RESUMEN
Catalytic poly(ADP-ribose) production by PARP1 is allosterically activated through interaction with DNA breaks, and PARP inhibitor compounds have the potential to influence PARP1 allostery in addition to preventing catalytic activity. Using the benzimidazole-4-carboxamide pharmacophore present in the first generation PARP1 inhibitor veliparib, a series of 11 derivatives was designed, synthesized, and evaluated as allosteric PARP1 inhibitors, with the premise that bulky substituents would engage the regulatory helical domain (HD) and thereby promote PARP1 retention on DNA breaks. We found that core scaffold modifications could indeed increase PARP1 affinity for DNA; however, the bulk of the modification alone was insufficient to trigger PARP1 allosteric retention on DNA breaks. Rather, compounds eliciting PARP1 retention on DNA breaks were found to be rigidly held in a position that interferes with a specific region of the HD domain, a region that is not targeted by current clinical PARP inhibitors. Collectively, these compounds highlight a unique way to trigger PARP1 retention on DNA breaks and open a path to unveil the pharmacological benefits of such inhibitors with novel properties.
Asunto(s)
Antineoplásicos , Inhibidores de Poli(ADP-Ribosa) Polimerasas , Inhibidores de Poli(ADP-Ribosa) Polimerasas/farmacología , Poli(ADP-Ribosa) Polimerasas/metabolismo , Poli(ADP-Ribosa) Polimerasa-1/metabolismo , Bencimidazoles/farmacología , Reparación del ADN , Roturas del ADN , Daño del ADNRESUMEN
INTRODUCTION: Discovery of small molecules that impede the activity of single-strand DNA repair enzyme, PARP1, has led to four marketed drugs for the treatment of advanced-stage cancers. Hence, there is a renewed enthusiasm in the PARP inhibitor discovery arena. To reduce nonspecific interactions or potential toxicities, and to understand the role of other minimally explored PARP enzymes, exciting new findings have emerged toward the development of selective inhibitors and targeted chemical biology probes. Importantly, the conventional PARP inhibitor design has evolved in a way that could potentially lead to multienzyme-targeting - a polypharmacological approach against aggressive cancers. AREAS COVERED: This review comprises recent progress made in the development of PARP inhibitors, primarily focused on human cancers. Discovery of novel PARP inhibitors with pan, selective, and multi-target inhibition using in vitro and in vivo cancer models is summarized and critically evaluated. Emphasis is given to patents published during 2016-2020, excluding TNKS 1/2 inhibitors. EXPERT OPINION: The outstanding success demonstrated by the FDA approved PARP inhibitors has fueled further clinical evaluations for expansion of their clinical utilities. The current clinical investigations include new candidates as well as marketed PARP-targeted drugs, both as single agents and in combination with other chemotherapeutics. Recent advances have also unveiled critical roles of other PARPs in oncogenic signal transduction, in addition to those of the well-documented PARP1/2 and TNKS1/2 enzymes. Further studies on lesser-known PARP members are urgently needed for functional annotations and for understanding their roles in cancer progression and other human diseases.
Asunto(s)
Antineoplásicos/farmacología , Neoplasias/tratamiento farmacológico , Inhibidores de Poli(ADP-Ribosa) Polimerasas/farmacología , Animales , Diseño de Fármacos , Desarrollo de Medicamentos , Descubrimiento de Drogas , Humanos , Neoplasias/patología , Patentes como Asunto , Poli(ADP-Ribosa) Polimerasa-1/antagonistas & inhibidoresRESUMEN
Poly(ADP-ribose) polymerase 1 (PARP1), a widely explored anticancer drug target, plays an important role in single-strand DNA break repair processes. High-throughput virtual screening (HTVS) of a Maybridge small molecule library using the PARP1-benzimidazole-4-carboxamide co-crystal structure and pharmacophore model led to the identification of eleven compounds. These compounds were evaluated using recombinant PARP1 enzyme assay that resulted in the acquisition of three PARP1 inhibitors: 3 (IC50 = 12 µM), 4 (IC50 = 5.8 µM), and 10 (IC50 = 0.88 µM). Compound 4 (2,3-dihydro-1,4-benzodioxine-5-carboxamide) was selected as a lead and was subjected to further chemical modifications, involving analogue synthesis and scaffold hopping. These efforts led to the identification of (Z)-2-(4-hydroxybenzylidene)-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-8-carboxamide (49, IC50 = 0.082 µM) as the most potent inhibitor of PARP1 from the series.
Asunto(s)
Dioxinas/síntesis química , Dioxinas/uso terapéutico , Ensayos Analíticos de Alto Rendimiento/métodos , Inhibidores de Poli(ADP-Ribosa) Polimerasas/síntesis química , Inhibidores de Poli(ADP-Ribosa) Polimerasas/uso terapéutico , Dioxinas/farmacología , Humanos , Simulación del Acoplamiento Molecular , Inhibidores de Poli(ADP-Ribosa) Polimerasas/farmacología , Relación Estructura-ActividadRESUMEN
Clostridium difficile infection (CDI) is the leading cause of healthcare-associated infection in the United States. Therefore, development of novel treatments for CDI is a high priority. Toward this goal, we began in vitro screening of a structurally diverse in-house library of 67 compounds against two pathogenic C. difficile strains (ATCC BAA 1870 and ATCC 43255), which yielded a hit compound, 2-methyl-8-nitroquinazolin-4(3H)-one (2) with moderate potency (MIC = 312/156 µM). Optimization of 2 gave lead compound 6a (2-methyl-7-nitrothieno[3,2-d]pyrimidin-4(3H)-one) with improved potency (MIC = 19/38 µM), selectivity over normal gut microflora, CC50s > 606 µM against mammalian cell lines, and acceptable stability in simulated gastric and intestinal fluid. Further optimization of 6a at C2-, N3-, C4-, and C7-positions resulted in a library of >50 compounds with MICs ranging from 3 to 800 µM against clinical isolates of C. difficile. Compound 8f (MIC = 3/6 µM) was identified as a promising lead for further optimization.
Asunto(s)
Antibacterianos/química , Antibacterianos/farmacología , Clostridioides difficile/efectos de los fármacos , Pirimidinas/química , Pirimidinas/farmacología , Animales , Antibacterianos/toxicidad , Células CACO-2 , Chlorocebus aethiops , Diseño de Fármacos , Humanos , Pruebas de Sensibilidad Microbiana , Modelos Moleculares , Conformación Molecular , Pirimidinas/toxicidad , Estereoisomerismo , Relación Estructura-Actividad , Células VeroRESUMEN
Poly(adenosine 5'-diphosphate-ribose) polymerase (PARP) inhibitors are a class of anticancer drugs that block the catalytic activity of PARP proteins. Optimization of our lead compound 1 (( Z)-2-benzylidene-3-oxo-2,3-dihydrobenzofuran-7-carboxamide; PARP-1 IC50 = 434 nM) led to a tetrazolyl analogue (51, IC50 = 35 nM) with improved inhibition. Isosteric replacement of the tetrazole ring with a carboxyl group (60, IC50 = 68 nM) gave a promising new lead, which was subsequently optimized to obtain analogues with potent PARP-1 IC50 values (4-197 nM). PARP enzyme profiling revealed that the majority of compounds are selective toward PARP-2 with IC50 values comparable to clinical inhibitors. X-ray crystal structures of the key inhibitors bound to PARP-1 illustrated the mode of interaction with analogue appendages extending toward the PARP-1 adenosine-binding pocket. Compound 81, an isoform-selective PARP-1/-2 (IC50 = 30 nM/2 nM) inhibitor, demonstrated selective cytotoxic effect toward breast cancer gene 1 ( BRCA1)-deficient cells compared to isogenic BRCA1-proficient cells.