Rational Design of Melittin-Derived Peptides with Reduced Cytotoxicity and Antitumor Activity

Melittin, the main peptide component of bee venom, has antitumor potential, but its high cytotoxicity and low selectivity limit its therapeutic use. To address this, we aimed to develop melittin-derived mutant peptides using in silico approaches to reduce toxicity and investigate changes in molecular interactions. We first replaced the nonpolar residues at positions K21 and K23. Subsequently, additional modifications were introduced at positions P14 and Q25 to evaluate their effects on the physicochemical, structural, and toxicological properties of the peptides. We analyzed hydrophobicity, hydrophobic moment, net charge, theoretical isoelectric point, and predicted cytotoxicity, hemotoxicity, and neurotoxicity. We assessed structural models using Ramachandran plots, and we docked the selected mutant with Na⁺/K⁺-ATPase. The results showed that isolated substitutions at K21 and K23 did not substantially reduce predicted toxicity. However, further modifications reduced the cytotoxic profile of the modified peptides. The K21A-K23L-P14Y-Q25H mutant, designated ALYH, showed predicted cytotoxicity of 17.7%, compared with 99.3% for native melittin, an approximately 82% reduction. Furthermore, the peptide retained a predominantly alpha-helical structure similar to that of the original molecule, and molecular docking revealed a distinct interaction profile between native melittin and the ALYH mutant. While native melittin interacted with the TGES motif of Na⁺/K⁺-ATPase, a region associated with its catalytic activity, and has been reported to inhibit the enzyme, the ALYH mutant showed no predicted interaction with this domain. In conclusion, the molecular engineering of melittin represents a promising strategy for investigating derivatives with lower predicted toxicity. However, experimental in vitro and in vivo assays must confirm preserved antitumor activity and reduced toxicity.