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It’s all About Construction

Valeant’s Canadian Patent No. 2,524,300 claims a modified-release bupropion tablet with three parts:

  • a core comprising the active ingredient and various excipients;
  • a first control-releasing coat surrounding the core; and
  • a moisture barrier surrounding the first control-releasing coat comprising an enteric polymer and a permeation enhancer and optionally a plasticizer “wherein the permeation enhancer is present in an amount of from about 20% to about 40% of the moisture barrier dry weight.”

The claimed tablets must also be bioequivalent to Wellbutrin or Zyban/Wellbutrin SR tablets.

Ranbaxy served a Notice of Allegation alleging non-infringement on the sole basis that its tablets do not contain a permeation enhancer in an amount of “about 20% to about 40%” of the moisture barrier dry weight. Although Ranbaxy’s tablets contained silicon dioxide, the preferred permeation enhancer identified in the patent, the amount was below the claimed range (the actual amount was redacted in the Court’s decision).

The main issues in this case involved construction. The Court had to construe the terms “permeation enhancer” and “about” and determine whether a permeation enhancer in an amount of about 20% to about 40% was an essential element of the claims. The Court found for Ranbaxy on all three issues. The decision reinforces the principles of purposive construction and the concept that the claim language is paramount.

“Permeation Enhancer

In addition to silicon dioxide, Ranbaxy’s tablets contain polyethylene glycol (PEG) and triethyl citrate (TEC) as plastizers. Valeant argued that these excipients also functioned as permeation enhancers and should be included in determining whether Ranbaxy’s tablets contained permeation enhancers within the claimed range.

The Court disagreed holding that Valeant erred in construing the term “permeation enhancer” using a functional approach – by considering whether PEG and TEC could function as permeation enhancers – rather than purposively construing the term based on the language of the patent. For example, while the patent identified PEG and TEC as plasticizers and stated that PEG also acted as a glidant, neither was said to serve as a permeation enhancer. In coming to this conclusion, the Court also relied on the definition of “permeation enhancer” in the disclosure – a hydrophilic substance, which allows water to enter without physical disruption of the coating. According to Ranbaxy, PEG dissolves when exposed to water which would create a defect in the coating such that PEG could not fall within the patent’s definition of a permeation enhancer.

The Court also relied statements in the patent, including the claims, that the moisture barrier comprised  an enteric/acrylic polymer, a plasticizer and a permeation enhancer in a specified ratio. The Court accepted that the skilled person would know that calculating this three-part ratio requires three separate elements and nothing in the patent explained how to calculate this ratio if PEG acted as both a permeation enhancer and a plasticizer.


All asserted claims require a permeation enhancer in an amount of “about 20% to about 40%” of the moisture barrier dry weight. The Court rejected Valeant’s position that “about” should be construed to allow a range of “10% to 45%”. Justice McVeigh preferred Ranbaxy’s evidence that the skilled person would understand “about” to mean a range of plus or minus 10%, i.e. 18% to 44%. The amount of silicon dioxide in the Ranbaxy tablets was less than 18%.

Is “About 20% to About 40%” an Essential Element?

Valeant further argued that the “about 20 to about 40%” limitation was not an essential claim element because the only requirement is that the tablet be bioequivalent with Wellbutrin or Zyban/Wellbtrin SR tablets. Justice McVeigh rejected this argument holding the claimed range to be an essential element:

[47]  I find that the permeation enhancer in the amount of “about 20% to about 40%” is an essential element, and prefer Dr. Laskar’s opinion on this. Although I have been asked to turn to the description which may imply the weight is optional, the claims hold the meaning (Free World Trust at para 66). Claim 1 unambiguously states that the permeation enhancer must be in the claimed percentage of the moisture barrier dry weight.

Expert Blinding

Valeant argued that the evidence of Ranbaxy’s expert witness should be given less weight because he had received Ranbaxy’s formulation before rendering his opinion and, therefore, could have tailored his construction in Ranbaxy’s favour. Valeant’s experts, in contrast, were blinded and had not been provided Ranbaxy’s formulation until after giving their opinions. The Court rejected this argument as a basis for preferring Valeant’s blinded experts:

[26]  In addition, Dr. Laskar’s evidence (directed by counsel to what needed constructing) was not given in a way that would breach the Code of Conduct for Expert Witnesses. I get no whiff of tailored evidence from Dr. Laskar’s evidence and will not give it less weight, as I do not believe he was influenced by the Ranbaxy formulation. His evidence was as fair and impartial as all Valeant’s experts (who knew who both the Applicant and Respondent are, and so would of course surmise the positions of the parties).

A copy of the decision may be found here.