Many disease processes are mediated by protein-protein interactions that involve large molecular surfaces and highly specific contacts, making them difficult to disrupt using small organic molecules. Peptides are able to fill the size and specificity requirements needed to target protein-protein interactions, and cyclic peptides have the additional advantage that they have the stability needed to withstand protease-rich biological environments. Theta-defensins are cyclic peptides from mammals and have inherent antimicrobial and immunomodulatory properties, and low cytotoxicity. In addition to these inherent properties, we have demonstrated that the core structural motif of theta-defensins, the cyclic cystine ladder, can also be used as a structured and stable scaffold for the design of peptide therapeutics. We explored the role of the cyclic peptide backbone and three disulfide bonds comprising the cyclic cystine ladder and showed that one or two disulfides can be removed without compromising the thermal or serum stability. Inclusion of an integrin-binding RGD motif in either or both of the turn regions demonstrated that a desired bioactivity can be imparted to the cyclic cystine ladder, and also highlighted the potential for designing dual-functionalised theta-defensin analogues. This study demonstrates that the cyclic cystine ladder of theta-defensins is a versatile scaffold for providing stability and conformational restriction to bioactive epitopes in a beta-strand or hairpin conformation and has the potential to be applied as a scaffold for targeting protein-protein interactions involved in a variety of diseases.