The Federal Court has allowed an infringement action concerning sitagliptin phosphate monohydrate products under the Patented Medicines (Notice of Compliance) Regulations (the Regulations). The Court dismissed allegations of obviousness and insufficiency, and it found the asserted claims to be valid and infringed. In reaching its decision, the Court provided substantive guidance on hearsay evidence in infringement actions under the Regulations.


Merck Canada Inc. markets JANUVIA® in Canada for the treatment of type 2 diabetes. JANUVIA® is a tablet containing sitagliptin phosphate monohydrate. Pharmascience Inc. (PMS) submitted an Abbreviated New Drug Submission to obtain approval for a generic sitagliptin phosphate monohydrate product. Merck Canada Inc. and Merck Sharp & Dohme Corp. (collectively, Merck) brought an infringement action under subsection 6(1) of the Regulations, arguing that the PMS’s product will infringe its Canadian Patent No. 2,529,400 (400 Patent), which is listed on the Patent Register against JANUVIA®. PMS did not dispute infringement, but argued that the 400 Patent was invalid for obviousness and/or insufficiency.

Hearsay Issues

PMS objected to large portions of the evidence from Merck’s main fact witness, Dr. Wenslow, including on the basis that it was inadmissible hearsay. Dr. Wenslow was one of the inventors of the 400 Patent and was Merck’s discovery representative. Under an agreement between the parties, he was the only inventor examined. At the time of sitagliptin’s development, Dr. Wenslow directly supervised the work of his co-inventors. He provided evidence about the development of sitagliptin through his oral testimony and by way of affidavit, relying on documents, most of which were accepted by PMS for the truth of their contents.

The Court rejected most of PMS’s objections. The Court accepted that Dr. Wenslow’s supervisory role allowed him to speak to his team’s experimental work. Further, most of his impugned statements were based on documents which PMS had already accepted for the truth of their contents. The Court also found that it was inconsistent for PMS to accept that Dr. Wenslow could provide evidence during discovery, but then to argue that he could not provide the same evidence at trial.

The 400 Patent is Valid

Obviousness. The Court held that the 400 Patent was not obvious.

The 400 Patent is a salt patent that claims the monohydrate form of the phosphate salt of sitagliptin. The obviousness analysis focussed on a prior patent application (WO498) that was referenced in the description of the 400 Patent. WO498 disclosed sitagliptin and 32 other molecules in the same class, as well as pharmaceutical salts thereof. The class included sitagliptin phosphate monohydrate.

The Court found that the 400 Patent was selection patent. While selection is not an independent ground of invalidity, it contextualizes the validity analysis. The Court found that the selection in the 400 Patent disclosed a substantial advantage over the salts in WO498 that were not selected, namely enhanced chemical stability, enhanced physical stability, and high solubility.

The Court found that the inventive concepts of the asserted claims included the same advantages that made the 400 Patent a selection patent, even though they were not claimed. This analysis was performed on a claim-by-claim basis. The Court confirmed that identification of the inventive concept is distinct from, albeit informed by, claims construction.

The Court also noted that there are no generalizable rules about the obviousness of salt patents. The analysis turns on the facts and argument in each case. In this case, the Court found that the asserted claims were not obvious. The Court accepted that the advantages of the claimed salt of sitagliptin were unpredictable. Further, the skilled person would have had no motivation to develop this particular product from among the class disclosed in WO498.

Insufficiency. The Court found that the 400 Patent was not invalid for insufficiency of disclosure.

PMS argued that the 400 Patent did not fully disclose the process for creating sitagliptin phosphate monohydrate. PMS alleged that the disclosed process would not create the claimed salt, pointing to failed experiments to create the salt in Merck’s evidence. The Court noted that there were also experiments in Merck’s evidence where the salt was successfully created. Merck argued that PMS’s argument was speculative, as it did not show that any of the steps required to make the salt were omitted from the patent.

The Court agreed with Merck. In reaching this conclusion, the Court noted that PMS could have tasked its experts with attempting to create sitagliptin phosphate monohydrate by following the disclosed process. While contemporaneous testing cannot be used to defend against insufficiency allegations (as such testing would benefit from hindsight), it can be used to support insufficiency allegations: If a process were shown to be insufficient as of the hearing, there would be no basis to suggest that the process would have been sufficient as of the filing date.


Merck Sharp & Dohme Corp. v Pharmascience Inc., 2022 FC 417