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Using Clinical Trial Results from a Parent Patient Population as Prior Art to Challenge Inventive Step
In the pharmaceutical field, with respect to an existing active ingredient, pharmaceutical companies may explore application thereof to different patient populations or indications through various clinical trials, and file patent applications accordingly. However, during the course of development, if the efficacy results of a clinical trial conducted on a broad patient population (i.e., a parent patient population) have already been publicly disclosed, does this creates a risk that a medical use invention directed to a treatment regimen for a particular sub-population within that parent patient population may be found to lack an inventive step, even when the disclosed trial data does not independently present efficacy results specific to that sub-population? This query remains unresolved.
In this regard, the 2025 Xing Zhuan Su Zi No. 50 judgment, rendered by the Intellectual Property and Commercial Court on 18 June 2026, adopts an affirmative position. The facts and the parties' respective arguments are summarized as follows.
In this case, the patent at issue regards medical use (the “Invention at Issue”) as when active ingredient A, administered according to a specific dosing regimen B, is used to treat rheumatoid arthritis (“RA”) patients who had an inadequate response to the specific agents (the “Patient Population C”). Exhibit 3 concerns a clinical trial in which active ingredient A was administered to RA patients according to dosing regimen B, with approximately 27% to 32% of Patient Population C included among the enrolled patients. Exhibit 3 also provides corresponding efficacy. Exhibit 4, cited by Exhibit 3, discloses efficacy outcomes observed in a different category of RA patients who received active ingredient A according to dosing regimen B.
Both the defendant and the intervenor (the party who filed the invalidation action) argued that one of ordinary skill in the art to which the Invention at Issue pertains could readily complete the Invention at Issue by combining Exhibits 3 and 4. The plaintiff, however, argued as follows: (1) treatment of disease in the medical field involves a high degree of unpredictability, such that supporting trial data is required, and dosing regimens applicable to different patient populations cannot be readily substituted for, or combined with, one another; (2) Exhibit 3 lacks any independent sub-population efficacy analysis for Patient Population C, or disclosure of how many patients within Patient Population C were among those who withdrew from the trial, and (3) Exhibit 4 presents a treatment regimen for a different sub-population and likewise fails to disclose Patient Population C, such that no motivation to combine it with Exhibit 3 can be found.
The court dismissed the plaintiff’s arguments, holding that the combination of Exhibits 3 and 4 were sufficient to negate the inventive step of the Invention at Issue. The court’s rationale is summarized as follows.
- In determining whether an exhibit, or combination of two or more exhibits, is sufficient to establish that Claim 1 of the patent at issue lacks an inventive step, it should be considered whether, through logical analysis, reasoning, or experimentation, one of ordinary skill in the art could anticipate or readily arrive at the claimed invention based on such exhibit or combination and general knowledge as of the filing date. It is not necessary for the exhibit to disclose every technical feature recited in the claim.
- The enrolled patients in Exhibit 3 were recited as falling approximately 27% to 32% within Patient Population C. For one of ordinary skill in the art, in order for the trial results to be appropriately representative, it would be reasonable to expect that each patient population would be normally distributed across the different trial arms, such that Patient Population C would be present within each. Accordingly, the overall efficacy results could reasonably be considered applicable to that sub-population (i.e., Patient Population C).
In sum, the court appears to have taken the position that, even where a clinical trial’s results do not independently present treatment outcomes specific to a particular sub-population, as long as the trial clearly recites that enrolled subjects include that particular sub-population, it can still be reasonably inferred that efficacy results are applicable to that particular sub-population. Whether this will develop into a settled position in practice remains to be seen.