Synthesis and beta-lactamase-mediated activation of a cephalosporin-taxol prodrug

Chem Biol. 1995 Apr;2(4):223-7. doi: 10.1016/1074-5521(95)90272-4.


Background: Enzyme-activatable prodrugs in conjunction with antibody-enzyme fusion proteins may enhance the anti-tumor efficacy of antibodies and reduce the toxic side effects of conventional chemotherapeutics. Cephalosporins have proven to be highly versatile triggers for the enzymatic activation of such prodrugs.

Results: A cephem prodrug of taxol (PROTAX) was synthesized by substituting the C-3' position of cephalothin with 2'-(gamma-aminobutyryl) taxol. Hydrolysis of PROTAX by beta-lactamase rapidly released 2'-(gamma-aminobutyryl) taxol (kcat/K(M) = (1.4 +/- 0.1) x 10(5) s-1 M-1), which yielded taxol following intramolecular displacement. PROTAX is inactive in a microtubule assembly assay in vitro but has similar activity to taxol following prolonged activation with beta-lactamase. PROTAX is approximately 10-fold less toxic than taxol against SK-BR-3 breast tumor cells in vitro but has activity approaching that of taxol following prolonged activation with a fusion protein comprising beta-lactamase fused to a tumor-targeting antibody fragment.

Conclusions: Tubulin polymerization activity is abolished and cytotoxicity is reduced in the PROTAX prodrug compared to taxol. Activation of PROTAX by beta-lactamase followed by self-immolation restores the activity of PROTAX to that of free taxol.

MeSH terms

  • Animals
  • Antineoplastic Agents, Phytogenic / chemical synthesis*
  • Antineoplastic Agents, Phytogenic / chemistry
  • Antineoplastic Agents, Phytogenic / metabolism*
  • Biotransformation
  • Brain Chemistry
  • Breast Neoplasms / metabolism
  • Cattle
  • Humans
  • Hydrolysis
  • Kinetics
  • Microtubules / chemistry
  • Microtubules / metabolism
  • Paclitaxel / analogs & derivatives*
  • Paclitaxel / chemical synthesis*
  • Paclitaxel / chemistry
  • Paclitaxel / metabolism*
  • Prodrugs / chemical synthesis*
  • Prodrugs / chemistry
  • Prodrugs / metabolism*
  • Recombinant Fusion Proteins / chemistry
  • Taxoids*
  • Tumor Cells, Cultured
  • beta-Lactamases / chemistry*


  • Antineoplastic Agents, Phytogenic
  • Prodrugs
  • Recombinant Fusion Proteins
  • Taxoids
  • protax
  • beta-Lactamases
  • Paclitaxel