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Chemoresistance of cancer cells is a hallmark of treatment failure and the poor patient prognosis. The mechanism of resistance is often connected to the overexpression of specific kinases involved in DNA damage response cascade. Contrary, selected kinase inhibition can augment cancer cell sensitization to conventional therapy, enabling more efficient treatment. Among those kinases, ataxia-telangiectasia and Rad3-related kinase (ATR), the major responder to replication stress, stands out as one of the most attractive targets. Inspired by clinical candidates targeting ATR, we designed and prepared a small, focused library of 40 novel compounds building on 7-azaindoles, 2,7-diazaindoles, and 1H-pyrazoles as core structures. All the compounds alone or combined with cisplatin (CDDP) were screened against a panel of nine cancer cell lines and one healthy cell line. Three highlighted compounds (3, 22, and 29) were selected for broad oncology panel screening containing 104 kinases. Only compound 29, the 2,7-diazaindole representative, showed ATR inhibitory efficacy with the IC

A quickly developing chemoresistance is the hallmark of the standard treatment failure and the poor patient prognosis. Resistance is often connected to the overexpression of the specific kinases that are involved in DNA damage response. Contrary, their inhibition could lead to augmented cancer cell sensitization to conventional approach. Among them, ataxia-telangiectasia and Rad3-related kinase (ATR), the major replication stress responder, is one of the most attractive target. Within this study our aim was to find novel chemosensitizing agents for the cancer treatment employment. Inspired by clinical candidates targeting ATR, we designed and prepared large library of 40 novel compounds utilizing 7-azaindoles, 2,7-diazaindoles, and 1H-pyrazoles as core structures. Initially, our presumption to have ATR inhibitors were confirmed by molecular dynamic study. All the compounds alone or in combination with cisplatin were screened against panel of nine cancer cell lines and one healthy cell line. The results were compared with well-known ATR inhibitor VE-821. Several compounds significantly inhibit the cell viability and some were able to potentiate cisplatin effect. From structure-activity relationship point of view, 7-azaindoles were the most cytotoxic compounds when substituted in position 3 and 5. Contrary, 2,7-diazaindoles expressed the most potent chemosensitizing capabilities. 1H-Pyrazoles were the least potent compounds within this screen. Interestingly, the status of tumor suppressor protein p53 (defect in G1) did not significantly influence chemosensitization or cytotoxic effect. Three highlighted compounds 3, 22, and 29 were selected for Broad oncology panel screening containing 104 kinases which could be potentially targeted. Only compound 29, the 2,7-diazaindole representative, showed ATR inhibitory efficacy with the IC50 around 10 µM. In contrast, the compound 22, 7-azaindole and the most cytotoxic one, expressed the multi-kinase activity with the substantial inhibitory capability against vascular endothelial growth factor receptor 3 protein (VEGFR-3). VEGFR-3 is also very attractive anticancer target with several inhibitors already approved. Finally, several compounds showed chemosensitizing potencies for temozolomide against secondary astrocytoma cell line. In overall, we showed that both, 7-azaindoles, and 2,7-diazaindoles, could be effectively utilized as novel anticancer agents. Whereas 2,7-diazaindoles could become efficient ATR inhibitors, 7-azaindoles have potential as antiangiogenics, VEGFR-3 inhibitors. Besides, both structures could be used for a glioblastoma treatment as temozolomide sensitizers. More research is currently ongoing to fully exploit potential of these compounds. Citation Format: Lukas Gorecki, Darina Muthna, Sara Merdita, Martin Andrs, Tomas Kucera, Tereza Kobrlova, Martina Rezacova, Jan Korabecny. Utilizing 7-azaindoles, 2,7-diazaindoles, and 1H-pyrazoles as core structures for novel cancer chemosensitizers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1411.

RECQ5 belongs to the RecQ family of DNA helicases. It is conserved from Drosophila to humans and its deficiency results in genomic instability and cancer susceptibility in mice. Human RECQ5 is known for its ability to regulate homologous recombination by disrupting RAD51 nucleoprotein filaments. It also binds to RNA polymerase II (RNAPII) and negatively regulates transcript elongation by RNAPII. Here, we summarize recent studies implicating RECQ5 in the prevention and resolution of transcription-replication conflicts, a major intrinsic source of genomic instability during cancer development.

Formation of co-transcriptional R-loops underlies replication fork stalling upon head-on transcription-replication encounters. Here, we demonstrate that RAD51-dependent replication fork reversal induced by R-loops is followed by the restart of semiconservative DNA replication mediated by RECQ1 and RECQ5 helicases, MUS81/EME1 endonuclease, RAD52 strand-annealing factor, the DNA ligase IV (LIG4)/XRCC4 complex, and the non-catalytic subunit of DNA polymerase δ, POLD3. RECQ5 disrupts RAD51 filaments assembled on stalled forks after RECQ1-mediated reverse branch migration, preventing a new round of fork reversal and facilitating fork cleavage by MUS81/EME1. MUS81-dependent DNA breaks accumulate in cells lacking RAD52 or LIG4 upon induction of R-loop formation, suggesting that RAD52 acts in concert with LIG4/XRCC4 to catalyze fork religation, thereby mediating replication restart. The resumption of DNA synthesis after R-loop-associated fork stalling also requires active transcription, the restoration of which depends on MUS81, RAD52, LIG4, and the transcription elongation factor ELL. These findings provide mechanistic insights into transcription-replication conflict resolution.

The main aim of current cancer research is to find a way to selectively affect the tumor cells, while leaving normal cells intact. Ataxia telangiectasia and Rad3-related kinase (ATR), a member of the phosphatidylinositol-3-related protein kinases (PIKK), represents a candidate target for achieving this goal. ATR kinase is one of the main kinases of the DNA damage response signaling pathway and responds to DNA damage caused by replication stress and various genotoxic agents (i.e. chemotherapy, ionizing radiation, ultraviolet light). ATR activation triggers cell cycle checkpoints, DNA repair and apoptosis, but also resistance of tumor cells to DNA damaging agents, through stress support under replication stress. Thus, the inhibition of ATR leads to increased effectiveness of cancer therapy and in addition enables highly selective targeting of cancer cells through synthetic lethal interactions. Despite this great potential, only a few potent and selective inhibitors of ATR kinase have been developed to date. However, those which have been developed provide great promise, and are under evaluation in many current preclinical and clinical trials. The purpose of this review is to summarize the potential of ATR inhibitors and the medicinal chemistry efforts which resulted in their identification.

Caffeine is probably the best known and most widely used psychoactive substance in the world. Beside its psychoactive effects, caffeine has been found to affect the cell cycle and DNA repair, as a consequence of the inhibition of ATM and ATR kinases. These two DNA damage response kinases, members of the phosphatidylinositol 3-kinase related protein kinase family, represent very attractive anticancer drug targets. Their inhibition can selectively sensitize cancer cells to DNA damaging agents and even kill various tumour cells in monotherapy. We developed a series of caffeine derivatives and evaluated their antiproliferative effects on 11 human tumour cell lines and compared them against caffeine and a standard ATR inhibitor VE-821. Although the new caffeine derivatives did not achieve the overall potency of VE-821, several compounds exhibited enhanced antiproliferative activity compared to caffeine and in some cell lines showed at least comparable activity to VE-821.

Chemoresistance, radioresistance, and the challenge of achieving complete resection are major driving forces in the search for more robust and targeted anticancer therapies. Targeting the DNA damage response has recently attracted research interest, as these processes are enhanced in tumour cells. The major replication stress responder is ATM and Rad3-related (ATR) kinase, which is attracting attention worldwide with four drug candidates currently in phase I/II clinical trials. This review addresses a potent and selective small-molecule ATR inhibitor, which is known as VX-970 (also known as berzosertib or M6620), and summarizes the existing preclinical data to provide deep insight regarding its real potential. We also outline the transition from preclinical to clinical studies, as well as its relationships with other clinical candidates (AZD6738, VX-803 [M4344], and BAY1895344). The results suggest that VX-970 is indeed a promising anticancer drug that can be used both as monotherapy and in combination with either chemotherapy or radiotherapy strategies. Based on patient anamnesis and biomarker identification, VX-970 could become a valuable tool for oncologists in the fight against cancer.

Aim: DNA damage response plays an eminent role in patients’ response to conventional chemotherapy and radiotherapy. Its inhibition is of great interest as it can overcome cancer cell resistance and reduce the effective doses of DNA damaging agents. Results & methodology: We have focused our research on phosphatidylinositol 3-kinase-related kinases and prepared 35 novel compounds through a scaffold hopping approach. The newly synthesized inhibitors were tested on a panel of nine cancer and one healthy cell lines alone and in combination with appropriate doses of doxorubicin. Conclusion: Five novel compounds 4f, 10b, 15g, 7e and 15f in combination with doxorubicin showed significant antiproliferative effect on seven cancer cell lines while not affecting the cell growth alone.

We report the design, synthesis and biological evaluation of 17 novel 8-aryl-2-morpholino-3,4-dihydroquinazoline derivatives based on the standard model of DNA-PK and PI3K inhibitors. Novel compounds are sub-divided into two series where the second series of five derivatives was designed to have a better solubility profile over the first one. A combination of in vitro and in silico techniques suggested a plausible synergistic effect with doxorubicin of the most potent compound 14d on cell proliferation via DNA-PK and poly(ADP-ribose) polymerase-1 (PARP-1) inhibition, while alone having a negligible effect on cell proliferation.

A novel series of 7-methoxytacrine (7-MEOTA)–donepezil like compounds was synthesized and tested for their ability to inhibit electric eel acetylcholinesterase (EeAChE), human recombinant AChE (hAChE), equine serum butyrylcholinesterase (eqBChE) and human plasmatic BChE (hBChE). New hybrids consist of a 7-MEOTA unit, representing less toxic tacrine (THA) derivative, connected with analogues of N-benzylpiperazine moieties mimicking N-benzylpiperidine fragment from donepezil. 7-MEOTA–donepezil like compounds exerted mostly non-selective profile in inhibiting cholinesterases of different origin with IC50 ranging from micromolar to sub-micromolar concentration scale. Kinetic analysis confirmed mixed-type inhibition presuming that these inhibitors are capable to simultaneously bind peripheral anionic site (PAS) as well as catalytic anionic site (CAS) of AChE. Molecular modeling studies and QSAR studies were performed to rationalize studies from in vitro. Overall, 7-MEOTA–donepezil like derivatives can be considered as interesting candidates for Alzheimer's disease treatment.

Alzheimer’s disease (AD) is a debilitating progressive neurodegenerative disorder that ultimately leads to the patient’s death. Despite the fact that novel pharmacological approaches endeavoring to block the neurodegenerative process are still emerging, none of them have reached use in clinical practice yet. Thus, palliative treatment represented by acetylcholinesterase inhibitors (AChEIs) and memantine are still the only therapeutics used. Following the multi-target directed ligands (MTDLs) strategy, herein we describe the synthesis, biological evaluation and docking studies for novel 7-methoxytacrine-p-anisidine hybrids designed to purposely target both cholinesterases and the amyloid cascade. Indeed, the novel derivatives proved to be effective non-specific cholinesterase inhibitors showing non-competitive AChE inhibition patterns. This compounds’ behavior was confirmed in the subsequent molecular modeling studies.

Coupling of two distinct pharmacophores, tacrine and trolox, endowed with different biological properties, afforded 21 hybrid compounds as novel multifunctional candidates against Alzheimer's disease. Several of them showed improved inhibitory properties toward acetylcholinesterase (AChE) in relation to tacrine. These hybrids also scavenged free radicals. Molecular modeling studies in tandem with kinetic analysis exhibited that these hybrids target both catalytic active site as well as peripheral anionic site of AChE. In addition, incorporation of the moiety bearing antioxidant abilities displayed negligible toxicity on human hepatic cells. This striking effect was explained by formation of nontoxic metabolites after 1 h incubation in human liver microsomes system. Finally, tacrine-trolox hybrids exhibited low in vivo toxicity after im administration in rats and potential to penetrate across blood-brain barrier. All of these outstanding in vitro results in combination with promising in vivo outcomes highlighted derivative 7u as the lead structure worthy of further investigation.

Phosphatidylinositol 3-kinases (PI3Ks) and phosphatidylinositol 3-kinase-related protein kinases (PIKKs) are two related families of kinases that play key roles in regulation of cell proliferation, metabolism, migration, survival, and responses to diverse stresses including DNA damage. To design novel efficient strategies for treatment of cancer and other diseases, these kinases have been extensively studied. Despite their different nature, these two kinase families have related origin and share very similar kinase domains. Therefore, chemical inhibitors of these kinases usually carry analogous structural motifs. The most common feature of these inhibitors is a critical hydrogen bond to morpholine oxygen, initially present in the early nonspecific PI3K and PIKK inhibitor 3 (LY294002), which served as a valuable chemical tool for development of many additional PI3K and PIKK inhibitors. While several PI3K pathway inhibitors have recently shown promising clinical responses, inhibitors of the DNA damage-related PIKKs remain thus far largely in preclinical development.

Radiation and genotoxic drugs are two of the cornerstones of current cancer treatment strategy. However, this type of therapy often suffers from radio- or chemo-resistance caused by DNA repair mechanisms. With the aim of increasing the efficacy of these treatments, there has been great interest in studying DNA damage responses (DDR). Among the plethora of signal and effector proteins involved in DDR, three related kinases ATM (ataxia telangiectasia mutated), ATR (ATM and Rad3-related) and DNA-PK (DNA-dependent protein kinase) play the main roles in initiation and regulation of signaling pathways in response to DNA double and single strand breaks (DSB and SSB). ATM inhibitors, as well as those of ATR and DNA-PK, provide an opportunity to sensitize cancer cells to therapy. Moreover, they can lead to selective killing of cancer cells, exploiting a concept known as synthetic lethality. However, only a very few selective inhibitors have been identified to this date. This mini-review is focused both on the development of selective inhibitors of ATM and other inhibitors which have ATM as one of their targets.

Organophosphates are used as pesticides or misused as warfare nerve agents. Exposure to them can be fatal and death is usually caused by respiratory arrest. For almost six decades, pyridinium oximes represent a therapeutic tool used for the management of poisoning with organophosphorus (OP) compounds. However, these compounds possess several drawbacks. Firstly, they are inefficient in the restoration of brain acetylcholinesterase (AChE) activity due to a hard blood-brain barrier penetration. Secondly, there is no broad-spectrum AChE reactivator. Lastly, none of the oximes can reactivate "aged" AChE. In this context, uncharged reactivators represent a new hope in a way of increased bioavailability in the central compartment and better therapeutic management of the OP poisoning.