On 31 May 2022, the Federal Court released a decision by Justice Pallotta in a patent infringement action pursuant to subsection 6(1) of the Patented Medicines (Notice of Compliance) Regulations in relation to macitentan (Janssen's Opsumit). The Court found claims 21-31 (the asserted claims) of Canadian Patent No. 2,659,770 (the 770 patent) valid and granted a declaration of infringement.(1)
Macitentan belongs to a class of drugs known as endothelin receptor antagonists (ERAs). Janssen markets macitentan in Canada for the treatment of pulmonary arterial hypertension (PAH). The 770 patent relates to macitentan in combination with a phosphodiesterase type-5 inhibitor (PDE5-I) (eg, sildenafil) to treat diseases where vasoconstriction is involved, including PAH.
Sandoz submitted that the 770 patent was invalid on the grounds of obviousness, lack of utility, overbreadth and insufficiency, but conceded infringement.
Asserted claims not obvious
As a preliminary matter, the parties disagreed on how to define the skilled person. Sandoz argued that the skilled person included a clinician who would treat diseases wherein vasoconstriction is involved, including diseases of the systemic circulation and pulmonary circulation. Janssen's experts opined that the skilled person would have a narrower focus on the treatment of pulmonary hypertension (PH), and more specifically PAH. The Court agreed with Sandoz that the attributes of the skilled person do not change on a claim-by-claim basis. As the 770 patent was not limited to the treatment of PH/PAH, the skilled person was not limited to those who focus on PH/PAH.
The Court found that the inventive concept of the asserted claims was the use of macitentan in combination with a PDE5-I to treat a disease involving vasoconstriction, or the use of macitentan in combination with specific PDE5-Is and/or in specific diseases according to the dependent claims.
The Court rejected Sandoz's argument that the only difference between the state of the art and the inventive concept was limiting the ERA that would be combined with a PDE5-I to macitentan. Following a detailed analysis of the prior art relied on by Sandoz (including a genus patent application, "WO 557", that listed macitentan as one of 78 preferred compounds), the Court found that the state of the art would not have led the skilled person to combine monotherapies, including of an ERA with a PDE5-I, with the expectation that they would work based on their differing mechanisms of action. Furthermore, the skilled person was not focused on combinations of ERAs and PDE5-Is, and did not understand, based on the available evidence on the combination of bosentan (another ERA) and sildenafil, that there would be a class effect for ERAs and PDE5-I drugs when used in combination for treating diseases involving vasoconstriction.
The Court concluded that Sandoz had not established that the difference between the state of the art and the inventive concept was obvious. The skilled person would not expect that any ERA would be useful in combination with a PDE5-I. In any event, there was no basis, apart from hindsight, that would lead the skilled person to identify a group of candidate ERA compounds that would include macitentan for testing. There was no direct path to macitentan specifically, as it was effectively unknown to the skilled person as of the relevant date. Even assuming the skilled person would be directed to WO 557, which Sandoz did not establish as a first step, the evidence did not establish how the skilled person would be led to focus on macitentan or a group of compounds that includes macitentan as candidate compounds.
Utility of asserted claims soundly predicted by filing date
The Court found that the requirements for a sound prediction of utility were met. The 770 patent disclosed experimental results from in vivo rat models for hypertension using macitentan in combination with two PDE5-Is. The skilled person, considering the common general knowledge together with the test results disclosed in the patent, had the factual basis and sound line of reasoning to predict that macitentan in combination with a PDE5-I would be useful to treat diseases involving vasoconstriction.
However, the cumulative weight of test results before the filing date did not reach the level of demonstrated utility, as the results from rat studies would not necessarily translate to the same effect in humans.
The Court also rejected Sandoz's overbreadth and lack of sufficiency of disclosure attacks.
Sandoz has appealed.(2)
For further information on this topic please contact Chen Li at Smart & Biggar by telephone (+1 416 593 5514) or email ([email protected]). The Smart & Biggar website can be accessed at www.smartbiggar.ca.
(1) Janssen Inc v Sandoz Canada Inc, 2022 FC 715.