First-in-human study of the PARP/tankyrase inhibitor E7449 in patients with advanced solid tumours and evaluation of a novel drug-response predictor

Beyond monotherapy: An era ushering in combinations of PARP inhibitors with immune checkpoint inhibitors for solid tumors

The introduction of PARP inhibitors (PARPis) and immune checkpoint inhibitors (ICIs) has marked a significant shift in the treatment landscape for solid tumors. Emerging preclinical evidence and initial clinical trials have indicated that the synergistic application of PARPis and ICIs may enhance treatment efficacy and potentially improve long-term patient outcomes. Nonetheless, how to identify specific tumor types and molecular subgroups most likely to benefit from this combination remains an area of ongoing research. This review thoroughly examines current studies on the co-administration of PARPis and ICIs across various solid tumors. It explores the underlying mechanisms of action, evaluates clinical efficacy, identifies potential responder populations, and delineates common adverse events alongside strategic management approaches. The aim is to offer a detailed understanding of this combination therapy, potentially guiding future therapeutic strategies for solid tumors.

Shaping DNA damage responses: Therapeutic potential of targeting telomeric proteins and DNA repair factors in cancer

Shelterin proteins regulate genomic stability by preventing inappropriate DNA damage responses (DDRs) at telomeres. Unprotected telomeres lead to persistent DDR causing cell cycle inhibition, growth arrest, and apoptosis. Cancer cells rely on DDR to protect themselves from DNA lesions and exogenous DNA-damaging agents such as chemotherapy and radiotherapy. Therefore, targeting DDR machinery is a promising strategy to increase the sensitivity of cancer cells to existing cancer therapies. However, the success of these DDR inhibitors depends on other mutations, and over time, patients develop resistance to these therapies. This suggests the need for alternative approaches. One promising strategy is co-inhibiting shelterin proteins with DDR molecules, which would offset cellular fitness in DNA repair in a mutation-independent manner. This review highlights the associations and dependencies of the shelterin complex with the DDR proteins and discusses potential co-inhibition strategies that might improve the therapeutic potential of current inhibitors.

Study of the mechanism by which Xiaoyan decoction combined with E7449 regulates tumorigenesis in lung adenocarcinoma

TNKS is a new target for the treatment of lung adenocarcinoma, the synergistic effects of the TCM compound Xiaoyan decoction and the TNKS inhibitor E7449 in the intervention on TNKS were investigated, and the possible underlying mechanisms involved were clarified. Immunohistochemistry was used to analyse TNKS expression in tumour tissues. The impact of targeting TNKS on cell growth, invasion, apoptosis, key genes and signalling pathways was investigated in tumour cells by Western blotting, rescue experiments, colony formation assays, flow cytometry and label-free experiments. Tumour xenografts with A549 cells were then transplanted for in vivo study. We found that TNKS high expression was closely related to the advanced tumour stage and tumour size in lung adenocarcinom. After TNKS was knocked down in vitro, the growth, proliferation, migration and invasion were markedly reduced in A549 and H1975 cells. We subsequently applied the Xiaoyan decoction and TNKS inhibitors to intervene in lung adenocarcinoma. Xiaoyan decoction and E7449 suppressed TNKS expression and inhibited adenocarcinoma cell proliferation, migration, invasion and apoptosis in vitro. Proteomic analysis revealed that E7449 treatment may be most closely associated with the classic Wnt/β-catenin pathway, whereas Xiaoyan decoction treatment may be related to the WNT/PLAN pathway. Xenograft studies confirmed that E7449 or Xiaoyan decoction inhibited lung tumour growth in vivo and attenuated the Wnt signalling pathway in adenocarcinoma. These findings suggest that TNKS is a novel therapeutic target. TCM preparations and small molecule inhibitors are expected to constitute an effective combination strategy.

The therapeutic effect of traditional Chinese medicine on breast cancer through modulation of the Wnt/β-catenin signaling pathway

Breast cancer, the most prevalent malignant tumor among women globally, is significantly influenced by the Wnt/β-catenin signaling pathway, which plays a crucial role in its initiation and progression. While conventional chemotherapy, the standard clinical treatment, suffers from significant drawbacks like severe side effects, high toxicity, and limited prognostic efficacy, Traditional Chinese Medicine (TCM) provides a promising alternative. TCM employs a multi-targeted therapeutic approach, which results in fewer side effects and offers a high potential for effective treatment. This paper presents a detailed analysis of the therapeutic impacts of TCM on various subtypes of breast cancer, focusing on its interaction with the Wnt/β-catenin signaling pathway. Additionally, it explores the effectiveness of both monomeric and compound forms of TCM in the management of breast cancer. We also discuss the potential of establishing biomarkers for breast cancer treatment based on key proteins within the Wnt/β-catenin signaling pathway. Our aim is to offer new insights into the prevention and treatment of breast cancer and to contribute to the standardization of TCM.

BET protein-dependent E2F pathway activity confers bell-shaped type resistance to tankyrase inhibitors in APC-mutated colorectal cancer

WNT/β-catenin signaling is aberrantly activated in colorectal cancer (CRC) mainly by loss-of-function mutations in adenomatous polyposis coli (APC) and is involved in tumor progression. Tankyrase inhibitors, which suppress WNT/β-catenin signaling, are currently in pre-clinical and clinical trials. However, the mechanisms of resistance to tankyrase inhibitors remain unclear. In this study, we established tankyrase inhibitor-resistant CRC cells, JC73-RK100, from APC-mutated patient-derived CRC cells. JC73-RK100 cells and several CRC cell lines were sensitive to tankyrase inhibitors at low concentrations but were resistant at high concentrations, showing an intrinsic/acquired bell-shaped dose response. Mechanistically, tankyrase inhibitors at high concentrations promoted BRD3/4-dependent E2F target gene transcription and over-activated cell cycle progression in these cells. BET inhibitors canceled the bell-shaped dose response to tankyrase inhibitors. Combination of tankyrase and BET inhibitors significantly suppressed tumor growth in a mouse xenograft model. These observations suggest that the combination of tankyrase and BET inhibitors may be a useful therapeutic approach to overcome the resistance of a subset of CRCs to tankyrase inhibitors.

Tankyrase inhibition interferes with junction remodeling, induces leakiness, and disturbs YAP1/TAZ signaling in the endothelium

Tankyrase inhibitors are increasingly considered for therapeutic use in malignancies that are characterized by high intrinsic β-catenin activity. However, how tankyrase inhibition affects the endothelium after systemic application remains poorly understood. In this study, we aimed to investigate how the tankyrase inhibitor XAV939 affects endothelial cell function and the underlying mechanism involved. Endothelial cell function was analyzed using sprouting angiogenesis, endothelial cell migration, junctional dynamics, and permeability using human umbilical vein endothelial cells (HUVEC) and explanted mouse retina. Underlying signaling was studied using western blot, immunofluorescence, and qPCR in HUVEC in addition to luciferase reporter gene assays in human embryonic kidney cells. XAV939 treatment leads to altered junctional dynamics and permeability as well as impaired endothelial migration. Mechanistically, XAV939 increased stability of the angiomotin-like proteins 1 and 2, which impedes the nuclear translocation of YAP1/TAZ and consequently suppresses TEAD-mediated transcription. Intriguingly, XAV939 disrupts adherens junctions by inducing RhoA-Rho dependent kinase (ROCK)-mediated F-actin bundling, whereas disruption of F-actin bundling through the ROCK inhibitor H1152 restores endothelial cell function. Unexpectedly, this was accompanied by an increase in nuclear TAZ and TEAD-mediated transcription, suggesting differential regulation of YAP1 and TAZ by the actin cytoskeleton in endothelial cells. In conclusion, our findings elucidate the complex relationship between the actin cytoskeleton, YAP1/TAZ signaling, and endothelial cell function and how tankyrase inhibition disturbs this well-balanced signaling.

High-throughput screening assay for PARP-HPF1 interaction inhibitors to affect DNA damage repair

ADP-ribosyltransferases PARP1 and PARP2 play a major role in DNA repair mechanism by detecting the DNA damage and inducing poly-ADP-ribosylation dependent chromatin relaxation and recruitment of repair proteins. Catalytic PARP inhibitors are used as anticancer drugs especially in the case of tumors arising from sensitizing mutations. Recently, a study showed that Histone PARylation Factor (HPF1) forms a joint active site with PARP1/2. The interaction of HPF1 with PARP1/2 alters the modification site from Aspartate/Glutamate to Serine, which has been shown to be a key ADP-ribosylation event in the context of DNA damage. Therefore, disruption of PARP1/2-HPF1 interaction could be an alternative strategy for drug development to block the PARP1/2 activity. In this study, we describe a FRET based high-throughput screening assay to screen inhibitor libraries against PARP-HPF1 interaction. We optimized the conditions for FRET signal and verified the interaction by competing the FRET pair in multiple ways. The assay is robust and easy to automate. Validatory screening showed the robust performance of the assay, and we discovered two compounds Dimethylacrylshikonin and Alkannin, with µM inhibition potency against PARP1/2-HPF1 interaction. The assay will facilitate the discovery of inhibitors against HPF1-PARP1/2 complex and to develop potentially new effective anticancer agents.

Design, synthesis, and biological activity evaluation of new tankyrase-2 directed inhibitors

A new series of flavonoids and quinolone derivatives were designed, synthesized and, evaluated for their biological activity. Among them, compound 14e showed better inhibition potency against TNKS2 in comparison with G007-LK, one of the most potent preclinical stage TNKS inhibitor. Molecular docking results showed that 14e occupied both the adenosine and nicotinamide pockets and formed a hydrogen bond with Met1054 of TNKS2. This study provides a lead for the design and discovery of potent and selective TNKS2 inhibitors.

Tankyrase: a promising therapeutic target with pleiotropic action

Tankyrase 1 (TNKS1) and tankyrase 2 (TNKS2) enzymes belong to the poly (ADP-ribose) polymerase (PARP) family participates in process of poly-ADP-ribosylation of different target proteins which leads to ubiquitin-mediated proteasomal degradation. Tankyrases are also involved in the pathophysiology of many diseases, especially cancer. Their functions include cell cycle homeostasis (primarily in mitosis), telomere maintenance, Wnt signaling pathway regulation, and insulin signaling (particularly GLUT4 translocation). Studies have implicated that genetic changes, mutations in the tankyrase coding sequence, or up regulation and down regulation of tankyrase are reflected in the numerous disease conditions. Investigations are pursued to develop putative molecules that target tankyrase in various diseases such as cancer, obesity, osteoarthritis, fibrosis, cherubism, and diabetes, thereby providing a new therapeutic treatment option. In the present review, we described the structure and function of tankyrase along with its role in different disease conditions. Furthermore, we also presented cumulative experimental evidences of different drugs acting on tankyrase.

The strategies to cure cancer patients by eradicating cancer stem-like cells

Cancer stem-like cells (CSCs), a subpopulation of cancer cells, possess remarkable capability in proliferation, self-renewal, and differentiation. Their presence is recognized as a crucial factor contributing to tumor progression and metastasis. CSCs have garnered significant attention as a therapeutic focus and an etiologic root of treatment-resistant cells. Increasing evidence indicated that specific biomarkers, aberrant activated pathways, immunosuppressive tumor microenvironment (TME), and immunoevasion are considered the culprits in the occurrence of CSCs and the maintenance of CSCs properties including multi-directional differentiation. Targeting CSC biomarkers, stemness-associated pathways, TME, immunoevasion and inducing CSCs differentiation improve CSCs eradication and, therefore, cancer treatment. This review comprehensively summarized these targeted therapies, along with their current status in clinical trials. By exploring and implementing strategies aimed at eradicating CSCs, researchers aim to improve cancer treatment outcomes and overcome the challenges posed by CSC-mediated therapy resistance.

A novel drug specific mRNA biomarker predictor for selection of patients responding to dovitinib treatment of advanced renal cell carcinoma and other solid tumors

PURPOSE

Dovitinib is a receptor tyrosine kinase inhibitor of VEGFR1-3, PDGFR, FGFR1/3, c-KIT, FLT3 and topoisomerase 1 and 2. The drug response predictor (DRP) biomarker algorithm or DRP-Dovitinib is being developed as a companion diagnostic to dovitinib and was applied retrospectively.

PATIENTS AND METHODS

Archival tumor samples were obtained from consenting patients in a phase 3 trial comparing dovitinib to sorafenib in renal cell carcinoma patients and the DRP-Dovitinib was applied. The biomarker algorithm combines the expression of 58 messenger RNAs relevant to the in vitro sensitivity or resistance to dovitinib, including genes associated with FGFR, PDGF, VEGF, PI3K/Akt/mTOR and topoisomerase pathways as well as ABC drug transport, and provides a likelihood score between 0-100%.

RESULTS

The DRP-Dovitinib divided the dovitinib treated RCC patients into two groups, sensitive (n = 49, DRP score >50%) or resistant (n = 86, DRP score ≤ 50%) to dovitinib. The DRP sensitive population was compared to the unselected sorafenib arm (n = 286). Median progression-free survival (PFS) was 3.8 months in the DRP sensitive dovitinib arm and 3.6 months in the sorafenib arm (hazard ratio 0.71, 95% CI 0.51-1.01). Median overall survival (OS) was 15.0 months in the DRP sensitive dovitinib arm and 11.2 months in the sorafenib arm (hazard ratio 0.69, 95% CI 0.48-0.99). The observed clinical benefit increased with increasing DRP score. At a cutoff of 67% the median OS was 20.6 months and the median PFS was 5.7 months in the dovitinib arm. The results were confirmed in five smaller phase II trials of dovitinib which showed a similar trend.

CONCLUSION

The DRP-Dovitinib shows promise as a potential biomarker for identifying advanced RCC patients most likely to experience clinical benefit from dovitinib treatment, subject to confirmation in an independent prospective trial of dovitinib in RCC patients.

Privileged Scaffolds for Potent and Specific Inhibitors of Mono-ADP-Ribosylating PARPs

The identification of new targets to address unmet medical needs, better in a personalized way, is an urgent necessity. The introduction of PARP1 inhibitors into therapy, almost ten years ago, has represented a step forward this need being an innovate cancer treatment through a precision medicine approach. The PARP family consists of 17 members of which PARP1 that works by poly-ADP ribosylating the substrate is the sole enzyme so far exploited as therapeutic target. Most of the other members are mono-ADP-ribosylating (mono-ARTs) enzymes, and recent studies have deciphered their pathophysiological roles which appear to be very extensive with various potential therapeutic applications. In parallel, a handful of mono-ARTs inhibitors emerged that have been collected in a perspective on 2022. After that, additional very interesting compounds were identified highlighting the hot-topic nature of this research field and prompting an update. From the present review, where we have reported only mono-ARTs inhibitors endowed with the appropriate profile of pharmacological tools or drug candidate, four privileged scaffolds clearly stood out that constitute the basis for further drug discovery campaigns.

Dual-target inhibitors of PARP1 in cancer therapy: a drug discovery perspective

Poly (ADP-ribose) polymerase 1 (PARP1), a key enzyme in DNA repair, has emerged as a promising anticancer druggable target. An increasing number of PARP1 inhibitors have been discovered to treat cancer, most notably those characterized by BRCA1/2 mutations. Although PARP1 inhibitors have achieved great clinical success, their cytotoxicity, development of drug resistance, and restriction of indication have weakened their clinical therapeutic effects. To address these issues, dual PARP1 inhibitors have been documented as a promising strategy. Here, we review recent progress in the development of dual PARP1 inhibitors, summarize the different designs of dual-target inhibitors, and introduce their antitumor pharmacology, shedding light on the discovery of dual PARP1 inhibitors for cancer treatment.

A New Wave of Targeting 'Undruggable' Wnt Signaling for Cancer Therapy: Challenges and Opportunities

Aberrant Wnt signaling activation is frequently observed in many cancers. The mutation acquisition of Wnt signaling leads to tumorigenesis, whereas the inhibition of Wnt signaling robustly suppresses tumor development in various in vivo models. Based on the excellent preclinical effect of targeting Wnt signaling, over the past 40 years, numerous Wnt-targeted therapies have been investigated for cancer treatment. However, Wnt signaling-targeting drugs are still not clinically available. A major obstacle to Wnt targeting is the concomitant side effects during treatment due to the pleiotropic role of Wnt signaling in development, tissue homeostasis, and stem cells. Additionally, the complexity of the Wnt signaling cascades across different cancer contexts hinders the development of optimized targeted therapies. Although the therapeutic targeting of Wnt signaling remains challenging, alternative strategies have been continuously developed alongside technological advances. In this review, we give an overview of current Wnt targeting strategies and discuss recent promising trials that have the potential to be clinically realized based on their mechanism of action. Furthermore, we highlight new waves of Wnt targeting that combine recently developed technologies such as PROTAC/molecular glue, antibody-drug conjugates (ADC), and anti-sense oligonucleotides (ASO), which may provide us with new opportunities to target 'undruggable' Wnt signaling.

Therapeutic strategies of dual-target small molecules to overcome drug resistance in cancer therapy

Despite some advances in targeted therapeutics of human cancers, curative cancer treatment still remains a tremendous challenge due to the occurrence of drug resistance. A variety of underlying resistance mechanisms to targeted cancer drugs have recently revealed that the dual-target therapeutic strategy would be an attractive avenue. Compared to drug combination strategies, one agent simultaneously modulating two druggable targets generally shows fewer adverse reactions and lower toxicity. As a consequence, the dual-target small molecule has been extensively explored to overcome drug resistance in cancer therapy. Thus, in this review, we focus on summarizing drug resistance mechanisms of cancer cells, such as enhanced drug efflux, deregulated cell death, DNA damage repair, and epigenetic alterations. Based upon the resistance mechanisms, we further discuss the current therapeutic strategies of dual-target small molecules to overcome drug resistance, which will shed new light on exploiting more intricate mechanisms and relevant dual-target drugs for future cancer therapeutics.

Metabolic Activation of PARP as a SARS-CoV-2 Therapeutic Target-Is It a Bait for the Virus or the Best Deal We Could Ever Make with the Virus? Is AMBICA the Potential Cure?

The COVID-19 pandemic has had a great impact on global health and is an economic burden. Even with vaccines and anti-viral medications we are still scrambling to get a balance. In this perspective, we have shed light upon an extremely feasible approach by which we can control the SARS-CoV-2 infection and the associated complications, bringing some solace to this ongoing turmoil. We are providing some insights regarding an ideal agent which could prevent SARS-CoV-2 multiplication. If we could identify an agent which is an activator of metabolism and is also bioactive, we could prevent corona activation (AMBICA). Some naturally occurring lipid molecules best fit this identity as an agent which has the capacity to replenish our host cells, specifically immune cells, with ATP. It could also act as a source for providing a substrate for host cell PARP family members for MARylation and PARylation processes, leading to manipulation of the viral macro domain function, resulting in curbing the virulence and propagation of SARS-CoV-2. Identification of the right lipid molecule or combination of lipid molecules will fulfill the criteria. This perspective has focused on a unique angle of host-pathogen interaction and will open up a new dimension in treating COVID-19 infection.

New molecular insights for 4H-1,2,4-triazole derivatives as inhibitors of tankyrase and Wnt-signaling antagonist: a molecular dynamics simulation study

Tankyrase (TNKS) enzymes remained central biotargets to treat Wnt-driven colorectal cancers. The success of Olaparib posited the druggability of PARP family enzymes depending on their role in tumor proliferation. In this work, an MD-simulation-based comparative assessment of the protein-ligand interactions using the best-docked poses of three selected compounds (two of the designed and previously synthesized molecules obtained through molecular docking and one reported TNKS inhibitor) was performed for a 500 ns period. The PDB:ID-7KKP and 3U9H were selected for TNKS1 and TNKS2, respectively. The Molecular Mechanics Generalized Born Surface Area (MM-GBSA) based binding energy data exhibited stronger binding of compound-15 (average values of -102.92 and -104.32 kcal/mol for TNKS1 and TNKS2, respectively) as compared to compound-22 (average values of -82.99 and -85.68 kcal/mol for TNKS1 and TNKS2, respectively) and the reported compound-32 (average values of -81.89 and -74.43 kcal/mol for TNKS1 and TNKS2, respectively). Compound-15 and compound-22 exhibited comparable or superior binding to both receptors forming stable complexes when compared to that of compound-32 upon examining their MD trajectories. The key contributors were hydrophobic stacking and optimum hydrogen bonding allowing these molecules to occupy the adenosine pocket by interfacing D-loop residues. The results of bond distance analysis, radius of gyration, root mean square deviation, root mean square fluctuation, snapshots at different time intervals, LUMO-HUMO energy differences, electrostatic potential calculations, and binding free energy suggested better binding efficiency for compound-15 to TNKS enzymes. The computed physicochemical and ADMET properties of compound-15 were encouraging and could be explored further for drug development.Communicated by Ramaswamy H. Sarma.

DGG-300273, a novel WNT/β-catenin inhibitor, induces apoptotic cell death by activating ROS-BIM signaling in a Wnt-dependent manner in colon cancer cells

Dysregulated Wnt signaling is associated with malignant oncogenic transformation, especially in colon cancer. Recently, numerous drugs have been developed based on tumorigenesis biomarkers, thus having high potential as drug targets. Likewise, WNT/β-catenin pathway members are attractive therapeutic targets for colon cancer and are currently in various stages of development. However, although inhibitors of proteins regulating the WNT/β-catenin signaling pathway have been extensively studied, they have yet to be clinically approved, and the underlying molecular mechanism(s) of their anticancer effects remain poorly understood. Herein, we show that a novel WNT/β-catenin inhibitor, DGG-300273, inhibits colon cancer cell growth in a Wnt-dependent manner due to upregulation of the BCL2-family protein Bim and caspase-dependent apoptotic cell death. Additionally, DGG-300273-mediated cell death occurs by increased reactive oxygen species (ROS), as shown by abrogation of apoptotic cell death and ROS production following pretreatment with the antioxidant N-acetylcysteine. These results suggest that DGG-300273 represents a promising investigational drug for the treatment of Wnt-associated cancer, thus warranting further characterization and study.

Targeting cancer stem cell pathways for lung cancer therapy

PURPOSE OF REVIEW

The unique properties of cancer stem cells (CSCs) make lung cancer untargetable for quite an extended period. The functional mechanism of this cell type has been illustrated step by step. However, the outcomes of lung cancer patients are still lower than expected clinically. The attempts made by scientists to make challenge history against stemness maintenance of lung cancer cells and their druggable targets are worth elucidating.

RECENT FINDINGS

Many agents, including the Bispecific T-cell engager (BiTE) and AMG 119 targeting DLL3-positive cells, are a tremendous breakthrough in the preclinical and clinical treatment of SCLC. More studies focus on targeting CSCs to overcome TKI resistance in NSCLC. The combo targeting of CSC and the immune microenvironment can favor the treatment of lung cancer patients.

SUMMARY

The current review elucidates the characteristics and related regulating pathways of lung CSCs from essential to preclinical research. We retrospectively introduce an update on the clinical development of therapeutics targeting CSC-associated developmental signaling pathways and discuss the opportunities to target CSC-immune interactions in lung cancer.

Differentially Expressed Genes and Signaling Pathways Potentially Involved in Primary Resistance to Chemo-Immunotherapy in Advanced-Stage Gastric Cancer Patients

Recently, the combination of chemotherapy plus nivolumab (chemo-immunotherapy) has become the standard of care for advanced-stage gastric cancer (GC) patients. However, despite its efficacy, up to 40% of patients do not respond to these treatments. Our study sought to identify variations in gene expression associated with primary resistance to chemo-immunotherapy. Diagnostic endoscopic biopsies were retrospectively obtained from advanced GC patients previously categorized as responders (R) or non-responders (NR). Thirty-four tumor biopsies (R: n = 16, NR: n = 18) were analyzed by 3′ massive analysis of cDNA ends (3′MACE). We found >30 differentially expressed genes between R and NRs. Subsequent pathway enrichment analyses demonstrated that angiogenesis and the Wnt-β-catenin signaling pathway were enriched in NRs. Concomitantly, we performed next generation sequencing (NGS) analyses in a subset of four NR patients that confirmed alterations in genes that belonged to the Wnt/β-catenin and the phosphoinositide 3-kinase (PI3K) pathways. We speculate that angiogenesis, the Wnt, and the PI3K pathways might offer actionable targets. We also discuss therapeutic alternatives for chemo-immunotherapy-resistant advanced-stage GC patients.

Trends in Melanoma Phase 3 Clinical Trials since 2010: Is there Hope for Advanced Melanoma Therapies beyond Approved Treatment Mechanisms?

BACKGROUND

Several drugs and treatment modalities are under investigation to improve current melanoma therapy options. This review profiles the trends in clinical trial investment in late-stage melanoma, and anticipates what changes are expected in melanoma treatment, with a focus on exploratory drug mechanisms.

METHODS

We reviewed nine international clinical trial databases for registered, interventional, and phase 3 cutaneous melanoma clinical trials since 2010.

RESULTS

73 trials studied drug therapies in late-stage (stage III and IV) melanoma. Exploratory mechanisms were investigated in 32% (23/73) of the late-stage melanoma drug therapy trials. Most exploratory drug trials include immunotherapy drug mechanisms (15/23 trials). Two exploratory mechanisms showed promise: the anti-LAG3 antibody, relatlimab, and the hapten modified vaccine, MVax. Many (52%) trials of exploratory mechanisms are ongoing including the use of adoptive cell transfer immunotherapies, dendritic cell vaccine therapy, and histone deacetylase (HDAC) inhibitors, among others.

CONCLUSIONS

Since most clinical trials focus on previously approved drug mechanisms, it is likely that paradigm-changing treatments will involve these therapies being used in new treatment contexts or combinations. Only 2 exploratory drug mechanisms studied since 2010 have achieved promising results in the phase 3 setting, though many other trials are ongoing at this time.

Targeting Homologous Recombination Deficiency in Ovarian Cancer with PARP Inhibitors: Synthetic Lethal Strategies That Impact Overall Survival

Simple Summary

Synthetic lethality approaches to cancer therapy involves combining events to cause cancer cell death. Using this strategy, major advances have occurred in the treatment of women with ovarian cancer who have defects in the Homologous Recombination Repair (HRR) pathway. When the HRR pathway is defective, due to mutations or epigenetic changes in genes such as BRCA1 or BRCA2, cells can no longer accurately repair double strand breaks (DSBs). Capitalising on this weakness, pharmacological inhibition of poly (ADP-ribose) polymerase (PARP) that function to repair single strand breaks (SSBs) leads to synthetic lethality in cells with defective HRR. PARP inhibitors (PARPis) including olaparib, niraparib and rucaparib are approved for the clinical management of women with ovarian cancer. Understanding and overcoming issues of acquired resistance to PARPis, extending these strategies to benefit more patients and combining PARPis with other drugs, including immunotherapies, are of high priority in the field today.

Abstract

The advent of molecular targeted therapies has made a significant impact on survival of women with ovarian cancer who have defects in homologous recombination repair (HRR). High-grade serous ovarian cancer (HGSOC) is the most common histological subtype of ovarian cancer, with over 50% displaying defective HRR. Poly ADP ribose polymerases (PARPs) are a family of enzymes that catalyse the transfer of ADP-ribose to target proteins, functioning in fundamental cellular processes including transcription, chromatin remodelling and DNA repair. In cells with deficient HRR, PARP inhibitors (PARPis) cause synthetic lethality leading to cell death. Despite the major advances that PARPis have heralded for women with ovarian cancer, questions and challenges remain, including: can the benefits of PARPis be brought to a wider range of women with ovarian cancer; can other drugs in clinical use function in a similar way or with greater efficacy than currently clinically approved PARPis; what can we learn from long-term responders to PARPis; can PARPis sensitise ovarian cancer cells to immunotherapy; and can synthetic lethal strategies be employed more broadly to develop new therapies for women with ovarian cancer. We examine these, and other, questions with focus on improving outcomes for women with ovarian cancer.

Comparative Analyses of Poly(ADP-Ribose) Polymerase Inhibitors

Poly(ADP-ribose) polymerase inhibitors (PARPi) are approved as monotherapies in BRCA1/2-mutated (m BRCA1/2) metastatic breast and ovarian cancers, and in advanced pancreatic and metastatic castration-resistant prostate cancers. Differential safety profiles across PARPi necessitate improved mechanistic understanding of inhibitor differences, especially with expansion of PARPi indications and drug combinations. Here, we report in vitro evaluations of PARPi (–/+ PARP trapper temozolomide, TMZ) with reference to total clinical mean concentration average or maximum (tCavg, tCmax), to elucidate contributions of primary pharmacology and structural differences to clinical efficacy and safety. In biochemical assays, rucaparib and niraparib demonstrated off-target secondary pharmacology activities, and in selectivity assays, talazoparib, olaparib, and rucaparib inhibited a broader panel of PARP enzymes. In donor-derived human bone marrow mononuclear cells, only olaparib both increased early apoptosis and decreased the cell viability half inhibitory concentration (IC50) at ≤ tCavg, whereas other PARPi only did so in the presence of TMZ. In cancer cell lines with DNA damage repair mutations, all PARPi decreased cell viability in H1048 but not TK6 cells, and only talazoparib decreased cell growth in DU145 cells at ≤ tCavg concentrations. When combined with low dose TMZ, only talazoparib left-shifted the functional consequences of PARP trapping (S-phase arrest, apoptosis, S-phase double-stranded breaks) and reduced cell viability/growth in TK6 and DU145 cell lines at ≤ tCavg, whereas the other inhibitors required high-dose TMZ. Our study suggests structural differences across PARPi may contribute to differences in PARP selectivity and off-target activities, which along with distinct pharmacokinetic properties, may influence inhibitor-specific toxicities in patients.

Medicinal Chemistry Perspective on Targeting Mono-ADP-Ribosylating PARPs with Small Molecules

Major advances have recently defined functions for human mono-ADP-ribosylating PARP enzymes (mono-ARTs), also opening up potential applications for targeting them to treat diseases. Structural biology combined with medicinal chemistry has allowed the design of potent small molecule inhibitors which typically bind to the catalytic domain. Most of these inhibitors are at the early stages, but some have already a suitable profile to be used as chemical tools. One compound targeting PARP7 has even progressed to clinical trials. In this review, we collect inhibitors of mono-ARTs with a typical "H-Y-Φ" motif (Φ = hydrophobic residue) and focus on compounds that have been reported as active against one or a restricted number of enzymes. We discuss them from a medicinal chemistry point of view and include an analysis of the available crystal structures, allowing us to craft a pharmacophore model that lays the foundation for obtaining new potent and more specific inhibitors.

The Tankyrase Inhibitor OM-153 Demonstrates Antitumor Efficacy and a Therapeutic Window in Mouse Models

The catalytic enzymes tankyrase 1 and 2 (TNKS1/2) alter protein turnover by poly-ADP-ribosylating target proteins, which earmark them for degradation by the ubiquitin-proteasomal system. Prominent targets of the catalytic activity of TNKS1/2 include AXIN proteins, resulting in TNKS1/2 being attractive biotargets for addressing of oncogenic WNT/β-catenin signaling. Although several potent small molecules have been developed to inhibit TNKS1/2, there are currently no TNKS1/2 inhibitors available in clinical practice. The development of tankyrase inhibitors has mainly been disadvantaged by concerns over biotarget-dependent intestinal toxicity and a deficient therapeutic window. Here we show that the novel, potent, and selective 1,2,4-triazole-based TNKS1/2 inhibitor OM-153 reduces WNT/β-catenin signaling and tumor progression in COLO 320DM colon carcinoma xenografts upon oral administration of 0.33-10 mg/kg twice daily. In addition, OM-153 potentiates anti-programmed cell death protein 1 (anti-PD-1) immune checkpoint inhibition and antitumor effect in a B16-F10 mouse melanoma model. A 28-day repeated dose mouse toxicity study documents body weight loss, intestinal damage, and tubular damage in the kidney after oral-twice daily administration of 100 mg/kg. In contrast, mice treated oral-twice daily with 10 mg/kg show an intact intestinal architecture and no atypical histopathologic changes in other organs. In addition, clinical biochemistry and hematologic analyses do not identify changes indicating substantial toxicity. The results demonstrate OM-153-mediated antitumor effects and a therapeutic window in a colon carcinoma mouse model ranging from 0.33 to at least 10 mg/kg, and provide a framework for using OM-153 for further preclinical evaluations.

Significance

This study uncovers the effectiveness and therapeutic window for a novel tankyrase inhibitor in mouse tumor models.

Small-Molecule Inhibitors of Tankyrases as Prospective Therapeutics for Cancer

Tankyrases are multifunctional poly(adenosine diphosphate-ribose) polymerases that regulate diverse biological processes including telomere maintenance and cellular signaling. These processes are often implicated in a number of human diseases, with cancer being the most prevalent example. Accordingly, tankyrase inhibitors have gained increasing attention as potential therapeutics. Since the discovery of XAV939 and IWR-1 as the first tankyrase inhibitors over two decades ago, tankyrase-targeted drug discovery has made significant progress. This review starts with an introduction of tankyrases, with emphasis placed on their cancer-related functions. Small-molecule inhibitors of tankyrases are subsequently delineated based on their distinct modes of binding to the enzymes. In addition to inhibitors that compete with oxidized nicotinamide adenine dinucleotide (NAD⁺) for binding to the catalytic domain of tankyrases, non-NAD⁺-competitive inhibitors are detailed. This is followed by a description of three clinically trialled tankyrase inhibitors. To conclude, some of challenges and prospects in developing tankyrase-targeted cancer therapies are discussed.

PARP Inhibitor Applicability: Detailed Assays for Homologous Recombination Repair Pathway Components

Poly(ADP-ribose) polymerase inhibitors (PARPi) have been in clinical use since 2014 for certain patients with germline BRCA1/2 mutations, but as evidence and approvals for their use in a wider range of patients grow, the question of how best to identify patients who would benefit from PARPi becomes ever more complex. Here, we discuss the development and current state of approved selection testing for PARPi therapy and the ongoing efforts to define a broader range of homologous recombination repair deficiencies that are susceptible to PARP inhibition.

Molecular methods for increasing the effectiveness of ovarian cancer treatment: a systematic review

Background: The aim of the current study is to analyze and summarize the latest research on improving therapy in ovarian cancer. Materials & methods: Data analysis was based on a review of publications from 2011 to 2021 in the PubMed database with use of the search terms including 'EGFR ovarian cancer', 'folate receptor inhibitors ovarian cancer', 'VEGF ovarian cancer', 'PDGF ovarian cancer' and 'CTLA-4 ovarian cancer'. Results: 6643 articles were found; 238 clinical trials and randomized control trials were analyzed; 122 studies were rejected due to inconsistency with the topic of the work. Conclusion: Extensive research on the treatment of ovarian cancer increases the chance of developing the most effective therapy suited to the individual needs of the patient.

Development of a 1,2,4-Triazole-Based Lead Tankyrase Inhibitor: Part II

Tankyrase 1 and 2 (TNKS1/2) catalyze post-translational modification by poly-ADP-ribosylation of a plethora of target proteins. In this function, TNKS1/2 also impact the WNT/β-catenin and Hippo signaling pathways that are involved in numerous human disease conditions including cancer. Targeting TNKS1/2 with small-molecule inhibitors shows promising potential to modulate the involved pathways, thereby potentiating disease intervention. Based on our 1,2,4-triazole-based lead compound 1 (OM-1700), further structure–activity relationship analyses of East-, South- and West-single-point alterations and hybrids identified compound 24 (OM-153). Compound 24 showed picomolar IC₅₀ inhibition in a cellular (HEK293) WNT/β-catenin signaling reporter assay, no off-target liabilities, overall favorable absorption, distribution, metabolism, and excretion (ADME) properties, and an improved pharmacokinetic profile in mice. Moreover, treatment with compound 24 induced dose-dependent biomarker engagement and reduced cell growth in the colon cancer cell line COLO 320DM.

Analogs of TIQ-A as inhibitors of human mono-ADP-ribosylating PARPs

The scaffold of TIQ-A, a previously known inhibitor of human poly-ADP-ribosyltransferase PARP1, was utilized to develop inhibitors against human mono-ADP-ribosyltransferases through structure-guided design and activity profiling. By supplementing the TIQ-A scaffold with small structural changes, based on a PARP10 inhibitor OUL35, selectivity changed from poly-ADP-ribosyltransferases towards mono-ADP-ribosyltransferases. Binding modes of analogs were experimentally verified by determining complex crystal structures with mono-ADP-ribosyltransferase PARP15 and with poly-ADP-ribosyltransferase TNKS2. The best analogs of the study achieved 10-20-fold selectivity towards mono-ADP-ribosyltransferases PARP10 and PARP15 while maintaining micromolar potencies. The work demonstrates a route to differentiate compound selectivity between mono- and poly-ribosyltransferases of the human ARTD family.

Insight Into Nicotinamide Adenine Dinucleotide Homeostasis as a Targetable Metabolic Pathway in Colorectal Cancer

Tumour cells modify their cellular metabolism with the aim to sustain uncontrolled proliferation. Cancer cells necessitate adequate amounts of NAD and NADPH to support several enzymes that are usually overexpressed and/or overactivated. Nicotinamide adenine dinucleotide (NAD) is an essential cofactor and substrate of several NAD-consuming enzymes, such as PARPs and sirtuins, while NADPH is important in the regulation of the redox status in cells. The present review explores the rationale for targeting the key enzymes that maintain the cellular NAD/NADPH pool in colorectal cancer and the enzymes that consume or use NADP(H).

Tankyrase inhibitors hinder Trypanosoma cruzi infection by altering host-cell signalling pathways

Chagas disease is a potentially life-threatening protozoan infection affecting around 8 million people, for which only chemotherapies with limited efficacy and severe adverse secondary effects are available. The aetiological agent, Trypanosoma cruzi, displays varied cell invading tactics and triggers different host cell signals, including the Wnt/β-catenin pathway. Poly(ADP-ribose) (PAR) can be synthetized by certain members of the poly(ADP-ribose) polymerase (PARP) family: PARP-1/-2 and Tankyrases-1/2 (TNKS). PAR homoeostasis participates in the host cell response to T. cruzi infection and TNKS are involved in Wnt signalling, among other pathways. Therefore, we hypothesized that TNKS inhibitors (TNKSi) could hamper T. cruzi infection. We showed that five TNKSi (FLALL9, MN64, XAV939, G007LK and OULL9) diminished T. cruzi infection of Vero cells. As most TNKSi did not affect the viability of axenically cultivated parasites, our results suggested that TNKSi were interfering with parasite–host cell signalling. Infection by T. cruzi induced nuclear translocation of β-catenin, as well as upregulation of TNF-α expression and secretion. These changes were hampered by TNKSi. Further signals should be monitored in this model and in vivo. As a TNKSi has entered cancer clinical trials with promising results, our findings encourage further studies aiming at drug repurposing strategies.

Poly (ADP-ribose) polymerase-1 (PARP1) as a therapeutic target in acute myeloid leukemia and myelodysplastic syndrome

Poly(ADP‐ribose) polymerase 1 (PARP1) is a key mediator of various forms of DNA damage repair and plays an important role in the progression of several cancer types. The enzyme is activated by binding to DNA single-strand and double-strand breaks. Its contribution to chromatin remodeling makes PARP1 crucial for gene expression regulation. Inhibition of its activity with small molecules leads to the synthetic lethal effect by impeding DNA repair in the treatment of cancer cells. At first, PARP1 inhibitors (PARPis) were developed to target breast cancer mutated cancer cells. Currently, PARPis are being studied to be used in a broader variety of patients either as single agents or in combination with chemotherapy, antiangiogenic agents, ionizing radiation, and immune checkpoint inhibitors. Ongoing clinical trials on olaparib, rucaparib, niraparib, veliparib, and the recent talazoparib show the advantage of these agents in overcoming PARPi resistance and underline their efficacy in targeted treatment of several hematologic malignancies. In this review, focusing on the crucial role of PARP1 in physiological and pathological effects in myelodysplastic syndrome and acute myeloid leukemia, we give an outline of the enzyme’s mechanisms of action and its role in the pathophysiology and prognosis of myelodysplastic syndrome/acute myeloid leukemia and we analyze the available data on the use of PARPis, highlighting their promising advances in clinical application.

WNT as a Driver and Dependency in Cancer

The WNT signaling pathway is a critical regulator of development and adult tissue homeostasis and becomes dysregulated in many cancer types. Although hyperactivation of WNT signaling is common, the type and frequency of genetic WNT pathway alterations can vary dramatically between different cancers, highlighting possible cancer-specific mechanisms for WNT-driven disease. In this review, we discuss how WNT pathway disruption contributes to tumorigenesis in different organs and how WNT affects the tumor cell and immune microenvironment. Finally, we describe recent and ongoing efforts to target oncogenic WNT signaling as a therapeutic strategy. SIGNIFICANCE: WNT signaling is a fundamental regulator of tissue homeostasis and oncogenic driver in many cancer types. In this review, we highlight recent advances in our understanding of WNT signaling in cancer, particularly the complexities of WNT activation in distinct cancer types, its role in immune evasion, and the challenge of targeting the WNT pathway as a therapeutic strategy.

Targeting the Wnt/β-Catenin Signaling Pathway as a Potential Therapeutic Strategy in Renal Tubulointerstitial Fibrosis

The Wnt/β-catenin signaling pathway plays important roles in embryonic development and tissue homeostasis. Wnt signaling is induced, and β-catenin is activated, associated with the development and progression of renal fibrosis. Wnt/β-catenin controls the expression of various downstream mediators such as snail1, twist, matrix metalloproteinase-7, plasminogen activator inhibitor-1, transient receptor potential canonical 6, and renin-angiotensin system components in epithelial cells, fibroblast, and macrophages. In addition, Wnt/β-catenin is usually intertwined with other signaling pathways to promote renal interstitial fibrosis. Actually, given the crucial of Wnt/β-catenin signaling in renal fibrogenesis, blocking this signaling may benefit renal interstitial fibrosis. There are several antagonists of Wnt signaling that negatively control Wnt activation, and these include soluble Fzd-related proteins, the family of Dickkopf 1 proteins, Klotho and Wnt inhibitory factor-1. Furthermore, numerous emerging small-molecule β-catenin inhibitors cannot be ignored to prevent and treat renal fibrosis. Moreover, we reviewed the knowledge focusing on anti-fibrotic effects of natural products commonly used in kidney disease by inhibiting the Wnt/β-catenin signaling pathway. Therefore, in this review, we summarize recent advances in the regulation, downstream targets, role, and mechanisms of Wnt/β-catenin signaling in renal fibrosis pathogenesis. We also discuss the therapeutic potential of targeting this pathway to treat renal fibrosis; this may shed new insights into effective treatment strategies to prevent and treat renal fibrosis.

Bioactivity Studies of Hesperidin and XAV939

The present work aimed to evaluate the reactivity of natural bioflavonoid hesperidin (HSP) and synthetically derived XAV939 (XAV) against human hepatocellular carcinoma (HepG2), human breast cancer (MDA-MB231) cancer cell lines, and related molecular and pathological profiles. Data recorded revealed that the cytotoxic potential of the tested products was found to be cell type- and concentration-dependent. The half-maximal inhibitory concentration (IC₅₀) value of the HSP-XAV mixture against MDA-MB231 was significantly decreased in the case of using the HSP-XAV mixture against the HepG2 cell line. Also, there was a significant upregulation of the phosphotumor suppressor protein gene (P53) and proapoptotic genes such as B-cell lymphoma-associated X-protein (Bax, CK, and Caspase-3), while antiapoptotic gene B-cell lymphoma (Bcl-2) was significantly downregulated compared with the untreated cell control. The cell cycle analysis demonstrated that DNA accumulation was detected mainly during the G2/M phase of the cell cycle accompanied with the elevated reactive oxygen species level in the treatment of HepG2 and MDA-MB231 cell lines by the HSP-XAV mixture, more significantly than that in the case of cell control. Finally, our finding suggests that both HSP and XAV939 and their mixture may offer an alternative in human liver and breast cancer therapy.

An Algorithm Combining Patient Performance Status, Second Hit Analysis, PROVEAN and Dann Prediction Tools Could Foretell Sensitization to PARP Inhibitors in Digestive, Skin, Ovarian and Breast Cancers

Simple Summary

PARP inhibitors, a family of targeted cancer therapeutics, have been shown to be efficient in patients with some deficiencies in the homologous recombination machinery. However, a quick and reliable identification of patients who would benefit from such therapies remains a challenge. In particular, patients with tumors carrying variants of unknown significance (VUS) in homologous recombination genes do not currently benefit from PARP inhibitor treatments. In this study, we present an algorithm that may allow classification of these variants with regard to their impact on tumor responsiveness to PARP inhibitors. If validated on a larger patient sample, our algorithm would allow patients with tumors potentially responsive to PARP inhibitors to benefit from this therapy.

Abstract

PARP inhibitors yield interesting outcomes for patients with ovarian tumors harboring BRCA1 or BRCA2 mutation, but also with other tumors with homologous repair (HR) deficiency. About 40% of variants are variants of unknown significance (VUS), blocking the use of PARP inhibitors. In this study, we analyzed NGS data from 78 metastatic patients treated with PARP inhibitors. We tested NGS data and in silico predictions to classify VUS as potentially benign or deleterious. Among 41 patients treated with olaparib, three had tumors harboring benign and 26 pathogenic variants, while 12 had VUS. Progression-Free Survival (PFS) analysis showed that benign variants did not respond to olaparib whereas pathogenic variants were associated with a median PFS of 190 days. Surprisingly, median PFS of patients with VUS-carrying tumors suggested that some of them may be sensitive to PARP inhibitors. By testing different in silico predictions and variant allelic frequency, we obtained an algorithm predicting VUS sensitivity to PARP inhibitors for patients with a Performance Status below 3. Our work suggests that VUS in HR genes could be predicted as benign or deleterious, which may increase the number of patients eligible for PARP inhibitor treatment. Further studies in a larger sample are warranted to validate our prediction algorithm.

Recent Advances in Therapeutic Application of DNA Damage Response Inhibitors against Cancer

DNA integrity is continuously challenged by intrinsic cellular processes and environmental agents. To overcome this genomic damage, cells have developed multiple signaling pathways collectively named as DNA damage response (DDR) and composed of three components: (i) sensor proteins, which detect DNA damage, (ii) mediators that relay the signal downstream and recruit the repair machinery, and (iii) the repair proteins, which restore the damaged DNA. A flawed DDR and failure to repair the damage lead to the accumulation of genetic lesions and increased genomic instability, which is recognized as a hallmark of cancer. Cancer cells tend to harbor increased mutations in DDR genes and often have fewer DDR pathways than normal cells. This makes cancer cells more dependent on particular DDR pathways and thus become more susceptible to compounds inhibiting those pathways compared to normal cells, which have all the DDR pathways intact. Understanding the roles of different DDR proteins in the DNA damage response and repair pathways and identification of their structures have paved the way for the development of their inhibitors as targeted cancer therapy. In this review, we describe the major participants of various DDR pathways, their significance in carcinogenesis, and focus on the inhibitors developed against several key DDR proteins.

The PARP Enzyme Family and the Hallmarks of Cancer Part 1. Cell Intrinsic Hallmarks

The 17-member poly (ADP-ribose) polymerase enzyme family, also known as the ADP-ribosyl transferase diphtheria toxin-like (ARTD) enzyme family, contains DNA damage-responsive and nonresponsive members. Only PARP1, 2, 5a, and 5b are capable of modifying their targets with poly ADP-ribose (PAR) polymers; the other PARP family members function as mono-ADP-ribosyl transferases. In the last decade, PARP1 has taken center stage in oncology treatments. New PARP inhibitors (PARPi) have been introduced for the targeted treatment of breast cancer 1 or 2 (BRCA1/2)-deficient ovarian and breast cancers, and this novel therapy represents the prototype of the synthetic lethality paradigm. Much less attention has been paid to other PARPs and their potential roles in cancer biology. In this review, we summarize the roles played by all PARP enzyme family members in six intrinsic hallmarks of cancer: uncontrolled proliferation, evasion of growth suppressors, cell death resistance, genome instability, reprogrammed energy metabolism, and escape from replicative senescence. In a companion paper, we will discuss the roles of PARP enzymes in cancer hallmarks related to cancer-host interactions, including angiogenesis, invasion and metastasis, evasion of the anticancer immune response, and tumor-promoting inflammation. While PARP1 is clearly involved in all ten cancer hallmarks, an increasing body of evidence supports the role of other PARPs in modifying these cancer hallmarks (e.g., PARP5a and 5b in replicative immortality and PARP2 in cancer metabolism). We also highlight controversies, open questions, and discuss prospects of recent developments related to the wide range of roles played by PARPs in cancer biology. Some of the summarized findings may explain resistance to PARPi therapy or highlight novel biological roles of PARPs that can be therapeutically exploited in novel anticancer treatment paradigms.

Tankyrase inhibitors as antitumor agents: a patent update (2013 - 2020)

INTRODUCTION

Tankyrase inhibitors gained significant attention as therapeutic targets in oncology because of their potency. Their primary role in inhibiting the Wnt signaling pathway makes them an important class of compounds with the potential to be used as a combination therapy in future treatments of colorectal cancer.

AREAS COVERED

This review describes pertinent work in the development of tankyrase inhibitors with a great emphasis on the recently patented TNKS inhibitors published from 2013 to 2020. This article also highlights a couple of promising candidates having tankyrase inhibitory effects and are currently undergoing clinical trials.

EXPERT OPINION

Following the successful clinical applications of PARP inhibitors, tankyrase inhibition has gained significant attention in the research community as a target with high therapeutic potential. The ubiquitous role of tankyrase in cellular homeostasis and Wnt-dependent tumor proliferation brought difficulties for researchers to strike the right balance between potency and on-target toxicity. The need for novel tankyrase inhibitors with a better ADMET profile can introduce an additional regimen in treating various malignancies in monotherapy or adjuvant therapy. The development of combination therapies, including tankyrase inhibitors with or without PARP inhibitory properties, can potentially benefit the larger population of patients with unmet medical needs.

Therapeutic targeting of the oncogenic Wnt signaling pathway for treating colorectal cancer and other colonic disorders

The canonical Wnt pathway is one of the key cellular signaling cascades that regulates, via the transcriptional co-activator β-catenin, numerous embryogenic developmental processes, as well as tissue homeostasis. It is therefore not surprising that misregulation of the Wnt/β-catenin pathway has been implicated in carcinogenesis. Aberrant Wnt signaling has been reported in a variety of malignancies, and its role in both hereditary and sporadic colorectal cancer (CRC), has been the subject of intensive study. Interestingly, the vast majority of colorectal tumors harbor mutations in the tumor suppressor gene adenomatous polyposis coli (APC). The Wnt pathway is complex, and despite decades of research, the mechanisms that underlie its functions are not completely known. Thus, although the Wnt cascade is an attractive target for therapeutic intervention against CRC, one of the malignancies with the highest morbidity and mortality rates, achieving efficacy and safety is yet extremely challenging. Here, we review the current knowledge of the Wnt different epistatic signaling components and the mechanism/s by which the signal is transduced in both health and disease, focusing on CRC. We address some of the important questions in the field and describe various therapeutic strategies designed to combat unregulated Wnt signaling, the development of targeted therapy approaches and the emerging challenges that are associated with these advanced methods.

Stenoparib, an Inhibitor of Cellular Poly(ADP-Ribose) Polymerase, Blocks Replication of the SARS-CoV-2 and HCoV-NL63 Human Coronaviruses In Vitro

By late 2020, the coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), had caused tens of millions of infections and over 1 million deaths worldwide. A protective vaccine and more effective therapeutics are urgently needed. We evaluated a new poly(ADP-ribose) polymerase (PARP) inhibitor, stenoparib, that recently advanced to phase II clinical trials for treatment of ovarian cancer, for activity against human respiratory coronaviruses, including SARS-CoV-2, in vitro Stenoparib exhibits dose-dependent suppression of SARS-CoV-2 multiplication and spread in Vero E6 monkey kidney and Calu-3 human lung adenocarcinoma cells. Stenoparib was also strongly inhibitory to the human seasonal respiratory coronavirus HCoV-NL63. Compared to remdesivir, which inhibits viral replication downstream of cell entry, stenoparib impedes entry and postentry processes, as determined by time-of-addition (TOA) experiments. Moreover, a 10 μM dosage of stenoparib-below the approximated 25.5 μM half-maximally effective concentration (EC50)-combined with 0.5 μM remdesivir suppressed coronavirus growth by more than 90%, indicating a potentially synergistic effect for this drug combination. Stenoparib as a stand-alone or as part of combinatorial therapy with remdesivir should be a valuable addition to the arsenal against COVID-19.IMPORTANCE New therapeutics are urgently needed in the fight against COVID-19. Repurposing drugs that are either already approved for human use or are in advanced stages of the approval process can facilitate more rapid advances toward this goal. The PARP inhibitor stenoparib may be such a drug, as it is currently in phase II clinical trials for the treatment of ovarian cancer and its safety and dosage in humans have already been established. Our results indicate that stenoparib possesses strong antiviral activity against SARS-CoV-2 and other coronaviruses in vitro. This activity appears to be based on multiple modes of action, where both pre-entry and postentry viral replication processes are impeded. This may provide a therapeutic advantage over many current options that have a narrower target range. Moreover, our results suggest that stenoparib and remdesivir in combination may be especially potent against coronavirus infection.

Zooming in on the WNT/CTNNB1 Destruction Complex: Functional Mechanistic Details with Implications for Therapeutic Targeting

WNT/CTNNB1 signaling is crucial for balancing cell proliferation and differentiation in all multicellular animals. CTNNB1 accumulation is the hallmark of WNT/CTNNB1 pathway activation and the key downstream event in both a physiological and an oncogenic context. In the absence of WNT stimulation, the cytoplasmic and nuclear levels of CTNNB1 are kept low because of its sequestration and phosphorylation by the so-called destruction complex, which targets CTNNB1 for proteasomal degradation. In the presence of WNT proteins, or as a result of oncogenic mutations, this process is impaired and CTNNB1 levels become elevated.Here we discuss recent advances in our understanding of destruction complex activity and inactivation, focusing on the individual components and interactions that ultimately control CTNNB1 turnover (in the "WNT off" situation) and stabilization (in the "WNT on" situation). We especially highlight the insights gleaned from recent quantitative, image-based studies, which paint an unprecedentedly detailed picture of the dynamic events that control destruction protein complex composition and function. We argue that these mechanistic details may reveal new opportunities for therapeutic intervention and could result in the destruction complex re-emerging as a target for therapy in cancer.