Overbreadth: The wildcard of the invalidity arguments

Cara Parisien [1]
ROBIC, LLP
Lawyers, Patent and Trademark Agents

This spring, the Federal Court published two patent-related decisions, Laboratoires Servier[2] and Aux Sable[3], touching on the issue of overbreadth or “covetous claiming”. The jurisprudential doctrine of overbreadth is based on the principle that an inventor, in their patent, may not claim more than: (1) what they have actually invented, and (2) what they have disclosed in their specification.[4]

The overbreadth of a particular claim will generally be linked to another legislative motive for invalidity. Where the claims are not adequately supported by the specification, they will be invalid for insufficiency. Where the inventor has rather claimed more than what they invented, the claims will be overbroad for the very reason that they also encompass subject matter that is non-novel, non-useful or obvious.

As a result, overbreadth is often thrown into the mix of allegations as an extra precaution. It is the wildcard of the invalidity arguments, with an uncanny ability to take on the form of its statutorily founded counterparts, echoing whichever is most appropriate under the circumstances. The first one lays the foundation and sets the scene; if it is well-received, then overbreadth is there to drive the point home. However, as evidenced by Laboratoires Servier and Aux Sable, the doctrine of overbreadth has begun to take on a life of its own.

In Aux Sables, the patented invention at issue related to a method of transporting natural gas by pipeline. The specification disclosed the addition of C₂ or C₃ hydrocarbons to a natural gas mixture in order to increase the average molecular weight of the substance, thereby making it more compressible and decreasing the energy required for its transportation through the pipeline at certain pressures and temperatures. The inventors also proposed a method of determining whether such a reduction in energy would effectively be achieved, involving a comparison between the zMw products of both the treated and untreated gas mixtures.

In its construction of the claims, the Court determined that the addition of heavier hydrocarbons and subsequent comparison of zMw products were the two essential elements of claims 1 to 8, but not claims 9 and 10. Aux Sable argued that claims 9 and 10 were overbroad for the very reason that they did not include these two elements. According to Aux Sable, the addition of C₂ or C₃ hydrocarbons and the measurement of the zMw products were central to the inventive concept disclosed in the patent specification, and as a result, their presence within the claims was necessary.

In its analysis, the Court applied the principles from Amfac Foods[5], a decision that predates by several decades the emergence of the claim construction process outlined in Free World Trust[6] and Whirlpool[7]. The Court essentially concluded that there was overbreadth because an element determined to be essential to the inventive concept was absent from the claims. 

In Laboratoires Servier, generic pharmaceutical manufacturer Apotex challenged the validity of Servier’s patent in the context of a PM(NOC) proceeding. The invention claimed by the patent was the arginine salt of perindopril. The perindopril molecule and any pharmaceutically available salts thereof had already been the subject of a patent. However, the tests performed on the arginine salt demonstrated significantly reduced instability to heat and humidity.

Although the patent claims referred to “the arginine salt of perindopril and its hydrates”, the specification expressed a preference for arginine in its natural form, L-arginine, above D-arginine or a racemate. Furthermore, the tests disclosed in the specification were only performed on the L-arginine salt, and all but one expert opined that the Person of Skill in the Art would understand the patent claims as being limited to L-arginine. The Court nevertheless construed the claims as including arginine salt of perindopril in all of its forms.

The Court ultimately determined that the claims were overbroad in that they referred to the arginine salt of perindopril, when the specification of the patent expressed a preference for the L-arginine configuration. Furthermore, the Court ruled that by including the hydrates of the compound, Servier’s claims exceeded what they had actually invented, as they had not conducted any tests that demonstrated the formation of hydrates or disclosed a factual basis and sound line of reasoning as to the formation of hydrates.

These two decisions highlight some of the looming issues relating to the overbreadth doctrine. In Aux Sable, certain reasons stated by the court in their finding of overbreadth admittedly echoed those given for lack of utility, a glimpse of the doctrine being applied in its traditional, harmlessly redundant form. However, the hovering uncertainty as to how the overbreadth analysis will unfold and the lack of an objective set of criteria are arguably at the core of its shape-shifting nature. This is even more clear in Laboratoires Servier, where the reasons for overbreadth do not mimic those given for another, legislatively founded motive of invalidity. It remains to be seen whether these new principles will be followed or clarified by the Court from here on in.