Naturally occurring peptides offer great potential as leads for drug design, and molecules derived from marine organisms are a particularly rich source for drug treasure hunters1,2. More than 50% of the FDA-approved drugs during the 1980s and the 1990s were derived from marine life. Most of these marine pharmaceutical drugs originated from marine invertebrates, including sponges, tunicates, mollusks, and bryozoans. Eight out of ten marine-derived drugs approved for cancer treatment came from marine invertebrates. Our work focuses on disulfide-rich peptides from plants and animals, including conotoxins3,4 from marine cone snails. We also work on a class of plant-derived cyclic peptides known as cyclotides5, which are topologically unique in that they have a head-to-tail cyclised peptide backbone and a cystine knotted arrangement of disulfide bonds. This makes cyclotides exceptionally stable to heat or enzymatic treatments and, indeed, they are amongst nature’s most stable proteins. Their stability and compact structure favours them as attractive protein frameworks onto which bioactive peptide epitopes can be grafted to stabilise them. This presentation will describe our efforts to improve the drug-like properties of marine conotoxins by re-engineering them to adopt some of the biophysical properties of cyclotides.