title: Pilot trial of genetically modified, attenuated Salmonella expressing the E. coli cytosine deaminase gene in refractory cancer patients.
abstract: 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).
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D043525:Cytosine Deaminase / Q000008:administration & dosage / Q000032:analysis / Q000235:genetics* / Q000627:therapeutic use*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005260:Female; D005437:Flucytosine / Q000032:analysis / Q000097:blood / Q000378:metabolism; D005472:Fluorouracil / Q000032:analysis / Q000097:blood / Q000378:metabolism; D015316:Genetic Therapy / Q000009:adverse effects / Q000379:methods*; D006257:Head / Q000473:pathology; D006258:Head and Neck Neoplasms / Q000097:blood / Q000235:genetics / Q000378:metabolism / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000473:pathology; D009369:Neoplasms / Q000097:blood / Q000235:genetics* / Q000378:metabolism / Q000628:therapy*; D010865:Pilot Projects; D012475:Salmonella / Q000235:genetics* / Q000502:physiology
chemical_list: D005437:Flucytosine; D043525:Cytosine Deaminase; D005472:Fluorouracil