Date: 19 May 2025

【Volume 152】

The China National Intellectual Property Administration (CNIPA) recently issued decisions upholding the validity of two patents covering crystal forms of Indobufen, rejecting the invalidation requests filed against them.

Indobufen, an antithrombotic agent with significant commercial potential, has attracted considerable attention, leading to multiple invalidation challenges against its core patents in China filed by several generic drug manufacturers. The patents at issue,  CN202011484428.X and CN202211596913.5, are owned by Hangzhou Zhongmei Huadong Pharmaceutical Co., Ltd., and respectively claim specific crystal forms of Indobufen, referred to as Crystal Form X and Crystal Form D. Upon examination, the CNIPA dismissed all invalidation requests and upheld the validity of both patents¹.

The main issue in this case concerns the construction of claims directed to crystal forms. One view holds that such claims should be limited to the specific crystal forms explicitly disclosed in the specification, while an alternative perspective argues that they may encompass a broader scope of protection, including but not limited to those specific forms. 

In this case, the CNIPA adopted the former view, holding that where a claimed crystal form is represented by a particular code, a person having ordinary skill in the art, based on the disclosure of the specification, would recognize that the code conveys a specific meaning. As such, whether the crystal form is defined by selected characteristic peaks or by a complete XRPD pattern, the claim is directed to the specific crystal form disclosed in the specification. Therefore, the scope of the claim shall be construed as  limited to that particular form, along with its properties and parameters as described in the specification.

By contrast, judicial practice in Taiwan tends to favor the latter perspective, holding that the code used to designate the claimed subject matter is merely an arbitrary label without technical significance. Therefore, the inherent properties of a specific crystal form as described in the specification and drawings shall not be read into the claims. Doing so would violate the principle prohibiting the importation of limitations from the specification into the claims.

The following section provides a detailed overview of the CNIPA’s reasoning, along with a comparison to the differing perspectives on claim construction under Taiwanese practice:

Main technical features of the patents at issue

Claim 1 of the Crystal Form X patent:

“A crystal form X of indobufen, characterized in that: the crystal form X belongs to the monoclinic crystal system and space group P2₁/n, with its unit cell parameters of {a = 7.7027(4) Å, b = 13.4256(7) Å, c = 14.6383(8) Å, α = 90°, β = 102.646(5)°, γ = 90°, and V = 1477.07(14) ų}.” 

Claim 1 of the Crystal Form D patent:

“A crystal form D of indobufen, characterized in that: the X-ray powder diffraction pattern of the crystal form D exhibits characteristic diffraction angles 2θ, with a 2θ error of ±0.2 degrees; the characteristic 2θ diffraction angles include: 12.3, 14.4, 15.7, 17.9, and 20.6.”

Main Disputed Issue

In construing the claims, how should the scope of “Crystal Form X” and “Crystal Form D” be defined?

Opinions of CNIPA

The CNIPA held that, according to Paragraph 1, Article 64 of the Patent Law of the People’s Republic of China, “The extent of protection of a patent right shall be determined by the terms of the claims; the description and the appended drawings may be used to interpret the claims.” In the field of crystal inventions involving organic compounds, two approaches are commonly adopted when drafting claims: one defines the invention by reference to selected characteristic peaks (including unit cell parameters), while the other relies on a complete XRPD pattern. Generally, where a claim is drafted with reference to only partial characteristic peaks, it typically reflects the patentee’s intention to obtain a relatively broader scope of protection, rather than to confine the claim to the specific crystal form actually prepared and exemplified in the specification. This approach stands in contrast to claims that are defined by a complete XRPD pattern.

However, where the claimed subject matter is not only defined by selected characteristic peaks, but also by a code denoting a specific crystal form, then, a person having ordinary skill in the art, based on the disclosure of the specification, would recognize that the code conveys a specific meaning. As such, whether the claim is defined by selected characteristic peaks or by a complete XRPD pattern, the claim is directed to the specific crystal form disclosed in the specification. Therefore, the scope of the claim shall be construed as limited to that particular form, along with its properties and parameters as described in the specification. 

With respect to the Crystal Form X patent, the CNIPA held that Claims 1 to 3 clearly refers to a specific crystal form, namely Crystal Form X. Accordingly, based on the disclosure of the specification, the technical features recited in Claims 1 to 3 should be understood as characterizing the same crystal form, Crystal Form X, using different sets of parameter features. This crystal form is considered to possess all relevant features described in the specification, particularly those illustrated in the schematic diagrams of the unit cell structure shown in Figures 1 to 6, as well as the characteristics reflected in the XRPD, TGA, DSC, DVS, and PLM profiles. Therefore, when addressing other issues, a comprehensive evaluation must also be conducted with reference to all the features of the crystal form as disclosed in the specification.

Similarly, with respect to the Crystal Form D patent, the CNIPA held that the claimed subject matter of Claims 1 to 4 is clearly limited to Crystal Form D. Based on the disclosure of the specification, particularly the descriptions in Paragraphs [0026] to [0031], it is evident that the five or sixteen characteristic peaks recited in Claims 1 and 2 are essentially derived from the XRPD pattern shown in Figure 7 of the specification, which is directly employed in Claim 3 to define the crystal form , while the data recited in Claim 4 is derived from the TGA pattern shown in Figure 8. Accordingly, the technical features recited in Claims 1 to 3 should be understood as characterizing the same crystal form, Crystal Form D, using different sets of parameter features. This crystal form is considered to possess all relevant features described in the specification, particularly those depicted in the XRPD patterns shown in Figures 7 to 11, as well as the characteristics reflected in the TGA, DSC, DVS, and PLM profiles. Therefore, when addressing other issues, a comprehensive evaluation must also be conducted with reference to all the features of the crystal form as disclosed in the specification.

On this basis, the CNIPA held that the XRPD pattern of Crystal Form C disclosed in Evidence 1 differs significantly from the XRPD patterns of Crystal Form X and Crystal Form D as illustrated in the drawings of the specification of the patents at issue, in terms of the number of diffraction peaks, peak positions, and peak intensities. A person having ordinary skill in the art would not reasonably conclude that the Crystal Form X or Crystal Form D, as defined in the claims, is the same as Crystal Form C described in Evidence 1. Therefore, the patent rights should be upheld as valid.