bmn-673 and olaparib

New molecular therapeutic approaches have emerged in recent years for advanced gynaecological cancers, including targeted therapies such as poly-ADP-ribose polymerase inhibitors (PARPi). These have demonstrated efficacy in high-grade serous ovarian cancers in patients carrying a mutation in the BRCA gene, which predisposes them to breast and ovarian cancers. Clinical and pre-clinical data suggest that the activity of PARPi inhibitors may not be limited to BRCA mutated tumours and may involve the homologous recombination pathway. These data raise the question of the potential efficacy of PARPi in advanced endometrial and cervical cancers where treatment options are currently limited. At present, there are few data available on the activity of PARPi in endometrial and cervical cancers, but some results seem promising. In this review, we present a synthesis of the available studies concerning PARPi in endometrial and cervical cancer.

Topics: Antineoplastic Agents; Cell Line, Tumor; Cisplatin; Clinical Trials as Topic; DNA Damage; DNA Repair-Deficiency Disorders; Endometrial Neoplasms; Female; Humans; Indazoles; Indoles; Ovarian Neoplasms; Papillomavirus Infections; Phthalazines; Piperazines; Piperidines; Poly(ADP-ribose) Polymerase Inhibitors; Uterine Cervical Neoplasms

We aimed to evaluate comparative safety and tolerability of the approved PARP inhibitors in people with cancer.. Eligible studies included randomized controlled trials comparing an approved PARP inhibitor (fluzoparib, olaparib, rucaparib, niraparib, or talazoparib) with placebo or chemotherapy in cancer patients. Outcomes of interest included: serious adverse event (SAE), discontinuation due to adverse event (AE), interruption of treatment due to AE, dose reduction due to AE, and specific grade 1-5 AEs.. Ten trials including 3763 participants and six treatments (olaparib, rucaparib, niraparib, talazoparib, placebo, and protocol-specified single agent chemotherapy) were identified. SAE and discontinuation of treatment did not differ significantly among the four approved PARP inhibitors. Regarding interruption of treatment and dose reduction due to AE, statistically significant differences and statistically non-significant trend were observed. Talazoparib is associated with a higher risk of interruption of treatment and dose reduction (excluding rucaparib) due to AE as compared with the other drugs. Niraparib showed a trend of lower risk of AE related dose reduction as compared with the other drugs. Furthermore, there were significant differences in specific grade 1-5 AE among the four drugs.. The safety profile of the four approved PARP inhibitors is comparable in terms of SAE and AE-related discontinuation of treatment. Statistically significant differences in the AEs spectrum and AEs related dose interruption and dose reduction demonstrated the prompt identification of AE and dose personalization seem mandatory to obtain maximal benefit from PARP inhibitors.

Topics: Humans; Indazoles; Indoles; Neoplasms; Network Meta-Analysis; Phthalazines; Piperazines; Piperidines; Poly(ADP-ribose) Polymerase Inhibitors; Randomized Controlled Trials as Topic

The standard treatment for advanced ovarian cancer is cytoreductive surgery followed by cytotoxic chemotherapy. However, it has high risk of recurrence and poor prognosis. Poly(ADPribose) polymerase (PARP) inhibitors selectively target DNA double-strand breaks (DSBs) in tumor cells that cannot be repaired and induce the synthetic lethality of BRCA1/2 mutation cancers. PARP inhibitors are clinically used to treat recurrent ovarian cancer and show significant efficacy in ovarian cancer patients with homologous recombination repair (HRR) pathway defects. PARP inhibitors also have significant clinical benefits in patients without HR defects. With the increasingly extensive clinical application of PARP inhibitors, the possibility of acquiring drug resistance is high. Therefore, clinical strategies should be adopted to manage drug resistance of PARP inhibitors. This study aims to summarize the indications and toxicity of PARP inhibitors, the mechanism of action, targeted treatment of drug resistance, and potential methods to manage drug-resistant diseases. We used the term "ovarian cancer" and the names of each PARP inhibitor as keywords to search articles published in the Medical Subject Headings (MeSH) on Pubmed, along with the keywords "clinicaltrials.gov" and "google.com/patents" as well as "uspto.gov." The FDA has approved olaparib, niraparib, and rucaparib for the treatment of recurrent epithelial ovarian cancer (EOC). Talazoparib and veliparib are currently in early trials and show promising clinical results. The mechanism underlying resistance to PARP inhibitors and the clinical strategies to overcome them remain unclear. Understanding the mechanism of resistance to PARP inhibitors and their relationship with platinum resistance may help with the development of antiresistance therapies and optimization of the sequence of drug application in the future clinical treatment of ovarian cancer.

Topics: Antineoplastic Agents; Benzimidazoles; BRCA1 Protein; BRCA2 Protein; Carcinoma, Ovarian Epithelial; DNA Repair; Drug Resistance, Neoplasm; Female; Humans; Indazoles; Indoles; Neoplasm Recurrence, Local; Ovarian Neoplasms; Phthalazines; Piperazines; Piperidines; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases

The poly-(ADP-ribose) polymerase (PARP) inhibitors olaparib and talazoparib, have recently been approved for use in patients with metastatic breast cancer (BC) and germline BRCA 1 or 2 mutations due to improved progression-free survival compared to chemotherapy. An increasing number of clinical trials are evaluating the role of PARP inhibitors (PARPi) in BC, alone and in combination with other therapies (including immunotherapy), as well as in earlier stages of the disease. This review describes the unique mechanism of action of these drugs and puts into clinical context the results of pivotal clinical trials. We also discuss the future development of PARPi in BC, their potential combination with other strategies, including chemotherapy and immune-checkpoint inhibitors, and the impact of these treatments in current genetic counselling.

Topics: Antineoplastic Agents; BRCA1 Protein; BRCA2 Protein; Breast Neoplasms; Female; Humans; Immunotherapy; Mutation; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases

Breast cancer is the most commonly diagnosed cancer and is the leading cause of cancer death in women worldwide. Both talazoparib and olaparib are approved by the US Food and Drug Administration for treating. To compare the efficacy, safety, and acceptability of single-agent poly (ADP-ribose) polymerase (PARP) inhibitors for patients with. We included two trials comprising 733 participants. Compared with talazoparib, olaparib was not associated with improved PFS (. Both talazoparib and olaparib have similar efficacy, safety, and acceptability in patients with. We performed a systematic review and network meta-analysis. We performed a systematic search of Web of Science, Embase, PubMed, Medline, ClinicalTrials.gov, the Cochrane Central Register of Controlled Trials, and the World Health Organization International Clinical Trials Registry Platform, and international registers for published and unpublished double-blind randomized controlled trials from database inception to July 20, 2019. The pooled estimates of hazard ratios (HR) with 95% credible intervals (CrIs) were calculated for PFS, OS, and the time to deterioration of quality of life (QoL). The pooled estimates of odds ratio (

Topics: Anemia; Breast Neoplasms; Female; Genes, BRCA1; Humans; Mutation; Neoplasm Metastasis; Network Meta-Analysis; Neutropenia; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Progression-Free Survival; Proportional Hazards Models; Quality of Life; Receptor, ErbB-2; Survival Rate; Treatment Outcome

Advanced triple negative breast cancer (TNBC) is an aggressive disease (high probability of visceral metastasis) with poor outcome. Triple negative breast cancer is characterized by lack of expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER2), high histologic grade, and high mitotic rate. Chemotherapy remains the primary systemic treatment, with international guidelines supporting the use of single-agent taxanes (with or without bevacizumab) or anthracyclines as first-line therapy, with a median overall survival of approximately 18 months or less. Given the suboptimal outcomes with chemotherapy, new targeted therapies for advanced TNBC are urgently needed. This review summarizes the current status of treatment, and future challenges of using new treatment options for advanced TNBC, such as poly-adenosine-diphosphate-ribose-polymerase inhibitors (olaparib and talazoparib) and immune checkpoint inhibitors (eg atezolizumab) as monotherapy or in combination with chemotherapy.

Topics: Antibodies, Monoclonal, Humanized; Antineoplastic Combined Chemotherapy Protocols; Bevacizumab; Female; Humans; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Triple Negative Breast Neoplasms

Genomic instability is a hallmark of cancer, and often is the result of altered DNA repair capacities in tumour cells. DNA damage repair defects are common in different cancer types; these alterations can also induce tumour-specific vulnerabilities that can be exploited therapeutically. In 2009, a first-in-man clinical trial of the poly(ADP-ribose) polymerase (PARP) inhibitor olaparib clinically validated the synthetic lethal interaction between inhibition of PARP1, a key sensor of DNA damage, and BRCA1/BRCA2 deficiency. In this review, we summarize a decade of PARP inhibitor clinical development, a work that has resulted in the registration of several PARP inhibitors in breast (olaparib and talazoparib) and ovarian cancer (olaparib, niraparib and rucaparib, either alone or following platinum chemotherapy as maintenance therapy). Over the past 10 years, our knowledge on the mechanism of action of PARP inhibitor as well as how tumours become resistant has been extended, and we summarise this work here. We also discuss opportunities for expanding the precision medicine approach with PARP inhibitors, identifying a wider population who could benefit from this drug class. This includes developing and validating better predictive biomarkers for patient stratification, mainly based on homologous recombination defects beyond BRCA1/BRCA2 mutations, identifying DNA repair deficient tumours in other cancer types such as prostate or pancreatic cancer, or by designing combination therapies with PARP inhibitors.

Topics: BRCA1 Protein; BRCA2 Protein; Breast Neoplasms; Female; Genomic Instability; Humans; Indazoles; Indoles; Ovarian Neoplasms; Phthalazines; Piperazines; Piperidines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors

Treatment of Epithelial Ovarian Cancer (EOC), historically based on surgery and platinum doublet chemotherapy, is associated with high risk of relapse and poor prognosis for recurrent disease. In this landscape, the innovative treatment with PARP inhibitors (PARPis) demonstrated an outstanding activity in EOC, and is currently changing clinical practice in BRCA mutant patients.. The study aimed to highlight the mechanism of action, pharmacokinetics, clinical activity, indications and current strategies of development of Olaparib, Niraparib, Rucaparib, Talazoparib and Veliparib, the 5 most relevant PARPis.. We performed a review on Pubmed using 'ovarian cancer' and the name of each PARPi (PARP inhibitor) discussed in the review as Medical Subject Headings (MeSH) keywords. The same search was performed on "clinicaltrial.gov" to identify ongoing clinical trials and on "google. com/patents" and "uspto.gov" for recent patents exploring PARPIs in ovarian cancer.. Olaparib, Niraparib and Rucaparib are already approved for the treatment of recurrent EOC and their indications are partially overlapping. Talazoparib and Veliparib are promising PARPis, but currently under investigation in early phase trials. Several studies are evaluating PARPis in monotherapy or in associations, in a wide range of settings (i.e. first line, neoadjuvant, platinum-sensitive and resistant disease).. PARPis are valuable options in patients with recurrent ovarian cancer with promising activity in different stages of this disease. Further studies are required to better define optimal clinical settings, predictors of response beyond BRCA mutations and strategies to overcome secondary resistance of PARPis therapy in EOC.

Topics: Animals; Antineoplastic Agents; Drug Resistance, Neoplasm; Female; Humans; Ovarian Neoplasms; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors

The single agent activity of PARP inhibitors (PARPi) in germline BRCA mutated (gBRCAm) breast and ovarian cancer suggests untapped potential for this new class of drug in breast cancer. The US Food and Drug Administration has approved three PARPi (olaparib, rucaparib, and niraparib) so far to treat certain ovarian cancers, including those with gBRCAm and olaparib for treatment of gBRCAm breast cancers. Several PARPi are now under clinical development for breast cancer in the various treatment settings. Recently, two phase III trials of olaparib (OlympiaD) and talazoparib (EMBRACA) demonstrated 3-month progression-free survival improvement with PARPi compared to physician's choice single agent chemotherapy in metastatic gBRCAm breast cancer. To date, PARPi seems less efficacious in metastatic breast cancer patients than those with BRCA mutated platinum-sensitive recurrent ovarian cancer, perhaps reflecting the biologic heterogeneity and low somatic BRCA mutation rate in breast cancer. The use of PARPi is gradually evolving, including combination strategies with chemotherapy, targeted agents, radiotherapy, or immunotherapy in women with and without gBRCAm. The role of predictive biomarkers, including molecular signatures and homologous recombination repair deficiency scores based on loss of heterozygosity and other structural genomic aberrations, will be crucial to identify a subgroup of patients who may have benefit from PARPi. An improved understanding of the mechanisms underlying PARPi clinical resistance will also be important to enable the development of new approaches to increase efficacy. This is a field rich in opportunity, and the coming years should see a better understanding of which breast cancer patients we should treat with PARPi and where these agents should come in over the course of treatment.

Topics: BRCA1 Protein; BRCA2 Protein; Breast Neoplasms; Female; Humans; Indazoles; Indoles; Neoplasm Recurrence, Local; Phthalazines; Piperazines; Piperidines; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Progression-Free Survival

PARP enzymes are essential for DNA damage repair. Cancers with defective homologous recombination DNA repair, such has

Topics: Antineoplastic Combined Chemotherapy Protocols; BRCA1 Protein; BRCA2 Protein; Breast Neoplasms; DNA Repair; Female; Germ-Line Mutation; Humans; Neoplasm Staging; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Randomized Controlled Trials as Topic; Synthetic Lethal Mutations; Treatment Outcome

Use of poly(ADP-ribose) polymerase (PARP) inhibitors has greatly increased over the past 5 years. With several new Food and Drug Administration (FDA) approvals, three PARP inhibitors have entered into standard of care treatment for epithelial ovarian cancer (including ovarian, fallopian tube, and primary peritoneal cancer). Olaparib and rucaparib currently have indications for treatment of recurrent BRCA mutant ovarian cancer. Olaparib, rucaparib, and niraparib all have indications for maintenance therapy in recurrent platinum-sensitive ovarian cancer after response to platinum-based therapy. In our practice, we use both olaparib and rucaparib in the recurrent setting, and all three PARP inhibitors in the maintenance setting. Choice of which PARP inhibitor to use in either setting is largely based upon baseline laboratory values, number of prior therapies, and presence of a BRCA mutation and/or homologous recombination deficiency (HRD). As (HRD) and other biomarker assessments continue to improve, we anticipate being able to better identify which patients might most benefit from PARP inhibitor therapy in the future. The clinically available PARP inhibitors are currently undergoing extensive investigations in clinical trials. Other newer agents such as talazoparib, veliparib, 2X-121, and CEP-9722 are in earlier stages of development. As more FDA-approved indications for PARP inhibitor therapy in ovarian cancer become available, we anticipate the decision of which PARP inhibitor to use will become increasingly complex.

Topics: Antineoplastic Combined Chemotherapy Protocols; Benzimidazoles; BRCA1 Protein; BRCA2 Protein; Carbazoles; Carcinoma, Ovarian Epithelial; Female; Humans; Indazoles; Indoles; Neoplasm Recurrence, Local; Ovarian Neoplasms; Ovary; Phthalazines; Phthalimides; Piperazines; Piperidines; Poly(ADP-ribose) Polymerase Inhibitors

SCLC accounts for 15% of lung cancer worldwide. Characterised by early dissemination and rapid development of chemo-resistant disease, less than 5% of patients survive 5 years. Despite 3 decades of clinical trials there has been no change to the standard platinum and etoposide regimen for first line treatment developed in the 1970's. The exceptionally high number of genomic aberrations observed in SCLC combined with the characteristic rapid cellular proliferation results in accumulation of DNA damage and genomic instability. To flourish in this precarious genomic context, SCLC cells are reliant on functional DNA damage repair pathways and cell cycle checkpoints. Current cytotoxic drugs and radiotherapy treatments for SCLC have long been known to act by induction of DNA damage and the response of cancer cells to such damage determines treatment efficacy. Recent years have witnessed improved understanding of strategies to exploit DNA damage and repair mechanisms in order to increase treatment efficacy. This review will summarise the rationale to target DNA damage response in SCLC, the progress made in evaluating novel DDR inhibitors and highlight various ongoing challenges for their clinical development in this disease.

Topics: Aurora Kinases; Azepines; Benzimidazoles; Carbolines; Cell Cycle Checkpoints; Cell Proliferation; Cytotoxins; DNA Damage; DNA Repair; Etoposide; Genomic Instability; Heterocyclic Compounds, 4 or More Rings; Humans; Lung Neoplasms; Molecular Targeted Therapy; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Protein Kinase Inhibitors; Pyrimidines; Rad51 Recombinase; Small Cell Lung Carcinoma

Poly(ADP-ribose) polymerases(PARP) synthesize the ADP-ribose polymers onto proteins and play a role in DNA repair. PARP inhibitors block the repair of single-strand breaks, which in turn gives rise to double-strand breaks during DNA replication. Thus, PARP inhibitors elicit synthetic lethality in cancer with BRCA1/2 loss-of-function mutations that hamper homologous recombination repair of double-strand breaks. Olaparib, the first-in-class PARP inhibitor, was approved for treatment of BRCA-mutated ovarian cancer in Europe and the United States in 2014. Other PARP inhibitors under clinical trials include rucaparib, niraparib, veliparib, and the "PARP-trapping" BMN-673. BRCA1/2 sequencing is an FDA-approved companion diagnostics, which predicts the cancer vulnerability to PARP inhibition. Together, synthetic lethal PARP inhibition is a novel promising strategy for cancer intervention even in cases without prominent driver oncogenes.

Topics: Antineoplastic Agents; Benzimidazoles; BRCA1 Protein; BRCA2 Protein; DNA Breaks, Double-Stranded; DNA Replication; DNA, Single-Stranded; Enzyme Inhibitors; Humans; Indazoles; Indoles; Molecular Targeted Therapy; Mutation; Neoplasms; Phthalazines; Piperazines; Piperidines; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Recombinational DNA Repair

Clinical investigation of poly(ADP-ribose) polymerase (PARP) inhibitors for ovarian cancer treatment has rapidly evolved from observations of single-agent in vitro activity of these agents in BRCA-deficient cancer cells in 2005 to the initiation of multiple phase III studies in 2013. With clinical trial design and treatment of ovarian cancer increasingly based on histological and molecular characteristics, PARP inhibitors are on the horizon of becoming the first biologic agents to be used to treat ovarian cancer based upon pre-selection characteristics of the patient's cancer. PARP inhibitors are most active in ovarian cancers that have defects or aberrations in DNA repair; use of these agents has been of particular interest in high grade serous cancers (HGSC), where studies have shown that ~50% of HGSC have abnormalities of DNA repair through BRCA germline and somatic mutation, post-translational changes of BRCA, and abnormalities of other DNA repair molecules. In addition, as aberrant DNA pathways in other histological subtypes of ovarian cancer are identified, and through the combination of PARP inhibitors with other biologic agents, the pool of eligible patients who may benefit from PARP inhibitors will likely expand. Pending review by the Food and Drug Administration (FDA) and the outcome of confirmatory phase III studies, PARP inhibitors could become the first FDA-approved biologic agent for ovarian cancer and also the first new FDA-approval in ovarian cancer since carboplatin and gemcitabine were approved for platinum sensitive ovarian cancer in 2006. This review discusses the PARP inhibitors that are currently in testing for ovarian cancer treatment and the future of this class of anti-cancer agents.

Topics: Antineoplastic Agents; Benzimidazoles; DNA Repair; Female; Genes, BRCA1; Genes, BRCA2; Humans; Indazoles; Indoles; Ovarian Neoplasms; Phthalazines; Piperazines; Piperidines; Poly(ADP-ribose) Polymerase Inhibitors

Topics: Adenosine Diphosphate Ribose; Alkylating Agents; DNA; DNA Damage; DNA Repair; Methyl Methanesulfonate; Phthalazines; Piperazines; Poisons; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Temozolomide

Inhibition of Poly (ADP-ribose) Polymerases (PARP) results in the blocking of DNA repair cascades that eventually leads to apoptosis and cancer cell death. PARP inhibitors (PARPi) exhibit their actions either by inhibiting PARP-induced PARylation and/or by trapping PARP at the DNA damage site. But, the mechanism of PARPi-mediated induction of cellular toxicity via PARP-trapping is largely unknown.. The cellular toxicity of PARPi [Talazoparib (BMN) and/or Olaparib (Ola)] was investigated in oral cancer cells and the underlying mechanism was studied by using in vitro, in silico, and in vivo preclinical model systems.. The experimental data suggested that induction of DNA damage is imperative for the optimal effectiveness of PARPi. Curcumin (Cur) exhibited maximum DNA damaging capacity in comparison to Resveratrol and 5-Flurouracil. Combination of BMN + Ola induced cell death in Cur pre-treated cells at much lower concentrations than their individual treatments. BMN + Ola treatment deregulated the BER cascade, potentiated PARP-trapping, caused cell cycle arrest and apoptosis in Cur pre-treated cells in a much more effective manner than their individual treatments. In silico data indicated the involvement of different amino acid residues which might play important roles in enhancing the BMN + Ola-mediated PARP-trapping. Moreover, in vivo mice xenograft data also suggested the BMN + Ola-mediated enhancement of apoptotic potentiality of Cur.. Thus, induction of DNA damage was found to be essential for optimal functioning of PARPi and BMN + Ola combination treatment enhanced the apoptotic potentiality of Cur in cancer cells by enhancing the PARP-trapping activity via modulation of BER cascade.

Topics: Adenosine Diphosphate; Amino Acids; Animals; Apoptosis; Cell Line, Tumor; Curcumin; DNA; Humans; Mice; Mouth Neoplasms; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Resveratrol; Ribose

Triple negative breast cancer (TNBC) represents approximately 10-15% of all breast cancers and has a poor outcome as it lacks a receptor target for therapy, and TNBC is frequently associated with a germline mutation of BRCA1. Poly (ADP-ribose) polymerase inhibitor (PARPi) drugs have demonstrated some effectiveness in treating BRCA1 or BRCA2 mutated breast and ovarian cancers but resistance to PARPi is common. Published results found that resistance to Olaparib, a PARPi, can be due to downregulation of EMI1 and the consequent upregulation of the RAD51 recombinase. Using a tissue culture-based cell viability assay, we extended those observations to another PARPi and to other chemotherapy drugs that affect DNA repair or the cell cycle. As we expected, EMI1 downregulation resulted in resistance to another PARPi drug, Talazoparib. EMI1 downregulation also led to resistance to other cytotoxic drugs, Cisplatin and CHK1 inhibitor. Notably, increasing the RAD51 protein expression only recapitulated some, but not all, of the effects of EMI1 depletion in conferring to the cell resistance to different PARPi and the other cytotoxic drugs. These results suggest that the downstream effects of EMI1 downregulation that contribute to PARPi resistance are increasing the concentration of RAD51 protein in the cell and blocking mitotic entry. We found that combining CHK1 inhibitor with olaparib results in restoration of sensitivity even when EMI1 expression is downregulated. This combination therapy may be a means to overcome the PARPi resistance in BRCA1-deficient TNBC cells.

Topics: BRCA1 Protein; BRCA2 Protein; Cell Cycle; Cell Cycle Proteins; Cell Line, Tumor; Cisplatin; Down-Regulation; Drug Resistance, Neoplasm; F-Box Proteins; Female; Germ-Line Mutation; Humans; Ovarian Neoplasms; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Rad51 Recombinase; Triple Negative Breast Neoplasms

Poly-(ADP-ribose) polymerase 1 and 2 (PARP1 and PARP2) are key enzymes in the DNA damage response. Four different inhibitors (PARPi) are currently in the clinic for treatment of ovarian and breast cancer. Recently, histone PARylation Factor 1 (HPF1) has been shown to play an essential role in the PARP1- and PARP2-dependent poly-(ADP-ribosylation) (PARylation) of histones, by forming a complex with both enzymes and altering their catalytic properties. Given the proximity of HPF1 to the inhibitor binding site both PARPs, we hypothesized that HPF1 may modulate the affinity of inhibitors toward PARP1 and/or PARP2. Here we demonstrate that HPF1 significantly increases the affinity for a PARP1 - DNA complex of some PARPi (i.e., olaparib), but not others (i.e., veliparib). This effect of HPF1 on the binding affinity of Olaparib also holds true for the more physiologically relevant PARP1 - nucleosome complex but does not extend to PARP2. Our results have important implications for the interpretation of PARP inhibition by current PARPi as well as for the design and analysis of the next generation of clinically relevant PARP inhibitors.

Topics: Antineoplastic Agents; Benzamides; Benzimidazoles; Binding Sites; Carrier Proteins; Catalysis; Catalytic Domain; DNA Repair Enzymes; Humans; Indazoles; Indoles; Nuclear Proteins; Phthalazines; Piperazines; Piperidines; Poly (ADP-Ribose) Polymerase-1; Protein Binding

There is emerging interest in the role of poly(ADP-ribose) polymerase-1 (PARP-1) in neurodegeneration and potential of its therapeutic targeting in neurodegenerative disorders. New generations of PARP inhibitors exhibit polypharmacological properties; they do not only block enzymatic activity with lower doses, but also alter how PARP-1 interacts with DNA. While these new inhibitors have proven useful in cancer therapy due to their ability to kill cancer cell, their use in neurodegenerative disorders has an opposite goal: cell protection. We hypothesize that newer generation PARP-1 inhibitors jeopardize the viability of dividing CNS cells by promoting DNA damage upon the PARP-DNA interaction. Using enriched murine astrocyte cultures, our study evaluates the effects of a variety of drugs known to inhibit PARP; talazoparib, olaparib, PJ34 and minocycline. Despite similar PARP enzymatic inhibiting activities, we show here that these drugs result in varied cell viability. Talazoparib and olaparib reduce astrocyte growth in a dose-dependent manner, while astrocytes remain unaffected by PJ34 and minocycline. Similarly, PJ34 and minocycline do not jeopardize DNA integrity, while treatment with talazoparib and olaparib promote DNA damage. These two drugs impact astrocytes similarly in basal conditions and upon nitrosative stress, a pathological condition typical for neurodegeneration. Mechanistic assessment revealed that talazoparib and olaparib promote PARP trapping onto DNA in a dose-dependent manner, while PJ34 and minocycline do not induce PARP-DNA trapping. This study provides unique insight into the selective use of PARP inhibitors to treat neurodegenerative disorders whereby inhibition of PARP enzymatic activity must occur without deleteriously trapping PARP onto DNA.

Topics: Animals; Astrocytes; Cell Survival; DNA; DNA Damage; Mice; Minocycline; Neurodegenerative Diseases; Phenanthrenes; Phthalazines; Piperazines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors

Topics: Bayes Theorem; Breast Neoplasms; Female; Germ Cells; Germ-Line Mutation; Humans; Phthalazines; Piperazines

PARP1 inhibitor (Niraparib, Olaparib, Rucaparib) maintenance therapy improves progression-free survival in platinum sensitive sporadic epithelial ovarian cancers. However, biomarkers of response to PARPi therapy is yet to be clearly defined. XRCC1, a scaffolding protein, interacts with PARP1 during BER and SSBR. In a large clinical cohort of 525 sporadic ovarian cancers, high XRCC1 or high PARP1 protein levels was not only associated with aggressive phenotypes but was also significantly linked with poor progression-free survival (p = 0.048 & p = 0.001 respectively) and poor ovarian cancer-specific survival (p = 0.020 & p = 0.008 respectively). Pre-clinically, Olaparib and Talazoparib therapy were selectively toxic in XRCC1 deficient or knock-out platinum sensitive ovarian cancer cells in 2D and 3D models. Increased sensitivity was associated with DNA double-strand break accumulation, cell cycle arrest and apoptotic cell accumulation. We conclude that XRCC1 deficiency predicts sensitivity to PARP inhibitor therapy. PARP1 targeting is a promising new approach in XRCC1 deficient ovarian cancers.

Topics: Carcinoma, Ovarian Epithelial; Cell Cycle Checkpoints; Cell Line, Tumor; DNA Breaks, Double-Stranded; Drug Resistance, Neoplasm; Female; Follow-Up Studies; Gene Expression Profiling; Gene Knockout Techniques; Humans; Kaplan-Meier Estimate; Ovarian Neoplasms; Ovary; Phthalazines; Piperazines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Prognosis; Progression-Free Survival; Synthetic Lethal Mutations; Tissue Array Analysis; X-ray Repair Cross Complementing Protein 1

Poly(adenosine diphosphate ribose) polymerase (PARP) inhibitors exhibit promising activity against ovarian cancers, but their efficacy can be limited by acquired drug resistance. This study explores the role of autophagy in regulating the sensitivity of ovarian cancer cells to PARP inhibitors.. Induction of autophagy was detected by punctate LC3 fluorescence staining, LC3I to LC3II conversion on Western blot analysis, and electron microscopy. Enhanced growth inhibition and apoptosis were observed when PARP inhibitors were used with hydroxychloroquine, chloroquine (CQ), or LYS05 to block the hydrolysis of proteins and lipids in autophagosomes or with small interfering RNA against ATG5 or ATG7 to prevent the formation of autophagosomes. The preclinical efficacy of the combination of CQ and olaparib was evaluated with a patient-derived xenograft (PDX) and the OVCAR8 human ovarian cancer cell line.. Four PARP inhibitors (olaparib, niraparib, rucaparib, and talazoparib) induced autophagy in a panel of ovarian cancer cells. Inhibition of autophagy with CQ enhanced the sensitivity of ovarian cancer cells to PARP inhibitors. In vivo, olaparib and CQ produced additive growth inhibition in OVCAR8 xenografts and a PDX. Olaparib inhibited PARP activity, and this led to increased reactive oxygen species (ROS) and an accumulation of γ-H2AX. Inhibition of autophagy also increased ROS and γ-H2AX and enhanced the effect of olaparib on both entities. Treatment with olaparib increased phosphorylation of ATM and PTEN while decreasing the phosphorylation of AKT and mTOR and inducing autophagy.. PARP inhibitor-induced autophagy provides an adaptive mechanism of resistance to PARP inhibitors in cancer cells with wild-type BRCA, and a combination of PARP inhibitors with CQ or other autophagy inhibitors could improve outcomes for patients with ovarian cancer.

Topics: Animals; Antineoplastic Agents; Apoptosis; Autophagy; Cell Line, Tumor; Chloroquine; Drug Resistance, Neoplasm; Drug Synergism; Female; Humans; Indazoles; Mice, Nude; Mice, SCID; Ovarian Neoplasms; Phthalazines; Piperazines; Piperidines; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Xenograft Model Antitumor Assays

Polypharmacology plays an important role in defining response and adverse effects of drugs. For some mechanisms, experimentally mapping polypharmacology is commonplace, although this is typically done within the same protein class. Four PARP inhibitors have been approved by the FDA as cancer therapeutics, yet a precise mechanistic rationale to guide clinicians on which to choose for a particular patient is lacking. The four drugs have largely similar PARP family inhibition profiles, but several differences at the molecular and clinical level have been reported that remain poorly understood. Here, we report the first comprehensive characterization of the off-target kinase landscape of four FDA-approved PARP drugs. We demonstrate that all four PARP inhibitors have a unique polypharmacological profile across the kinome. Niraparib and rucaparib inhibit DYRK1s, CDK16 and PIM3 at clinically achievable, submicromolar concentrations. These kinases represent the most potently inhibited off-targets of PARP inhibitors identified to date and should be investigated further to clarify their potential implications for efficacy and safety in the clinic. Moreover, broad kinome profiling is recommended for the development of PARP inhibitors as PARP-kinase polypharmacology could potentially be exploited to modulate efficacy and side-effect profiles.

Topics: Antineoplastic Agents; Binding Sites; Cyclin-Dependent Kinases; Dyrk Kinases; HEK293 Cells; Humans; Indazoles; Indoles; Isoenzymes; Molecular Docking Simulation; Neoplasms; Phthalazines; Piperazines; Piperidines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Polypharmacology; Protein Binding; Protein Interaction Domains and Motifs; Protein Serine-Threonine Kinases; Protein Structure, Secondary; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Substrate Specificity

In this study, we addressed the underlying mechanisms for the association between enzalutamide (ENZ) treatment and neuroendocrine prostate cancer (NEPC), and the critical involvement of MYCN, and loss of RB1 function in neuroendocrine differentiation (NED) of prostatic epithelial cells, and the development of NEPC. We further sought to determine whether PARP inhibition could suppress NEPC, and to identify molecular determinants of this therapeutic activity.. We used a novel prostate cancer patient-derived xenograft (PDX) treatment model, prostatic adenocarcinoma and NEPC cell lines, an NEPC organoid line, and NEPC xenograft models to address the mechanistic basis of ENZ-induced NED, and to analyze suppression of NED and NEPC growth by PARP inhibition.. We identified an ENZ treatment-associated glucocorticoid receptor (GR)-MYCN-CDK5-RB1-E2F1 signaling pathway that drives NED in prostatic adenocarcinoma PDX and cell line models. Mechanistically, long-term ENZ treatment transcriptionally upregulates signaling of the GR-MYCN axis, leading to CDK5R1 and CDK5R2 upregulation, Rb1 phosphorylation, and N-Myc-mediated and E2F1-mediated NED gene expression. Importantly, olaparib (OLA) or talazoparib (TALA) suppressed these activities, and the combination of OLA and dinaciclib (DINA), an inhibitor of CDK2 and CDK5, which also inhibits Rb1 phosphorylation, suppressed NED and significantly improved therapeutic efficiency in NEPC cells. The results of our study indicate an important role of GR-MYCN-CDK5R1/2-RB1-NED signaling in ENZ-induced and PARP inhibitor-suppressed NEPC. We also demonstrated efficacy for OLA+DINA combination therapy in NEPC xenograft models.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Benzamides; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Cyclic N-Oxides; Cyclin-Dependent Kinase 5; E2F1 Transcription Factor; Gene Expression Regulation, Neoplastic; Humans; Indolizines; Male; Mice, Nude; N-Myc Proto-Oncogene Protein; Neuroendocrine Tumors; Nitriles; Phenylthiohydantoin; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Prostatic Neoplasms, Castration-Resistant; Proteins; Pyridinium Compounds; Receptors, Glucocorticoid; Retinoblastoma Binding Proteins; Signal Transduction; Treatment Outcome; Ubiquitin-Protein Ligases; Xenograft Model Antitumor Assays

Up to 40% of lung adenocarcinoma have been reported to lack ataxia-telangiectasia mutated (ATM) protein expression. We asked whether ATM-deficient lung cancer cell lines are sensitive to poly-ADP ribose polymerase (PARP) inhibitors and determined the mechanism of action of olaparib in ATM-deficient A549 cells.. We analysed drug sensitivity data for olaparib and talazoparib in lung adenocarcinoma cell lines from the Genomics of Drug Sensitivity in Cancer (GDSC) project. We deleted ATM from A549 lung adenocarcinoma cells using CRISPR/Cas9 and determined the effects of olaparib and the ATM/Rad3-related (ATR) inhibitor VE-821 on cell viability.. IC. Patients with tumours characterised by ATM-deficiency may benefit from treatment with a PARP inhibitor in combination with an ATR inhibitor.

Topics: Adenocarcinoma; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Ataxia Telangiectasia Mutated Proteins; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Clustered Regularly Interspaced Short Palindromic Repeats; Gene Deletion; Histones; Humans; Lung Neoplasms; Mutation; Nitroso Compounds; Phosphorylation; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Pyrazines; Pyrimidines; RNA, Messenger; Sulfones; Tumor Suppressor Protein p53

Poly (ADP-ribose) polymerase (PARP) inhibitors have demonstrated great promise in the treatment of patients with deficiencies in homologous recombination (HR) DNA repair, such as those with loss of BRCA1 or BRCA2 function. However, emerging studies suggest that PARP inhibition can also target HR-competent cancers, such as non-small-cell lung cancer (NSCLC), and that the therapeutic effect of PARP inhibition may be improved by combination with chemotherapy agents. In our study, it was found that PARP inhibitors talazoparib (BMN-673) and olaparib (AZD-2281) both had synergistic activity with the common first-line chemotherapeutic gemcitabine in a panel of lung cancer cell lines. Furthermore, the combination demonstrated significant in vivo antitumor activity in an H23 xenograft model of NSCLC compared to either agent as monotherapy. This synergism occurred without loss of HR repair efficiency. Instead, the combination induced synergistic single-strand DNA breaks, leading to accumulation of toxic double-strand DNA lesions in vitro and in vivo. Our study elucidates the underlying mechanisms of synergistic activity of PARP inhibitors and gemcitabine, providing a strong motivation to pursue this combination as an improved therapeutic regimen.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; BRCA1 Protein; BRCA2 Protein; Carcinoma, Non-Small-Cell Lung; Cell Line, Tumor; Deoxycytidine; DNA Damage; Drug Synergism; Female; Gemcitabine; Humans; Lung Neoplasms; Male; Mice; Mice, Nude; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Recombinational DNA Repair; Xenograft Model Antitumor Assays

With increasing uses of poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) for cancer therapy, understanding their resistance is becoming urgent. However, acquired PARPi resistance in the phosphatase and tensin homolog (PTEN)-deficient background is poorly understood. We generated 3 PARPi-resistant PTEN-deficient glioblastoma U251 variants separately with olaparib (U251/OP), talazoparib (U251/TP) and simmiparib (U251/SP). These variants displayed consistent resistance (2.46-71.78-fold) to all 5 PARPi, including niraparib and rucaparib, and showed higher degrees of resistance to the PARPi to which the parental cells were more sensitive. The resistance was characteristic of fast emergence and high stability. However, the resistance acquirement did not cause an increasingly aggressive phenotype. The resistance was not correlated to various factors, including PTEN mutations. The PARPi-treated variants produced less γH2AX and G2/M arrest. Consistently, loss of 53BP1 occurred in all variants and its compensation enhanced their sensitivity to PARPi by approximately 76%. The variants revealed slightly different cross-resistance profiles to 13 non-PARPi anticancer drugs. All were resistant to Ara-C (6-8-fold) but showed differential resistance to 5-fluorouracil, gemcitabine and paclitaxel. Almost no resistance was observed to the rest drugs, including cisplatin. SAMHD1 was overexpressed in all the variants and its knockout completely restored their sensitivity to Ara-C but did not affect their PARPi sensitivity. The present study demonstrates a consistent resistance profile to PARPi and a unique cross-resistance profile to non-PARPi drugs in different PARPi-resistant U251 cells and reveals 53BP1 loss and SAMHD1 overexpression as the primary mechanisms responsible for their resistance to PARPi and Ara-C, respectively. These effects probably result from heritable gene change(s) caused by persistent PARPi exposure.

Topics: Antineoplastic Agents; Cell Line, Tumor; Cytarabine; Drug Resistance, Neoplasm; Gene Expression Regulation, Neoplastic; Glioblastoma; Humans; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; PTEN Phosphohydrolase; SAM Domain and HD Domain-Containing Protein 1; Tumor Suppressor p53-Binding Protein 1

Insufficient chemotherapy response and rapid disease progression remain concerns for small-cell lung cancer (SCLC). Oncologists rely on serial CT scanning to guide treatment decisions, but this cannot assess in vivo target engagement of therapeutic agents. Biomarker assessments in biopsy material do not assess contemporaneous target expression, intratumoral drug exposure, or drug-target engagement. Here, we report the use of PARP1/2-targeted imaging to measure target engagement of PARP inhibitors in vivo. Using a panel of clinical PARP inhibitors, we show that PARP imaging can quantify target engagement of chemically diverse small molecule inhibitors in vitro and in vivo. We measure PARP1/2 inhibition over time to calculate effective doses for individual drugs. Using patient-derived xenografts, we demonstrate that different therapeutics achieve similar integrated inhibition efficiencies under different dosing regimens. This imaging approach to non-invasive, quantitative assessment of dynamic intratumoral target inhibition may improve patient care through real-time monitoring of drug delivery.

Topics: Animals; Cell Line, Tumor; Dose-Response Relationship, Drug; Humans; Lung Neoplasms; Mice, Inbred NOD; Mice, Knockout; Mice, SCID; Molecular Targeted Therapy; Phthalazines; Piperazines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Positron Emission Tomography Computed Tomography; Small Cell Lung Carcinoma; Xenograft Model Antitumor Assays

Poly (ADP-ribose) polymerase (PARP) inhibitors have been shown to enhance the radiosensitivity of cancer cells in vitro in a replication-dependent manner. Their in vivo radiosensitizing effects have also been demonstrated in preclinical tumor models. However, whether PARP inhibition can enhance the response to radiation therapy in normal tissues has been largely neglected. We hypothesized that PARP inhibition might also potentiate the response of replicating normal tissues to radiation therapy. In this study, we examined the normal tissue response in mice treated with PARP inhibitors (BMN673 or AZD2281) in combination with thoracic irradiation.. The antitumor effects of fractionated irradiation (5 Gy × 4) in combination with BMN673 were evaluated in nude mice bearing established Calu-6 human lung cancer xenografts. The normal tissue response was evaluated in C57BL6 mice that were treated with BMN673 or AZD2281 combined with fractionated irradiation, 5 Gy × 4, delivered to the whole thorax. Body weight and histology of the esophagus and skin in the field of irradiation were examined. The DNA damage response in the esophagus and skin was assessed by γH2AX immunohistochemistry.. While PARP inhibition enhanced irradiation-induced tumor growth inhibition in nude mice, it was also associated with significant body weight loss and increased damage to the esophagus and skin within the field of irradiation in C57BL6 mice. PARP inhibition compromised the repair of irradiation-induced DNA damage in the esophagus and skin.. Although PARP inhibition enhanced the antitumor response to fractionated irradiation, it also enhanced the irradiation response in replicating normal tissues. Therefore, our study suggests that additional caution may be warranted in the clinical development of combination therapies using PARP inhibitors and radiation therapy, in particular where the field of irradiation includes the esophagus.

Topics: Animals; Combined Modality Therapy; DNA Damage; Esophagus; Female; Heterografts; Histones; Humans; Lung Neoplasms; Mice; Mice, Inbred C57BL; Mice, Nude; Organs at Risk; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Radiation Injuries, Experimental; Radiation-Sensitizing Agents; Skin; Weight Loss

PARP-l is a DNA repair protein that plays a role in a number of repair pathways and also helps in transcriptional regulation; thus PARP inhibitors (PARPi), such as olaparib and BMN-673, act by inhibiting DNA damage repair. This leads to an accumulation of deleterious mutations leading to genetic instability as a result of a number of cell replications. Currently, olaparib is only available in an oral form and has poor bioavailability, consequently leading to poor accumulation in the tumor due to first-pass metabolism. Therefore, in the present study, an injectable nanoparticle formulation of olaparib was created that offers a delivery route in which the drug would be fully bioavailable in the vasculature, suggesting greater tumor accumulation. Our results illustrated that injectable nanoformulations of olaparib and BMN-673, a next generation PARPi, could be developed, and an efficacy test indicated that BMN-673 is a much more potent PARPi than olaparib. The success of these molecular inhibitors as a monotherapy in inhibiting colony formation suggests enhanced efficacy of these treatments in combination with other therapies, even in tumors which have developed resistance.

Topics: Antineoplastic Agents; Biological Availability; Cell Line, Tumor; Drug Delivery Systems; Humans; Nanostructures; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors

Mutations in FMS-like tyrosine kinase 3 (FLT3), such as internal tandem duplications (ITDs), can be found in up to 23% of patients with acute myeloid leukemia (AML) and confer a poor prognosis. Current treatment options for FLT3(ITD)-positive AMLs include genotoxic therapy and FLT3 inhibitors (FLT3i's), which are rarely curative. PARP1 inhibitors (PARP1i's) have been successfully applied to induce synthetic lethality in tumors harboring BRCA1/2 mutations and displaying homologous recombination (HR) deficiency. We show here that inhibition of FLT3(ITD) activity by the FLT3i AC220 caused downregulation of DNA repair proteins BRCA1, BRCA2, PALB2, RAD51, and LIG4, resulting in inhibition of 2 major DNA double-strand break (DSB) repair pathways, HR, and nonhomologous end-joining. PARP1i, olaparib, and BMN673 caused accumulation of lethal DSBs and cell death in AC220-treated FLT3(ITD)-positive leukemia cells, thus mimicking synthetic lethality. Moreover, the combination of FLT3i and PARP1i eliminated FLT3(ITD)-positive quiescent and proliferating leukemia stem cells, as well as leukemic progenitors, from human and mouse leukemia samples. Notably, the combination of AC220 and BMN673 significantly delayed disease onset and effectively reduced leukemia-initiating cells in an FLT3(ITD)-positive primary AML xenograft mouse model. In conclusion, we postulate that FLT3i-induced deficiencies in DSB repair pathways sensitize FLT3(ITD)-positive AML cells to synthetic lethality triggered by PARP1i's. Therefore, FLT3(ITD) could be used as a precision medicine marker for identifying AML patients that may benefit from a therapeutic regimen combining FLT3 and PARP1i's.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Benzothiazoles; BRCA1 Protein; BRCA2 Protein; Cell Line, Tumor; DNA Ligase ATP; DNA Repair; Fanconi Anemia Complementation Group N Protein; fms-Like Tyrosine Kinase 3; Humans; Leukemia, Myeloid, Acute; Mice; Mutation; Phenylurea Compounds; Phthalazines; Piperazines; Poly (ADP-Ribose) Polymerase-1; Protein Kinase Inhibitors; Rad51 Recombinase; Tumor Suppressor Proteins; Xenograft Model Antitumor Assays

The observation that BRCA1- and BRCA2-deficient cells are sensitive to inhibitors of poly(ADP-ribose) polymerase (PARP) has spurred the development of cancer therapies that use these inhibitors to target deficiencies in homologous recombination

Topics: Animals; BRCA1 Protein; Cell Line; CRISPR-Cas Systems; DNA Damage; DNA Repair; DNA Replication; DNA Topoisomerases, Type I; Female; Gene Editing; Genes, BRCA1; Genome; HeLa Cells; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Male; Mice; Neoplasms; Phthalazines; Piperazines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Prostatic Neoplasms; Ribonuclease H; Ribonucleotides; Synthetic Lethal Mutations; Xenograft Model Antitumor Assays

: Targeting PARP1 for synthetic lethality is a new strategy for breast cancers harboring germline mutations in BRCA. However, these mutations are rare, and reactivation of BRCA-mediated pathways may result in eventual resistance to PARP1 inhibitor therapy. Alternative synthetic lethality approaches targeting more common sporadic breast cancers and preinvasive ductal carcinoma

Topics: Apoptosis; Breast Neoplasms; Carcinoma, Intraductal, Noninfiltrating; Cell Cycle; Cell Line, Tumor; Chemoprevention; CRISPR-Cas Systems; DNA Breaks, Double-Stranded; DNA Repair; Female; Germ-Line Mutation; HeLa Cells; Humans; Indazoles; Neoplasm Invasiveness; Neoplasm Recurrence, Local; Phthalazines; Piperazines; Piperidines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Spheroids, Cellular; Synthetic Lethal Mutations; X-ray Repair Cross Complementing Protein 1

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Drug Discovery; Drug Screening Assays, Antitumor; Humans; Male; Mice; Mice, Nude; Molecular Structure; Neoplasms, Experimental; Phthalazines; Piperazines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Rats; Rats, Sprague-Dawley; Structure-Activity Relationship

Approximately 20% of metastatic prostate cancers harbor mutations in genes required for DNA repair by homologous recombination repair (HRR) such as

Topics: Antineoplastic Agents; BRCA2 Protein; Cell-Free Nucleic Acids; DNA Copy Number Variations; Drug Resistance, Neoplasm; Exome Sequencing; Germ-Line Mutation; Humans; Male; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Prostatic Neoplasms

Quiescent and proliferating leukemia cells accumulate highly lethal DNA double-strand breaks that are repaired by 2 major mechanisms: BRCA-dependent homologous recombination and DNA-dependent protein kinase-mediated (DNA-PK-mediated) nonhomologous end-joining, whereas DNA repair pathways mediated by poly(ADP)ribose polymerase 1 (PARP1) serve as backups. Here we have designed a personalized medicine approach called gene expression and mutation analysis (GEMA) to identify BRCA- and DNA-PK-deficient leukemias either directly, using reverse transcription-quantitative PCR, microarrays, and flow cytometry, or indirectly, by the presence of oncogenes such as BCR-ABL1. DNA-PK-deficient quiescent leukemia cells and BRCA/DNA-PK-deficient proliferating leukemia cells were sensitive to PARP1 inhibitors that were administered alone or in combination with current antileukemic drugs. In conclusion, GEMA-guided targeting of PARP1 resulted in dual cellular synthetic lethality in quiescent and proliferating immature leukemia cells, and is thus a potential approach to eradicate leukemia stem and progenitor cells that are responsible for initiation and manifestation of the disease. Further, an analysis of The Cancer Genome Atlas database indicated that this personalized medicine approach could also be applied to treat numerous solid tumors from individual patients.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Cell Proliferation; Cell Transformation, Neoplastic; Cricetinae; DNA Breaks, Double-Stranded; DNA End-Joining Repair; Genes, abl; Genes, BRCA1; Genes, BRCA2; Genes, Lethal; Humans; Leukemia; Mice; Mice, Inbred NOD; Mice, Knockout; Mice, SCID; Mouse Embryonic Stem Cells; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Transcriptome; Xenograft Model Antitumor Assays

Phosphatase and Tensin homolog (PTEN) is a tumor suppressor gene. Loss of its function is the most frequent genetic alteration in endometrioid endometrial cancers (70-80%) and high grade tumors (90%). We assessed the sensitivity of endometrial cancer cell lines to PARP inhibitors (olaparib and BMN-673) and a PI3K inhibitor (BKM-120), alone or in combination, in the context of their PTEN mutation status. We also highlighted a direct pathway linking PTEN to DNA repair.. Using endometrial cancer cellular models with known PTEN status, we evaluated their homologous recombination (HR) functionality by RAD51 foci formation assay. The 50% Inhibitory concentration (IC50) of PI3K and PARP inhibitors in these cells was assessed, and western blotting was performed to determine the expression of proteins involved in the PI3K/mTOR pathway. Moreover, we explored the interaction between RAD51 and PI3K/mTOR by immunofluorescence. Next, the combination effect of PI3K and PARP inhibitors on cell proliferation was evaluated by a clonogenic assay.. Cells with mutated PTEN showed over-activation of the PI3K/mTOR pathway. These cells were more sensitive to PARP inhibition compared to PTEN wild-type cells. In addition, PI3K inhibitor treatment reduced RAD51 foci formation in PTEN mutated cells, and sensitized these cells to PARP inhibitor.. Targeting both PARP and PI3K might lead to improved personalized therapeutic approaches in endometrial cancer patients with PTEN mutations. Understanding the complex interaction of PTEN mutations with DNA repair in endometrial cancer will help to better select patients that are likely to respond to some of the new and costly targeted therapies.

Topics: Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Cell Proliferation; DNA Repair; Drug Resistance, Neoplasm; Endometrial Neoplasms; Female; Gene Expression Regulation, Neoplastic; Humans; Mutation; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; PTEN Phosphohydrolase; Rad51 Recombinase; Signal Transduction; TOR Serine-Threonine Kinases

PARP inhibitors (PARPi) are a novel class of small molecule therapeutics for small cell lung cancer (SCLC). Identification of predictors of response would advance our understanding, and guide clinical application, of this therapeutic strategy.. Efficacy of PARP inhibitors olaparib, rucaparib, and veliparib, as well as etoposide and cisplatin in SCLC cell lines, and gene expression correlates, was analyzed using public datasets. HRD genomic scar scores were calculated from Affymetrix SNP 6.0 arrays. In vitro talazoparib efficacy was measured by cell viability assays. For functional studies, CRISPR/Cas9 and shRNA were used for genomic editing and transcript knockdown, respectively. Protein levels were assessed by immunoblotting and immunohistochemistry (IHC). Quantitative synergy of talazoparib and temozolomide was determined in vitro In vivo efficacy of talazoparib, temozolomide, and the combination was assessed in patient-derived xenograft (PDX) models.. We identified SLFN11, but not HRD genomic scars, as a consistent correlate of response to all three PARPi assessed, with loss of SLFN11 conferring resistance to PARPi. We confirmed these findings in vivo across multiple PDX and defined IHC staining for SLFN11 as a predictor of talazoparib response. As temozolomide has activity in SCLC, we investigated combination therapy with talazoparib and found marked synergy in vitro and efficacy in vivo, which did not solely depend on SLFN11 or MGMT status.. SLFN11 is a relevant predictive biomarker of sensitivity to PARP inhibitor monotherapy in SCLC and we identify combinatorial therapy with TMZ as a particularly promising therapeutic strategy that warrants further clinical investigation. Clin Cancer Res; 23(2); 523-35. ©2016 AACR.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Benzimidazoles; Cell Line, Tumor; Cisplatin; Dacarbazine; Drug Synergism; Etoposide; Gene Expression Regulation, Neoplastic; Genomics; Humans; Indoles; Mice; Nuclear Proteins; Phthalazines; Piperazines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Small Cell Lung Carcinoma; Temozolomide; Xenograft Model Antitumor Assays

Selective inhibitors could help unveil the mechanisms by which inhibition of poly(ADP-ribose) polymerases (PARPs) elicits clinical benefits in cancer therapy. We profiled 10 clinical PARP inhibitors and commonly used research tools for their inhibition of multiple PARP enzymes. We also determined crystal structures of these compounds bound to PARP1 or PARP2. Veliparib and niraparib are selective inhibitors of PARP1 and PARP2; olaparib, rucaparib, and talazoparib are more potent inhibitors of PARP1 but are less selective. PJ34 and UPF1069 are broad PARP inhibitors; PJ34 inserts a flexible moiety into hydrophobic subpockets in various ADP-ribosyltransferases. XAV939 is a promiscuous tankyrase inhibitor and a potent inhibitor of PARP1 in vitro and in cells, whereas IWR1 and AZ-6102 are tankyrase selective. Our biochemical and structural analysis of PARP inhibitor potencies establishes a molecular basis for either selectivity or promiscuity and provides a benchmark for experimental design in assessment of PARP inhibitor effects.

Topics: Animals; Benzimidazoles; Enzyme Inhibitors; HEK293 Cells; Humans; Indazoles; Models, Molecular; Phenanthrenes; Phthalazines; Piperazines; Piperidines; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Tankyrases

Topics: Animals; Antibodies, Monoclonal, Humanized; Antineoplastic Combined Chemotherapy Protocols; BRCA1 Protein; BRCA2 Protein; Camptothecin; Cell Line, Tumor; DNA Repair; DNA Topoisomerases, Type I; Drug Resistance, Neoplasm; Female; Gene Expression Regulation, Neoplastic; Humans; Immunoconjugates; Indoles; Mice; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Synthetic Lethal Mutations; Triple Negative Breast Neoplasms; Xenograft Model Antitumor Assays

Poly(ADP-ribose) polymerase inhibitors (PARPIs) kill cancer cells by trapping PARP1 and PARP2. Talazoparib, the most potent PARPI inhibitor (PARPI), exhibits remarkable selectivity among the NCI-60 cancer cell lines beyond BRCA inactivation. Our genomic analyses reveal high correlation between response to talazoparib and Schlafen 11 (SLFN11) expression. Causality was established in four isogenic SLFN11-positive and -negative cell lines and extended to olaparib. Response to the talazoparib-temozolomide combination was also driven by SLFN11 and validated in 36 small cell lung cancer cell lines, and in xenograft models. Resistance in SLFN11-deficient cells was caused neither by impaired drug penetration nor by activation of homologous recombination. Rather, SLFN11 induced irreversible and lethal replication inhibition, which was independent of ATR-mediated S-phase checkpoint. The resistance to PARPIs by SLFN11 inactivation was overcome by ATR inhibition, mechanistically because SLFN11-deficient cells solely rely on ATR activation for their survival under PARPI treatment. Our study reveals that SLFN11 inactivation, which is common (~45%) in cancer cells, is a novel and dominant resistance determinant to PARPIs.

Topics: Animals; Antineoplastic Agents; Apoptosis; Ataxia Telangiectasia Mutated Proteins; Cell Cycle; Cell Line, Tumor; Cell Survival; Disease Models, Animal; Drug Resistance, Neoplasm; Female; Gene Expression; Gene Silencing; Homologous Recombination; Humans; Mice; Nuclear Proteins; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Transcriptional Activation; Xenograft Model Antitumor Assays

Colorectal cancer (CRC) is a leading cause of cancer-related death throughout the world. Despite improved screening efforts, most CRCs are diagnosed at late stages when surgery alone is not curative. Moreover, the low 5-year survival rate (~8-13%) for those living with stage IV CRC highlights the need for better treatment options. Many current chemotherapeutic approaches are non-specific and associated with side effects due to their tendency to target both normal and cancer cells. To address this issue, synthetic lethal (SL) approaches are now being explored in cancer and are defined as the lethal combination of two independently viable mutations/deletions. From a therapeutic perspective, SL interactors of genes mutated in cancer serve as candidate drug targets. The present study focuses on RAD54B, a gene that is aberrantly expressed in many cancer types, including CRC. We show that PARP1 silencing or inhibition (BMN673 or Olaparib) leads to selective killing within RAD54B-deficient cells relative to controls, and is accompanied by increases in γ-H2AX (a surrogate marker of DNA double strand breaks) and cleaved Caspase-3 (an apoptotic indicator). We further show that BMN673 synergizes with LCS-1 (an inhibitor of an established RAD54B SL interactor) to induce enhanced killing in RAD54B-deficient cells. Collectively, these data identify RAD54B and PARP1 as SL interactors, and thus reveal PARP1 as a novel candidate drug target in RAD54B-deficient CRCs. These findings further show that combinatorial chemotherapies involving multiple SL targets may promote synergistic killing within cancer cells, a strategy that may hold potential in many cancer contexts.

Topics: Apoptosis; Caspase 3; Cell Survival; Colorectal Neoplasms; DNA Helicases; HCT116 Cells; Histones; Humans; Nuclear Proteins; Phthalazines; Piperazines; Poly (ADP-Ribose) Polymerase-1; Superoxide Dismutase-1

Poly(ADP-ribose) polymerases (PARP1, -2, and -3) play important roles in DNA damage repair. As such, a number of PARP inhibitors are undergoing clinical development as anticancer therapies, particularly in tumors with DNA repair deficits and in combination with DNA-damaging agents. Preclinical evidence indicates that PARP inhibitors potentiate the cytotoxicity of DNA alkylating agents. It has been proposed that a major mechanism underlying this activity is the allosteric trapping of PARP1 at DNA single-strand breaks during base excision repair; however, direct evidence of allostery has not been reported. Here the data reveal that veliparib, olaparib, niraparib, and talazoparib (BMN-673) potentiate the cytotoxicity of alkylating agents. Consistent with this, all four drugs possess PARP1 trapping activity. Using biochemical and cellular approaches, we directly probe the trapping mechanism for an allosteric component. These studies indicate that trapping is due to catalytic inhibition and not allostery. The potency of PARP inhibitors with respect to trapping and catalytic inhibition is linearly correlated in biochemical systems but is nonlinear in cells. High-content imaging of γH2Ax levels suggests that this is attributable to differential potentiation of DNA damage in cells. Trapping potency is inversely correlated with tolerability when PARP inhibitors are combined with temozolomide in mouse xenograft studies. As a result, PARP inhibitors with dramatically different trapping potencies elicit comparable in vivo efficacy at maximum tolerated doses. Finally, the impact of trapping on tolerability and efficacy is likely to be context specific.. Understanding the context-specific relationships of trapping and catalytic inhibition with both tolerability and efficacy will aid in determining the suitability of a PARP inhibitor for inclusion in a particular clinical regimen.

Topics: Animals; Antineoplastic Agents, Alkylating; Benzimidazoles; Cell Line; Cell Line, Tumor; DNA Damage; DNA Repair; DNA-Binding Proteins; Drug Tolerance; Humans; Indazoles; Mice; Neoplasms, Experimental; Phthalazines; Piperazines; Piperidines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases

Anti-PARP drugs were initially developed as catalytic inhibitors to block the repair of DNA single-strand breaks. We recently reported that several PARP inhibitors have an additional cytotoxic mechanism by trapping PARP-DNA complexes, and that both olaparib and niraparib act as PARP poisons at pharmacologic concentrations. Therefore, we have proposed that PARP inhibitors should be evaluated based both on catalytic PARP inhibition and PARP-DNA trapping. Here, we evaluated the novel PARP inhibitor, BMN 673, and compared its effects on PARP1 and PARP2 with two other clinical PARP inhibitors, olaparib and rucaparib, using biochemical and cellular assays in genetically modified chicken DT40 and human cancer cell lines. Although BMN 673, olaparib, and rucaparib are comparable at inhibiting PARP catalytic activity, BMN 673 is ∼100-fold more potent at trapping PARP-DNA complexes and more cytotoxic as single agent than olaparib, whereas olaparib and rucaparib show similar potencies in trapping PARP-DNA complexes. The high level of resistance of PARP1/2 knockout cells to BMN 673 demonstrates the selectivity of BMN 673 for PARP1/2. Moreover, we show that BMN 673 acts by stereospecific binding to PARP1 as its enantiomer, LT674, is several orders of magnitude less efficient. BMN 673 is also approximately 100-fold more cytotoxic than olaparib and rucaparib in combination with the DNA alkylating agents methyl methane sulfonate (MMS) and temozolomide. Our study demonstrates that BMN 673 is the most potent clinical PARP inhibitor tested to date with the highest efficiency at trapping PARP-DNA complexes.

Topics: Adenosine Triphosphate; Animals; Cell Cycle; Cell Line, Tumor; Cell Survival; Dacarbazine; DNA; Dose-Response Relationship, Drug; Drug Synergism; Enzyme Inhibitors; Fluorescence Polarization; Humans; Immunoblotting; Indoles; Inhibitory Concentration 50; Methyl Methanesulfonate; Molecular Structure; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Stereoisomerism; Temozolomide

Ewing sarcoma (EWS) is a tumor of the bone and soft tissue that primarily affects adolescents and young adults. With current therapies, 70% of patients with localized disease survive, but patients with metastatic or recurrent disease have a poor outcome. We found that EWS cell lines are defective in DNA break repair and are sensitive to PARP inhibitors (PARPis). PARPi-induced cytotoxicity in EWS cells was 10- to 1,000-fold higher after administration of the DNA-damaging agents irinotecan or temozolomide. We developed an orthotopic EWS mouse model and performed pharmacokinetic and pharmacodynamic studies using three different PARPis that are in clinical development for pediatric cancer. Irinotecan administered on a low-dose, protracted schedule previously optimized for pediatric patients was an effective DNA-damaging agent when combined with PARPis; it was also better tolerated than combinations with temozolomide. Combining PARPis with irinotecan and temozolomide gave complete and durable responses in more than 80% of the mice.

Topics: Animals; Benzimidazoles; Camptothecin; Cell Death; Cell Line, Tumor; Dacarbazine; DNA Breaks, Double-Stranded; DNA Repair; Drug Synergism; Enzyme Inhibitors; Irinotecan; Mice, Nude; Molecular Targeted Therapy; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Sarcoma, Ewing; Temozolomide; Xenograft Model Antitumor Assays

Excision repair cross-complementation group 1 (ERCC1) is a DNA repair enzyme that is frequently defective in non-small cell lung cancer (NSCLC). Although low ERCC1 expression correlates with platinum sensitivity, the clinical effectiveness of platinum therapy is limited, highlighting the need for alternative treatment strategies. To discover new mechanism-based therapeutic strategies for ERCC1-defective tumours, we performed high-throughput drug screens in an isogenic NSCLC model of ERCC1 deficiency and dissected the mechanism underlying ERCC1-selective effects by studying molecular biomarkers of tumour cell response. The high-throughput screens identified multiple clinical poly (ADP-ribose) polymerase 1 and 2 (PARP1/2) inhibitors, such as olaparib (AZD-2281), niraparib (MK-4827) and BMN 673, as being selective for ERCC1 deficiency. We observed that ERCC1-deficient cells displayed a significant delay in double-strand break repair associated with a profound and prolonged G₂/M arrest following PARP1/2 inhibitor treatment. Importantly, we found that ERCC1 isoform 202, which has recently been shown to mediate platinum sensitivity, also modulated PARP1/2 sensitivity. A PARP1/2 inhibitor-synthetic lethal siRNA screen revealed that ERCC1 deficiency was epistatic with homologous recombination deficiency. However, ERCC1-deficient cells did not display a defect in RAD51 foci formation, suggesting that ERCC1 might be required to process PARP1/2 inhibitor-induced DNA lesions before DNA strand invasion. PARP1 silencing restored PARP1/2 inhibitor resistance in ERCC1-deficient cells but had no effect in ERCC1-proficient cells, supporting the hypothesis that PARP1 might be required for the ERCC1 selectivity of PARP1/2 inhibitors. This study suggests that PARP1/2 inhibitors as a monotherapy could represent a novel therapeutic strategy for NSCLC patients with ERCC1-deficient tumours.

Topics: Antineoplastic Agents; Carcinoma, Non-Small-Cell Lung; Cell Line; Cell Line, Tumor; DNA Breaks, Double-Stranded; DNA Repair; DNA-Binding Proteins; Endonucleases; Enzyme Inhibitors; G2 Phase Cell Cycle Checkpoints; High-Throughput Screening Assays; Humans; Indazoles; Lung Neoplasms; Phthalazines; Piperazines; Piperidines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Protein Isoforms; Rad51 Recombinase; RNA Interference; RNA, Small Interfering