Testing of the topoisomerase 1 inhibitor Genz-644282 by the pediatric preclinical testing program

Pediatr Blood Cancer. 2012 Feb;58(2):200-9. doi: 10.1002/pbc.23016. Epub 2011 May 5.


Background: Genz-644282 is a novel non-camptothecin topoisomerase I poison that is in clinical development.

Procedures: Genz-644282 was tested against the PPTP in vitro panel (0.1 nM to 1 µM), and in vivo using three times per week × 2 schedule repeated at day 21 at its maximum tolerated dose (MTD) of 4 mg/kg. Subsequently Genz-644282 was tested at 4, 3, 2, and 1 mg/kg in 3 models to assess the dose-response relationship. mRNA gene signatures predictive for Genz-644282 response in vitro were applied to select 15 tumor models that were evaluated prospectively.

Results: In vitro, Genz-644282 demonstrated potent cytotoxic activity with a median IC(50) of 1.2 nM (range 0.2-21.9 nM). In vivo, Genz-644282 at its MTD (4 mg/kg) induced maintained complete responses (MCR) in 6/6 evaluable solid tumor models. At 2 mg/kg Genz-644282 induced CR or MCR in 3/3 tumor models relatively insensitive to topotecan, but there were no objective responses at 1 mg/kg. Further testing at 2 mg/kg showed that Genz-644282 induced objective regressions in 7 of 17 (41%) models. There was a significant correlation between predictive response scores based on Affymetrix U133Plus2 baseline tumor expression profiles and the observed in vivo responses to Genz-644282.

Conclusions: Genz-644282 was highly active within a narrow dose range (2-4 mg/kg), typical of other topoisomerase I poisons. As with other topoisomerase I poisons, how accurately these data will translate to clinical activity will depend upon the drug exposures that can be achieved in children treated with this agent.

Publication types

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

MeSH terms

  • Animals
  • Cell Proliferation / drug effects*
  • Child
  • DNA Topoisomerases, Type I / chemistry*
  • DNA Topoisomerases, Type I / metabolism
  • Disease-Free Survival
  • Drug Evaluation, Preclinical
  • Drug Resistance, Neoplasm
  • Female
  • Gene Expression Profiling
  • Humans
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred NOD
  • Mice, SCID
  • Naphthyridines / therapeutic use*
  • Neoplasms, Experimental / drug therapy*
  • Neoplasms, Experimental / enzymology
  • Neoplasms, Experimental / mortality
  • Survival Rate
  • Topoisomerase I Inhibitors / therapeutic use*
  • Topotecan / therapeutic use
  • Tumor Burden
  • Tumor Cells, Cultured
  • Xenograft Model Antitumor Assays


  • Genz-644282
  • Naphthyridines
  • Topoisomerase I Inhibitors
  • Topotecan
  • DNA Topoisomerases, Type I
  • TOP1 protein, human