person would have understood the article at the relevant time.

The authors also testified regarding the dosage forms and concentrations of methotrexate used in July 2006 (the relevant date for assessing obviousness) and how they and their colleagues drew on information about the use of methotrexate for cancer treatment when treating IADs. Justice Pallotta concluded that this amounted to improper expert opinion.

The authors’ testimony also included whether they or others had considered increasing the concentration of methotrexate or creating a new methotrexate formulation. The Court noted that this evidence was unclear and did not assist the Court to resolve any contentious issue.

Invalidity

The 662 Patent claims the use of methotrexate to produce a medicament for the treatment of IADs that is subcutaneously administered where the concentration of methotrexate is specified.

Accord asserted that the 662 Patent was invalid for ambiguity because some claims refer to a concentration of methotrexate that is “about 50 mg/ml” but the patent does not provide a definition of “about”. Justice Pallotta noted that claims are to be interpreted by a mind willing to understand and that claims that can be understood using grammatical rules and common sense cannot be ambiguous. The Court concluded that “about” has an ordinary grammatical meaning conveying an approximation. Although Justice Pallotta did not identify the limits of “about 50 mg/ml”, she concluded that the claim was not ambiguous because the skilled person would be able to construe it:

[256] In conclusion, the defendants have not established that ‘about’ is incapable of understanding, nor have they established that ‘about 50 mg/ml’ cannot provide an unambiguous boundary defining the scope of the monopoly. The defendants have not established that claims 3, 20, and their dependent claims are invalid for ambiguity because the skilled person, with the assistance of the specification and a mind willing to understand, would be unable to construe the claim term ‘about 50 mg/ml’.

The Court ultimately concluded that the 662 Patent was obvious because any differences between the state of the art and the inventive concept were obvious. Formulating higher concentration of methotrexate was obvious given the existence of other commercial products containing concentrations of methotrexate up to 100 mg/ml. The skilled person would have considered the claimed subcutaneous injections interchangeable with the intramuscular injections in the state of the art. The skilled person would not have identified any concerns with using a higher dose of methotrexate for subcutaneous injection.

A copy of the decision may be found here.