Background <p>A chemometric approach using amino acid descriptors was employed to evaluate the effect of various mutations on the aggregation propensity of human calcitonin (hCt), an approved peptide therapeutic.</p> Findings <p>Models based on well-established amino acid descriptors, like z-scores and F scores, explained nearly all of the variance in aggregation propensity. The likelihood of a mutant to aggregate was found to depend largely on hydrophobicity of key residues, although interactions between aromatic residues are also important. Residues within the central core of the peptide were influential, along with specific sites in the C-terminal region. Meanwhile, electrostatic interactions play only a minor role in governing hCt aggregation.</p> Conclusions <p>In contrast to previous studies, Phe19 and Tyr12 were found not to have a significant impact on aggregation propensity, whereas Phe16 and Phe22 exerted a somewhat larger effect. The importance of specific C-terminal residues on aggregation propensity of hCt has now been delineated. These findings are relevant to the manufacturing and handling of hCt and are also of importance to its clinical utilization. This work could also guide the potential development of new biobetters of human calcitonin.</p> Graphical Abstract <p></p>