Abstract: A process for producing a peptide antigen conjugate suitable for administration to a mammal is disclosed. The peptide antigen conjugate comprises a peptide antigen linked to a hydrophobic block. The process comprises reacting a hydrophobic block fragment with a peptide antigen fragment comprising the peptide antigen in a pharmaceutically acceptable organic solvent in a hydrophobic block fragment to peptide antigen fragment molar ratio of 1:1 or greater under conditions to directly or indirectly link the peptide antigen to the hydrophobic block and obtaining a product solution comprising the peptide antigen conjugate, unreacted hydrophobic block fragment and pharmaceutically acceptable organic solvent.