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Discussion on the Distribution of Burden of Proof in Presumption of Novelty about Drug Crystal Forms
Yu BAI
Chinese Patent Attorney
Chemistry & Biotechnology Department
Linda Liu & Partners
In the context of the booming pharmaceuticals industry, patents for crystal forms of pharmaceutical compounds are playing a more and more important role. For pharmaceuticals enterprises that develop original medications, such patents may act as means for prolonging a patent term. And for manufacturers of generic drugs, patents of that kind are also effective in enabling the manufacturers to gain more market share.
Patent applications for crystal forms of pharmaceutical compounds have their own characteristics, which brings about many problems in the examination of the applications that are worth discussing. We will talk about how the burden of proof should be shared when the examiner “presumes a crystal form of a compound not to be novel”.
(1) The common rejections from examiners and the usual responding way of applicants
When the examiner presumes a crystal form of a compound not to be novel, he usually presents opinions like this:
Claim 1 is directed to a crystal form of compound XX. Reference 1 discloses compound XX in a solid form (or a crystalline form). Although Reference 1 says nothing about parameters that characterize the compound as a crystal, those skilled in the art would find it impossible to distinguish, on the basis of Reference 1, the crystal of claim 1 from the solid form (or crystalline form) of the compound disclosed by Reference 1. It is therefore presumed that the crystal form of claim 1 is the same as the product disclosed by Reference 1, so claim 1 is not novel.
To overcome that rejection, the applicant usually needs to provide experimental data capable of proving that the product obtained using the method described in the reference is different from the claimed crystal form. To this end, the applicant needs to reproduce the product of the reference and measure its physicochemical parameters so as to prove it is different from the claimed invention.
Since the administrative department is incapable of experimentation, the burden of proof is transferred to the applicant, who has to provide evidence against the examiner’s presumption. However, in Chinese practice the burden may be really heavy for the applicant, especially when the examiner cites more than one reference to support his presumption. The applicant needs to reproduce all the products of the references and measure the physicochemical parameters of each of them within the responding time limit for this situation.
(2) Relevant rules in the Guidelines for Patent Examination
The SIPO’s Guidelines for Patent Examination does not clearly give examination standards on when a crystal form of a compound should be presumed not to be novel. A crystal form of a compound, however, is usually characterized by its microscopic physical parameters. Therefore, in theory, it can be categorized as a chemical product characterized by parameters.
The Guidelines for Patent Examination reads, in section 5.3 of chapter 10 in part II, as follows:
With a claim of a chemical product characterized by physicochemical parameters, if it is impossible to compare the product characterized by the parameters with the product disclosed by the reference using the parameters and thus impossible to determine whether the product characterized by the parameters is different from the disclosed product, then it is presumed that the claim is not novel under Article 22.2 of the Chinese Patent Law.
The above examination principle actually records a definite precondition for the judgment of "presumption of novelty", that is: It is necessary to determine whether the claimed product is distinguishable from the disclosed product. If so, it is determined that the claimed product is novel—that is, presumption is unnecessary. If not, it is presumed that the claimed product is not novel.
We think that when the examiner follows the above examination principle and presumes the claimed product not to be novel, the examiner should first bear the burden of proof.
(3) Distribution of the burden of proof
We think the examiner should follow the general principle of the art in determining whether a patent for a crystal form of a compound, special though it is, is novel or not. When the examiner is going to presume the claimed product not to be novel, what he is supposed to do is at least to determine whether the claimed compound is likely to be the same as the disclosed one—that is, to give preliminary reason or evidence that they are possibly the same.
In other words, before the examiner concludes that the claimed product is presumed not to be novel, he should first compare the claimed product with the disclosed one and determine whether the former is distinguishable from the latter. In doing so, the examiner is supposed to compare them from the perspective of those skilled in the art. To determine whether two chemical products are the same, the general approach is to compare them from such aspects as structure and/or composition, parameter or preparation method. When it comes to determining whether a crystal compound is the same as the disclosed product, it is usually difficult to compare them from their chemical structures, and thus their parameters, preparation methods, shapes, properties, etc. may be used.
What characteristics a chemical product has are closely associated with how it is prepared. A crystal compound is usually can be obtained by the method including a step of crystallization. For this reason, if the preparation method disclosed in the reference does not comprise a step of recrystallization but results in merely a solid, and the reference is silent about crystal-related parameters, then it is reasonable to think that no crystal can be obtained from the reference. In this case, in the eyes of those skilled in the art, the claimed compound is distinguishable from the disclosed one, and thus presumption as above is not necessary.
Additionally, a crystal compound usually has a special appearance and special properties. When what is disclosed by the reference is only a solid, the reference actually discloses an upper concept. As you know, an upper concept is unqualified to deprive a lower concept of its novelty. We therefore think that if the reference does not disclose crystal-related information but merely discloses a solid, it is not appropriate to presume the claimed crystal not to be novel on the basis of the upper concept of solid.
According to the Guidelines for Patent Examination, when facing with the examiner’s conclusion that the claimed crystal is presumed not to be novel, the applicant is entitled to provide evidence against the rejection. But since the applicant must provide the evidence in addition to preparing a reply to the examiner’s rejection within the specified time limit, the burden of proof on the applicant is rather heavy, especially when the examiner cites several references.
The examining authority, we think, should also bear initial burden of proof by determining, from the perspective of those skilled in the art, whether the claimed invention is distinguishable from the reference and giving some grounds, even if preliminary grounds, for his determination that they are probably the same, before going to presume the claimed invention not to be novel. If, on the other hand, from the reference only, those skilled in art can determine that the disclosed product is unlikely to be the same as the claimed invention, it is inappropriate to presume the claimed invention not be novel on the basis of the reference. Along this way, the office action can become more specific, enabling the applicant to respond in a more targeted way; and the burden of proof on the applicant is alleviated, in favor of improving the overall efficiency of administration.
