SYNTHETIC CALCITONIN PEPTIDES

Synthetic hypocalcemic peptides which are similar in biological properties to native calcitonins as clinically useful agents. The peptides comprise analogues of native calcitonins having amino acid substitutions and deletions which act to improve potency, prolong duration of the hormonal effect, enhance receptor binding, and increase oral or nasal bioavailability. The calcitonin peptide analogues are less expensive and more easily synthesized than native calcitonins, and have improved resistance to inactivation or degradation. Methods are provided for the synthesis of these peptides. Also, disclosed are novel cyclic peptides, including calcitonin, having increased stability with respect to proteolysis. Methods for the synthesis of these peptides are provided, comprising converting disulfide cyclic peptides and proteins to enzymatically and chemically stable cyclic peptide structures by the replacement of cysteine residues with dicarboxylic acids and diamino acids. The method is applicable to various naturally occurring peptides, their synthetic analogues or derivatives, and proteins.