Influence of Macrocyclization Strategies on DNA-Encoded Cyclic Peptide Libraries

Discovery of cyclic peptide hits using DNA-encoded libraries (DELs) has recently been extensively researched, with significant efforts directed toward developing DEL-compatible macrocyclization methods. To investigate how different cyclic linkers influence DEL selection outcomes, we constructed eight distinct sub-libraries and screened them against two protein targets, MDM2 and GIT1, resulting in two representative yet contrasting scenarios. Validation studies for MDM2 revealed that structural similarity patterns observed across multiple sub-libraries could enhance confidence in the authenticity of identified hits. Notably, cmp-10 demonstrated potent inhibitory activity, exhibiting an inhibition constant of 11 nM. In contrast, selections against GIT1 produced discrete enrichment patterns. From these outcomes, two exemplary compounds were selected and validated through both on-DNA and off-DNA modes. cmp-17 was confirmed to bind specifically to the desired binding pocket, displaying a dissociation constant of 1.22 μM. Furthermore, ITC experiments using mutant GIT1 proteins (GIT1 ^L271A/L279A and GIT1 ^L271L/L279L ) provided additional insights into the mechanism by which cmp-17 disrupts the interaction between GIT1 and β-Pix.