Markush claims

Chemical Abstracts and GAS Registry. CAS is especially notable for the thoroughness and high quaUty of its products. The CAS Registry system does a superb job of identifying any chemical that is either involved in new chemistry with hard data, or, since about 1980, specifically claimed in a patent. The MARPAT database has also led CAS to identify the perhaps nonexistent but prophetic substances covered by Markush claims in patents. 

Before diving into claim interpretation, let s first review some basic aspects of claims, such as the types of claims, the structure of claims, universal claim transitions, and finally, Markush claiming in chemical patents. 

FIGURE 9.5 Species disclosed in application and later attempted Markush claim. 

Claims can describe various types of inventions or embodiments of the same invention. The most common types of claims are product claims and process claims. Product claims confer protection over any aspects of a product specified, regardless of how that product was derived. Process claims describe a particular means of making a product, and it is the described process that is granted patent protection. Also relevant for biotechnology patents are Markush claims, which are used where embodiments of the invention can include a class of compounds (e.g., chemicals or DNA sequences). By opting to use a Markush claim, the applicant need not spell out every possible combination individually, instead he can claim a range of products that may be used in an embodiment of the invention. This range is compiled on the basis of a limited number of representative samples. 

Chemical structures in patents fall broadly into two types specific compounds and Markush structures. The term Markush Structure refers to a generic structure that appears in patent claims, and typically encompasses a broad family of potential compounds well beyond any specific compounds named or exemplified in the patent. Thus, Markush structures in patents contain prophetic material, but this material can be used as prior art against others. Therefore, the indexing and searching of Markush chemical structures in patents is extremely important. The patent offices from all major countries and patent issuing authorities (e.g., the European Patent Office) recognize Markush claims as patentable material. 

A significant problem in the universe of Markush chemical structures is the matter of extreme complexity. Markush chemical representations leave room for ambiguity, and often extremely complex Markush structures are created that become very difficult for Markush database producers to code. Additionally, the scope of these Markush claims can be excessively broad, making establishment of the prior art essentially impossible to determine for purposes of a meaningful and defensible patent examination. Sibley has commented most eloquently on this subject, as have others. " ... 

Maikush structures are mainly used in patents, for protecting compounds related to an invention. The first generic claim, submitted by Markush, was granted in 1924 by the US Patent Office [87-90]. 

Between the time of their filing the patent application and its issue, the company was planning several clinical studies when it came to their attention that another issued U.S. patent existed, which was filed before their chemist synthesized the compound of formula I. The patent of concern was directed to steroidal compounds, although it did not disclose their particular compound of formula I, nor did it indicate any specific utility in combination with a progestin for contraception. The patent specification (the entirety of the document) disclosed a number of Markush structures of varying scope as well as a description of the compounds as having utility for the treatment of prostate cancer. Claim 13 from the issued patent is illustrated in Figure 1.5 and it particularly concerned them. 

A simpler but equivalent way of presenting these three claims is illustrated in Figure 5.2. The Markush structure is not repeated because it is understood that the dependent claim is importing the entire Markush that it is dependent from, and then further limiting that structure according to the specified language. 

The claim set can be drafted to avoid this difficulty by redrafting claim 2 as an independent claim and providing die desired Markush definition for X. 

In practice, where a chemical structure is claimed according to a Markush format, the variable descriptors at each position of the molecule will almost always (if not always) be read in a closed fashion unless the implication is clearly otherwise. To leave a molecule truly open at any single position might allow for an infinite set of molecules to be generated. Where the compound is an object of the claim, an infinite set of potential molecules is likely to draw a rejection for failure to satisfy the written description and enablement requirements of 112 1, to be discussed in Chapter 9. 

When a Markush group is used for claiming a chemical invention, the members of the group either need to belong to a common or recognized class or share at least one... 

If the inventor in our hypothetical had carefully read the specification, he would have realized that Ci 6 alkyl was defined broadly enough that together with the rest of the claimed Markush would encompass the compound he wished to make and use.34... 

This example, while being of a fairly typical ilk for patents dealing with organic chemistry subject material, is somewhat straightforward in the sense that a fairly clear definition for the claimed Markush was available in the specification. Often, however, the specification does not provide such a clear definition, and one needs to look for clues through the context in which the term is used. In the absence of a clear definition, a consistent association of a term in a particular nexus can reinforce the term s meaning just as clearly as if the term had been set out and separately defined.35... 

Recall that in this chapter, we are discussing a basic tenant of patentability—That is, for an invention to be patentable, it must be novel. Since the Markush format is a very common way to claim chemical genera,15 it is critical that the practicing chemist appreciate the effect that disclosures in the prior art have upon the patentability of their claimed Markush structure. For this reason it is quite reasonable to ask, What... 

Let s consider a patent application that contains a claim including the Markush group we have drawn in Figure 7.1. The claim containing the naphthalene Markush is shown in Figure 7.2. A prior art search reveals the following disclosures ... 

Let s move to the other end of the spectrum and analyze prior art genus 1. This Markush contains 14 hypothetical members, all of which share a common naphthalene core. The variability of the Ra is not great, containing the possibility of hydrogen, methyl and //-propyl only. Given these facts, it is quite likely that Petering would be controlling and Markush 1 would anticipate the later claimed species compound 4 and thus render it nonpatentable. 

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