Cyclic peptides have attracted increasing attention as a privileged class of molecules addressing undruggable targets. Cell permeability of cyclic peptides has remained a challenging issue owing to their molecular properties. Various efficiency metrics have emerged to assess this issue. Among them, the lipophilic permeability efficiency (LPE) metric is the difference between an experimental 1,9-decadiene-water partition coefficient at pH 7.4 (log Ddec/w) and calculated octanol/water partition coefficients (ALogP). This metric provides insight into how structural changes affect permeability. Here, we demonstrate the chromatographic capacity factor (log k') of cyclic peptides using reversed-phase liquid chromatography as an alternative to log Ddec/w, which enables efficient and reliable experimental lipophilicity for the adoption of LPE in early drug discovery. The log k' indicates the passive membrane permeability of cyclic peptides and can be used to optimize passive membrane permeability in combination with other parameters. In addition, intestinal membrane permeability of cyclic peptides on human induced pluripotent stem cell-derived intestinal epithelial cells was achieved with log k' and high passive membrane permeability, although cyclic peptides are P-glycoprotein substrates. These approaches could facilitate optimization of properties of cyclic peptides for oral administration and contribute to the successful discovery and development of cyclic peptides.
Keywords: ALogP; Cell permeability; Chromatographic lipophilicity; Cyclic peptides; Human iPS-derived intestinal epithelial; P-glycoprotein; log k'.
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