Designer peptides: learning from nature.

Recent advances in designing peptide ligands for therapeutic targets are making peptides an attractive alternative to small molecules and proteins. It is now common to see peptides developed with affinities comparable to antibodies and specificities much better than small molecules or antibodies. This is especially true in the case of tumor targeting cytotoxic drugs or targeted diagnostics where peptides can be used as a delivery vehicle for drugs or diagnostics. Moreover, lessons learned from nature in understanding peptide ligands are proving to be useful in designing better antibodies and small molecule therapeutics.