Baxter Healthcare Corporation & Anor v Abbott Laboratories & Anor

Patent claims must be construed objectively and purposively in the context of the specification. Functional language such as an amount sufficient to prevent degradation must have an ascertainable practical meaning. Where the specification identifies no representative degree of harm or test for determining sufficiency, the claim may be insufficient unless construed by reference to a clear numerical threshold supplied by the disclosure. Combining a liquid inhibitor with a fluoroether means homogeneous combination; merely contacting the product with a solid container lining does not suffice. A declaration of non-infringement may be granted where the product description, supported by an available sample, establishes that no described product infringes.

Baxter sought a declaration of non-infringement and revocation of a patent concerning sevoflurane containing water as a Lewis acid inhibitor. The issues included construction of an anaesthetic composition, the expressions preventing degradation and combining, infringement on the pleaded product and process description, novelty and obviousness over prior disclosures and use, insufficiency, and added matter.

The court considered whether the claimed functional requirement could be applied without a defined degree of Lewis acid challenge, whether a container liner formed part of the claimed combination, and whether the patent could survive the objections to validity.

1. Construction. Patent claims are construed objectively, by determining the meaning of the words used in the context of the specification. The approach accords with Art. 69 of the European Patent Convention, and the Protocol questions may assist where appropriate. The expression an anaesthetic composition was construed as describing the claimed mixture, rather than imposing a narrow requirement that it be immediately suitable for administration to a patient.
2. Functional language and sufficiency. Degradation could not be prevented absolutely. In this pharmaceutical context, stability meant stability to the level required by the relevant marketing authorisation and stability testing. However, the specification gave no workable criterion for identifying the magnitude and nature of the Lewis acid insult. Claims 2 to 4 were therefore insufficient if construed as requiring only a functionally defined effective amount. To avoid that result, the court treated the claims as requiring at least the 150 ppm water-equivalent minimum identified in the specification, in effect making them coextensive with Claim 5.
3. Combining. In context, combining meant homogeneous combination. It did not include merely contacting sevoflurane with a solid potential Lewis acid inhibitor, such as a container liner. The evidence did not establish that such a liner protected against the insoluble Lewis acids contemplated by the patent.
4. Infringement. The described product contained no more than 130 ppm water and therefore did not infringe on the preferred construction. A product which, under the specified accelerated challenge, produced more than 300 ppm impurities and a pH below 4 could not be regarded as having degradation prevented. The court also observed that where a sample identified in the description conclusively demonstrates non-infringement or infringement, the court may adopt a robust approach to obstructive non-admissions.
5. Validity. Kawai disclosed sevoflurane saturated with water and anticipated Claims 1 to 5. The claims were also obvious on the alternative analysis. Public sales in Japan of sevoflurane containing approximately 460 ppm water independently anticipated the claims. The claims were not saved by the information disclosure statement analysis.
6. Added matter and disposal. The reference to the absence of soda lime was added matter under section 72(1)(d) of the Patents Act 1977. It could not be removed from Claim 1 without extending protection contrary to section 76. The patent was invalid and was revoked in its entirety. Had it been valid, the court would have granted the declaration of non-infringement.