Can A Factual Precedent Bind Another Party?

• Published date: 13 May 2025
• Subject Matter: Intellectual Property, Patent
• Law Firm: Gilbert's
• Author: Thomas Dumigan

The Top Line

A recent Federal Court decision prevented a generic from pleading a prior art-based defence, based on a fact finding from a case with different parties.

Are prospective generics now collectively limited to one kick at the (in)validity can? And who gets to take the kick? Better hope they're a good striker.

The Federal Court recently rendered an interesting decision on pleading amendments in Janssen v Pharmascience (Macitentan), 2025 FC 718. Although seemingly a simple pleadings motion, there was a notable result that appears to depart from foundational doctrines of res judicata and judicial comity: Pharmascience was held to a factual finding from a case to which it was not party.

The (simple) background of the case: Janssen claims Pharmascience infringes its patent, which claims a combination composition: macitentan and a PDE5 inhibitor. Pharmascience initially pleaded that it does not infringe because its product is a monotherapy, not a combination. But, through its proposed pleading amendments, it sought to plead that it just practices prior art allegedly teaching the combination therapy. In patent parlance, Pharmascience wanted to take advantage of the "Gillette Defence"'if I...