Article 26.4 of the Patent Law of the PRC: " The claims shall be supported by the description and shall define the extent of the patent protection sought for in a clear and concise manner."

New drug development is of the essence to the pharmas, making pharmaceutical one of the hottest fields in intellectual property regime.

Part II of the Guidelines for Patent Examination requires that the patent application shall be sufficiently clear and complete to be carried out by a person skilled in the art, which means a person skilled in the art, having read the specification, should be able to carry out the invention without inventive skill, solve the technical problems and produce the anticipated technical effects.

Enablement of drug patent must be established upon concrete experimental data. Generally speaking, to demonstrate the technical solution produces anticipated technical effects, one shall prove that the technical solution solves the technical problem. Predictabilities of the technical effects are different among various technical fields. Due to the difficulty in predicting whether chemical invention can be carried out, especially in human body where the reaction takes place, predictability of the chemistry or biotech field is generally lower than that in the mechanical engineering field. Therefore, anticipated technical effect in chemistry or biotech field is required to be supported by experiment data. If drug compounds includes various substitute functional groups (such as alkyl, alkenyl, aryl…), their similar characteristics and therefore their technical effect can be predicted. Otherwise, experimental data of each and every compound sought for protection in claims are required to prove that the compounds work as claimed. In China, examiners tend to confine the protection scope of the claims to the technical solutions supported by experimental data. For example, accepted claims will be limited to compound with aryl group provided with testing data, or the specific compounds with data support.

Statistic shows the “unclear” issue is frequently raised by the examiners during substantive examination of patent application, especially the PCT Applications entering Chinese National Phase. In response to the issue, the applicant will usually submit supporting documents (data or evidence) to justify the claiming of protection scope . Generally speaking, sufficiency of disclosure must be fulfilled at the time of filing. For drug patents, the essential experimental data is required to be disclosed at the time of filing in order to prove that the invention has been completed on the filing date or the priority date. Submitting of supplementary document during prosecution after the filing date of application may not be accepted by the examiner. For example, in the application document of an invention about a method for treating tumor, the applicant discloses the animal experiments showing destruction of two types of solid-tumor and asserts that the method can be used to destroy them in the same way in view of the drug function mechanism. The examiner indicates that “solid tumor” in claim 1 is unclear. The examiner believes that the originally disclosed data does not naturally lead to such conclusion. Examiners generally require claimed scope to be closely confined to embodiments as carried out in the experimental date.

In the case mentioned above, the examiner believes that data or evidence submitted after the application date fails to support claim 1 although the fact has been written down in the specification. It is worthwhile to note that it does not mean that data or evidence published before the application will always be accepted without question. In Practice, the data or evidence which is used to prove technical solution and facts in the specification may still be accepted.

Recently, we had a discussion with the examiner about “unclear” terms such as “about, almost, reduce drastically, minimizing, maximizing, etc”. The examiner indicated that even if these “unclear” words used in claims have been reasonably and logically explained and the patent has been granted, these words may become the possible loophole when the patent validity is challenged. During invalidity stage, Article 26.4 may be applied to claim that these words are essentially not clear. For example, when it comes to drug ingredient, “about 10 μg” may be claimed as not explicitly known by those skilled in the art.

How abroad should the patent be claimed to manage the risk of invalidity?

For the compound case, if the applicant claims only the specific compound supported by experiment data, the protection scope would be too narrow. However, if the applicant wishes to claim all that have similar structure, it would be impractical to include all of them in the specification. A more balanced approach would be to claim proper scope of protection based on the chemical compound and the therapeutic result. Including in the specification the extent of the therapeutic application of the product, which is sufficiently clear, may fulfill the requirement.

In the pharmaceutical field, for broad patents, patentees are claiming possible compounds or therapy uses, but this may lead to “no patent should be granted”. Here are some typical “performances” of unclear specifications:

  1. Lack of materials, preparation methods and evidences of drug activity in a pharmaceutical compound invention; Lack of ingredients, amounts and evidences of drug activity in a pharmaceutical composition invention; Lack of experiment method and result in a pharmaceutical use invention which is claimed to have certain therapeutic effects;
  2. Too many specific terms or functional features which cannot be supported by the specification;
  3. Unclear terms such as “about, almost, reduce drastically, minimizing, maximizing, etc”;
  4. Including unpatentable subject matter.


For drug patents, first of all, the applicant should make sure the product is patentable. On this premise, the applicant should include all possible subject matters associated to the product in the claims. For example, compounds, its isomer, crystal structure, medical use, composition, dosage form, preparation method and so on can be claimed in one applicant. Such drafting strategy will enable the applicant to overcome the possible defects such as lack of novelty, lack of inventive steps or unsupported claims.