What is considered a “modified amino acid” according to the MPEP?

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.

According to MPEP 2412.03(c), a “modified amino acid” is defined as follows:

“Modified amino acid” includes any amino acid as described in paragraph 3(e) of WIPO Standard ST.26.

This definition is further elaborated in WIPO Standard ST.26, which states that a modified amino acid is any amino acid other than the 22 standard amino acids (20 common amino acids plus pyrrolysine and selenocysteine). This includes naturally occurring modified amino acids as well as synthetic modifications.