biostudies-literatureRodriguez-Alfonso ADeutsche ForschungsgemeinschaftUlm UniversityGerman Research Foundation (DFG)Baden-Württemberg StiftungUniversity of Ulm15029https://www.ebi.ac.uk/biostudies/studies/S-EPMC9735595biostudies-literatureUnknown23(23)Advanced derivatives of the Endogenous Peptide Inhibitor of CXCR4 (EPI-X4) have shown therapeutic efficacy upon topical administration in animal models of asthma and dermatitis. Here, we studied the plasma stability of the EPI-X4 lead compounds WSC02 and JM#21, using mass spectrometry to monitor the chemical integrity of the peptides and a functional fluorescence-based assay to determine peptide function in a CXCR4-antibody competition assay. Although mass spectrometry revealed very rapid disappearance of both peptides in human plasma within seconds, the functional assay revealed a significantly higher half-life of 9 min for EPI-X4 WSC02 and 6 min for EPI-X4 JM#21. Further analyses demonstrated that EPI-X4 WSC02 and EPI-X4 JM#21 interact with low moleculaInternational journal of molecular sciencesAdvanced EPI-X4 Derivatives Covalently Bind Human Serum Albumin Resulting in Prolonged Plasma Stability.PMC9735595EXC 2033 - 390677874 614 - RESOLVCRC1279MU 3115/8-1L.SBN.02093115/11-1436586093EXC 2033—390677874—RESOLVBWST_WSF-025Kuan SLWeil TMunch JRuiz-Blanco YBStandker LWiese SSanchez-Garcia EHeck AGilg AHarms MRodriguez-Alfonso AfalseAdvanced EPI-X4 Derivatives Covalently Bind Human Serum Albumin Resulting in Prolonged Plasma Stability.Advanced derivatives of the Endogenous Peptide Inhibitor of CXCR4 (EPI-X4) have shown therapeutic efficacy upon topical administration in animal models of asthma and dermatitis. Here, we studied the plasma stability of the EPI-X4 lead compounds WSC02 and JM#21, using mass spectrometry to monitor the chemical integrity of the peptides and a functional fluorescence-based assay to determine peptide function in a CXCR4-antibody competition assay. Although mass spectrometry revealed very rapid disappearance of both peptides in human plasma within seconds, the functional assay revealed a significantly higher half-life of 9 min for EPI-X4 WSC02 and 6 min for EPI-X4 JM#21. Further analyses demonstrated that EPI-X4 WSC02 and EPI-X4 JM#21 interact with low molecula2022-01-01T00:00:00Z2022 Nov2026-04-08T11:58:34.924Z2025-04-19T12:16:18.078ZS-EPMC97355953649935710.3390/ijms232315029