Smithkline Beecham Plc & Ors. v Apotex Europe Ltd & Ors

A prior-art document does not anticipate a later patent claim unless, read as a whole and without hindsight through the eyes of the skilled person, it gives clear and unambiguous directions whose inevitable result falls within the claim. A step which is merely easy or harmless to try is not necessarily obvious.

For obviousness, separate documents may be combined only where an unimaginative skilled person would itself make that mosaic. Discovering a problem by experiment does not supply a reason to search for and combine an otherwise unrelated disclosure. Patent claims must be construed purposively in the context of the specification. A claimed displacing agent was confined to one that displaces bound solvent during the contact stage, rather than a material that only assists removal on later drying.

SKB appealed from Pumfrey J’s decision in the Patents Court dismissing its claim that Apotex infringed patent No 2,297,550, holding the patent invalid and ordering its revocation. The patent, as amended after earlier litigation, contained process claims for preparing paroxetine hydrochloride anhydrate substantially free of bound organic solvent.

Apotex relied principally on an earlier patent application, ‘407, and a 1958 erythromycin patent. It also contended that its acetone-treatment process did not use the claimed displacing agent. The appeal concerned whether the prior art anticipated or made the claims obvious, and the proper construction of the claims.

1. Appeal allowed in part. The Court reversed the finding that the patent was invalid, but upheld the finding that Apotex’s process did not infringe. The patent was therefore to be restored to the register.
2. The ‘407 document did not anticipate the claims. Read without hindsight and in the context of its general teaching, its example taught that drying removed the solvent and produced an anhydrate. The skilled person would not understand the subsequent water slurry to displace bound solvent from a solvate. The instruction to add “more IPA” was also ambiguous. It could not yield the clear and unambiguous directions required by [1972] RPC 457.
3. The claims were not obvious over ‘407. A skilled person who obtained hemihydrate, or who feared conversion to hemihydrate, had no reason to omit water until the intermediate stage and then reintroduce it in the expectation that it would remove bound solvent. Apotex’s experiments included unexplained, stringent precautions against moisture and were contrived rather than a valid demonstration of what the ordinary skilled person would do.
4. The erythromycin attack depended on an impermissible mosaic. The skilled person could not combine the Buxton and Lynch paper with the erythromycin patent merely because an experiment under the former might reveal a bound-solvent problem. There was no uninventive reason to find and use the latter disclosure. Applying the Windsurfing analysis, the differences required to reach the invention were not shown to be obvious.
5. Construed purposively in its specification, a displacing agent directly displaces the solvent of solvation during contact with the solvate, reducing it beyond what drying can achieve. It does not include acetone which forms a mixed solvate and permits solvent removal only during subsequent heating and vacuum drying. Apotex therefore did not use the claimed process. The Court made no ruling on the remaining contingent construction and insufficiency arguments.

• Court of Appeal (Civil Division): Allowed SKB’s appeal to the extent of reversing invalidity, while affirming the dismissal of the infringement claim.
• High Court of Justice, Chancery Division, Patents Court: Pumfrey J dismissed the infringement claim, held the patent invalid and ordered revocation. The citation of that judgment is not stated in the judgment.