Stability in human serum and plasma of the HIV peptide drug candidate CIGB‐210 and improved variants

The peptide CIGB-210 inhibits HIV replication, inducing a rearrangement of vimentin intermediate filaments. The assessment of the in vitro serum and plasma stability of this peptide is important to develop an optimal pharmacological formulation. A half-life of 17.68 ± 0.59 min was calculated for CIGB-210 in human serum by reverse-phase high-performance liquid chromatography (HPLC) and mass spectrometry (MS). Eight metabolites of CIGB-210 were identified with this methodology, all of them lacking the N-terminal moiety. A previously developed CIGB-210 in-house competitive ELISA was used to compare the stability of CIGB-210 derivatives containing either D-amino acids, acetylation at the N-terminus, or both modifications. The half-life of CIGB-210 in serum was five times higher when measured by ELISA than by HPLC/MS, and twice higher in plasma as compared to serum. The substitution of D-asparagine on position 6 doubled the half-life, while D-amino acids on positions 8 and 9 did not improve the stability. The acetylation of the N-terminus resulted in a 24-fold more stable peptide in plasma. The positive effect of N-terminal acetylation on CIGB-210 serum stability was confirmed by the HPLC/MS method, as the half-life of the peptide was not reached after 2 h of incubation, which represents more than a 6.8-fold increase in the half-life with respect to the original peptide.