Adriamycin(hydrazone)-antibody conjugates require internalization and intracellular acid hydrolysis for antitumor activity

Cancer Immunol Immunother. 1991;33(6):367-74. doi: 10.1007/BF01741596.


Adriamycin hydrazone (ADM-Hzn) immunoconjugates have previously been shown to exhibit antibody-directed antitumor activity in vitro and in vivo. In this report, the biological and biochemical properties of the mAb and linker were investigated. Conjugates prepared with two antibodies 5E9 [anti-(transferrin receptor)] and G28.1 (anti-CD37), (which internalize from the surface of target cells following binding) were more cytotoxic in vitro and had greater antitumor activity against Daudi B lymphoma tumor xenografts than a non-internalizing immunoconjugate prepared with mAb 2H7 (anti-CD20). In addition, the 13-acylhydrazone bond linking the drug to the mAb was labile at pH 5 and released unmodified ADM at a rapid rate (t1/2 = 2.5 h). Immunoconjugates prepared with an oxime linkage at the C-13 position were stable to acid and were not cytotoxic. These findings suggest that internalization of ADM-Hzn immunoconjugates and release of free ADM from the mAb in acidic intracellular compartments were important steps in the mechanism of action of ADM-Hzn immunoconjugates.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / metabolism*
  • Antibodies, Monoclonal / pharmacology*
  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / metabolism*
  • Chromatography, High Pressure Liquid
  • Doxorubicin / chemistry
  • Doxorubicin / metabolism*
  • Doxorubicin / pharmacology*
  • Fluorescent Antibody Technique
  • Hydrolysis
  • Immunotoxins / metabolism*
  • Immunotoxins / pharmacology*
  • Iodine Radioisotopes
  • Lymphoma / metabolism*
  • Mice
  • Mice, Inbred BALB C
  • Mice, Nude
  • Molecular Structure
  • Neoplasm Transplantation
  • Tumor Cells, Cultured / drug effects
  • Tumor Stem Cell Assay


  • Antibodies, Monoclonal
  • Antineoplastic Agents
  • Immunotoxins
  • Iodine Radioisotopes
  • Doxorubicin