Crosstalk with lung fibroblasts shapes the growth and therapeutic response of mesothelioma cells

Mesothelioma is an aggressive cancer of the mesothelial layer associated with an extensive fibrotic response. The latter is in large part mediated by cancer-associated fibroblasts which mediate tumour progression and poor prognosis. However, understanding of the crosstalk between cancer cells and fibroblasts in this disease is mostly lacking. Here, using co-cultures of patient-derived mesothelioma cell lines and lung fibroblasts, we demonstrate that fibroblast activation is a self-propagated process producing a fibrotic extracellular matrix (ECM) and triggering drug resistance in mesothelioma cells. Following characterisation of mesothelioma cells/fibroblasts signalling crosstalk, we identify several FDA-approved targeted therapies as far more potent than standard-of-care Cisplatin/Pemetrexed in ECM-embedded co-culture spheroid models. In particular, the SRC family kinase inhibitor, Saracatinib, extends overall survival well beyond standard-of-care in a mesothelioma genetically-engineered mouse model. In short, we lay the foundation for the rational design of novel therapeutic strategies targeting mesothelioma/fibroblast communication for the treatment of mesothelioma patients.

The role of PARP inhibitor combination therapy in ovarian cancer

The use of PARP inhibitors (PARPi) has transformed the care of advanced high-grade serous/endometrioid ovarian cancer. PARPi are now available to patients in both the first-line and recurrent platinum-sensitive disease settings; therefore, most patients will receive PARPi at some point in their treatment pathway. The majority of this expanding population of patients eventually acquire resistance to PARPi, in addition to those with primary PARPi resistance. We discuss the rationale behind developing combination therapies, to work synergistically with PARPi and overcome mechanisms of resistance to restore drug sensitivity, and clinical evidence of their efficacy to date.

Identification of Promising Drug Candidates against Prostate Cancer through Computationally-Driven Drug Repurposing

Prostate cancer (PC) is one of the most common types of cancer in males. Although early stages of PC are generally associated with favorable outcomes, advanced phases of the disease present a significantly poorer prognosis. Moreover, currently available therapeutic options for the treatment of PC are still limited, being mainly focused on androgen deprivation therapies and being characterized by low efficacy in patients. As a consequence, there is a pressing need to identify alternative and more effective therapeutics. In this study, we performed large-scale 2D and 3D similarity analyses between compounds reported in the DrugBank database and ChEMBL molecules with reported anti-proliferative activity on various PC cell lines. The analyses included also the identification of biological targets of ligands with potent activity on PC cells, as well as investigations on the activity annotations and clinical data associated with the more relevant compounds emerging from the ligand-based similarity results. The results led to the prioritization of a set of drugs and/or clinically tested candidates potentially useful in drug repurposing against PC.

Rational Combinations of PARP Inhibitors with HRD-Inducing Molecularly Targeted Agents

Cancers with wild-type BRCA, homologous recombination proficiency, or de novo or acquired resistance to PARP inhibition represent a growing population of patients who may benefit from combinatorial PARP inhibitor strategies. We review targeted inhibitors of angiogenesis, epigenetic regulators, and PI3K, MAPK, and other cellular signaling pathways as inducers of homologous recombination deficiency, providing support for the use of PARP inhibitors in contexts not previously considered susceptible to PARP inhibition.

PARP inhibitors as single agents and in combination therapy: the most promising treatment strategies in clinical trials for BRCA-mutant ovarian and triple-negative breast cancers

INTRODUCTION

Poly (ADP-ribose) polymerase inhibitors (PARPis) are an exciting class of agents that have shown efficacy, particularly for BRCA-mutant triple-negative breast cancer (TNBC) and high-grade serous ovarian cancer (HGSOC). However, most patients who receive PARPi as their standard of care therapy inevitably develop resistance and this underscores the need to identify additional targets that can circumvent such resistance. Combination treatment strategies have been developed in preclinical and clinical studies to address the challenges of efficacy and resistance.

AREAS COVERED

This review examines completed or ongoing clinical trials of PARPi mono- and combination therapies. PARPi monotherapy in HER2 negative breast (HR+ and TNBC subtypes) and ovarian cancer is a focal point. The authors propose potential strategies that might overcome resistance to PARPi and discuss key questions and future directions.

EXPERT OPINION

While the advent of PARPis has significantly improved the treatment of tumors with defects in DNA damage and repair pathways, careful patient selection will be essential to enhance these treatments. The identification of molecular biomarkers to predict disease response and progression is an endeavor.

PARP inhibitors in hereditary breast and ovarian cancer and other cancers: A review

There has been a paradigm shift in the management of cancer, with the immense progress in cancer genomics. More and more targeted therapies are becoming available by the day and personalized medicine is becoming popular with specific drugs being designed for selected subgroups of patients. One such new class of targeted drugs in the armamentarium is Poly ADP Ribose Polymerase (PARP) inhibitors (PARPi), which inhibit the enzyme PARP, thus interfering with DNA repair. This strategy utilizes a pre-existing genomic lesion in tumors with homologous recombination repair defects (including BRCA mutations), weakening tumor cells further by blocking the alternate pathway of DNA repair. In this review, we discuss in detail, the evolution, genetics, mechanism of action, mechanism of resistance, indications of use of PARP inhibitors, as well as combination with other agents and future directions.

PARP-inhibitors in epithelial ovarian cancer: Actual positioning and future expectations

Poly-(ADP)-ribose polymerase inhibitors (PARPi) are a class of oral anticancer drugs first developed as "synthetically lethal" in cancers harboring BRCA1/BRCA2 inactivating mutations. In high-grade serous or endometrioid ovarian cancers (HGOC), PARPi demonstrated benefit as maintenance therapy in relapsing BRCA-mutated and non-mutated tumors. Recently, they extended their indications to frontline maintenance therapy. This review summarizes the current place of PARPi (i) as maintenance or single agent in recurrent disease and (ii) frontline maintenance with different settings. We reviewed the course of biomarker identification, the challenge of overcoming resistance to PARPi and future combinations with targeted therapies, including anti-angiogenic, immune checkpoint inhibitors and DNA damage response inhibitors.

Investigational PARP inhibitors for the treatment of biliary tract cancer: spotlight on preclinical and clinical studies

Introduction: Alterations in DNA damage repair (DDR) genes are observed in up to 60% of biliary tract cancer (BTC) patients. Patients with advanced/metastatic BTC have few therapeutic options, so there is a demand for the development of new and innovative treatment approaches. The use of poly-adenosine diphosphate-ribose polymerase (PARP) inhibitors (PARPis), either as a monotherapy or in combination, is being extensively studied in clinical trials.Areas Covered: This review examines the targeting of the DDR pathway with PARPis as a potential novel treatment option for the management of BTCs. The rationale behind the use of PARPis and current clinical experience is discussed. Moreover, further insights into potential future directions concerning the applicability of PARPis in the treatment of BTCs are proposed.Expert Opinion: Prospective clinical data with PARPis in the treatment of BTCs are limited. The potential combination of PARPis and IDH1 inhibitors or immune checkpoint inhibitors in clinical trials is interesting because of the potential synergistic preclinical data. There are other possible combinations including those drugs that target the angiogenesis or STAT3 pathways. An enhanced understanding of acquired resistance to PARPis is necessary to progress the use of these agents in clinical trials.

Current and future landscape of poly (ADP-ribose) polymerase inhibition resistance

PURPOSE OF REVIEW

To highlight relevant strategies to overcome poly(ADP-ribose) polymerase (PARP) inhibitor resistance and present key clinical trials.

RECENT FINDINGS

The use of PARP inhibition (PARPi) for frontline maintenance offers substantial clinical benefit in patients with homologous recombination-deficient tumors. However, expanding PARPi from recurrent therapy to frontline maintenance may potentially result in more PARPi resistant tumors earlier in the treatment continuum and data for the use of PARPi after PARPi remain limited. Clinical evidence demonstrates tumors may develop resistance to PARPi through demethylation of the BRCA promoter or BRCA reversion mutations. Multiple clinical trials investigating therapeutic strategies to overcome resistance, such as combinations of PARPi with antiangiogenic drugs, PI3K/AKT/mTOR, or MEK inhibitors have already been reported and more are ongoing. Furthermore, increasing the amount of DNA damage in the tumor using chemotherapy or cell cycle inhibitors such as ATM, ATR/CHK1/WEE1 is also under exploration.

SUMMARY

There is increasing clinical interest to identify options to enhance PARPi efficacy and overcome adaptive resistance. PARPi represent a class of drugs that have significantly impacted the treatment and maintenance of ovarian cancer; as the use of PARPi increases, better understanding of resistance mechanisms is essential.

Update on the Role of Poly (ADP-Ribose) Polymerase Inhibitors in the DNA Repair-Deficient Pancreatic Cancers: A Narrative Review

Purpose: Pancreatic ductal adenocarcinoma (PDAC) is the most common cancer found in the pancreas. It has a dismal prognosis and current therapeutic options, including surgical resection, provide only a temporary or limited response due to the development of treatment resistance. Methods: A narrative review of studies investigating poly (ADP-ribose) polymerase (PARP) pathway inhibitors in metastatic PDAC to highlight recent advances. Results: Mutations in BRCA genes confer a higher risk of PDAC, while germ line mutations are found in 4-7% of individuals harboring pancreatic cancer. Although solid tumors with defective DNA damage repair defect (DDR) genes such as BRCA show heightened sensitivity to platinum agents, tumors can exploit the PARP pathway as salvage pathways. Therefore, blocking this pathway will trigger cell death in vulnerable tumor cells with BRCA/DNA repair deficiency. Several drugs with inhibitory activity on the PARP pathway have been approved for breast and ovarian tumors harboring germ line or somatic BRCA mutations. Based on these results, the phase III POLO study showed a significant improvement in progression-free survival compared with placebo in BRCA mutant pancreatic tumors and highlighted the importance of germ line testing in everyone diagnosed with pancreatic cancer. In addition, expansion of the PARP inhibitor indication beyond BRCA mutations to other genes involved in DDR such as ATM and PALB2 merits attention. Conclusion: PARP inhibitors represent a safe and efficacious treatment for a subset of PDAC patients with BRCA mutations. Ongoing trials are evaluating PARP inhibitors in PDAC patients with non-BRCA DDR gene deficiencies as well as PARP inhibitors in combination with other agents, notably immune checkpoint inhibitors to expand the group of patients that derive benefit from this treatment.

The new world of poly-(ADP)-ribose polymerase inhibitors (PARPi) used in the treatment of gynecological cancers

The clinical development of poly-(ADP)-ribose polymerase inhibitors (PARPi) began with the treatment of ovarian cancer patients harboring BRCA1/2 mutations and continues to be expanded to other gynecological cancers. Furthermore, The Cancer Genome Atlas (TCGA) analysis of endometrial and cervical cancers offered rationale that PARPi may be an option for treatment based on the molecular profiles of these cancer types. This review summarizes the current indications of PARPi, such as its role in the treatment and maintenance of recurrent ovarian cancer and for first-line maintenance therapy in advanced ovarian cancer. We also outline new concepts for PARPi therapy in other gynecological cancers such as endometrial and cervical cancers based on recent clinical data. Finally, we present potential future directions to continue exploring the world of PARPi resistance and combining PARPi with other therapies.

Targeted therapies in gynecological cancers: a comprehensive review of clinical evidence

Advanced and recurrent gynecological cancers are associated with poor prognosis and lack of effective treatment. The developments of the molecular mechanisms on cancer progression provide insight into novel targeted therapies, which are emerging as groundbreaking and promising cancer treatment strategies. In gynecologic malignancies, potential therapeutic targeted agents include antiangiogenic agents, poly (ADP-ribose) polymerase (PARP) inhibitors, tumor-intrinsic signaling pathway inhibitors, selective estrogen receptor downregulators, and immune checkpoint inhibitors. In this article, we provide a comprehensive review of the clinical evidence of targeted agents in gynecological cancers and discuss the future implication.

Targeting the PI3K pathway and DNA damage response as a therapeutic strategy in ovarian cancer

Ovarian cancer is the most lethal gynecological malignancy worldwide although exponential progress has been made in its treatment over the last decade. New agents and novel combination treatments are on the horizon. Among many new drugs, a series of PI3K/AKT/mTOR pathway (referred to as the PI3K pathway) inhibitors are under development or already in clinical testing. The PI3K pathway is frequently upregulated in ovarian cancer and activated PI3K signaling contributes to increased cell survival and chemoresistance. However, no significant clinical success has been achieved with the PI3K pathway inhibitor(s) to date, reflecting the complex biology and also highlighting the need for combination treatment strategies. DNA damage repair pathways have been active therapeutic targets in ovarian cancer. Emerging data suggest the PI3K pathway is also involved in DNA replication and genome stability, making DNA damage response (DDR) inhibitors as an attractive combination treatment for PI3K pathway blockades. This review describes an expanded role for the PI3K pathway in the context of DDR and cell cycle regulation. We also present the novel treatment strategies combining PI3K pathway inhibitors with DDR blockades to improve the efficacy of these inhibitors for ovarian cancer.

Olaparib for advanced breast cancer

Olaparib, an oral PARP-inhibitor, has shown clinical benefit for HER2-negative advanced breast cancer patients carrying a germinal BRCA1/2 mutation. In a randomized Phase III trial, olaparib significantly prolonged progression-free survival as compared with chemotherapy of physician choice. Moreover, in the same trial, a prespecified subgroup analysis reported an overall survival benefit for patients not previously pretreated with chemotherapy for metastatic disease. This review focuses on available preclinical, pharmacokinetic and pharmacodynamic data regarding olaparib and clinical evidence of its antitumor efficacy (both as monotherapy and in combination) and tolerability in breast cancer patients. Open questions, such as use of appropriate biomarkers for patient selection and combination/sequencing with other anticancer drugs, are also addressed.

PARP Inhibitors in Gynecologic Cancers: What Is the Next Big Development?

PURPOSE OF REVIEW

Conventional and novel applications of Poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibitors (PARPi) are reviewed in the context of recently published clinical trials and preclinical data supporting rapidly expanding uses of this class of chemotherapy.

RECENT FINDINGS

PARPi block a pathway of DNA repair and target defects in homologous recombination repair (HRR), a pathway responsible for high-fidelity repair of double-strand breaks in DNA. BRCA1/2 proteins are essential to this pathway. Approximately 15-30% of women with ovarian cancer will have a germline or somatic BRCA mutation, and PARPi have shown promise in this population in a variety of settings. With growing understanding of the HRR pathway and its role in gynecologic malignancies, the potential applications of PARPi continue to expand. While the role of PARPi in gynecologic malignancies is most established in ovarian cancer, there are also promising applications in uterine and cervical cancer. We review current indications for PARPi use and promising applications of these medications in gynecologic malignancies.

Choosing wisely: Selecting PARP inhibitor combinations to promote anti-tumor immune responses beyond BRCA mutations

PARP inhibitors have transformed the management of advanced high-grade serous ovarian cancer. Despite the overwhelming success of PARP inhibition, particularly in BRCA-mutated ovarian cancer, several limitations and unanswered questions remain. With PARP inhibitors now being used in earlier treatment settings, the issue of both de novo and acquired resistance mechanisms and appropriate post-PARP management are pressing concerns. In addition, the population appropriate to target with PARP inhibitors and their use in patients without BRCA mutations is controversial and evolving. In this review we will discuss exciting PARP combinations and biologic rationale for the development and selection of PARP inhibitor combinations.

Olaparib in the treatment of ovarian cancer

The poly ADP ribose polymerase olaparib is currently approved in front line BRCA-associated epithelial ovarian cancer (EOC), platinum-sensitive recurrence agnostic to BRCA status and for gBRCA as treatment in the fourth line and beyond. Women who are diagnosed with advanced stage EOC face a formidable challenge in overcoming their disease and achieving long-term, disease-free survival. The qualifier here is disease free. EOC is largely exquisitely chemosensitive, especially in the treatment naive (first line) setting and the expectation is that the vast majority of women will complete front line platinum-based chemotherapy with a response. When unselected (not selected by BRCA) women are enrolled on clinical trials, the response rate among those who have measurable disease at the time of chemotherapy initiation is 48% for carboplatin/paclitaxel and 67% for carboplatin/paclitaxel plus bevacizumab. When one considers the addition of women who start chemotherapy without measurable disease, they will likely also end chemotherapy without measurable disease and the overall rate of no evidence of disease at conclusion of chemotherapy approaches 80%. Despite this, the majority of women will suffer relapse of their disease, typically within the first 3 years following completion of therapy. Once recurrent, the disease is highly treatable for many years but no longer considered curable. This review will cover indications for olaparib in ovarian cancer as well as ongoing combination trials and rationale for these combinations.

Combined Strategies with Poly (ADP-Ribose) Polymerase (PARP) Inhibitors for the Treatment of Ovarian Cancer: A Literature Review

Poly (ADP-ribose) polymerase (PARP) inhibitors are the first clinically approved drugs designed to exploit synthetic lethality, and were first introduced as a cancer-targeting strategy in 2005. They have led to a major change in the treatment of advanced ovarian cancer, and altered the natural history of a disease with extreme genetic complexity and defective DNA repair via homologous recombination (HR) pathway. Furthermore, additional mechanisms apart from breast related cancer antigens 1 and 2 (BRCA1/2) mutations can also result in HR pathway alterations and consequently lead to a clinical benefit from PARP inhibitors. Novel combinations of PARP inhibitors with other anticancer therapies are challenging, and better understanding of PARP biology, DNA repair mechanisms, and PARP inhibitor mechanisms of action is crucial. It seems that PARP inhibitor and biologic agent combinations appear well tolerated and clinically effective in both BRCA-mutated and wild-type cancers. They target differing aberrant and exploitable pathways in ovarian cancer, and may induce greater DNA damage and HR deficiency. The input of immunotherapy in ovarian cancer is based on the observation that immunosuppressive microenvironments can affect tumour growth, metastasis, and even treatment resistance. Several biologic agents have been studied in combination with PARP inhibitors, including inhibitors of vascular endothelial growth factor (VEGF; bevacizumab, cediranib), and PD-1 or PD-L1 (durvalumab, pembrolizumab, nivolumab), anti-CTLA4 monoclonal antibodies (tremelimumab), mTOR-(vistusertib), AKT-(capivasertib), and PI3K inhibitors (buparlisib, alpelisib), as well as MEK 1/2, and WEE1 inhibitors (selumetinib and adavosertib, respectively). Olaparib and veliparib have also been combined with chemotherapy with the rationale of disrupting base excision repair via PARP inhibition. Olaparib has been investigated with carboplatin and paclitaxel, whereas veliparib has been tested additionally in combination with temozolomide vs. pegylated liposomal doxorubicin, as well as with oral cyclophosphamide, and topoisomerase inhibitors. However, overlapping myelosuppression observed with PARP inhibitor and chemotherapy combinations requires further investigation with dose escalation studies. In this review, we discuss multiple clinical trials that are underway examining the antitumor activity of such combination strategies.

Tailoring Ovarian Cancer Treatment: Implications of BRCA1/2 Mutations

High grade serous ovarian cancer (HGSOC) is the most common epithelial ovarian cancer, harbouring more than 20% germline or somatic mutations in the tumour suppressor genes BRCA1 and BRCA2. These genes are involved in both DNA damage repair process via homologous recombination (HR) and transcriptional regulation. BRCA mutation confers distinct characteristics, including an increased response to DNA-damaging agents, such us platinum chemotherapy and poly-ADP ribose polymerase inhibitors (PARPi). However, several mechanisms of resistance to these agents have been described, including increased HR capacity through reverse BRCA mutations, non-homologous end-joint (NHEJ) repair alterations and drug efflux pumps. Current treatments of ovarian cancer including surgery, chemotherapy, targeted treatment and maintenance strategies, as well as resistance mechanisms will be reviewed, focusing on future trends with respect to BRCA mutation carriers.

Using PARP Inhibitors in the Treatment of Patients With Ovarian Cancer

OPINION STATEMENT

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.