Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.31 (beta-glucuronidase)
 7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The anti-pan carcinoma monoclonal antibody (MAb) 323/A3, linked to E. coli-derived beta-glucuronidase (GUS) was used to study the tumour-site-selective activation of the prodrug Epirubicin-glucuronide (Epi-glu). Epi-glu was isolated from the urine of patients treated with Epirubicin (Epi) by reversed phase chromatography on a silica-C18 column. Epi-glu was stable in human blood and was not converted into Epi by A2780, MCF-7, or OVCAR-3 cancer cells, despite the presence of intracellular GUS. The stability of the prodrug was confirmed in BALB/c mice. MAb 323/A3 and GUS were linked through a stable thioether bond. The conjugate (1:1) was purified by ion exchange and gel filtration chromatography. Binding to target cells revealed an immunoreactivity of at least 60% and good retention of enzyme activity. A protein dye (sulforhodamine B) assay was used to analyse cytotoxicity. Epi (IC50 of 0.003-0.2 microM) was 100-1,000 times more toxic than Epi-glu (IC50 of greater than 20 microM), when cancer cells were exposed for 4 or 24 h to the drugs. The low cytotoxicity of Epi-glu was most likely due to the reduced cellular uptake rate of the prodrug (2.7 pmol 10(-6) cells min-1) as compared to that of the parent compound (25 pmol 10(-6) cells min-1). Pretreatment of antigen-positive cells with the 323/A3-GUS conjugate prior to prodrug exposure completely restored cytotoxicity as a result from hydrolysis of Epi-glu into Epi. Our results demonstrate that the 323/A3-GUS conjugate can specifically activate the stable non-toxic prodrug Epi-glu at the tumour cell level.
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PMID:A monoclonal antibody-beta-glucuronidase conjugate as activator of the prodrug epirubicin-glucuronide for specific treatment of cancer. 152 May 85

Antibody-directed enzyme prodrug therapy (ADEPT) aims at the specific activation of a prodrug by an enzyme-immunoconjugate localized in tumor tissue. The use of an enzyme of human origin is preferable in ADEPT because it might not be immunogenic when administered to patients. In the case of human beta-glucuronidase, prodrugs should be designed that are rapidly and completely activated at a neutral pH. Four new daunorubicin glucuronides were synthesized by coupling a glucuronide group to daunorubicin via an aliphatic (GA1 and GB1) or an aromatic (GA3, GB6) carbamate spacer, to be released by electron shift (A-type) or by ring closure (B-type). These prodrugs were characterized in vitro for their usefulness in ADEPT and were compared with the previously described prodrugs epirubicin-glucuronide and doxorubicin-nitrophenyl-glucuronide. The four new prodrugs were stable in serum, hydrophilic when compared to the lipophilic daunorubicin, and at least 20-fold less toxic than the parent compound. The hydrolysis rate at clinically relevant enzyme and prodrug concentrations (1 microgram/mL human beta-glucuronidase, 100 microM prodrug) at pH 6.8 were similar for GA3 (T1/2 160 min) and higher for GB6 (T1/2 40 min) when compared to that of doxorubicin-nitrophenyl-glucuronide (T1/2 170 min). Epirubicin-glucuronide, GA1, and GB1 showed a low hydrolysis rate (T1/2 > 400 min). GA1 and GA3, but not GB1 or GB6, were activated to the parent compound. Complete activation was confirmed in OVCAR-3 cells pretreated with a specific antibody-human beta-glucuronidase conjugate, where GA3 had similar antiproliferative effects to those of daunorubicin.
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PMID:Characterization of novel anthracycline prodrugs activated by human beta-glucuronidase for use in antibody-directed enzyme prodrug therapy. 868