From the preceding section, we know that a prior art genus that does not overlap a later claimed genus will not anticipate that claimed genus. We also know that aprior art genus that partially overlaps a later claimed genus but that does not containactual examples falling within the later claimed genus will not anticipate the later claimed genus. Finally we also know that a prior art disclosure of a species falling within the scope of a later claimed genus will anticipate that later claimed genus.A situation we did not discuss is that which occurs when the prior art discloses agenus of compounds and the practicing chemist wishes to claim a single species that happens to fall within that genus. Will the claim to that species be novel in view of the prior art disclosure of the genus?

Imagine you are a chemist who has been laboring to find a compound that is capable of inhibiting a very important pathway in a human disease state. After many years of hard work and false leads, you find a compound—compound 4 in Figure below—that appears to possess all of the necessary attributes. However, your information scientist reports that there are prior art references that disclose a total of three different Markush structures, each of which encompasses your compound as shown in Figure below. The prior art reference(s) that contain(s) these three genera provide(s) the general methods of making the compounds, and the preparation is enabled for one skilled in the art.

A few specific examples have been made that fall within genus 1 (and hence genera 2 and 3 as well) of the prior art, but your exact compound 4 has not been specifically disclosed. The question is now whether compound 4 is anticipated and rendered non patentable per se in view of any or all of the three prior art Markush disclosures.

Take a few moments to look at the three prior art Markush structures and see if you can determine which Markush structure represents the broadest disclosure?We hope you’ve determined that the genus represented by formula 3 is the broadest disclosure since it contains within its reach many thousands of hypothetical compounds. The next broadest disclosure is the genus represented by formula 2, which contains hundreds of hypothetical compounds, followed by the narrowest disclosure represented by formula 1, containing only 14 hypothetical compounds. Since we are interested in


FIGURE :Prior art genera and species to be claimed.

determining the anticipatory effect (if any) of these three prior art Markush structures on our claimed species (compound), we might find it useful to engage in a little thought exercise to make better sense of the rule of law that will eventually follow. In this experiment, we will exaggerate the scope of the prior art Markush structures with our goal being to determine whether a narrower or broader encompassing scope in the prior art is more likely to be anticipatory. To begin, let’s imagine that the intellectual property space occupied by the broadest Markush, structure 3, was grabbed on each end and stretched so large that instead of containing thousands of hypothetical compounds,it now contains millions or even billions of hypothetical compounds. Now let’s take the smallest Markush, structure 1, and shrink it down to a single species point, that species point being our claimed compound 4. With these exaggeratedMarkush embodiments in hand, let’s think back to what anticipation means—the ability of a prior art reference to allow one to “at once envisage” the later claimed invention. In our case, the claimed invention is the single compound represented by formula 4, and so the question at hand is which hypothetical (stretched or shrunk)Markush will allow us to at once envisage our claimed compound having the structure of formula 4? Let’s start with the very broad (hypothetically stretched) Markush first.

If we wished to derive our claimed compound from its many variables, we would have to limit each variable group to a single choice such that we would get just the right combination. It would be like trying to open a huge combination padlock without any clues. Certainly one could not at once envision our compound from the millions or billions of hypothetical compounds contained within this broad disclosure and even more certainly, such a broad disclosure does not identify any single compound sufficiently enough to satisfy the requisite specificity needed for chemical anticipation.
In contrast, the Markush that had been shrunk down to a single species clearly anticipates our claimed structure because it would allow us to at once envisage our claimed structure from its disclosure since . . . it is our claimed structure! Between these two extremes is a molecular Grand Canyon of uncertainty. The primary issue can then be presented as: At what point, if any, can a prior art genus become small enough to anticipate a later claimed species falling within the scope of that genus?

For guidance, we begin by looking to see if there are any federal court decisions likely to be controlling for our situation. In the case of In re Petering, a patentee was attempting to claim a particular compound in view of a prior art reference that contained a generic class of 20 hypothetical compounds, the members of which were very similar in structure and all of which would be expected to possess the same properties. In its analysis, the court noted that even though the prior art reference did not specifically disclose the compound that the applicant later attempted to claim,the court found that such a narrow disclosure (genus of 20 compounds) of related compounds sharing the same core would allow one to at once envisage the later claimed compound falling within that generic scope. The court’s characterization of the relationship between the prior art disclosure and the later claimed compound clearly foreshadowed their ultimate conclusion; the narrow prior art genus anticipated the later claimed compound. In so doing, the Petering court established the important precedent that forms the basis for our own hypothetical analysis.

We can begin our analysis with Markush 3, which represents the broadest set of compounds. While the exact number of compounds has not been calculated, it contains at least many thousands of hypothetical compounds. Furthermore, there is not even a constant core, as the variables Y and Z allow for C or N, and thus the core can be naphthalenes, quinolines, and 1,8-naphthyridines as well. This is not atight set of compounds as in Petering, where there were only 20 possible compounds sharing a common core. Thus it would appear that the holding in Petering would not be controlling for our situation as it relates to genus 3, and thus genus 3 would likely not anticipate our later claimed species compound 4.

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 naphthalenecore. The variability of the Ra is not great, containing the possibility of hydrogen,methyl and n-propyl only. Given these facts, it is quite likely that Petering would be controlling and Markush 1 would anticipate the later claimed species compound 4and thus render it nonpatentable.

How about the genus of formula 2? Let’s pull out the crystal ball and take a look.Darn, the crystal ball has a lot of dust on the glass and we can’t see very much!The reason for the cloudy crystal ball is that there is very little case law beyond Peteringto light our way. We do know that the prior art Markush represented by formula 2 does not contain nearly as many hypothetical compounds as the Markush of formula 3, but it still contains at least several hundred hypothetical compounds.Moreover, even though the core does not vary from a naphthalene, it does have fairly widely varying substitution on the pendent phenyl, since Rb can range from hydrogen to trifluoromethyl to a phenyl group. Given the fact that there are still many more compounds in formula 2 then what was found in the prior art references discussed in Petering, together with the relative disparate nature of the subsistent (especially forRb), it is plausible/reasonable to expect that the Markush of formula 2, absent more,would not anticipate the later claimed compound 4.27Summarizing, our actual determination based on the case law precedent of Peteringparalleled our general prediction based on the hypothetical stretching and shrinking we did to the same prior art genera disclosures. As we saw, the broader the disclosure,the less likely it was to anticipate and vice versa. Thus we saw that the broadest disclosure represented by genus 3 did not anticipate our later claimed species whereas the narrow genus 1 did anticipate. The genus of formula 2 occupies the middle ground and may not anticipate our claimed species. Having just invested our time learning the law of Petering and anticipation of species by a narrow prior art genus, we might logically ask in what context this situation is most likely to arise. In other words, why is such a seemingly very specialized situation worthy of such a detailed discussion?One important situation where anticipation of a species by a prior art genus(Petering-type situation) can occur is in the case of a selection invention. A selection invention happens when a later claimed invention falls within the boundary of an earlier invention (like the species falling within a genus). The reason why selection inventions often occur is that one may wish to improve on an earlier disclosed genus.More specifically, a chemist may discover interesting activity in a series of compounds and wish to claim that series of compounds through the use of a Markush structure.After the patent application filing, the chemist or the organization she works for may continue working within the genus by making additional analogs. In this later work, it often happens that some surprising or interesting activity is found within a narrower subgenus or a species falling within the original genus. This surprising activity might be in the form of a discovery that a change of one functional group to another functional group results in significantly improved properties or activity. For example, it may be found that changing a nitro group to an amino group may convert the compound from an agonist to an antagonist. The advantage to filing a subsequent application with claims to the subgenus or species falling within the earlier claim is that this will both provide more specific coverage for the subgenus or species and also might provide a new, later, filing date, (meaning the new subgenus or species can be covered by a whole new 20-year patent term, assuming the later claimed species is not considered obvious in view of the prior art genus).
Alternatively, a series of compounds may be made and claimed in a Markush format, and further work is dropped on that series of compounds. In the meantime, many of the compounds may have been deposited into the organization’s compound library where they are plated for screening. Many years down the road, one or more of the compounds may hit on a new target, and work is taken up on the old series of compounds. In the process of optimizing the old compounds to the new use,new species will be discovered, and it is possible that some of these new species of compounds might fall within the boundaries of one of the previously claimed or described Markush structures. Although the species is new in the sense that it has never been made or specifically described, for it to be patentable, it must be novel according to the legal requirements of §102. And as we saw earlier, it is possible that a compound can be found not novel despite the fact that it has not been specifically identified in the prior art disclosure. This can occur when the prior art genus is relatively narrow with a common core and closely related groups for allowed substituents. Petering-type anticipation is very important in this venue because onceit is determined that the earlier disclosed genus anticipates the later claimed species,that species can no longer be patented as a chemical species (although patents directed to methods, dosages, formulations, etc. might still be possible). Thus Petering can conceivably have significant ramifications for the practicing chemist and is always worth keeping in mind.

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