The Supreme People's Court of The People's Republic of China ("SPC") recently issued its long-awaited retrial judgment in a patent validity action, holding that a Markush claim should be considered a single technical solution, instead of multiple solutions for each of the possible compounds covered, overruling the lower judgment by Beijing Higher People's Court ("BHPC"). This retrial judgment also casts doubt on the effect of a new judgment just made by BHPC on the same issue less than 2 months ago. SPC apparently intends to put the disagreement on this issue to an end by this judgment.

The patent in dispute is Chinese invention patent No. 97126347.7 owned by Daiichi-Sankyo.

Overall, this SPC judgment makes it more difficult to defend a Markush claim in an invalidation action by restricting the patent owner's capability of amending the claim. This certainly is good news for potential generic challengers.

Allowable amendments in an invalidation action

When a Markush claim is regarded as a single solution, on whether and how the patent owner can amend the claim during an invalidation action, SPC apparently intends to take a middle ground, although the rule it gives could be too vague to be used as a practical guidance for stakeholders in the future.

On the one hand, the retrial judgment did not fully adopt the Patent Reexamination Board's rigid position that when a Markush claim is a single solution, in an invalidation action, the patent owner cannot amend the claim by deleting an alternative option (likely for the purpose of distinguishing the claim from a prior-art reference teaching or suggesting a compound under that alternative option). On the other hand, SPC also flatly dismissed BHPC's more liberal position that the patent owner can freely delete an alternative option as such a deletion narrows the scope of the claim (BHPC took this position on the grounds that each compound under an alternative option is an independent solution).

Instead, SPC makes the following holdings:

(1) However special a Markush claim is, it must comply with the unity requirement of the patent law. The unity requirement implies that a Markush claim should be regarded as a set of its Markush elements, not a set of multiple compounds.

(2) Amendments to a Markush claim in an invalidation action should be strictly limited. The principle for allowable amendments should be that the amendments shall not generate a class of or a single compound with a new function or effect, although unique factors specific to a case should also be sufficiently considered. If the patent owner were allowed to delete any alternative option, it would generate uncertainty in the scope the patent.

The primary problem with the underlined principle is that it may be too vague to be used as a practical guidance. Particularly, in its judgment, SPC does not explain whether the amendments proposed by the patent owner meet this principle, which explanation could be useful for practitioners in the future.

Lateral consequence on priority claim

BHPC had issued a judgment less than 2 months earlier to hold that a Markush claim can enjoy partial priority claim because each compound covered by the claim should be regarded as an independent technical solution. This retrial judgment by SPC cast doubts on this BHPC judgment when SPC holds that a Markush claim is a single solution.