Biomedical subjects
C Monneret
Publications and source records attributed to C Monneret.
Targeting of acivicin prodrugs as antibody conjugates.
The ectopeptidase gamma-glutamyltranspeptidase (gamma-GT) is overexpressed in myeloid leukemias. Its specific inhibitor, acivicin, was previously shown to induce an inhibitory growth effect associated with an induction of morphological features characteristic of macrophage maturation. We have considered a construction in which an antibody linked to a prodrug of acivicin will target acivicin to tumoral cells. In a first set of experiments we have synthesized a chromogenic model of this prodrug to validate this concept of prodrug, allowing an amine function to be released upon esterase action. Thereafter this model was applied to acivicin. The acivicin prodrug is inactive toward purified gamma-GT, and recovers its inhibitory activity under the effect of esterase.
2-Nitro and 4-nitro-quinone-methides are not irreversible inhibitors of bovine beta-glucuronidase.
4-Benzylamino-(and 4-chloromethyl)-2-nitro-beta-D-glucuronides (4, 10) and their 2-substituted-4-nitro regioisomers (7, 13) were prepared by glycosidation of the 3-nitro-4-hydroxy- and the 2-hydroxy-5-nitro-benzylic alcohol, respectively, with a glucuronyl donor. Carbonate activation followed by reaction with benzylamine or methanesulfonyl chloride afforded, after complete deprotection, the target molecules 4, 7, 10 and 13. These compounds have been synthesized to determine whether these molecules are (or not) glucuronidase inhibitors. After incubation with bovine liver beta-glucuronidase, none of the cleavage products (the titled quinone-methides) showed to be irreversible inhibitors of this enzyme.
Recent developments in the field of antitumour anthracyclines.
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A new acivicin prodrug designed for tumor-targeted delivery.
Acivicin is an antitumor agent known to inhibit cell growth. A new prodrug 9b of acivicin 10 was synthesized, based on a p-hydroxybenzylcarbamate self-immolative spacer capable to release acivicin under esterase activity. The prodrug includes a maleimide-containing arm for linkage with thiol-containing macromolecules such as antibodies. This molecule is intended for the conception of bioconjugates to target an inactive acivicin precursor to tumor cells, when linked to a monoclonal antibody (mAb) which recognizes a tumor-specific antigen. Prodrug cleavage by plasmatic esterases will then restore the acivicin's activity toward tumor cells. We report here the synthesis and the in vitro characteristics of the prodrug. As expected, its inhibitory activity against the gamma-glutamyl transpeptidase (gamma-GT) enzyme and its cytotoxicity towards HL-60 cells were highly reduced compared to the parent drug. The chemical and plasmatic hydrolysis kinetics of the compound was studied by HPLC. The prodrug is stable, being slowly hydrolyzed in pH 7.6 buffer at 37 degrees C with a half-life of 37 h. It is converted into an active acivicin under the effect of pig liver esterase, and its half-life in human plasma is 3 h. These results indicate this compound may be further used as a prodrug-antibody conjugate, to target acivicin to malignant cells.
Synthesis and evaluation of "AZT-HEPT", "AZT-pyridinone", and "ddC-HEPT" conjugates as inhibitors of HIV reverse transcriptase.
To test the concept that HIV reverse transcriptase could be effectively inhibited by "mixed site inhibitors", a series of seven conjugates containing both a nucleoside analogue component (AZT 1, ddC 2) and a nonnucleoside type inhibitor (HEPT analogue 12, pyridinone 27) were synthesized and evaluated for their ability to block HIV replication. The (N-3 and C-5)AZT-HEPT conjugates 15, 22, and 23 displayed 2-5 microM anti-HIV activity, but they had no effect on the replication of HIV-2 or the HIV-1 strain with the Y181C mutation. The (C-5)AZT-pyridinone conjugates 34-37 were found to be inactive. In marked contrast, the ddC-HEPT molecule 26 displayed the same potency (EC(50) = 0.45 microM) against HIV-1 (wild type and the Y181C nevirapine-resistant strain) and HIV-2 in cell culture. No synergistic effect was observed for these bis-substrate inhibitors, suggesting that the two individual inhibitor components in these molecules do not bind simultaneously in their respective sites. Interestingly, however, the results indicate that the AZT-HEPT conjugates and the ddC-HEPT derivative 26 inhibit reverse transcriptase (RT) in an opposite manner. One explanation for this difference is that the former compounds interact preferentially with the hydrophobic pocket in RT, whereas 26 (after supposed triphosphorylation) inhibits RT through binding in the catalytic site.
Direct in vivo observation of 5-fluorouracil release from a prodrug in human tumors heterotransplanted in nude mice: a magnetic resonance study.
A glucuro-conjugated carbamate derivative of 5-fluorouracil (5-FU), originally designed as a prodrug for antibody-directed enzyme prodrug therapy (ADEPT) application, has been used for direct in vivo observation of in situ 5-FU generation in two human colon tumors heterotransplanted in nude mice. Because of the very fast elimination of glucuro-conjugated drugs, this observation required intratumoral injection. These tumors, when becoming necrotic, are rich enough in beta-glucuronidase to allow (19)F magnetic resonance spectroscopy monitoring, at the tumor level, of both prodrug elimination and 5-FU liberation without preliminary treatment by a specifically targeted enzyme conjugate. Convenient tumors have been selected by magnetic resonance imaging (MRI) on the basis of a correlative study between MRI and conventional histology. This contribution is the first report evidencing such a direct intra-tumoral conversion of a glucuro-conjugated prodrug into the expected active drug. This method, which should allow overall estimation of the beta-glucuronidase content of tumors, might also be helpful for selecting tumors as specific targets for non-toxic glucuro-conjugated prodrugs without prior treatment with a fusion protein.
Synthesis and antitumour activity of a new series of nitrosoureido sugars.
New nitrosoureido derivatives of di- or tri-deoxy-sugars have been synthesized. Very potent antitumour activity against L1210 leukaemia was exhibited by the compounds derived from methyl 3-amino-3, 4-dideoxy-beta- and alpha- and 4-amino-2,4-dideoxy-beta- and alpha-D-arabino-hexopyranosides, 24, 26, 28 and 29, respectively. In further evaluation against B16 melanocarcinoma bearing mice, only compounds 24 and 26 displayed significant activity. Owing to its lower acute toxicity, methyl 3-[3-(2-chloroethyl)-3-nitrosoureido]-3, 4-dideoxy-beta-D-arabino-hexopyranoside 24 appeared as the best candidate for preclinical studies.
[Targeting of antitumor drugs with monoclonal antibodies].
About forty years ago, immuno-targeting of antitumor drugs has been addressed as a way to improve their selectivity towards tumor cells. Despite the wide display of researches to solve inherent problems within this approach, rare were the immuno-conjugates which reached the clinical level. In any case, none of them was introduced in chemotherapy. However, there was a renewal of activity for the last ten years, due, in part, to the access to very highly cytotoxic-containing immuno-conjugates such as those elaborated from maytansinoides, enediynes or intercalating agents CC1065. It was also due to the design of the Adept concept. This antibody-directed enzyme prodrug therapy is based upon the use of monoclonal antibody to target an enzyme at the tumor cell surface which ultimately is expected to selectively deliver an antitumor drug from a suitable inactive prodrug. In both cases, clinical trials are in progress and one can expect that, at least, some immuno-conjugates will be soon introduced in cancer chemotherapy.
Design of two etoposide-amsacrine conjugates: topoisomerase II and tubuline polymerization inhibition and relation to cytotoxicity.
Topoisomerase II represents the main target for the antitumour drugs etoposide and amsacrine, which are both used clinically. Previous studies have shown that the glycoside moiety of etoposide is not necessary for cytotoxicity or DNA topoisomerase II inhibition. For this reason, we designed two epipodophyllotoxin derivatives for which the dispensable sugar moiety of etoposide has been replaced by a m-methoxy-methane-sulfonamide-anilino group analogous to the topoisomerase II-targeted domain of amsacrine. We report the synthesis of the hybrid molecules that have the epipodophyllotoxin and anilino groups directly linked (ICP-114) or connected by an ethylene spacer (ICP-147). Plasmid DNA relaxation and kinetoplast DNA decatenation assays were used to evaluate the effects of the drug on the catalytic activity of human topoisomerase II. We found that the hybrid ICP-147 was significantly more potent than both etoposide and amsacrine at stimulating DNA cleavage by the enzyme, whereas the hybrid ICP-114 lacking the linker chain was less potent. ICP-147 produces approximately 3 times more double-stranded breaks than ICP-114, suggesting that an ethylene spacer between the epipodophyllotoxin and amsacrine moieties is highly effective at inhibiting topoisomerase II. Sequencing data also supported the idea that the two moieties of ICP-147 participate to the interaction with topoisomerase II-DNA covalent complexes. Both hybrid compounds are more cytotoxic than etoposide but much less toxic than amsacrine toward L1210 leukemia cells. In addition to its effect on topoisomerase II, ICP-114 can inhibit tubulin polymerization, whereas ICP-147 is almost totally inactive in this assay. The unexpected capacity of ICP-114 to interfere with the polymerization of tubulin suggests that this compound can target tubulin dimers, as it is the case with certain antitumor sulfonamides. The design of etoposide-amsacrine hybrids may thus represent an opportunity for the discovery of dual inhibitors that target both topoisomerase II and tubulin.
Efficient synthesis of N-4 alkyl derivatives of 2',3'-dideoxycytidine (ddC).
The C-4 triisopropylphenylsulfonyl (TPS) group of the 2,3-dideoxyuridine derivative 2 is readily displaced in situ by nitrogen nucleophiles forming N-4 substituted ddC in acceptable yields.
Synthesis and biological evaluation of 5-arylfuro[2,3-d]pyrimidines as novel dihydrofolate reductase inhibitors.
A series of about fifty novel 5-arylfuro[2,3-d]pyrimidine derivatives were synthesized as potential inhibitors of dihydrofolate reductase (DHFR) arising from different species. Weak enzyme inhibition was observed for most of the compounds, with only a few reaching IC50 values less than 30 microM. With regards to antibacterial and anti-malarial potency, only seven compounds showed a modest in vitro activity against some bacteria strains and only three products proved significantly active against P. falciparum.
Application of the ADEPT strategy to the MDR resistance in cancer chemotherapy.
New prodrugs consisting of a beta-D-glucuronic acid linked to a MDR reversal agent (verapamil, quinine or dipyridamole) through a self-immolative spacer were synthesized. Four of them were selected for their reduced cytoxicity and beta-glucuronidase enzymatic efficient hydrolysis. Combined use of these prodrugs with a beta-D-glucuronyl-spacer-doxorubicin (HMR1826) according to an ADEPT strategy restored in vitro the sensibility of a MDR resistant strain.
[Glycochemistry: biological implications and therapeutic applications. Convened October 21, 1998 by the National Academy of Pharmacy].
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Synthesis and antitumor activity of new glycosides of epipodophyllotoxin, analogues of etoposide, and NK 611.
A series of 3-amino- and 3-alkylamino-2-deoxy-beta-D-ribo- and beta-D-arabino-glycosides of 4'-demethylepipodophyllotoxin have been synthesized by means of an improved trimethylsilyliodide procedure for the podophyllotoxin-4'-demethylepipodophyllotoxin conversion, an efficient and high yielding synthesis of silyl glycoside donors of 3-azido-2,3-dideoxy-beta-D-ribo- and beta-D-arabino-hexopyranosides and stereoselective glycosylations. In vitro evaluation of cytotoxic effects against murine L1210 leukemia critically demonstrates the essential role played by a 4,6-acetal for biological activity. Among the most cytotoxic compounds, 3-amino-2,3-dideoxy- and 3-N, N-(dimethylamino)-2,3-dideoxy etoposide analogues, 17 and 27-29 are at least as potent as etoposide on the in vivo P388 (iv/ip) murine leukemia models. However, surprisingly enough, none of these compounds inhibits the human DNA topoisomerases I or II or binds to tubulin to prevent its polymerization and microtubule assembly. Therefore, their mechanism of action remains to be cleared up.
Prodrugs of anthracyclines for use in antibody-directed enzyme prodrug therapy.
A series of new prodrugs of daunorubicin and doxorubicin which are candidates for antibody-directed enzyme prodrug therapy (ADEPT) is reported. These compounds (25a,b,c and 32a,b,c) have been designed to generate cytotoxic drugs after activation with beta-glucuronidase. As expected, recovery of the active drug was observed after enzymatic cleavage by Escherichia coli beta-glucuronidase as well as by a fusion protein which has been obtained from human beta-glucuronidase and humanized CEA-specific binding region. The six prodrugs are highly stable and are more than 100-fold less cytotoxic than doxorubicin against murine L1210 cell lines. The ortho-substituted phenyl carbamates 25a,b,c are better substrates for beta-glucuronidase than the corresponding para-substituted analogues. After taking into account additional factors such as stability in plasma and kinetics of enzymatic cleavage, we selected the o-nitro prodrug 25c for clinical trials.
Elucidation of the mechanism enabling tumor selective prodrug monotherapy.
Elucidation of the mechanism enabling tumor selective PMT in vivo with appropriate glucuronyl-spacer-doxorubicin prodrugs, such as HMR 1826, is important for the design of clinical studies, as well as for the development of more selective drugs. Enzyme histochemistry, immunohistochemistry, and the terminal deoxytransferase technique were applied using human cryopreserved cancer tissues, normal human, monkey, and mouse tissues, and human tumor xenografts to examine mechanisms underlying the selectivity of successful PMT with HMR 1826. It could unambiguously be shown by enzyme histochemistry that necrotic areas in human cancers are the sites in which lysosomal beta-glucuronidase is liberated extracellularly in high local concentrations. The cells responsible for the liberation of the enzyme are mainly acute and chronic inflammatory cells, as shown by IHC. Furthermore, it could be demonstrated that beta-glucuronidase liberated in necrotic areas of tumors can activate HMR 1826, resulting in increased doxorubicin deposition in human tumor xenografts or in human lung cancers subjected to extracorporal perfusion, compared to chemotherapy with doxorubicin. Additionally, the doxorubicin load to normal tissues was significantly reduced compared to chemotherapy with doxorubicin. Surprisingly, the increased doxorubicin deposition in tumors also resulted in strong antitumor effects also in cancers resistant to maximum tolerated doses of systemic doxorubicin. Finally, toxicity studies in mice and monkeys revealed an excellent tolerability of HMR 1826, up to a dose of 3 g/m2 (monkeys). These data suggest that HMR 1826 is a promising candidate for clinical development.
A new anthracycline with potent anti-leukemic activity overcomes P-glycoprotein multidrug resistance.
In this study, we assessed the ability of a new anthracycline, moflomycin, to circumvent multidrug resistance. Moflomycin showed superior anti-proliferative activity compared to daunorubicin and doxorubicin on two resistant cell lines: leukemic HL-60 cell line resistant to daunorubicin (HL-60/DR) and breast cancerous cell line resistant to doxorubicin (MCF-7/AR). The effect of moflomycin on cell proliferation was correlated with an increased uptake and a decreased cellular efflux. The data obtained in the presence of the P-gp inhibitor, verapamil, confirmed the absence of interaction between P-gp and moflomycin. Our results indicate that moflomycin exhibits an important reduction in cross-resistance with daunorubicin and doxorubicin resulting from its ability to circumvent P-gp.