Development and validation of an HPLC/UV assay for separation and quantification of peptide antigens from a liposomal vaccine delivery platform

The development and validation of an HPLC method for the quantification of eight peptide antigens from the therapeutic cancer vaccine DPX-0907 is described. The antigens were formulated in DepoVax™, a patented liposomal vaccine delivery platform used in a phase 1 study for breast, ovarian, and prostate cancers. A gradient reversed-phase method with UV detection was optimized for separating and quantifying the peptide mixture. Several extraction methods investigated to extract the peptides from the lipids led to poor recovery of one or more of the peptides. A simple, reproducible, and high-recovery extraction procedure for the simultaneous quantification of hydrophilic and hydrophobic peptides was discovered using a liquid–liquid extraction with water–saturated n-butanol and sodium bicarbonate (0.1 M). The method was found to be specific, linear, accurate, precise, and reliable within the range of 50–150% of the nominal concentration for DPX-0907. The validated method was successfully applied to the assay of peptide content in pre-clinical and clinical batches of DPX-0907.