Bispecific small molecule-antibody conjugate targeting prostate cancer

Proc Natl Acad Sci U S A. 2013 Oct 29;110(44):17796-801. doi: 10.1073/pnas.1316026110. Epub 2013 Oct 14.


Bispecific antibodies, which simultaneously target CD3 on T cells and tumor-associated antigens to recruit cytotoxic T cells to cancer cells, are a promising new approach to the treatment of hormone-refractory prostate cancer. Here we report a site-specific, semisynthetic method for the production of bispecific antibody-like therapeutics in which a derivative of the prostate-specific membrane antigen-binding small molecule DUPA was selectively conjugated to a mutant αCD3 Fab containing the unnatural amino acid, p-acetylphenylalanine, at a defined site. Homogeneous conjugates were generated in excellent yields and had good solubility. The efficacy of the conjugate was optimized by modifying the linker structure, relative binding orientation, and stoichiometry of the ligand. The optimized conjugate showed potent and selective in vitro activity (EC50 ~ 100 pM), good serum half-life, and potent in vivo activity in prophylactic and treatment xenograft mouse models. This semisynthetic approach is likely to be applicable to the generation of additional bispecific agents using drug-like ligands selective for other cell-surface receptors.

Keywords: antibody engineering; immunotherapy.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • CD3 Complex / immunology
  • Drug Discovery / methods*
  • Heterografts / immunology
  • Humans
  • Immunoglobulin Fab Fragments / immunology
  • Immunoglobulin Fab Fragments / therapeutic use*
  • Immunotherapy / methods
  • Leukocytes, Mononuclear
  • Male
  • Mice
  • Prostatic Neoplasms / drug therapy*
  • Prostatic Neoplasms / immunology
  • Protein Engineering


  • CD3 Complex
  • Immunoglobulin Fab Fragments