RESUMEN
Steroids are highly prevalent structures in small-molecule therapeutics, with the level of oxidation being key to their biological activity and physicochemical properties. These C(sp3 )-rich tetracycles contain many stereocentres, which are important for creating specific vectors and protein binding orientations. Therefore, the ability to hydroxylate steroids with a high degree of regio-, chemo- and stereoselectivity is essential for researchers working in this field. This review will cover three main methods for the hydroxylation of steroidal C(sp3 )-H bonds: biocatalysis, metal-catalysed C-H hydroxylation and organic oxidants, such as dioxiranes and oxaziridines.
Asunto(s)
Oxidantes , Esteroides , Hidroxilación , Oxidación-Reducción , Oxidantes/química , Esteroides/metabolismo , BiocatálisisRESUMEN
Hippuristanol is a marine derived steroidal natural product with promising anticancer activity. However, instability at low pH has precluded its development as an efficient therapy. We addressed this limitation by replacing one of the oxygen atoms of the spiroketal moiety with a carbon atom. Key steps in the synthesis include a Meyer-Schuster/Nazarov cascade, a hypoiodite mediated oxyfunctionalization, and the late-stage installation of a hydroxyl group on the C-ring of the steroid.
Asunto(s)
Productos Biológicos , Estructura Molecular , Productos Biológicos/química , Productos Biológicos/síntesis química , Compuestos de Espiro/química , Compuestos de Espiro/síntesis química , Esteroides/química , Esteroides/síntesis química , Antineoplásicos/síntesis química , Antineoplásicos/química , Antineoplásicos/farmacologíaRESUMEN
Human DNA polymerase theta (Polθ), which is essential for microhomology-mediated DNA double strand break repair, has been proposed as an attractive target for the treatment of BRCA deficient and other DNA repair pathway defective cancers. As previously reported, we recently identified the first selective small molecule Polθ in vitro probe, 22 (ART558), which recapitulates the phenotype of Polθ loss, and in vivo probe, 43 (ART812), which is efficacious in a model of PARP inhibitor resistant TNBC in vivo. Here we describe the discovery, biochemical and biophysical characterization of these probes including small molecule ligand co-crystal structures with Polθ. The crystallographic data provides a basis for understanding the unique mechanism of inhibition of these compounds which is dependent on stabilization of a "closed" enzyme conformation. Additionally, the structural biology platform provided a basis for rational optimization based primarily on reduced ligand conformational flexibility.
Asunto(s)
Reparación del ADN por Unión de Extremidades , Inhibidores de Poli(ADP-Ribosa) Polimerasas , Humanos , Ligandos , ADN/metabolismo , ADN Polimerasa thetaRESUMEN
To identify approaches to target DNA repair vulnerabilities in cancer, we discovered nanomolar potent, selective, low molecular weight (MW), allosteric inhibitors of the polymerase function of DNA polymerase Polθ, including ART558. ART558 inhibits the major Polθ-mediated DNA repair process, Theta-Mediated End Joining, without targeting Non-Homologous End Joining. In addition, ART558 elicits DNA damage and synthetic lethality in BRCA1- or BRCA2-mutant tumour cells and enhances the effects of a PARP inhibitor. Genetic perturbation screening revealed that defects in the 53BP1/Shieldin complex, which cause PARP inhibitor resistance, result in in vitro and in vivo sensitivity to small molecule Polθ polymerase inhibitors. Mechanistically, ART558 increases biomarkers of single-stranded DNA and synthetic lethality in 53BP1-defective cells whilst the inhibition of DNA nucleases that promote end-resection reversed these effects, implicating these in the synthetic lethal mechanism-of-action. Taken together, these observations describe a drug class that elicits BRCA-gene synthetic lethality and PARP inhibitor synergy, as well as targeting a biomarker-defined mechanism of PARPi-resistance.