Federal Court finds patent for concentrated methotrexate solutions obvious | Smart & Biggar
On March 26, 2024, the Federal Court dismissed Medexus and Medac’s action for patent infringement of Canadian Patent No 2,659,662 (the 662 Patent), finding the asserted claims invalid for obviousness: Medexus Pharmaceuticals Inc v Accord Healthcare Inc, 2024 FC 424.
Medexus markets and sells pre-filled syringes containing 50 mg/ml methotrexate solution in Canada as METOJECT. Accord received marketing approvals to market syringes and injector devices pre-filled with a 50 mg/ml methotrexate solution. Accord conceded infringement.
The narrowest claim of the 662 patent (claim 10) as modified by limitations of other claims (claims 1-9) is:
Use of methotrexate for the production of a subcutaneously administered medicament that is contained in a ready-made syringe for a single application and that is in a form suitable for patient self-administration, for the treatment of rheumatoid arthritis, wherein the methotrexate is present at a dosage of 5 to 40 mg in a pharmaceutically acceptable solvent selected from water, water for injection purposes, water comprising isotonization additives and sodium chloride, at a concentration of about 50 mg/ml.
The Court found that the inventive concept of each claim is the concentration of methotrexate – which for claim 10 (as read through claims 1-9), was a methotrexate concentration of “about 50 mg/ml”. The Court rejected that the following formed part of the inventive concept:
- “Improved formulations or advantageous properties”: The Court found that the 662 Patent did not explain why the described concentrations are preferred, that the inventor did not overcome problems in formulating the claimed solutions and the 662 Patent does not disclose any advantageous properties of such formulations;
- “Identifying a problem that others did not identify”: The Court found that the 662 Patent did not identify a problem that others in the field did not appreciate;
- “Combining claim elements”: The Court found that the 662 Patent is not a combination patent and that apart from the concentration of methotrexate, the claim elements in various combinations were already part of the state of the art or common general knowledge.
In identifying the difference between the inventive concept and the state of the art, the Court held that this is not a combination patent. The skilled person would not have to combine knowledge from different fields or different prior art references in the same field, since apart from the 50 mg/ml concentration of methotrexate, various combinations of claim elements were common general knowledge.
The Court accepted that:
- Methotrexate formulations for parenteral administration at concentrations up to 100 mg/ml were already commercially available as medicines for human use;
- Subcutaneous and parenteral administration were considered interchangeable; and
- The skilled person would not consider there to be a significant reason why a higher concentration methotrexate solution could not be administrated to patients subcutaneously to treat inflammatory autoimmune diseases, and the literature does not support that methotrexate’s side effects and toxicity were considered concentration-dependent (rather than dose-dependent).
Therefore, the Court found that the differences between the inventive concept of the claims and the state of the art would have been obvious to the skilled person, who would not view changing concentration as a big step, and the further elements did not impart inventiveness.
The Court dismissed Accord’s ambiguity attack on the term “about 50 mg/ml”, finding Accord had not established that “about” is incapable of understanding or that “about 50 mg/ml” cannot provide an unambiguous boundary defining the scope of the monopoly.
Medexus may appeal as of right.
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