How are partial structures of chemical compounds treated in patent claims?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

Partial structures of chemical compounds in patent claims are not automatically considered indefinite. The MPEP 2173.05(t) provides guidance on this matter:

“A claim to a chemical compound is not indefinite merely because a structure is not presented or because a partial structure is presented.”

This approach is exemplified in the case of In re Fisher, where a claim referring to a “polypeptide of at least 24 amino acids having the following sequence” was not found indefinite despite not identifying the entire structure. While partial structures may broaden the claim and raise questions about disclosure sufficiency, they do not inherently render the claim indefinite.