Pilot trial of genetically modified, attenuated Salmonella expressing the E. coli cytosine deaminase gene in refractory cancer patients

Cancer Gene Ther. 2003 Oct;10(10):737-44. doi: 10.1038/sj.cgt.7700634.


We performed a pilot trial in refractory cancer patients to investigate the feasibility of intratumoral injection of TAPET-CD, an attenuated Salmonella bacterium expressing the E. coli cytosine deaminase gene. A total of three patients received three dose levels of TAPET-CD (3 x 10(6)-3 x 10(7) CFU/m(2)) via intratumoral injection once every 28 days as long as progression of disease or intolerable toxicity was not observed. From days 4 to 14 of each 28 day cycle, patients also received 5-fluorocytosine (5-FC) at a dose of 100 mg/kg/day p.o. divided three times daily. Six cycles of treatment were administered. No significant adverse events clearly attributable to TAPET-CD were demonstrated. Two patients had intratumor evidence of bacterial colonization with TAPET-CD, which persisted for at least 15 days after initial injection. Conversion of 5-FC to 5-fluorouracil (5-FU) as a result of cytosine deaminase expression was demonstrated in these two patients. The tumor to plasma ratio of 5-FU for these two colonized patients was 3.0, demonstrating significantly increased levels of 5-FU at the site of TAPET-CD colonization and insignificant systemic spread of the bacteria. In contrast, the tumor to plasma ratio of 5-FU of the patient who did not show colonization of TAPET-CD was less than 1.0. These results support the principle that a Salmonella bacterium can be utilized as a delivery vehicle of the cytosine deaminase gene to malignant tissue and that the delivered gene is functional (i.e. able to convert 5-FC to 5-FU) at doses at or below 3 x 10(7) CFU/m(2).

Publication types

  • Clinical Trial

MeSH terms

  • Aged
  • Aged, 80 and over
  • Cytosine Deaminase / administration & dosage
  • Cytosine Deaminase / analysis
  • Cytosine Deaminase / genetics*
  • Cytosine Deaminase / therapeutic use*
  • Escherichia coli / enzymology
  • Escherichia coli / genetics
  • Female
  • Flucytosine / analysis
  • Flucytosine / blood
  • Flucytosine / metabolism
  • Fluorouracil / analysis
  • Fluorouracil / blood
  • Fluorouracil / metabolism
  • Genetic Therapy / adverse effects
  • Genetic Therapy / methods*
  • Head / pathology
  • Head and Neck Neoplasms / blood
  • Head and Neck Neoplasms / genetics
  • Head and Neck Neoplasms / metabolism
  • Head and Neck Neoplasms / therapy
  • Humans
  • Male
  • Middle Aged
  • Neck / pathology
  • Neoplasms / blood
  • Neoplasms / genetics*
  • Neoplasms / metabolism
  • Neoplasms / therapy*
  • Pilot Projects
  • Salmonella / genetics*
  • Salmonella / physiology


  • Flucytosine
  • Cytosine Deaminase
  • Fluorouracil