Development and validation of a bioanalytical method based on LC–MS/MS analysis for the quantitation of CIGB-814 peptide in plasma from Rheumatoid Arthritis patients

•A Bioanalytical method for a novel CIGB-814 APL was developed and fully validated.•An IS with three 13C615N2-Lys residues was used for peptide quantification by SRM.•The peptide was administered to patients with RA in a phase I clinical trial.•A LLOQ of 1.5ng/mL allowed proper PK parameters estimation.•The rapid clearance of CIGB-814 is very favorable for an immunomodulatory drug.