The USPTO is proposing changes in the rules related to the practice of writing “Markush” claims. Markush claims are used heavily in chemical patent applications and allow applicants to claim vast arrays of chemical species by way of composition of matter or by association with a claimed process. The Markush claim makes use of generic formulae that represent the substance of interest as well as a class of equivalent entities.  It is not difficult to specify features of a simple formula that claim many hundreds or thousands of chemical species. 

The PTO admits that it is overwhelmed with the workload associated with these large collections of substances.  I have no doubt that this is true. Patent prosecution requires a search of the prior art for the novelty requirement. A Markush space filled with a large number of compounds slows down the workflow.  

I would hope that the congress and the PTO consider the cost to the public in performing due diligence as well.  I wonder if our cheminformatics friends can find a way to map the space defined by a Markush claim. This would make a due diligence exercise more cost effective and reliable.