Pharmacia Corporation & Ors v Merck & Co Inc & Anor

A patent claim must receive a purposive construction which gives fair protection to the patentee while preserving reasonable certainty for third parties. A claim to a chemical species may therefore encompass an unspecified tautomer which is inseparable from, and inevitably interconverts with, the expressly claimed form in its intended environment.

A patent claiming a class of compounds must enable the invention across the full width of the monopoly. Where the disclosed technical contribution is a class possessing particular beneficial characteristics, substantially all claimed compounds must possess those characteristics. A priority document must itself contain an enabling disclosure of the claimed invention. A narrower claim does not obtain priority merely because its individual features can be found within a broader earlier disclosure.

The proprietors of European Patent (UK) 0 679 157 alleged that Merck infringed claims concerning anti-inflammatory compounds by manufacturing and selling MK-966, the active ingredient in Vioxx. Merck admitted the relevant acts but denied infringement and challenged the patent's validity.

Pumfrey J held that the patent was invalid and that MK-966 did not infringe. The patentees appealed from the Chancery Division. The principal issues were the patent's technical contribution, whether a claim expressly covering an enol also covered its keto tautomer, sufficiency across a very large class of compounds, entitlement to priority, novelty and obviousness.

1. The appeal was dismissed unanimously. Aldous LJ gave the principal judgment. Arden LJ delivered a concurring judgment, and Sedley LJ agreed with both. Although the patent, if valid, would have been directly infringed, it was invalid and therefore could not be infringed.

2. The technical contribution disclosed by the specification was a new class of anti-inflammatory compounds having reduced side effects through COX-II selectivity. Under section 125 of the Patents Act 1977, the invention is ordinarily that specified in the claims, but context may require the invention to include the technical contribution supporting the claimed monopoly.

3. The claim received the purposive construction required by the Protocol on the Interpretation of article 69. Although “hydroxy” had a precise chemical meaning, the claimed enol inevitably existed in solution in an inseparable equilibrium with its keto tautomer. Including that tautomer gave fair protection without depriving third parties of reasonable certainty. MK-966 therefore fell within claims 1 and 13, and its importation and sale would constitute direct infringement under section 60(1)(a). The court expressed no concluded view on indirect infringement under section 60(2).

4. Section 72(1)(c) requires an enabling disclosure across the full width of the claim. For a claimed class selected because its members possess beneficial characteristics, the specification must identify the class and enable its manufacture, and substantially all claimed compounds must possess those characteristics. The experimental evidence established that the claimed class was unpredictable and contained a substantial number of compounds lacking anti-inflammatory activity or COX-II selectivity. Claims 1, 13 and 20 were insufficient both as granted and as proposed to be amended. No independent validity was asserted for the remaining claims.

5. The priority document did not enable the subsequently claimed class or disclose its defining technical contribution. The claim could not obtain priority merely because individual features of the narrower class could be traced within a much broader disclosure. The loss of priority meant that the intervening Merck Frosst application destroyed the novelty of the admitted claims.

6. Brown anticipated claims 7 and 20. Independently, the claims were obvious. Applying Windsurfing, a medicinal chemist investigating DuP 697 would routinely examine close structural analogues, including the 3,4-diaryl isomer. Motivation or proof of a useful purpose may be relevant to obviousness, but neither is an essential legal requirement.

1. Court of Appeal (Civil Division): The appeal was dismissed by [2001] EWCA Civ 1610. The court held that the patent was invalid, although MK-966 would have infringed if the patent had been valid. Permission to appeal to the House of Lords was refused.
2. Chancery Division: Pumfrey J upheld Merck's challenges to validity and rejected the allegation of infringement. No citation for that decision is stated in the judgment.