Executive Summary: Key Legal and Evidentiary Issues

• Taiho sought to prevent Pharmascience from marketing a generic version of LONSURF®, alleging infringement of the 480 Patent (oral compositions) and the 999 Patent (crystal forms of tipiracil).

• Admissibility of Dr. Rowlings' responding expert report on non-infringement of the 480 Patent was challenged by Taiho, who sought to strike the bulk of his opinions as irrelevant and based on unpleaded defences.

• Taiho alternatively requested leave to file reply expert reports from Dr. Little (480 Patent), Dr. Gozzo, and Dr. Myerson (999 Patent) to address unanticipated opinions raised in the defendant's responding reports.

• Pharmascience contended that Taiho bore the burden of proof on infringement, advanced a thin case in chief, and was improperly attempting to split its case through reply evidence.

• Whether Dr. Rowlings' reliance on newly obtained third-party documents about sugar forms constituted a new non-infringement defence or fell within Pharmascience's existing pleadings was a central dispute.

• The Court applied the two-part test for expert evidence admissibility from White Burgess and the principles governing reply evidence summarized in Janssen Inc v Teva Canada Limited.

Background of the dispute

Taiho Pharmaceutical Co., Ltd and Taiho Pharma Canada, Inc. (collectively, Taiho) are the makers of LONSURF®, a prescription drug in tablet form containing trifluridine and tipiracil, approved for treating certain cancers. Pharmascience Inc. sought to market a generic version of this drug (the PMS Product). Taiho brought actions under subsection 6(1) of the Patented Medicines (Notice of Compliance) Regulations in the Federal Court of Canada, alleging that Pharmascience's proposed generic product would infringe two Canadian patents: Canadian Patent No. 2,861,480 (the 480 Patent), relating to oral compositions comprising trifluridine and tipiracil, and Canadian Patent No. 2,914,999 (the 999 Patent), relating to crystal forms of tipiracil. The patent trial was scheduled to start on February 23, 2026.

The pre-trial motion on expert evidence

Before the trial commenced, Taiho brought a motion addressing the proposed expert evidence on infringement. The motion had two main components. First, regarding the 480 Patent, Taiho sought to strike substantial portions of the responding expert report prepared by Pharmascience's expert, Dr. Colin Rowlings, arguing that his opinions were inadmissible. In the alternative, Taiho sought leave to file a reply report from their own expert, Dr. Steven Little. Second, regarding the 999 Patent, Taiho sought leave to file reply reports from their experts Dr. Fabia Gozzo and Dr. Allan Myerson to address opinions raised by Pharmascience's expert, Dr. Michael Zaworotko.

The 480 Patent — the sugar excipient dispute

The central issue for the 480 Patent concerned whether the PMS Product comprises "a sugar having a critical relative humidity of 85% or more at 25°C as an excipient," which is an element of claim 1. Taiho argued that Dr. Rowlings relied on newly obtained documents about different forms of sugar to opine that the sugar in the PMS Product was unlikely to have the requisite critical relative humidity. Taiho contended this raised an entirely new non-infringement defence that had not been pleaded, was unresponsive to Dr. Little's infringement opinions, relied on unsupported scientific theories, and was based on a hypothesis contradicted by information Dr. Rowlings himself relied upon. Taiho further argued that admitting Dr. Rowlings' challenged paragraphs would be prejudicial because they were based on new, unproduced documents inconsistent with Pharmascience's discovery answers and regulatory submissions to Health Canada.
Pharmascience responded that its pleadings specifically denied that its products contained a sugar with the requisite critical relative humidity, and it was not required to plead precisely how the PMS Product did not infringe. Pharmascience also argued that its productions had disclosed the name and manufacturer of the specific sugar in the PMS Product, but Taiho did nothing with the information. Dr. Rowlings, Pharmascience emphasized, relied on publicly available documents and scientific literature — not Pharmascience documents.

The 999 Patent — crystal form and testing methodology

For the 999 Patent, the dispute focused on whether the PMS Product met the elements of "Crystal I" claims, which covered a crystal form of tipiracil hydrochloride exhibiting claimed peaks in powder x-ray diffraction tests. Dr. Zaworotko's responding report raised issues about Dr. Gozzo's data collection process and the methodology used by Dr. Myerson in presenting the results from Dr. Gozzo's tests, including his use of "zoomed in" diffractograms. Taiho argued that Dr. Gozzo could not have anticipated Dr. Zaworotko's opinions because she had used a standard protocol, and that Dr. Zaworotko relied on a scientific paper about a different experimental technique. Taiho similarly argued that Dr. Myerson could not have foreseen every possible theory that might be advanced to explain the results.
Pharmascience did not object to most parts of Dr. Gozzo's proposed reply report, but argued that certain references to "standard practice" and Dr. Zaworotko's "mischaracterizations" went beyond clarification, were not necessary to assist the Court, and were needlessly inflammatory. For Dr. Myerson's proposed reply, Pharmascience argued it related entirely to matters that could be addressed through cross-examination and amounted to seeking the "last word."

The court's analysis and applicable legal principles

Madam Justice Pallotta applied the two-part test from White Burgess Langille Inman v Abbott and Haliburton Co, which requires expert evidence to meet threshold requirements of relevance, necessity, absence of exclusionary rules, and proper qualification, followed by a balancing of benefits and risks. The Court also considered the principles governing reply evidence as summarized in Janssen Inc v Teva Canada Limited, citing Halford v Seed Hawk Inc, including that confirmatory evidence is not to be allowed, evidence that should have been part of the case in chief is generally excluded, and that discretion may be exercised in determining whether excluded evidence should nonetheless be admitted.
On the motion to strike Dr. Rowlings' report, the Court found that Pharmascience had denied infringement and pleaded for each claim that the PMS Product would not comprise the elements of the claim. Taiho had not demonstrated that Pharmascience admitted meeting the sugar element or took a position that implicitly narrowed the infringement issues. The Court also found that Dr. Rowlings' opinions were responsive to Dr. Little's infringement opinion and relied on third-party and public documents, and Taiho had not shown any breach of discovery obligations or inconsistency with regulatory submissions. On the question of whether Taiho should have anticipated Dr. Rowlings' opinions, the Court disagreed with Pharmascience, noting that a party need not address every anticipated responding argument in chief.

Ruling and outcome

Taiho's motion was granted in part. Regarding the 480 Patent, the Court denied Taiho's request to strike paragraphs 14–16 and 35–79 of Dr. Rowlings' responding infringement report, finding that Taiho had not shown that any of Dr. Rowlings' paragraphs should be excluded. However, the Court granted Taiho leave to tender Dr. Little's proposed reply report in its entirety, concluding that the proposed reply did not offend the principle against case splitting and that Taiho could not reasonably have anticipated the details of Dr. Rowlings' responding opinion. Regarding the 999 Patent, the Court granted Taiho leave to tender the proposed reply reports of both Dr. Gozzo and Dr. Myerson, finding them responsive to unanticipated issues raised by Dr. Zaworotko. Costs of the motion were ordered in the cause. No specific monetary amount was awarded or ordered in this decision, as the ruling pertained solely to the admissibility of expert evidence ahead of trial.