Conjugation of doxorubicin to monoclonal anti-carcinoembryonic antigen antibody via novel thiol-directed cross-linking reagents Original Research Article

In order to improve the available methods to produce an immunoconjugate the use of longer heterobifunctional cross-linking reagents were investigated. Two new maleimidobenzoyl spacers have been synthesized in a one step process from 4-maleimidobenzoic acid. The new heterobifunctional cross-linking reagents were fully characterized by their IR, 1H NMR, 13C NMR and mass spectra. These spacers are selectively attached to NH2-3′ of the daunosamine moiety of doxorubicin. The spacer-doxorubicin derivatives were also characterized by 1H NMR spectrometry before coupling to thiol groups of thiolated anticarcinoembryonic antigen (CEA) monoclonal antibody (11-285-14). These conjugates contain 1.51 – 3.44 molecules of drug for each molecule of monoclonal antibody (MAb).