Discovery of the PARP (poly ADP-ribose polymerase) inhibitor 2-(1-(4,4-difluorocyclohexyl)piperidin-4-yl)-1H-benzo[d]imidazole-4-carboxamide for the treatment of cancer

Poly (ADP-ribose) polymerase (PARP) inhibitors as anticancer agents: An outlook on clinical progress, synthetic strategies, biological activity, and structure-activity relationship

Poly (ADP-ribose) polymerase (PARP) is considered an essential component in case of DNA (Deoxyribonucleic acid) damage, response by sensing DNA damage and engaging DNA repair proteins. Those proteins repair the damaged DNA via an aspect of posttranslational modification, known as poly (ADP-Ribosyl)ation (PARylation). Specifically, PARP inhibitors (PARPi) have shown better results when administered alone in a variety of cancer types with BRCA (Breast Cancer gene) mutation. The clinical therapeutic benefits of PARP inhibitors have been diminished by their cytotoxicity, progression of drug resistance, and limitation of indication, regardless of their tremendous clinical effectiveness. A growing number of PARP-1 inhibitors, particularly those associated with BRCA-1/2 mutations, have been identified as potential cancer treatments. Recently, several researchers have identified various promising scaffolds, which have resulted in the resuscitation of the faith in PARP inhibitors as cancer therapies. This review provided a comprehensive update on the anatomy and physiology of the PARP enzyme, the profile of FDA (Food and Drug Administration) and CFDA (China Food and Drug Administration)-approved drugs, and small-molecule inhibitors of PARP, including their synthetic routes, biological evaluation, selectivity, and structure-activity relationship.

Design, synthesis, and evaluation of 1H-benzo[d]imidazole-4-carboxamide PARP-1 inhibitors using different saturated nitrogen-contained heterocycle as linker group

Poly (ADP-ribose) polymerase-1 (PARP-1) inhibitors have been successfully applied in the clinical treatment of various cancer. Side effects and drug resistant cases were reported, and more effective PARP-1 inhibitors were required. However, studies on the AD site of PARP-1 inhibitors are currently incomplete. Therefore, to synthesize more potential candidate PARP-1 inhibitors and disclose some AD site SAR of the PARP-1 inhibitors, herein, a series of 2-phenyl-benzimidazole-4-carboxamide derivatives using different saturated nitrogen-contained heterocycles as linker group (6a-6t) have been designed, synthesized, and evaluated PARP-1 inhibitory activity and proliferation inhibitory against BRCA-1 mutant MDA-MB-436 cell line in vitro. The results showed 6b (IC50 = 8.65 nM) exhibited the most PARP-1 enzyme inhibitory activity comparable with Veliparib (IC50 = 15.54 nM) and Olaparib (IC50 = 2.77 nM); 6m exhibited the strongest MDA-MB-436 cell anti-proliferation activity (IC50 = 25.36 ± 6.06 μM) comparable with Olaparib (IC50 = 23.89 ± 3.81 μM). The compounds 6b, 6r, and 6m could be potential candidates for effective PARP-1 inhibitors and valuable for further optimization. The analysis of activity data also showed that the holistically anti-proliferation activity of the 1,4-diazepane group was about~twofold than that of the piperazine group. Meanwhile, the terminal 3-methyl-furanyl group exhibited the most robust PARP-1 inhibitory and anti-proliferation activity. It is hoped that the results could benefitable for further optimization of PARP-1 inhibitors. Furthermore, we note that some compounds (6d,6g,6n,6p,6s) showed poor PARP-1 inhibitory (>500 nM) but relatively good anti-proliferation activity, which indicates the proliferation inhibitory mechanism against MDA-MB-436 cell line was worth investigating in-depth.

New Quinoxaline-Based Derivatives as PARP-1 Inhibitors: Design, Synthesis, Antiproliferative, and Computational Studies

Herein, 2,3-dioxo-1,2,3,4-tetrahydroquinoxaline was used as a bio-isosteric scaffold to the phthalazinone motif of the standard drug Olaparib to design and synthesize new derivatives of potential PARP-1 inhibitory activity using the 6-sulfonohydrazide analog 3 as the key intermediate. Although the new compounds represented the PARP-1 suppression impact of IC₅₀ values in the nanomolar range, compounds 8a, 5 were the most promising suppressors, producing IC₅₀ values of 2.31 and 3.05 nM compared to Olaparib with IC₅₀ of 4.40 nM. Compounds 4, 10b, and 11b showed a mild decrease in the potency of the IC₅₀ range of 6.35–8.73 nM. Furthermore, compounds 4, 5, 8a, 10b, and 11b were evaluated as in vitro antiproliferative agents against the mutant BRCA1 (MDA-MB-436, breast cancer) compared to Olaparib as a positive control. Compound 5 exhibited the most significant potency of IC₅₀; 2.57 µM, whereas the IC₅₀ value of Olaparib was 8.90 µM. In addition, the examined derivatives displayed a promising safety profile against the normal WI-38 cell line. Cell cycle, apoptosis, and autophagy analyses were carried out in the MDA-MB-436 cell line for compound 5, which exhibited cell growth arrest at the G2/M phase, in addition to induction of programmed apoptosis and an increase in the autophagic process. Molecular docking of the compounds 4, 5, 8a, 10b, and 11b into the active site of PARP-1 was carried out to determine their modes of interaction. In addition, an in silico ADMET study was performed. The results evidenced that compound 5 could serve as a new framework for discovering new potent anticancer agents targeting the PARP-1 enzyme.

Benzimidazole hybrids as anticancer drugs: An updated review on anticancer properties, structure-activity relationship, and mechanisms of action (2019-2021)

Cancer, characterized by a deregulation of the cell cycle which mainly results in a progressive loss of cellular differentiation and uncontrolled cellular growth, remains a prominent cause of death across the world. Almost all currently available anticancer agents used in clinical practice have developed multidrug resistance, creating an urgent need to develop novel chemotherapeutics. Benzimidazole derivatives could exert anticancer properties through diverse mechanisms, inclusive of the disruption of microtubule polymerization, the induction of apoptosis, cell cycle (G2/M) arrest, antiangiogenesis, and blockage of glucose transport. Moreover, several benzimidazole-based agents have already been approved for the treatment of cancers. Hence, benzimidazole derivatives are useful scaffolds for the development of novel anticancer agents. In particular, benzimidazole hybrids could exert dual or multiple antiproliferative activities and had the potential to overcome drug resistance, demonstrating the potential of benzimidazole hybrids as potential prototypes for clinical deployment in the control and eradication of cancers. The purpose of the present review article is to provide a comprehensive landscape of benzimidazole hybrids as potential anticancer agents, and the structure-activity relationship as well as mechanisms of action are also discussed to facilitate the further rational design of more effective candidates, covering articles published from 2019 to 2021.