Introduction
Vortioxetine hydrobromide case
Lenvatinib methanesulfonate case
Comment
Given that China's Guidelines for Patent Examination make no mention of the examination of crystalline form patent applications, practitioners primarily rely on judicial decisions and the China National Intellectual Property Administration's (CNIPA's) invalidity decisions to fathom the examination criteria adopted by the judiciary and the agency.
Analysis of recent decisions in this regard suggests that the criteria for assessing the inventive step of a crystalline form invention tends to be consistent. The criteria adopted in assessing the inventiveness of a compound that shares a structure similar to a known compound should also be applicable to a crystalline form invention – that is, only those inventions which achieve an unexpected technical effect involve an inventive step.
Given that there are no explicit parameters in the Guidelines for Patent Examination as to how a crystalline form can achieve an unexpected technical effect, this article aims to unravel the parameters to be considered in establishing such an effect by analysing two recent invalidity decisions.
Vortioxetine hydrobromide case
Invention patent No. ZL200780022338.5 relates to the beta crystalline form of vortioxetine hydrobromide. The embodiments of its description prepare and characterise a variety of salts of vortioxetine and different crystalline forms of hydrobromide. The validity of the patent was challenged in an invalidity proceeding before the CNIPA. On 29 April 2021, the CNIPA rendered decision No. 48337, which upheld the patent's validity.
The decision found that the difference between claim 1 of the patent at issue and evidence 1 of the closest prior art was that evidence 1 merely disclosed the free base of vortioxetine, rather than the salt forms and crystalline forms of the patent.
The contention of the case focused on whether the beta form of vortioxetine hydrobromide brought any unexpected technical effect over the prior art. In assessing the unexpected technical effect, the decision not only compared the melting point, hygroscopicity and water solubility of the crystalline forms of the patent at issue with that of the free base of the prior art, but also extended the comparisons to the crystalline forms of other salts disclosed by the patent at issue.
It should be noted that the beta form claimed by the patent at issue was not the most superior among the crystalline forms disclosed by the patent at issue with regard to the melting point, hygroscopicity and water solubility. However, the decision opined that apart from maintaining a high melting point (thermal stability), the alpha and beta forms of vortioxetine hydrobromide retained substantially lower hygroscopicity and higher water solubility compared with other salts. Such overall performances could not be expected by the person skilled in the art based on the salt crystals enumerated by the patent at issue.
Lenvatinib methanesulfonate case
On 30 April 2021, the CNIPA rendered decision No. 49520, which found invention patent No. ZL 200480036184.1 – relating to the crystalline form of lenvatinib methanesulfonate – to be invalid.
The decision adopted an analogous approach to that utilised by decision No. 48337 in ascertaining the unexpected technical effect. It first compared the crystalline form of lenvatinib methanesulfonate (form C) in claim 1 of the patent at issue with the free base of the prior art. It then moved on to form C and the crystalline forms of other acid addition salts disclosed by the patent at issue.
Nevertheless, after a comparative analysis of the solid stability, hygroscopicity, solubility and bioavailability of form C, the free base and other salts, decision No. 49520 concluded that the technical features of form C were superior to those of the free base, but inferior to some other salts. Therefore, the achieved effect was within the expected range.
In these cases, the effects achieved by other technical solutions disclosed in the description of the patent at issue were used as a benchmark in ascertaining whether the technical effect of the claimed crystalline form could be expected.
Practitioners should be wary of the fact that such an approach is not applicable unless there is evidence showing that the effects achieved by the benchmark technical solutions are equivalent to those to be expected by the person skilled in the art based on the prior art, or else they risk jumping to an erroneous conclusion.
For example, if the exploitation of an invention leads to a single crystalline form, there will be no point of reference in conducting a comparison and proving the unexpected technical effect. However, if the exploitation of an invention simultaneously leads to two crystalline forms with varying properties, by employing the methodology utilised in the cases discussed in this article, it seems rational to establish one crystalline form in producing unexpected technical effect.
If the properties of the two crystalline forms are barely distinguishable, it would be difficult to establish an unexpected technical effect, even if both effects are superior. In such a context, the inventive step assessment of a crystalline form over the prior art, which hinges on the contents disclosed by the invention, may vary if the patentee opts to disclose different contents.
To conclude, the technical solutions simultaneously disclosed at the filing date should have no bearing on the objective assessment of the inventive step of an invention over the prior art. Whether it is justifiable to use the technical solutions achieved by the patent application as a frame of reference in attesting to the level of expectation of the person skilled in the art remains questionable.
For further information on this topic please contact Wu Xiaohui or Jianhui Li at Wanhuida Intellectual Property by telephone (+86 10 6892 1000) or email ([email protected] or [email protected]). The Wanhuida Intellectual Property website can be accessed at www.wanhuida.com.
An earlier version of this article was first published by MIP.