Modifications on palindromic peptide LfcinB (21-25)Pal RWQWRWQWR to improve its colon cancer cytotoxic effect

Anticancer peptides are considered alternatives in cancer treatment, due to their potency, selectivity, and low toxicity. The peptide LfcinB (21-25)_Pal has previously shown in vitro anticancer effect against Caco-2 colon cancer cell line (IC₅₀:86µM). In this work, we developed some modifications to the peptide sequence to increase its anticancer activity by means of N-terminal amino hexanoic (Ahx) inclusion, biotinylation, acetylation, and sequential Arg/Orn Changes. The molecules were synthesized by manual Solid Phase Peptide Synthesis (SPPS) and the synthetic feasibility (SAScore) ranged between 6.2 and 7.6, obtaining chromatographic purities higher than 90%. Finding better results on Ahx-RWQWRWQWR, and RWQWRWQW-Orn, as they presented activity against both cell lines Caco-2 and HT-29, and a decrease in the IC₅₀ of about 50% in Caco-2 cells (IC₅₀:40µM) when compared to the parent peptide. Equally, the hemolytic effect was lower for the modified peptides, showing values <10% when evaluated at 200µg/mL. For the best peptides, the toxicity was assessed under the Galleria Mellonella model, finding that the LD₅₀ was >100 mg/Kg, which means its toxicity is classified as moderately toxic or lower. At this same concentration, cisplatin demonstrated a lethality of 90%. The designed anticancer peptides presented good in vitro activity and low toxicity, which makes them molecules of interest for future drug development studies.