In the field of science, people use the name of the discoverer to name his/her theorem or theory, such as Newton's law, Archimedes' Principle, Ohm's Theorem, etc.; In the field of athletic gymnastics, the International Gymnastics Federation uses the name of the first athlete who completed a very difficult action as the name of his/her action combinations, such as the well-known LiuXuan one-arm giant swing, Thomas flair, Cheng Fei jump; in fact, in the field of patents, there are also claims named after a person's name, such as the "Markush" claims that often appear in chemical cases.

The "Markush" claim is a special drafting manner for claims in the field of chemistry, which was first successfully used by the inventor Eugene Markush in a US patent in 1920, and then claims of this kind are named after his family name.

Pursuant to the provisions in the Guidelines for Patent Examination of China, where a single claim of an application is defined by a number of alternative elements, the Markush claim is formed. Someone may ask: whether such way of drafting will cause a disordered extension of the protection scope of a claim and does it mean that several technical schemes are protected in one claim? To answer this question, we must first understand the original intention of the introduction of Markush claim. The existence of Markush claims is intended to address the issue that there is no generic term available in the field of chemistry for alternatively useable elements. Therefore, although the Markush claim is allowed to define alternatively useable elements in parallel in a single claim, it shall also comply with all the provisions on unity as stipulated in the patent law to get patented. Specifically, to meet the requirements of unity, the alternatively useable elements (i.e., Markush elements) in the Markush claim must:

  1. possess similar nature; and
  2. have the same or corresponding special technical feature.

Where the Markush elements are for alternatives of compounds,

  1. all alternative compounds shall possess a common property or activity; and
  2. all alternative compounds shall possess a common structure which constitutes the distinguishing feature between the compounds and those in the prior art, and is essential to the common property or activity of the compounds of general formula, or under the circumstances that they do not have a common structure, all of the alternative elements shall belong to the same class of compounds recognized in the technical field to which the invention pertains (which can replace each other and achiever the same effect).

Whether a Markush claim possesses unity shall depend on the specification, i.e. depend on whether the description of the corresponding alternatively useable elements in the specification meets the above requirements. Since this type of claims is very special, there are very few relevant cases in practice. In the Judgment No. Zai 41 made by the Supreme People's Court in 2016, a thorough discussion was made regarding various issues related to Markush claims, which showed a prudent attitude in the judicial field towards determination of Markush claims.

The aforementioned Judgment is related to a request for invalidation against an invention patent titled "Preparation Method of Pharmaceutical Compositions for Prevention and Treatment of Hypertension". After examination of the request, the Patent Reexamination Board made a decision to maintain the validity of the patent; unsatisfied with the decision, the petitioner filed an administrative lawsuit, and the court of first instance affirmed the decision of the Patent Reexamination Board, but the court of second instance upheld the petitioner's opinion and revoked the first instance judgment and the Decision of the Patent Reexamination Board; after a retrial, the Supreme People's Court affirmed the first instance judgment and revoked the second instance judgment.

The focus of dispute in this case is independent claim 1, mainly about the following three questions, through which we may now have a basic understanding of Markush claims.

I. Whether a compound claim drafted in the Markush type is a generalized technical scheme or a collection of multiple compounds?

This question is actually about whether a Markush claim possesses unity. According to the Supreme People's Court, Markush claim is a special drafting manner for claims in patent applications for chemical inventions, i.e. it is a claim that is generalized by defining alternatively useable elements in parallel in a single claim. The emergence of the drafting manner of Markush claims is to solve the problem that in the field of chemistry, there is no generic term available for alternatively useable elements. Such drafting manner per se is always considered as a structural but not functional expression. What is defined in a Markush claim is alternatively useable elements in parallel, but not sub-claims. All the alternatively useable elements defined in the Markush claim possess a common property or activity, or possess a common structure, or belong to the same class of compounds recognized in the field to which the invention relates. Despite the particularity of its drafting manner, the Markush claim shall comply with the provisions on unity as prescribed in the Patent Law and the Implementing Regulations of the Patent Law.

The Markush claim is highly generalized and thus, once granted, shall have protection scope covering all compounds having common structure, property or activity, thereby maximizing the rights and interests of the patentee. Essentially, a patent right means a monopoly of a certain right, and the greater the scope of the patent right enjoyed by the patentee is, the more limitation the public has. Thus, from the view of fairness, the interpretation of the Markush claim shall be made strictly. No matter how many variables and combinations the Markush claim comprises, it shall be deemed as a generalized combination solution. Where individual variables are selected, the corresponding individual pharmaceuticals as defined in this Markush claim shall have effects without too much difference, may be replaced with each other, and shall be expected to achieve the same effect. Such an interpretation is in line with the object of Markush claims. Therefore, the Markush claim shall be deemed as a collection of Markush elements rather than a collection of individual compounds. Only under specific situations, can Markush elements represent single compounds, but generally, the Markush elements shall be interpreted as representing one category of compounds having common properties and effects. If the compounds represented by the Markush claim are deemed as a collection of individual compounds, it apparently does not meet the requirements of unity.

II. Which manners of amendments can be adopted by the right holders in the invalidation procedure?

Pursuant to the current provisions of the Guidelines for Patent Examination on the amendments in the invalidation procedure, any amendment to the patent documents of a patent for invention or utility model shall be limited to the claims only, and shall follow the following principles:

  1. The title of the subject matter of a claim cannot be changed;
  2. The extent of protection cannot be extended as compared with that in the granted patent;
  3. The amendment shall not go beyond the scope of disclosure contained in the initial description and claims; and
  4. Addition of technical features not included in the claims as granted is generally not allowed.

As for manners of amendment, the specific manners are generally limited to deletion of a claim, deletion of a technical solution, further limitation of a claim, and correction of obvious errors. Further limitation of a claim means adding into a claim one or more technical features recorded in other claims to narrow down the protection scope. It can be seen that the manners of amendment in the invalidation procedure are more and more diversified.

However, the examination of patent applications for chemical inventions is very particular in some aspects, such as whether a chemical invention can be implemented depends on experimental results, that some chemical products rely on the definition of parameters or preparation method, and that the new property and use of a known chemical product do not mean any change in its structure or components. In view of the particularity of the inventions in the chemical field and that the applicant has opportunities to put all possible structural formulae into one claim when drafting the claims, so as to maximize the protection scope, the amendment to the Markush claim during the invalidation procedure shall be given strict restrictions, and in principle, the amendments to the Markush claim shall not result in a compound category or single compounds having new property and effect, and meantime the factors relating to individual cases shall be taken into full consideration. If the patentee is allowed to delete any option for any variable, even though the protection scope is narrowed and the benefit of the public is not damaged, it would be uncertain whether such deletion results in new protection scope, which neither gives the public stable legal expectation, nor helps to maintain the stability of the system of determining the patent right.

Therefore, if the patentee wants to modify the Markush claim during the invalidation proceeding, he/she must consider comprehensively. In addition to meeting the basic requirements for amendments, he/she must also pay attention not to cause the amended claim to produce a class of compounds or single compounds with new properties or functions.

III. How to assess the inventive step of a Markush claim?

To determine whether a Markush claim is inventive, the following three steps shall be followed:

  1. Determining the closest prior art, i.e. finding a technical solution in the prior art that is the most closely related to the claimed invention, from the aspects such as whether it is in the same technical field as the claimed invention, whether its technical problem to be solved and technical effects are the closest to the claimed invention, whether it has disclosed the greatest number of technical features of the claimed invention, and whether it is capable of performing the function of the claimed invention;
  2. Determining the distinguishing technical features of the claimed invention and the technical problem actually solved by the claimed invention, i.e. first determining the distinguishing technical features of the claimed invention as compared with the closest prior art (possessing novelty) and then determining the technical problem that is actually solve by the claimed invention on the basis of the technical effect of the distinguishing technical features;
  3. Determining whether or not the claimed invention is obvious to a person skilled in the art, i.e. determining whether or not there exists such a technical motivation in the closest prior art as a whole that would prompt a person skilled in the art, when confronted with the technical problem, to improve the closest prior art and thus reach the claimed invention.

Unexpected technical effect is an auxiliary factor used to assess the inventive step, and as a method of backward deduction, it is not generally applicable due to its particularity. Therefore, only when the non-obviousness cannot be determined by using the three-step examination method, can the inventive step of a patent application be assessed depending on whether it achieves unexpected technical effect. Generally, it is not appropriate to directly assess the inventive step of a patent application depending on whether it achieves unexpected technical effect, instead of first using the three-step examination method.

In this case, both the Patent Reexamination Board and the court of first instance followed the three-step method to compare the compounds involved, find the distinguishing technical features and then analyze whether the claimed invention is obvious, and finally determined the inventive step of claim 1. However, the court of second instance held that the effect of a specific embodiment covered by the patent claim involved was equivalent to the technical effect of an embodiment in the evidence of the prior art; thus, the patent did not achieve unexpected technical effect and was not inventive. The court of second instance analyzed and determined technical effects which were not compared or determined in the invalidation procedure, which is beyond the scope examined in the invalidation examination decision and thus does not comply with the provisions of the Administrative Procedure Law and relevant judicial interpretations. The Supreme People's Court finally affirmed the judgment of the court of first instance as well as the decision of the Patent Reexamination Board and revoked that of the court of second instance.

From the above, it can be seen that the Markush claim, which is drafted in a special manner, although broadening the protection scope in form, is given strict restrictions on its interpretations, amendments and requirements on unity. As for inventors, they should pay attention to the following when drafting such type of claims:

  1. Understand the initial intention of allowing the drafting manner of such claims based on the legal logic for emergence of the Markush claim, reasonably arrange the Markush elements, and make sure that the alternative compounds can achieve the same or similar technical effects;
  2. Record the properties, activities, structures, technical features and technical effects of the Markush elements in the specification, so as to provide support for examination and assessment of the claims;
  3. Bear in mind the strict rules on the examination and amendments of Markush claims, and reasonably select and control the protection scope to avoid unnecessary amendments in later procedures.

Editor's Remarks: This Chinese version of the article has also been published on AFD China's official Wechat account:

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