Fig. 6. Stabilities of cyclic hexapeptides in serum and simulated gastric/intestinal fluids.

a Chemical structure of DP1L-NH₂. b Mouse serum stability of CP1 (gray), DP1 (orange), MP1 (blue), and DP1L-NH₂ (brown). c Stability in a simulated gut fluid. 98% of a control peptide (somatostatin) was degraded at 4 h under the same conditions. d Stability in a simulated intestinal fluid. 94% of a control peptide (oxytocin) was degraded at 4 h under the same conditions. The degradation profiles of the control peptides are shown in Supplementary Fig. 50. In (b)–(d), each point represents the mean value, and the error bars the standard deviation from experiments carried out in triplicate.