Myristylated Grammistin Pp2a analogs show enhanced anticancer activity and reduced hemolytic toxicity

Antimicrobial peptides (AMPs) and anticancer peptides (ACPs) represent a promising class of therapeutics, particularly those derived from natural sources like venoms, due to their broad-spectrum activity and novel mechanisms. However, a major challenge in developing these peptides is their potential toxicity to host cells, notably hemolytic activity, and often limited solubility or stability. Grammistin Pp2a, a 13-amino acid peptide from the fish Pogonoperca punctata venom, has shown potential, but its therapeutic utility requires modifications to improve its safety profile and enhance specific activities, addressing the critical need for safer and more effective peptide-based drugs.

Researchers synthesized the wild type Grammistin Pp2a and 13 analogs, systematically modifying its sequence. A myristic acid chain was conjugated to the N-terminus of 7 of these peptide analogs to investigate the impact of lipidation. All synthesized peptides were rigorously evaluated for their biological activities using in vitro assays, specifically assessing antibacterial, antifungal, anticancer, and hemolytic activities. The study compared the modified analogs against the natural peptide to identify structural changes that optimize efficacy and reduce toxicity, focusing on how specific amino acid substitutions and fatty acid conjugation influenced these properties.

Most Grammistin Pp2a analogs demonstrated lower hemolytic activity compared to the natural peptide. Crucially, the addition of a myristic acid chain generally reduced the peptide's toxicity, with one exception: MPp2a-O2K, an analog with the highest net positive charge, showed similar hemolytic activity to the natural peptide despite myristylation. However, this fatty chain addition also reduced aqueous solubility. For antifungal activity, peptides Pp2A-EK and MPp2a-EK (both with a net negative charge) and Pp2a-NF (a truncated N-terminus without a fatty chain) were the most effective. Notably, myristylated peptides consistently exhibited significantly greater anticancer activity than their unmodified counterparts. The researchers confirmed that this enhanced anticancer effect was due to the conjugated myristic acid, as simply adding free myristic acid to peptide solutions did not improve their anticancer properties. This indicates a specific synergistic effect of the covalent modification.

Myristylated Grammistin Pp2a analogs showed significantly greater anticancer activity compared to non-myristylated versions, while generally reducing hemolytic toxicity.