Late-stage reshaping study in this paper was conducted on HCV protease variant NS3aH1 using pre-selected unmodified disulfide libraries. NGS analysis of the binding of the reshaped libraries to NS3aH1 unveiled two distinct landscapes: some peptides lost NS3aH1 binding upon bicyclization ('drop-out' peptides), while the others retained NS3aH1 binding after bicyclization ('developable' peptides). Late-stage reshaping narrows on the diversity of chemical space to maximize the likelihood of discovering advanced peptide-derived ligands, but the outcome of such an approach is not obvious a priori. For example, the ratio of 'drop out' and 'developable' population was strongly dependent on the architecture of the library (the placement of cysteine within the randomized segments). In conclusion, the example using KYL for late-stage reshaping suggested that thousands of previously discovered unmodified peptide binders can fuel discovery campaigns that aim to find chemically modified bicycles.