The Federal Court has found that prosecution history evidence is inadmissible to rebut representations made by a patent licensee (as opposed to the patentee) on claims construction. The Court also considered the issues of "essential elements", infringement, and obviousness in the context of a formulation patent.
Background
The Court's decision concerns Canadian Patent No. 2,507,002 (002 Patent), which is listed on the patent register against
The claims of the 002 Patent related to capsules comprising the active ingredient silodosin (used for the treatment of dysuria) and specific excipients, manufactured so as to achieve a defined rapid dissolution profile.
Claims valid but not infringed
The Court found against Allergan on the issues of claims construction and infringement, but rejected
The crux of the claims construction issue was whether claim elements relating to wet granulation-a manufacturing process that
Following from its finding on claims construction, the Court concluded that
On the issue of obviousness, the Court reiterated that "it may be inventive to recognize that a problem to be solved exists in the first place". Here, the Court found that the 002 Patent's invention overcame previously unknown problems relating to the "'potent adhesive and electrostatic properties' and the very low solubility of silodosin," as well as unknown capsule filling problems. Applying the "obvious to try" test, the Court concluded that the differences between the state of the art and the inventive concept of the 002 Patent constituted steps that were not obvious.
Licensee not bound by patentee's representations to the Patent Office
This decision adds to a growing list of judgments interpreting section 53.1 of the Patent Act (see e.g., here and here). Section 53.1 was introduced in 2018 and creates a limited exception to the long-standing rule that extrinsic evidence is inadmissible when construing the claims of a patent, providing that the prosecution history "may be admitted into evidence to rebut any representation made by the patentee in the action or proceeding as to the construction of a claim".
The Court held that the prosecution history evidence was inadmissible because it was being tendered to rebut the representations of a licensee (Allergan)-not the patentee (Kissei), as required by subsection 53.1(1). In particular, the Court reasoned that:
-
The plain wording of subsection 53.1(1) limits the scope of that provision to rebutting representations made by a patentee. Here, the patentee had made no such representations: Kissei had denied invalidity and adopted Allergan's submissions, but did not itself appear at the trial.
- Representations by Allergan could not trigger subsection 53.1(1) because a licensee is not a "patentee" as defined in section 2. Rather, a licensee is a "person claiming under" the patentee within the meaning of subsection 55(1).
- The legislative history suggests that
Parliament was aware of this distinction and intended to limit the scope of subsection 53.1(1) to representations made by patentees: in fact,Parliament rejected an amendment seeking to address the "loophole" in section 53.1 by including "persons claiming under the patentee" in the provision.
The case is
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