## Facts

- Edwards Lifesciences AG marketed the SAPIEN transcatheter artificial heart valve, a stent-mounted pericardial valve deliverable via catheter.
- Cook Biotech Inc. owned EP (UK) 1 255 510, directed to an expandable stent carrying a prosthetic valve made from a collagen-containing biomaterial; after central limitation at the EPO, claim 1 required the biomaterial to “comprise pericardium.”
- Edwards sued to revoke the patent; Cook counterclaimed for infringement of multiple claims.
- Cook’s asserted priority chain began with a January 2000 U.S. filing by three inventors; Cook did not hold assignments from all inventors when it filed a January 2001 PCT application claiming priority from the U.S. filing, and only later obtained full assignments.
- Edwards argued Cook was not entitled to claim priority because it was not the earlier applicant and was not the “successor in title” to all inventors at the PCT filing date.
- On infringement, Edwards’ valve used pericardium but also included a synthetic fabric component, and the valve structure extended only about 75% of the stent length.

## Issues

1. Whether Cook was entitled to claim Paris Convention priority from the earlier U.S. filing when it lacked assignments from all inventors at the date it filed the PCT application.
2. If priority failed, whether the asserted claims were invalid for lack of novelty and/or inventive step in light of intervening publications and other prior art, and whether additional attacks (insufficiency and added matter) succeeded.
3. Whether Edwards’ SAPIEN valve infringed the asserted claims under proper construction, including (a) “formed with” a biomaterial “compris[ing] pericardium,” and (b) extending “substantially” from the top to the bottom of the stent.

## Decision

- The court held Cook could not validly claim priority from the January 2000 U.S. filing because it was not the earlier applicant and was not the successor in title to all inventors at the PCT filing date.
- With the effective date moved to the PCT filing date, intervening disclosures became prior art, and the asserted claims were held invalid (for lack of novelty and/or inventive step in view of the cited art).
- Independently, Edwards did not infringe:
  - “Formed with” and “comprises pericardium” were construed to require a valve made only of pericardium; Edwards’ mixed-material construction fell outside.
  - “Substantially from the top of the stent to the bottom” was given limiting effect; a valve spanning about three-quarters of the stent was not “substantially” the full length.

## Legal Principles

- A party claiming Paris Convention priority must establish that, at the date of the later filing, it is the earlier applicant or has already become the successor in title to the earlier applicant(s); later assignments do not cure a defective priority claim.
- Claim language adopted or sharpened through post-grant limitation can constrain construction and narrow the claim scope for infringement purposes.
- Terms of approximation (e.g., “substantially”) may impose real spatial or quantitative limits when read in the technical context, and can defeat infringement where the accused product falls materially short.

## Conclusion

The court revoked the patent because Cook was not entitled to the claimed priority and the claims were invalid over prior art; it also held that Edwards’ SAPIEN valve did not infringe under the court’s constructions of the pericardium and “substantially” limitations.


Edwards Lifesciences AG v. Cook Biotech Inc., [2009] EWHC 1304 (Pat) (Eng.)