On the Utility of Chemical Strategies to Improve Peptide Gut Stability

Inherent susceptibility
of peptides to enzymatic degradation in
the gastrointestinal tract is a key bottleneck in oral peptide drug
development. Here, we present a systematic analysis of (i) the gut
stability of disulfide-rich peptide scaffolds, orally administered
peptide therapeutics, and well-known neuropeptides and (ii) medicinal
chemistry strategies to improve peptide gut stability. Among a broad
range of studied peptides, cyclotides were the only scaffold class
to resist gastrointestinal degradation, even when grafted with non-native
sequences. Backbone cyclization, a frequently applied strategy, failed
to improve stability in intestinal fluid, but several site-specific
alterations proved efficient. This work furthermore highlights the
importance of standardized gut stability test conditions and suggests
defined protocols to facilitate cross-study comparison. Together,
our results provide a comparative overview and framework for the chemical
engineering of gut-stable peptides, which should be valuable for the
development of orally administered peptide therapeutics and molecular
probes targeting receptors within the gastrointestinal tract.