peptides. Although stable than the linear counter parts, cyclic peptides are also subjected to poor membrane permeability, proteolytic degradation, and systemic clearance, which severely impedes their bioavailability. Hence, medicinal chemists have utilized backbone N-methylation which facilitates the passive permeability of peptides by lowering the desolvation penalty of amide bonds and providing protease resistance on masking the amide protons. One of the fundamental limitations of this modification is the reduced rotational barrier of the N-methylated peptide bond, which results in conformational heterogeneity that potentially compromises the bioactivity. Contrary to N-methylation and other amide bond modifications which restrict the number of H-bond donors (HBDs), we adopted a bottom-up approach, whereby altering the H-bond acceptor (HBA) by thioamidation, we assessed its impact on amide bond desolvation. Thioamidation on model dipeptides revealed stark enhancement in lipophilicity compared to the regular as well as N-methylated dipeptides. When this hypothesis was extended to model cyclic hexapeptides, remarkable improvement in in vitro permeability and proteolytic stability was observed which translated well in their in vivo pharmacokinetics. Out of the three peptides tested, SL_5 showed prolonged plasma exposure rats upon oral as well as intravenous administration and all three of them were found to be orally bioavailable. Further to explore the impact of thioamidation on biological activity, thio-scanning on a cyclic analog of Somatostatin was done. Three of the analogs showed prolonged inhibition of in vivo growth hormone release. Overall, our study highlights thiomidation as a potential chemical modification to improve drug-like properties of therapeutic macrocycles.