Background
The dispute concerns competing patents over a chemical process for manufacturing bromomethylcyclopropane (BMCP), a pharmaceutical intermediate. Minakem filed French patent application FR 3 010 997 (“FR 997”) on September 20, 2013, naming Mr. [Z] as inventor; the patent was granted by the French patent office (INPI) on November 6, 2015. The underlying invention had originally been developed in 1988–1989 within a company called Synthèse organique appliquée (SOA), which was subsequently absorbed by a successor entity (SEAC). SEAC then transferred part of its assets — including the relevant business activities — to Minakem under a partial asset contribution agreement dated March 30, 2005.
In January 2014, shortly after Minakem’s filing, the company MMLS — founded by a former executive of Minakem’s parent company and staffed in part by a former Minakem employee — filed its own French patent application on a closely related BMCP and bromomethylcyclobutane (BMCB) manufacturing process. MMLS was granted patent FR 3 016 166 (“FR 166”) in April 2017, along with international extensions covering Europe (EP 3 092 212) and the United States (US 2016/355452). Minakem responded by suing MMLS in October 2017 to claim ownership of FR 166 (an action en revendication) and, jointly, by suing both MMLS and its subsidiary M2I Salin for infringement of FR 997. The two proceedings were consolidated.
MMLS and M2I Salin contested the entire action on multiple fronts: they argued Minakem lacked standing because it had fraudulently designated an incorrect inventor on FR 997 and could not establish a valid chain of title through the 2005 asset transfer; they sought invalidity of FR 997’s claims 1–15 for lack of inventive step; and they denied that their own process fell within the scope of FR 997’s claims. The Paris Court of Appeal (Pôle 5, Chambre 2) rejected all of these arguments on February 9, 2024. MMLS and M2I Salin then petitioned the Court of Cassation on four grounds.
The Court’s Holding
The Court of Cassation rejected all four grounds and affirmed the Paris judgment. On the first and most legally significant ground — standing — the Court substituted its own pure-law reasoning for that of the court below. It held that, under Articles L. 611-6 and L. 611-8 of the Intellectual Property Code, the proper remedy when a patent has been obtained by someone who knew it had no right to the title is an action en revendication brought by the injured inventor or successor. Until such an action succeeds, the registered patent holder has both standing and interest to sue any third party for infringement. The Court stated expressly: “the fact that the applicant knows it has no right to the industrial property title at the time it files the patent application — affecting neither the patentability of the invention nor the validity of the patent protecting it — means the applicant has, until a successful revendication action is brought against it, standing and interest to sue in infringement against any third party.” Because no actual or putative inventor had brought such a claim against FR 997, Minakem’s standing was unimpeachable.
On inventive step (second ground), the Court confirmed that the Paris court had correctly applied the problem-solution approach: it identified the closest prior art (Bayer patent US 6 008 420, which achieved 97% purity and 77.5% yield using a triphenylphosphine/solvent system), defined the objective technical problem as achieving improved yield and purity simultaneously, and found that no combination of the cited prior art documents would have led a skilled person — an experienced chemical engineer — to substitute triphenylphosphite for triphenylphosphine and thereby arrive at the specific complex claimed in FR 997. The Court reiterated its settled case law that prior art documents are destructive of inventive step only when, combined in a manner reasonably accessible to the skilled person, they would obviously have led that person to the same solution as the invention.
On infringement scope (third ground) and the ownership claim (fourth ground), the Court found no legal error. The court below had correctly read claim 1 of FR 997 as specifying no particular ratio of dibromine to triphenylphosphite, so MMLS’s use of a different excess ratio did not place its process outside the claim. On the revendication claim, the appellate court had found that the technical differences between Minakem’s internal process sheets and the claims of FR 166 carried no technical effect — which sufficed to establish that the invention in FR 166 had been derived from Minakem’s protected process — and Minakem was accordingly subrogated retroactively into MMLS’s rights over FR 166 and its international extensions.
Key Takeaways
- A patent holder’s standing to bring infringement proceedings in France is not defeated by allegations that it fraudulently designated an incorrect inventor or lacked underlying title at the time of filing; only a successful action en revendication by the true inventor (or successor) can strip the registered holder of that standing.
- The problem-solution approach to inventive step is a permissible — though not mandatory — analytical method under French patent law; courts have sovereign discretion to assess the skilled person’s knowledge and the extent to which prior art would have motivated a particular technical combination.
- A patent claim that specifies no particular reagent ratio covers a manufacturing process regardless of the proportions used by the alleged infringer, provided the reaction intermediate described by the claim is produced.
- In an action to claim ownership of a competitor’s patent (revendication), the claimant must show that any differences between its own prior art and the contested patent’s claims carry no technical effect; that burden rests on the claimant, not on the alleged appropriator.
Why It Matters
This decision settles an important question of French patent enforcement procedure: the fraud-corrupts-all (fraus omnia corrumpit) doctrine cannot be weaponised by an alleged infringer to strip a patent holder of its right to sue simply by raising inventorship disputes. The Court makes clear that inventorship errors — even knowing ones — go to the validity of the patent holder’s underlying title, which must be contested through a revendication action by the injured party; they do not create a procedural bar that third-party infringers can invoke. This reinforces the stability of patent enforcement in France and aligns domestic practice with the general principle that INPI-registered titles carry a presumption of validity until challenged through the correct procedure.
The ruling also offers useful guidance on the evidentiary dynamics of patent ownership litigation between competing market participants. Where an inventor-employee leaves a company, joins or founds a competitor, and files a patent on a substantially identical process, French courts will examine technical equivalence closely and will require the party resisting the ownership claim to do more than point to superficial technical differences — it must show those differences produce a distinct technical effect. Combined with the inventive step analysis reaffirming the problem-solution methodology, the case provides a clear framework for pharmaceutical and specialty-chemistry patent disputes involving process patents.