Chelate oxorhenium to assemble new integrin antagonists.

Assembly of independent chemical modules through oxorhenium coordination by a NS(2)+S chelation motif was applied to the synthesis of RGD (Arg-Gly-Asp) analogs. Modules were assembled through oxorhenium chelation to give a series of 18 metal complexes in good yields and satisfactory purities. Screening of these oxorhenium coordinates as antagonists of integrins αVß3, αIIbß3 and αVß5 led to the identification of 3 bioactive compounds that exhibit submicromolar affinities for the 3 integrins. Preliminary studies showed that the corresponding oxotechnetium complexes are stable in mice plasma and therefore could be proposed for the molecular imaging of pathologies that overexpress integrins αVß3 and αVß5.

Synthesis, in vitro screening and in vivo evaluation of cyclic RGD analogs cyclized through oxorhenium and oxotechnetium coordination.

A library of RGD tripeptide analogs cyclized through oxorhenium coordination by an NS2/S chelation motif was synthesized. Screening towards integrins αVß3, αIIbß3 and αVß5 led to the identification of 6 oxorhenium complexes that bind to integrin αVß3 in the submicromolar range. In vivo evaluation of five of the corresponding oxotechnetium complexes using nude mice bearing a U87MG human tumor xenograft showed a significant and specific accumulation of radioactivity inside the tumor. The best results in vivo were obtained with complexes Tc-16 and Tc-50 that displayed a higher tumor accumulation and a lower distribution in other tissues relative to a reference cyclopentapeptide tracer.

Oxorhenium-mediated assembly of noncyclic selective integrin antagonists: a combinatorial approach.

The parallel oxorhenium-mediated assembly of 288 noncyclic RGD analogues is reported. All complexes contain a NS(2) +S chelating motif that enables the unambiguous coordination of the oxorhenium and oxotechnetium cores. In this study, "modules S" contain a variety of pending guanidinium groups whereas the "NS(2) modules" are made of a series of N-acylated amino acids. Combination of sets of "NS(2) " and "S modules" together with tetrabutylammonium tetrachlorooxorhenate gave the corresponding oxorhenium complexes in good yields and satisfactory purities. Evaluation of these metalloconstructs towards integrins α(V) ß(3) , α(IIb) ß(3) , and α(V) ß(5) led to the identification of micromolar and submicromolar antagonists of theses integrins. These compounds exhibit interesting selectivities and promise attractive applications for the molecular imaging of integrin-dependent pathologies.

Synthesis and biochemical evaluation of a cyclic RGD oxorhenium complex as new ligand of alphaVbeta3 integrin.

We report the design of a new ligand of integrins that might be used for the molecular imaging of tumor neoangiogenesis. For this purpose, we designed a modified RGD tripeptide bearing a N-terminal N-bis(thioethyl)glycinate (NS(2)) motif and a thioethyl moiety at the C-terminus. Simultaneous coordination of an oxorhenium core by the NS(2) and thioethyl moieties led to peptide cyclization and gave the corresponding monomers 13a and b (major isomer) resulting from the syn/anti-isomerism, along with dimers' species 16a and b. Cyclometallated peptide 13b showed the most promising activity with an IC(50) of 86 nM for integrin alpha(V)beta(3) whereas it binds integrin alpha(IIb)beta(3) with an affinity lower by an order of magnitude. Labeling with [(99m)Tc]oxotechnetium gluconate led exclusively to complex 17, the equivalent of compound 13b, which displayed satisfactory stabilities in mice plasma and towards glutathione.

Interplay between DNA N-glycosylases/AP lyases at multiply damaged sites and biological consequences.

Evidence has emerged that repair of clustered DNA lesions may be compromised, possibly leading to the formation of double-strand breaks (DSB) and, thus, to deleterious events. The first repair event occurring at a multiply damaged site (MDS) is of major importance and will largely contribute to the hazardousness of MDS. Here, using protein extracts from wild type or hOGG1-overexpressing Chinese hamster ovary cells, we investigated the initial incision rate at base damage and the formation of repair intermediates in various complex MDS. These MDS comprise a 1 nt gap and 3-4 base damage, including 8-oxoguanine (oG) and 5-hydroxyuracil (hU). We report a hierarchy in base excision that mainly depends on the nature and the distribution of the damage. We also show that excision at both oG and hU, and consequently DSB formation, can be modulated by hOGG1 overexpression. Anyhow, for all the MDS analyzed, DSB formation is limited, due to impaired base excision. Interestingly, repair intermediates contain a short single-stranded region carrying a potentially mutagenic base damage. This in vitro study provides new insight into the processing of MDS and suggests that repair intermediates resulting from the processing of such MDS are rather mutagenic than toxic.