Choosing wisely: Selecting PARP inhibitor combinations to promote anti-tumor immune responses beyond BRCA mutations. Gynecol Oncol. 2020;156:488-497. [PMID: 31630846 DOI: 10.1016/j.ygyno.2019.09.021]

Addressing Residual Disease in HER2-Positive and Triple-Negative Breast Cancer: What Is Next?

PURPOSE OF REVIEW

To summarize the treatment strategies for patients with human epidermal growth factor receptor 2 (HER2)-positive disease and triple-negative breast cancer (TNBC) who have residual disease after preoperative systemic therapy.

RECENT FINDINGS

There has been a shift towards neoadjuvant systemic therapy for selected patients with HER2-positive and TNBC. Assessing the tumor's response to therapy provides prognostic information and allows individualization of the postoperative treatment for these patients based on the tumor response to neoadjuvant therapy. Patients with TNBC with residual disease after neoadjuvant therapy can be treated with pembrolizumab, capecitabine, or olaparib. Those with HER2-positive disease are treated with adjuvant trastuzumab emtansine. The treatment of early breast cancer has evolved significantly, and patient outcomes continue to improve. As better treatments are developed, we will need biomarkers to determine which patients may benefit from certain therapies to continue to improve outcomes by right-sizing treatments and limiting toxicities.

Bevacizumab increases the sensitivity of olaparib to homologous recombination-proficient ovarian cancer by suppressing CRY1 via PI3K/AKT pathway

PARP inhibitors have changed the management of advanced high-grade epithelial ovarian cancer (EOC), especially homologous recombinant (HR)-deficient advanced high-grade EOC. However, the effect of PARP inhibitors on HR-proficient (HRP) EOC is limited. Thus, new therapeutic strategy for HRP EOC is desired. In recent clinical study, the combination of PARP inhibitors with anti-angiogenic agents improved therapeutic efficacy, even in HRP cases. These data suggested that anti-angiogenic agents might potentiate the response to PARP inhibitors in EOC cells. Here, we demonstrated that anti-angiogenic agents, bevacizumab and cediranib, increased the sensitivity of olaparib in HRP EOC cells by suppressing HR activity. Most of the γ-H2AX foci were co-localized with RAD51 foci in control cells. However, most of the RAD51 were decreased in the bevacizumab-treated cells. RNA sequencing showed that bevacizumab decreased the expression of CRY1 under DNA damage stress. CRY1 is one of the transcriptional coregulators associated with circadian rhythm and has recently been reported to regulate the expression of genes required for HR in cancer cells. We found that the anti-angiogenic agents suppressed the increase of CRY1 expression by inhibiting VEGF/VEGFR/PI3K pathway. The suppression of CRY1 expression resulted in decrease of HR activity. In addition, CRY1 inhibition also sensitized EOC cells to olaparib. These data suggested that anti-angiogenic agents and CRY1 inhibitors will be the promising candidate in the combination therapy with PARP inhibitors in HR-proficient EOC.

A novel targeted NGS panel identifies numerous homologous recombination deficiency (HRD)-associated gene mutations in addition to known BRCA mutations

Deleterious mutations in the BRCA1 and BRCA2 genes have significant therapeutic relevance in clinical settings regarding personalized therapy approaches. BRCA1 and BRCA2 play a pivotal role in homologous recombination (HR) and thus are sensitive for PARP inhibitors (PARPi). Beyond the narrow scope of evaluating only the BRCA mutation status, PARPi can be beneficial for HR deficient (HRD) patients, who harbor mutations in other HR-associated genes. In the present retrospective study, a novel targeted HRD gene panel was validated and implemented for use with FFPE tissue. Samples of patients with ovarian, breast, pancreatic and prostate cancer were included. Variants were robustly detected with various DNA input amounts and the use of test samples showed complete concordance between previously known mutations and HRD panel results. From all the 90 samples included in this cohort, TP53 was the most frequently altered gene (73%). Deleterious BRCA1/2 mutations were found in 20 (22%) of all samples. New pathogenic or likely pathogenic mutations in additional HR-associated genes were identified in 22 (24%) patients. Taken together, the present study proves the feasibility of a new HRD gene panel with reliable panel performance and offers the possibility to easily screen for resistance mutations acquired over treatment time.Mutations in HR-associated genes, besides BRCA1/2, might represent promising potential targets for synthetic lethality approaches. Thus, a substantial number of patients may benefit from expanding the scope of therapeutic agents like PARPi.

PARP Inhibitors in Colorectal Malignancies: A 2023 Update

BACKGROUND

Colorectal carcinoma (CRC) is one of the most common malignancies in the Western world, and metastatic disease is associated with a dismal prognosis. Poly-ADpribose polymerase (PARP) inhibitors gain increasing attention in the field of medical oncology, as they lead to synthetic lethality in malignancies with preexisting alterations in the DNA damage repair (DDR) pathway. As those alterations are frequently seen in CRC, a targeted approach through PARP inhibitors is expected to benefit these patients, both alone and in combination with other agents like chemotherapy, immunotherapy, antiangiogenics, and radiation.

OBJECTIVE

This review article aims to better clarify the role of PARP inhibitors as a treatment option in patients with metastatic CRC with alterations in the DDR pathway.

METHODS

We used the PubMed database to retrieve journal articles and the inclusion criteria were all human studies that illustrated the effective role of PARP inhibitors in patients with metastatic CRC with homologous repair deficiency (HRD) and the correct line of therapy.

RESULTS

Current evidence supports the utilization of PARP inhibitors in CRC subgroups, as monotherapy and in combination with other agents. Up to now, data are insufficient to support a formal indication, and further research is needed.

CONCLUSION

Efforts to precisely define the homologous repair deficiency (HRD) in CRC - and eventually the subgroup of patients that are expected to benefit the most - are also underway.

Differential DNA damage repair and PARP inhibitor vulnerability of the mammary epithelial lineages

It is widely assumed that all normal somatic cells can equally perform homologous recombination (HR) and non-homologous end joining in the DNA damage response (DDR). Here, we show that the DDR in normal mammary gland inherently depends on the epithelial cell lineage identity. Bioinformatics, post-irradiation DNA damage repair kinetics, and clonogenic assays demonstrated luminal lineage exhibiting a more pronounced DDR and HR repair compared to the basal lineage. Consequently, basal progenitors were far more sensitive to poly(ADP-ribose) polymerase inhibitors (PARPis) in both mouse and human mammary epithelium. Furthermore, PARPi sensitivity of murine and human breast cancer cell lines as well as patient-derived xenografts correlated with their molecular resemblance to the mammary progenitor lineages. Thus, mammary epithelial cells are intrinsically divergent in their DNA damage repair capacity and PARPi vulnerability, potentially influencing the clinical utility of this targeted therapy.

Clinical and translational advances in ovarian cancer therapy

Ovarian cancer is an aggressive disease that is frequently detected at advanced stages and is initially very responsive to platinum-based chemotherapy. However, the majority of patients relapse following initial surgery and chemotherapy, highlighting the urgent need to develop new therapeutic strategies. In this Review, we outline the main therapeutic principles behind the management of newly diagnosed and recurrent epithelial ovarian cancer and discuss the current landscape of targeted and immune-based approaches.

The dynamic process of covalent and non-covalent PARylation in the maintenance of genome integrity: a focus on PARP inhibitors

Poly(ADP-ribosylation) (PARylation) by poly(ADP-ribose) polymerases (PARPs) is a highly regulated process that consists of the covalent addition of polymers of ADP-ribose (PAR) through post-translational modifications of substrate proteins or non-covalent interactions with PAR via PAR binding domains and motifs, thereby reprogramming their functions. This modification is particularly known for its central role in the maintenance of genomic stability. However, how genomic integrity is controlled by an intricate interplay of covalent PARylation and non-covalent PAR binding remains largely unknown. Of importance, PARylation has caught recent attention for providing a mechanistic basis of synthetic lethality involving PARP inhibitors (PARPi), most notably in homologous recombination (HR)-deficient breast and ovarian tumors. The molecular mechanisms responsible for the anti-cancer effect of PARPi are thought to implicate both catalytic inhibition and trapping of PARP enzymes on DNA. However, the relative contribution of each on tumor-specific cytotoxicity is still unclear. It is paramount to understand these PAR-dependent mechanisms, given that resistance to PARPi is a challenge in the clinic. Deciphering the complex interplay between covalent PARylation and non-covalent PAR binding and defining how PARP trapping and non-trapping events contribute to PARPi anti-tumour activity is essential for developing improved therapeutic strategies. With this perspective, we review the current understanding of PARylation biology in the context of the DNA damage response (DDR) and the mechanisms underlying PARPi activity and resistance.

Triumphs and challenges in exploiting poly(ADP-ribose) polymerase inhibition to combat triple-negative breast cancer

Poly(ADP-ribose) polymerase 1 (PARP1) regulates a myriad of DNA repair mechanisms to preserve genomic integrity following DNA damage. PARP inhibitors (PARPi) confer synthetic lethality in malignancies with a deficiency in the homologous recombination (HR) pathway. Patients with triple-negative breast cancer (TNBC) fail to respond to most targeted therapies because their tumors lack expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Certain patients with TNBC harbor mutations in HR mediators such as breast cancer susceptibility gene 1 (BRCA1) and breast cancer susceptibility gene 2 (BRCA2), enabling them to respond to PARPi. PARPi exploits the synthetic lethality of BRCA-mutant cells. However, de novo and acquired PARPi resistance frequently ensue. In this review, we discuss the roles of PARP in mediating DNA repair processes in breast epithelial cells, mechanisms of PARPi resistance in TNBC, and recent advances in the development of agents designed to overcome PARPi resistance in TNBC.

The anti-PD-1 era of cervical cancer: achievement, opportunity, and challenge

Cervical cancer is one of the three major female gynecological malignancies, becoming a major global health challenge. Although about 90% of early-stage patients can be cured by surgery, advanced-stage patients still need new treatment methods to improve their efficacy, especially for those with recurrence and metastasis tumors. Anti-PD-1 is currently the most widely used immune checkpoint inhibitor, which has revolutionized cancer therapy for different types of cancer. Pembrolizumab has been approved for second-line treatment of R/M CC but has a modest overall response rate of about 15%. Therefore, multiple types of anti-PD-1 have entered clinical trials successively and evaluated the efficacy in combination with chemotherapy, targeted therapy, and immunotherapy. At the same time, the dual specific antibody of PD-1/CTLA-4 was also used in clinical trials of cervical cancer, and the results showed better than anti-PD-1 monotherapy. In addition, anti-PD-1 has also been shown to sensitize radiotherapy. Therefore, understanding the current research progress of anti-PD-1 will better guide clinical application. This review summarizes ongoing clinical trials and published studies of anti-PD-1 monotherapy and combination therapy in the treatment of cervical cancer, as well as discusses the potential molecular biological mechanisms of combination, aiming to provide the basic evidence for support anti-PD-1 in the treatment of cervical cancer and new insights in combination immunotherapy.

Metastatic Colorectal Cancer Patient with Microsatellite Stability and Germline BRAC2 Mutation Shows a Complete Response to Olaparib in Combination with a PD-1 Inhibitor and Bevacizumab: A Case Report and Review of the Literature

Metastatic colorectal cancer (mCRC) has a poor prognosis. Combining chemotherapy with targeted therapy constitutes a basic form of mCRC treatment. Immune checkpoint inhibitors have been recommended for microsatellite instability mCRC, while most patients harboring microsatellite stability (MSS) or proficient mismatch repair (pMMR) are less responsive to immunotherapy. Combinational targeted therapy, including poly-ADP ribose polymerase (PARP) inhibitors, has been considered a promising way to reverse immunotherapy resistance; however, there is no clear and consistent conclusions can be drawn from the current research. Here, we report the case of a 59-year-old woman diagnosed with stage IVB MSS mCRC who received three courses of capecitabine/oxaliplatin chemotherapy combined with bevacizumab as a first-line treatment, resulting in an overall evaluation of stable disease (-25.7%). However, the occurrence of adverse events of intolerable grade 3 diarrhea and vomiting forced the cessation of this therapy. A germline BRCA2 mutation was found by next-generation sequencing, and the patient further received a combination of olaparib, tislelizumab, and bevacizumab. This treatment regime resulted in a complete metabolic response and a partial response (-50.9%) after 3 months of treatment. Mild asymptomatic interstitial pneumonia and manageable hematologic toxicity were two adverse events associated with this combination therapy. This study provides new insights into the combination of PARP inhibitors and immunotherapy for MSS mCRC patients carrying germline BRCA2 mutations.

Case report: A de novo ERBB3 mutation develops in a gallbladder cancer patient carrying BRCA1 mutation after effective treatment with olaparib

Background

Gallbladder cancer (GBC) is highly lethal and resistant to most chemotherapeutic drugs. GBC was reported to carry multiple genetic mutations such as TP53, K-RAS, and ERBB2/3. Here, we unexpectedly identified a patient with GBC harboring germline BRCA1 p.Arg1325Lys heterozygous mutation. We sought to determine if olaparib, the poly ADP-ribose polymerase inhibitor (PARPi) commonly treated for BRCA mutation, can inhibit cancer development via a therapeutic trial on this patient.

Case presentation

The patient received GBC R0 resection after an 8-week olaparib treatment. After surgery and 6-month follow-up treatment with olaparib, the patient’s blood carbohydrate antigen 19-9 (CA19-9) level declined from 328 to 23.6 U/ml. No recurrence in CT scanning was observed, indicating a disease-free survival of 6 months with conventional therapy. Two months later, CT examination and CA19-9 level showed cancer relapse. A blood biopsy revealed a new ERBB3 p.Gly337Arg mutation. GBC cell lines ectopically expressing BRCA1 p.Arg1325Lys together with ERBB3 p.Gly337Arg mutations were challenged with olaparib and/or afatinib, an ERBB2/3 inhibitor. The dual mutation cells were more responsive to the combined olaparib with afatinib than a single drug in the cell proliferation assay.

Conclusion

Olaparib is effective in a GBC patient with a BRAC1 mutation. The efficacy of olaparib and afatinib in both cultured BRAC1 and ERBB3 mutation cell lines suggests that a combined regimen targeting BRCA1/2 and ERBB2/3 mutations may be an optimal strategy to treat GBC patients who carry both gene mutations.

Increased endogenous PKG I activity attenuates EGF-induced proliferation and migration of epithelial ovarian cancer via the MAPK/ERK pathway

The type I cGMP-dependent protein kinase (PKG I) is recognized as a tumor suppressor, but its role in EGFR regulated epithelial ovarian cancer (EOC) progression remains unclear. We evaluated the in vivo and in vitro effects of activated PKG I in EGF-induced EOC cell proliferation, migration, and invasion. The expressions of EGFR and PKG I were elevated, but the activated PKG I was decreased in EOC tissues of patients and cells lines. The addition of 8-Br-cGMP, a specific PKG I activator, attenuated the EGF-induced EOC cell proliferation, migration, and invasion in vitro. Similarly, activated PKG I also attenuated EOC progression in vivo using an EOC xenograft nude mouse model. The activated PKG I interacted with EGFR, causing increased threonine (693) phosphorylation and decreased tyrosine (1068) phosphorylation of EGFR, which resulted in disrupted EGFR-SOS1-Grb2 combination. Subsequently, the cytoplasmic phosphorylation of downstream proteins (c-Raf, MEK1/2, and ERK1/2) were declined, impeding the phosphorylated ERK1/2's nucleus translocation, and this reduction of phosphorylated tyrosine (1068) EGFR and ERK1/2 were also abolished by Rp-8-Br-cGMPS. Our results suggest that the activation of PKG I attenuates EGF-induced EOC progression, and the 8-Br-cGMP-PKG I-EGFR/MEK/ERK axis might be a potential target for EOC therapy.

Paclitaxel sensitizes homologous recombination-proficient ovarian cancer cells to PARP inhibitor via the CDK1/BRCA1 pathway

OBJECTIVE

An effective treatment strategy for epithelial ovarian cancer (EOC) with homologous recombination (HR)-proficient (HRP) phenotype has not been established, although poly (ADP-ribose) polymerase inhibitors (PARPi) impact the disease course with HR-deficient (HRD) phenotype. Here, we aimed to clarify the cellular effects of paclitaxel (PTX) on the DNA damage response and the therapeutic application of PTX with PARPi in HRP ovarian cancer.

METHODS

Two models with different PTX dosing schedules were established in HRP ovarian cancer OVISE cells. Growth inhibition and HR activity were analyzed in these models with or without PARPi. BRCA1 phosphorylation status was examined in OVISE cells by inhibiting CDK1, which was reduced by PTX treatment. CDK1 expression was evaluated in EOC patients treated with PTX-based neoadjuvant chemotherapy.

RESULTS

PTX suppressed CDK1 expression resulting in impaired BRCA1 phosphorylation in OVISE cells. The reduced CDK1 activity by PTX could decrease HR activity in response to DNA damage and therefore increase the sensitivity to PARPi. Immunohistochemistry showed that CDK1 expression was attenuated in samples collected after PTX-based chemotherapy compared to those collected before chemotherapy. The decrease in CDK1 expression was greater with dose-dense PTX schedule than with the conventional PTX schedule.

CONCULSIONS

PTX could act synergistically with PARPi in HRP ovarian cancer cells, suggesting that the combination of PTX with PARPi may be a novel treatment strategy extending the utility of PARPi to EOC. Our findings provide cules for future translational clinical trials evaluating the efficacy of PTX in combination with PARPi in HRP ovarian cancer.

Combined inhibition of BADSer99 phosphorylation and PARP ablates models of recurrent ovarian carcinoma

Background

Poly (ADP-ribose) polymerase inhibitors (PARPis) have been approved for the treatment of recurrent epithelial ovarian cancer (EOC), regardless of BRCA status or homologous recombination repair deficiency. However, the low response of platinum-resistant EOC, the emergence of resistance in BRCA-deficient cancer, and therapy-associated toxicities in patients limit the clinical utility of PARPis in recurrent EOC.

Methods

The association of phosphorylated (p) BADS99 with clinicopathological parameters and survival outcomes in an EOC cohort was assessed by immunohistochemistry. The therapeutic synergy, and mechanisms thereof, between a pBADS99 inhibitor and PARPis in EOC was determined in vitro and in vivo using cell line and patient-derived models.

Results

A positive correlation between pBADS99 in EOC with higher disease stage and poorer survival is observed. Increased pBADS99 in EOC cells is significantly associated with BRCA-deficiency and decreased Cisplatin or Olaparib sensitivity. Pharmacological inhibition of pBADS99 synergizes with PARPis to enhance PARPi IC₅₀ and decreases survival, foci formation, and growth in ex vivo culture of EOC cells and patient-derived organoids (PDOs). Combined inhibition of pBADS99 and PARP in EOC cells or PDOs enhances DNA damage but impairs PARPi stimulated DNA repair with a consequent increase in apoptosis. Inhibition of BADS99 phosphorylation synergizes with Olaparib to suppress the xenograft growth of platinum-sensitive and resistant EOC. Combined pBADS99-PARP inhibition produces a complete response in a PDX derived from a patient with metastatic and chemoresistant EOC.

Conclusions

A rational and efficacious combination strategy involving combined inhibition of pBADS99 and PARP for the treatment of recurrent EOC is presented.

Ovarian cancer is difficult to successfully treat because it often recurs as the cancer becomes resistant to drugs used to treat it. As such, new drugs or combinations of drugs are needed to treat patients with recurrent ovarian cancer. Here, a drug combination is reported that is effective in experimental models of ovarian cancer, including those derived from patients. The combination approach uses drugs that have previously been approved for use in patients, known as PARP inhibitors, and another drug to inhibit cancer cell survival by targeting activation of a specific protein involved in cancer cell survival. The net effect of this drug combination in ovarian cancer models is greater than the sum of the drugs used individually. With further testing, this combination may offer a potential strategy to treat patients with recurrent ovarian cancer.

Zhang et al. test the therapeutic potential of an inhibitor of BAD phosphorylation, NPB, in epithelial ovarian cancer. The authors show that the small molecule synergises with PARP inhibition to kill patient-derived ovarian cancer organoids and suppress the growth of xenograft tumours, including a cisplatin-resistant model.

Improving PARP inhibitor efficacy in high-grade serous ovarian carcinoma: A focus on the immune system

High-grade serous ovarian carcinoma (HGSOC) is a genomically unstable malignancy responsible for over 70% of all deaths due to ovarian cancer. With roughly 50% of all HGSOC harboring defects in the homologous recombination (HR) DNA repair pathway (e.g., BRCA1/2 mutations), the introduction of poly ADP-ribose polymerase inhibitors (PARPi) has dramatically improved outcomes for women with HR defective HGSOC. By blocking the repair of single-stranded DNA damage in cancer cells already lacking high-fidelity HR pathways, PARPi causes the accumulation of double-stranded DNA breaks, leading to cell death. Thus, this synthetic lethality results in PARPi selectively targeting cancer cells, resulting in impressive efficacy. Despite this, resistance to PARPi commonly develops through diverse mechanisms, such as the acquisition of secondary BRCA1/2 mutations. Perhaps less well documented is that PARPi can impact both the tumour microenvironment and the immune response, through upregulation of the stimulator of interferon genes (STING) pathway, upregulation of immune checkpoints such as PD-L1, and by stimulating the production of pro-inflammatory cytokines. Whilst targeted immunotherapies have not yet found their place in the clinic for HGSOC, the evidence above, as well as ongoing studies exploring the synergistic effects of PARPi with immune agents, including immune checkpoint inhibitors, suggests potential for targeting the immune response in HGSOC. Additionally, combining PARPi with epigenetic-modulating drugs may improve PARPi efficacy, by inducing a BRCA-defective phenotype to sensitise resistant cancer cells to PARPi. Finally, invigorating an immune response during PARPi therapy may engage anti-cancer immune responses that potentiate efficacy and mitigate the development of PARPi resistance. Here, we will review the emerging PARPi literature with a focus on PARPi effects on the immune response in HGSOC, as well as the potential of epigenetic combination therapies. We highlight the potential of transforming HGSOC from a lethal to a chronic disease and increasing the likelihood of cure.

DNA Damage Repair and Current Therapeutic Approaches in Gastric Cancer: A Comprehensive Review

DNA in cells is frequently damaged by endogenous and exogenous agents. However, comprehensive mechanisms to combat and repair DNA damage have evolved to ensure genomic stability and integrity. Improper DNA damage repair may result in various diseases, including some types of tumors and autoimmune diseases. Therefore, DNA damage repair mechanisms have been proposed as novel antitumor drug targets. To date, numerous drugs targeting DNA damage mechanisms have been developed. For example, PARP inhibitors that elicit synthetic lethality are widely used in individualized cancer therapies. In this review, we describe the latent DNA damage repair mechanisms in gastric cancer, the types of DNA damage that can contribute to the development of gastric cancer, and new therapeutic approaches for gastric cancer that target DNA damage repair pathways.

OGG1 Inhibition Triggers Synthetic Lethality and Enhances The Effect of PARP Inhibitor Olaparib in BRCA1-Deficient TNBC Cells

Background

PARP1 plays a critical role in the base excision repair (BER) pathway, and PARP1 inhibition leads to specific cell death, through a synthetic lethal interaction, in the context of BRCA1/2 deficiency. To date, up to five different PARP inhibitors (PARPi), have been approved, nevertheless, the acquisition of resistance to PARPi is common and there is increasing interest in enhancing responses and expand their use to other tumour types.

Methods

We hypothesized that other BER members could be additional synthetic lethal partners with mutated BRCA genes. To test this, we decided to evaluate the glycosylase OGG1 as a potential candidate, by treating BRCA1 proficient and deficient breast cancer cells with PARPi olaparib and the OGG1 inhibitor TH5478.

Results

Knocking out BRCA1 in triple-negative breast cancer cell lines causes hypersensitivity to the OGG1 inhibitor TH5487. Besides, TH5487 enhances the sensitivity to the PARP inhibitor olaparib, especially in the context of BRCA1 deficiency, reflecting an additive interaction.

Discussion

These results provide the first evidence that OGG1 inhibition is a promising new synthetic lethality strategy in BRCA1-deficient cells, and could lead to a new framework for the treatment of hereditary breast and ovarian cancer.

Combined PARP and HSP90 inhibition: preclinical and Phase 1 evaluation in patients with advanced solid tumours

PURPOSE

PARP inhibitor resistance may be overcome by combinatorial strategies with agents that disrupt homologous recombination repair (HRR). Multiple HRR pathway components are HSP90 clients, so that HSP90 inhibition leads to abrogation of HRR and sensitisation to PARP inhibition. We performed in vivo preclinical studies of the HSP90 inhibitor onalespib with olaparib and conducted a Phase 1 combination study.

PATIENTS AND METHODS

Tolerability and efficacy studies were performed in patient-derived xenograft(PDX) models of ovarian cancer. Clinical safety, tolerability, steady-state pharmacokinetics and preliminary efficacy of olaparib and onalespib were evaluated using a standard 3 + 3 dose-escalation design.

RESULTS

Olaparib/onalespib exhibited anti-tumour activity against BRCA1-mutated PDX models with acquired PARPi resistance and PDX models with RB-pathway alterations(CDKN2A loss and CCNE1 overexpression). Phase 1 evaluation revealed that dose levels up to olaparib 300 mg/onalespib 40 mg and olaparib 200 mg/onalespib 80 mg were safe without dose-limiting toxicities. Coadministration of olaparib and onalespib did not appear to affect the steady-state pharmacokinetics of either agent. There were no objective responses, but disease stabilisation ≥24 weeks was observed in 7/22 (32%) evaluable patients including patients with BRCA-mutated ovarian cancers and acquired PARPi resistance and patients with tumours harbouring RB-pathway alterations.

CONCLUSIONS

Combining onalespib and olaparib was feasible and demonstrated preliminary evidence of anti-tumour activity.

Repurposing Ceritinib Induces DNA Damage and Enhances PARP Inhibitor Responses in High-Grade Serous Ovarian Carcinoma

PARP inhibitors (PARPi) have activity in homologous recombination (HR) repair-deficient, high-grade serous ovarian cancers (HGSOC). However, even responsive tumors develop PARPi resistance, highlighting the need to delay or prevent the appearance of PARPi resistance. Here, we showed that the ALK kinase inhibitor ceritinib synergizes with PARPis by inhibiting complex I of the mitochondrial electron transport chain, which increases production of reactive oxygen species (ROS) and subsequent induction of oxidative DNA damage that is repaired in a PARP-dependent manner. In addition, combined treatment with ceritinib and PARPi synergized in HGSOC cell lines irrespective of HR status, and a combination of ceritinib with the PARPi olaparib induced tumor regression more effectively than olaparib alone in HGSOC patient-derived xenograft (PDX) models. Notably, the ceritinib and olaparib combination was most effective in PDX models with preexisting PARPi sensitivity and was well tolerated. These findings unveil suppression of mitochondrial respiration, accumulation of ROS, and subsequent induction of DNA damage as novel effects of ceritinib. They also suggest that the ceritinib and PARPi combination warrants further investigation as a means to enhance PARPi activity in HGSOC, particularly in tumors with preexisting HR defects. SIGNIFICANCE: The kinase inhibitor ceritinib synergizes with PARPi to induce tumor regression in ovarian cancer models, suggesting that ceritinib combined with PARPi may be an effective strategy for treating ovarian cancer.

Response to olaparib in metastatic lung adenocarcinoma with germline BRCA2 mutation: a case report

Mutation of BRCA2, a breast cancer susceptibility gene, is associated with the development of breast and ovarian cancer. Olaparib is an oral poly-adenosine diphosphate-ribose polymerase (PARP) inhibitor, which has been proven to treat BRCA-mutated tumors effectively, especially breast and ovarian cancer. Here, we report a case of a germline BRCA2-mutated metastatic lung adenocarcinoma, non-small-cell lung cancer, responded well to olaparib. A 41-year-old man with no history of smoking was diagnosed with advanced lung adenocarcinoma. The patient was treated with bevacizumab, pemetrexed disodium, and cis-platinum in the first-line therapy of 6 months, followed by bevacizumab, Abraxane, and sintilimab treatments for another 6 months. As disease progression was confirmed and the presence of germline BRCA2 mutation, the combinational treatment of olaparib/anlotinib was applied to achieve partial response 1 month later, and the progression-free survival was extended for another 5 months. This study shows metastatic lung adenocarcinoma with BRCA2 mutation could also respond well to PARP inhibitor, broadening the spectrum of BRCA-mutated cancers suitable for olaparib therapy. With acquired resistance to chemotherapy, bevacizumab, and immunotherapy, the patient still gained significant benefits from the targeted therapy.

Olaparib with or without bevacizumab or bevacizumab and 5-fluorouracil in advanced colorectal cancer: Phase III LYNK-003

Oxaliplatin-based chemotherapy with a regimen such as FOLFOX with or without targeted therapy is a standard of care option for advanced colorectal cancer; however, long-term exposure to oxaliplatin is associated with cumulative toxicity. Growing evidence suggests maintenance therapy with a less intensive regimen after platinum-based induction therapy can provide continuing benefit with reduced toxicity. We describe the rationale and design of the Phase III LYNK-003 trial, which will evaluate the efficacy and safety of olaparib with or without bevacizumab compared with 5-fluoruracil plus bevacizumab in patients with unresectable or metastatic colorectal cancer that has not progressed on an induction course of FOLFOX plus bevacizumab. The primary end point is progression-free survival by independent central review; secondary end points include overall survival, objective response, duration of response and safety. Clinical trial registration: NCT04456699.

Genetic Variants and Tumor Immune Microenvironment: Clues for Targeted Therapies in Inflammatory Breast Cancer (IBC)

To better understand the etiology of inflammatory breast cancer (IBC) and identify potential therapies, we studied genomic alterations in IBC patients. Targeted, next-generation sequencing (NGS) was performed on cell-free DNA (cfDNA) (n = 33) and paired DNA from tumor tissues (n = 29) from 32 IBC patients. We confirmed complementarity between cfDNA and tumor tissue genetic profiles. We found a high incidence of germline variants in IBC patients that could be associated with an increased risk of developing the disease. Furthermore, 31% of IBC patients showed deficiencies in the homologous recombination repair (HRR) pathway (BRCA1, BRCA2, PALB2, RAD51C, ATM, BARD1) making them sensitive to poly (ADP-ribose) polymerase (PARP) inhibitors. We also characterized the tumor-infiltrating lymphocytes (TILs) in tumor tissue biopsies by studying several markers (CD4, CD8, FoxP3, CD20, PD-1, and PD-L1) through immunohistochemistry (IHC) staining. In 7 of 24 (29%) patients, tumor biopsies were positive for PD-L1 and PD-1 expression on TILs, making them sensitive to PD-1/PD-L1 blocking therapies. Our results provide a rationale for considering PARP inhibitors and PD-1/PDL1 blocking immunotherapy in qualifying IBC patients.

A randomized, open-label, two-period crossover bridging study on fuzuloparib capsules of different specifications in healthy Chinese volunteers

AIMS

Fuzuloparib, also known as fluzoparib or SHR3162, is a poly ADP-ribose polymerase (PARP) inhibitor developed for the treatment of malignant tumours. Three specifications of fuzuloparib capsules (10 mg, 40 mg and 100 mg) were originally developed for clinical trials. After the recommended dose was determined, a new specification of fuzuloparib capsule (50 mg) was produced for clinical use. This bridging study was conducted to determine the bioequivalence of the new specification to the three other specifications at the recommended dose.

METHODS

A single-centre, randomized, open-label, two-period, crossover bridging study was conducted in 40 healthy Chinese subjects under fed conditions. Enrolled subjects received a single oral dose of test or reference preparations according to a randomization list in the first period and crossed over to receive the other preparations in the second period after a 6-day washout interval. Blood samples were collected pre-dose and post-dose at specified time intervals. Plasma fuzuloparib concentrations were analysed by liquid chromatography-mass spectroscopy (LC-MS). A non-compartment model was adopted to calculate pharmacokinetic parameters of investigational preparations. Primary PK parameters including area under the concentration-time curve (AUC) from administration to the last sampling time (AUC_0-t ), AUC extrapolated to infinity (AUC_0-∞ ) and C_max of test and reference preparations were compared to evaluate their bioequivalence.

RESULTS

The 90% confidence intervals (CIs) of geometric mean ratios of AUC_0-t , AUC_0-∞ and C_max were 96.99-104.95%, 97.03-104.93% and 96.53-108.98%, respectively, all of which were within the bioequivalence range of 80-125%. No serious adverse events were observed in this study and no subjects withdrew from the study due to adverse events.

CONCLUSIONS

The test preparations were bioequivalent to the reference preparations. All investigational products were well tolerated.

The evolving role of PARP inhibitors in advanced ovarian cancer

The field of ovarian cancer has been revolutionized with the use of poly (ADP-ribose) polymerase (PARP) inhibitors, which present greater inhibition effect in epithelial subtype due to high rates of homologous recombination deficiency. PARP inhibition exploits this cancer pitfall by disrupting DNA repair, leading to genomic instability and apoptosis. Three PARP inhibitors (olaparib, niraparib, and rucaparib) are now approved for use in women with epithelial ovarian cancer, while others are under development. Among women with BRCA1/2 mutations, maintenance PARP therapy has led to a nearly fourfold prolongation of PFS, while those without BRCA1/2 mutations experience an approximately twofold increase in PFS. Differences in trial design, patient selection and primary analysis population affect the conclusions on PARP inhibitors. Limited OS data have been published and there is also limited experience regarding long-term safety. With regard to toxicity profile, there are no differences in serious adverse events between the experimental and control groups. However, combining adverse event data from maintenance phases, a trend towards more events in the experimental group, compared with controls, has been shown. The mechanisms of PARP-inhibitor resistance include restoration of HR through reversion mutations in HR genes, leading to resumed HR function. Other mechanisms that sustain sufficient DNA repair are discussed as well. PARP inhibitors play a pivotal role in the management of ovarian cancer, affecting the future treatment choices. Defining exactly which patients will benefit from them is a challenge and the need for HRD testing to define ‘BRCA-ness’ will add additional costs to treatment.

Mechanisms of acquired resistance of BRCA1/2-driven tumors to platinum compounds and PARP inhibitors

Molecular pathogenesis of tumors arising in BRCA1/2 germ-line mutation carriers usually includes somatic inactivation of the remaining allele of the involved gene. Consequently, BRCA1/2-driven cancers are sensitive to platinum-based therapy and poly (ADP-ribose) polymerase inhibitors (PARPi). Long-term exposure to these drugs may result in the emergence of secondary BRCA1/2 mutations, which restore the open-reading frame of the affected allele. This platinum/PARPi cross-resistance mechanism applies both for BRCA1 and BRCA2 genes and has been repeatedly validated in various laboratory models and multiple clinical studies. There are some other routes associated with the partial rescue of BRCA1/2 function or the development of BRCA1/2-independent pathways for genomic maintenance; however, their actual clinical relevance remains to be established. In addition, studies on the short-term neoadjuvant therapy for ovarian cancer revealed that even chemonaive BRCA1-driven tumors contain a small proportion of BRCA1-proficient cells. These pre-existing cells with retained BRCA1 heterozygosity rapidly repopulate the tumor mass during platinum exposure, but become outcompeted by BRCA1-deficient cells during therapy holidays. Understanding of the platinum/PARPi resistance pathways has led to the development of novel therapeutic approaches, which aim to improve the management of BRCA1/2-related cancers and are currently undergoing preclinical and clinical evaluation.

PARP1: Structural insights and pharmacological targets for inhibition

Poly(ADP-ribose) polymerase 1 (PARP1, also known as ADPRT1) is a multifunctional human ADP-ribosyltransferase. It plays a role in multiple DNA repair pathways, including the base excision repair (BER), non-homologous end joining (NHEJ), homologous recombination (HR), and Okazaki-fragment processing pathways. In response to DNA strand breaks, PARP1 covalently attaches ADP-ribose moieties to arginine, glutamate, aspartate, cysteine, lysine, and serine acceptor sites on both itself and other proteins. This signal recruits DNA repair proteins to the site of DNA damage. PARP1 binding to these sites enhances ADP-ribosylation via allosteric communication between the distant DNA binding and catalytic domains. In this review, we provide a general overview of PARP1 and emphasize novel potential approaches for pharmacological inhibition. Clinical PARP1 inhibitors bind the catalytic pocket, where they directly interfere with ADP-ribosylation. Some inhibitors may further enhance potency by "trapping" PARP1 on DNA via an allosteric mechanism, though this proposed mode of action remains controversial. PARP1 inhibitors are used clinically to treat some cancers, but resistance is common, so novel pharmacological approaches are urgently needed. One approach may be to design novel small molecules that bind at inter-domain interfaces that are essential for PARP1 allostery. To illustrate these points, this review also includes instructive videos showing PARP1 structures and mechanisms.

Shaping Immune Responses in the Tumor Microenvironment of Ovarian Cancer

Reciprocal signaling between immune cells and ovarian cancer cells in the tumor microenvironment can alter immune responses and regulate disease progression. These signaling events are regulated by multiple factors, including genetic and epigenetic alterations in both the ovarian cancer cells and immune cells, as well as cytokine pathways. Multiple immune cell types are recruited to the ovarian cancer tumor microenvironment, and new insights about the complexity of their interactions have emerged in recent years. The growing understanding of immune cell function in the ovarian cancer tumor microenvironment has important implications for biomarker discovery and therapeutic development. This review aims to describe the factors that shape the phenotypes of immune cells in the tumor microenvironment of ovarian cancer and how these changes impact disease progression and therapy.

Carbon ion radiotherapy eradicates medulloblastomas with chromothripsis in an orthotopic Li-Fraumeni patient-derived mouse model

Background

Medulloblastomas with chromothripsis developing in children with Li-Fraumeni Syndrome (germline TP53 mutations) are highly aggressive brain tumors with dismal prognosis. Conventional photon radiotherapy and DNA-damaging chemotherapy are not successful for these patients and raise the risk of secondary malignancies. We hypothesized that the pronounced homologous recombination deficiency in these tumors might offer vulnerabilities that can be therapeutically utilized in combination with high linear energy transfer carbon ion radiotherapy.

Methods

We tested high-precision particle therapy with carbon ions and protons as well as topotecan with or without PARP inhibitor in orthotopic primary and matched relapsed patient-derived xenograft models. Tumor and normal tissue underwent longitudinal morphological MRI, cellular (markers of neurogenesis and DNA damage-repair), and molecular characterization (whole-genome sequencing).

Results

In the primary medulloblastoma model, carbon ions led to complete response in 79% of animals irrespective of PARP inhibitor within a follow-up period of 300 days postirradiation, as detected by MRI and histology. No sign of neurologic symptoms, impairment of neurogenesis or in-field carcinogenesis was detected in repair-deficient host mice. PARP inhibitors further enhanced the effect of proton irradiation. In the postradiotherapy relapsed tumor model, median survival was significantly increased after carbon ions (96 days) versus control (43 days, P < .0001). No major change in the clonal composition was detected in the relapsed model.

Conclusion

The high efficacy and favorable toxicity profile of carbon ions warrants further investigation in primary medulloblastomas with chromothripsis. Postradiotherapy relapsed medulloblastomas exhibit relative resistance compared to treatment-naïve tumors, calling for exploration of multimodal strategies.

Targeting Germline- and Tumor-Associated Nucleotide Excision Repair Defects in Cancer

PURPOSE

Nucleotide excision repair (NER) gene alterations constitute potential cancer therapeutic targets. We explored the prevalence of NER gene alterations across cancers and putative therapeutic strategies targeting these vulnerabilities.

EXPERIMENTAL DESIGN

We interrogated our institutional dataset with mutational data from more than 40,000 patients with cancer to assess the frequency of putative deleterious alterations in four key NER genes. Gene-edited isogenic pairs of wild-type and mutant ERCC2 or ERCC3 cell lines were created and used to assess response to several candidate drugs.

RESULTS

We found that putative damaging germline and somatic alterations in NER genes were present with frequencies up to 10% across multiple cancer types. Both in vitro and in vivo studies showed significantly enhanced sensitivity to the sesquiterpene irofulven in cells harboring specific clinically observed heterozygous mutations in ERCC2 or ERCC3. Sensitivity of NER mutants to irofulven was greater than to a current standard-of-care agent, cisplatin. Hypomorphic ERCC2/3-mutant cells had impaired ability to repair irofulven-induced DNA damage. Transcriptomic profiling of tumor tissues suggested codependencies between DNA repair pathways, indicating a potential benefit of combination therapies, which were confirmed by in vitro studies.

CONCLUSIONS

These findings provide novel insights into a synthetic lethal relationship between clinically observed NER gene deficiencies and sensitivity to irofulven and its potential synergistic combination with other drugs.See related commentary by Jiang and Greenberg, p. 1833.

Repurposing approved drugs for cancer therapy

BACKGROUND

Many drugs approved for other indications can control the growth of tumor cells and limit adverse events (AE).

DATA SOURCES

Literature searches with keywords 'repurposing and cancer' books, websites: https://clinicaltrials.gov/, for drug structures: https://pubchem.ncbi.nlm.nih.gov/.

AREAS OF AGREEMENT

Introducing approved drugs, such as those developed to treat diabetes (Metformin) or inflammation (Thalidomide), identified to have cytostatic activity, can enhance chemotherapy or even replace more cytotoxic drugs. Also, anti-inflammatory compounds, cytokines and inhibitors of proteolysis can be used to control the side effects of chemo- and immuno-therapies or as second-line treatments for tumors resistant to kinase inhibitors (KI). Drugs specifically developed for cancer therapy, such as interferons (IFN), the tyrosine KI abivertinib TKI (tyrosine kinase inhibitor) and interleukin-6 (IL-6) receptor inhibitors, may help control symptoms of Covid-19.

AREAS OF CONTROVERSY

Better knowledge of mechanisms of drug activities is essential for repurposing. Chemotherapies induce ER stress and enhance mutation rates and chromosome alterations, leading to resistance that cannot always be related to mutations in the target gene. Metformin, thalidomide and cytokines (IFN, tumor necrosis factor (TNF), interleukin-2 (IL-2) and others) have pleiomorphic activities, some of which can enhance tumorigenesis. The small and fragile patient pools available for clinical trials can cloud the data on the usefulness of cotreatments.

GROWING POINTS

Better understanding of drug metabolism and mechanisms should aid in repurposing drugs for primary, adjuvant and adjunct treatments.

AREAS TIMELY FOR DEVELOPING RESEARCH

Optimizing drug combinations, reducing cytotoxicity of chemotherapeutics and controlling associated inflammation.

Recent development in the discovery of PARP inhibitors as anticancer agents: a patent update (2016-2020)

INTRODUCTION

Discovery of small molecules that impede the activity of single-strand DNA repair enzyme, PARP1, has led to four marketed drugs for the treatment of advanced-stage cancers. Hence, there is a renewed enthusiasm in the PARP inhibitor discovery arena. To reduce nonspecific interactions or potential toxicities, and to understand the role of other minimally explored PARP enzymes, exciting new findings have emerged toward the development of selective inhibitors and targeted chemical biology probes. Importantly, the conventional PARP inhibitor design has evolved in a way that could potentially lead to multienzyme-targeting - a polypharmacological approach against aggressive cancers.

AREAS COVERED

This review comprises recent progress made in the development of PARP inhibitors, primarily focused on human cancers. Discovery of novel PARP inhibitors with pan, selective, and multi-target inhibition using in vitro and in vivo cancer models is summarized and critically evaluated. Emphasis is given to patents published during 2016-2020, excluding TNKS 1/2 inhibitors.

EXPERT OPINION

The outstanding success demonstrated by the FDA approved PARP inhibitors has fueled further clinical evaluations for expansion of their clinical utilities. The current clinical investigations include new candidates as well as marketed PARP-targeted drugs, both as single agents and in combination with other chemotherapeutics. Recent advances have also unveiled critical roles of other PARPs in oncogenic signal transduction, in addition to those of the well-documented PARP1/2 and TNKS1/2 enzymes. Further studies on lesser-known PARP members are urgently needed for functional annotations and for understanding their roles in cancer progression and other human diseases.

Overcoming PARPi resistance: Preclinical and clinical evidence in ovarian cancer

Ovarian cancer is the fifth cause of cancer-related deaths in women with high grade serous carcinoma (HGSOC) representing the most common histological subtype. Approximately 50 % of HGSOC are characterized by deficiency in homologous recombination (HR), one of the main cellular pathways to repair DNA double strand breaks and one of the well-described mechanisms is the loss of function of the BRCA1 or BRCA2 genes. Inhibition of the poly-ADP-ribose polymerase (PARP) is synthetic lethal with HR deficiency and the use of PARP inhibitors (PARPi) has significantly improved the outcome of patients with HGSOC with a greater benefit in patients with BRCA1/2 deficient tumors. However, intrinsic or acquired resistance to PARPi inevitably occurs in most HGSOC patients. Distinct heterogeneous mechanisms underlying the resistance to PARPi have been described, including a decrease in intracellular drug levels due to upregulation of multidrug efflux pumps, loss of expression/inactivating mutations in the PARP1 protein, restoration of HR and the protection of the replicative fork. Deciphering the molecular mechanisms of resistance to PARPi is of paramount importance towards the development of new treatment strategies and/or novel pharmacological agents to overcome this chemoresistance and optimize the treatment regimen for individual HGSOC patients. The current review summarizes the mechanisms underlying the resistance to PARPi, the available preclinical and clinical data on new combination treatment strategies (with chemotherapy, anti-angiogenic agents and immune checkpoint inhibitors) as well as agents under investigation which target the DNA damage response.

Targeting PARP-1 with metronomic therapy modulates MDSC suppressive function and enhances anti-PD-1 immunotherapy in colon cancer

Background

Poly(ADP-ribose) polymerase (PARP) inhibitors (eg, olaparib) are effective against BRCA-mutated cancers at/near maximum tolerated doses by trapping PARP-1 on damaged chromatin, benefitting only small patient proportions. The benefits of targeting non-DNA repair aspects of PARP with metronomic doses remain unexplored.

Methods

Colon epithelial cells or mouse or human bone marrow (BM)-derived-myeloid-derived suppressor cells (MDSCs) were stimulated to assess the effect of partial PARP-1 inhibition on inflammatory gene expression or immune suppression. Mice treated with azoxymethane/four dextran-sulfate-sodium cycles or APC^Min/+ mice bred into PARP-1^+/− or treated with olaparib were used to examine the role of PARP-1 in colitis-induced or spontaneous colon cancer, respectively. Syngeneic MC-38 cell-based (microsatellite instability, MSI^high) or CT-26 cell-based (microsatellite stable, MSS) tumor models were used to assess the effects of PARP inhibition on host responses and synergy with anti-Programmed cell Death protein (PD)-1 immunotherapy.

Results

Partial PARP-1 inhibition, via gene heterozygosity or a moderate dose of olaparib, protected against colitis-mediated/APC^Min-mediated intestinal tumorigenesis and APC^Min-associated cachexia, while extensive inhibition, via gene knockout or a high dose of olaparib, was ineffective or aggravating. A sub-IC50-olaparib dose or PARP-1 heterozygosity was sufficient to block tumorigenesis in a syngeneic colon cancer model by modulating the suppressive function, but not intratumoral migration or differentiation, of MDSCs, with concomitant increases in intratumoral T cell function and cytotoxicity, as assessed by granzyme-B/interferon-γ levels. Adoptive transfer of WT-BM-MDSCs abolished the protective effects of PARP-1 heterozygosity. The mechanism of MDSC modulation involved a reduction in arginase-1/inducible nitric oxide synthase/cyclo-oxygenase-2, but independent of PARP-1 trapping on chromatin. Although a high-concentration olaparib or the high-trapping PARP inhibitor, talazoparib, activated stimulator of interferon gene (STING) in BRCA-proficient cells and induced DNA damage, sub-IC50 concentrations of either drug failed to induce activation of the dsDNA break sensor. STING expression appeared dispensable for MDSC suppressive function and was not strictly required for olaparib-mediated effects. Ironically, STING activation blocked human and mouse MDSC function with no additive effects with olaparib. A metronomic dose of olaparib was highly synergistic with anti-PD-1-based immunotherapy, leading to eradication of MSI^high or reduction of MSS tumors in mice.

Conclusions

These results support a paradigm-shifting concept that expands the utility of PARP inhibitor and encourage testing metronomic dosing of PARP inhibitor to enhance the efficacy of checkpoint inhibitor-based immunotherapies in cancer.

Challenges of Genomic Testing for Hereditary Breast and Ovarian Cancers

Completion of genetic testing is increasingly important for the complex care of patients with suspected hereditary breast and ovarian cancers (HBOC) and their at-risk family members. Identification of individuals with pathogenic variants has implications for targeted treatment recommendations, risk reduction strategies, increased surveillance recommendations, as well as the genetic testing of family members, known as cascade testing or screening. Due to advances in technology and decreasing costs, what was once single-gene genetic testing has evolved into large-scale multi-gene panel genomic testing. As germline genomic testing for HBOC becomes more and more available, it is important to identify the challenges that are associated with its use. In this manuscript, we review the current issues faced by germline genomic testing for HBOC which include effectively managing the marked increases in genetic referrals, interpreting the vast amount of information yielded by newer testing methods such as next generation sequencing (NGS), recognizing the need for better cascade screening strategies, potential exacerbation of health disparities and improving support for patients navigating the emotional impact related to positive, negative and indeterminate testing results.

PARP Inhibitors for Ovarian Cancer: Current Indications, Future Combinations, and Novel Assets in Development to Target DNA Damage Repair

PARP inhibitors (PARPIs) have revolutionized the treatment of epithelial ovarian cancer, first for BRCA-associated cancer, and, recently, for all epithelial cancers of serous or high-grade endometrioid subtypes in the front line. Although there is hope that PARPIs will help prevent recurrences when used following frontline maintenance, cancer will still recur in most women, and the need for active combination strategies as well as continued development of novel assets, either as monotherapy or in combination, will be urgently needed. This review article discusses the current indications for PARPIs in both frontline and recurrent settings, current research in combination approaches, and finally, ongoing research on novel methods to target DNA damage response in an effort to exploit the common susceptibility to DNA damage repair in epithelial ovarian cancer and improve outcomes for patients.

The efficacy and adverse effects of PARP inhibitor combined with chemotherapy compared with chemotherapy alone in the treatment of cancer patient: A protocol for systematic review

BACKGROUND

There search of PARP inhibitors has made great breakthroughs and progress. Become a new type of medicine for cancer treatment,bringing hope to more advanced cancer patients.The purpose of this systematic review is to evaluate the clinical efficacy and adverse effects of PARP inhibitorscombined with chemotherapy and chemotherapy alone in the treatment of cancer patients.

METHODS

We searched the following 4 databases, including: PubMed, EMBASE, Web of Science, and Cochrane Library. The search will also be conducted at the clinical trial centers: ClinicalTrials.gov, ISRCTN Registry, WHO International Clinical Trials Registration Platform. The search date is as of September 22, 2020. There is no language restriction during this search, and the latest documents are kept updated through settings. The subject search terms were identified as "PARP Inhibitor", "Neoplasms" and "Dug therapy". The Phase 2 and Phase 3 clinical trials comparing PARP inhibitor combined with chemotherapy and chemotherapy alone were included. The results include overall survival (OS), progression-free survival (PFS), objective response rate (ORR) and adverse events. Two researchers separately completed the article inclusion, data extraction and quality evaluation of this study. The assessment of the risk of bias and data will be conducted using Review Manager.

ETHICS AND DISSEMINATION

All articles are published and do not require the approval of the ethics committee and the signed informed consent form. The results of this systematic review will be published through peer-reviewed publications.

REGISTERED

Registered on INPLASY and the registration number is INPLASY202090087.

Clinical assays for assessment of homologous recombination DNA repair deficiency

Homologous recombination DNA repair deficiency (HRD) is a functional defect in homologous recombination DNA repair, arising from germline or somatic mutations in BRCA1/2 or other mechanisms. Cells with HRD are more sensitive to platinum and poly(ADP-ribose) polymerase inhibitors (PARPi). HRD generates permanent changes in the genome with specific, quantifiable patterns ("genomic scars"). Clinical tests for HRD, such as the Myriad genomic instability score and Foundation Medicine loss of heterozygosity test, aim to predict the presence of HRD based on genomic features. Clinical trials of PARPi in ovarian cancer have evaluated genetic mutations and HRD genomic assays as potential biomarkers of response. Patients with HRD due to BRCA1/2 mutations are more likely to respond to PARPi than those with wild-type (WT) BRCA1/2. In some clinical trials, patients with WT BRCA1/2 who were predicted to be HRD by a genomic test exhibited greater clinical benefit from PARPi than patients with WT BRCA1/2 and no evidence of HRD. HRD tests therefore hold promise as predictive biomarkers for PARPi and other DNA-damaging agents. However, HRD tests vary in terms of the specific genomic features they measure, and the methods used to determine thresholds defining patients with HRD. Also, HRD test results and PARPi responses can be discordant: for instance, tumors with reversion mutations that restore HR function still exhibit a "genomic scar" of HRD, and PARPi resistance mechanisms independent of HR can result in lack of PARPi response despite HRD. Emerging methods to predict HRD, including genomic and functional assays, may overcome some of these challenges. Evaluation of HRD in the clinical setting is an important tool that has potential to aid patient selection for PARPi and other DNA-damaging agents in ovarian cancer, but understanding the details of these tests and their limitations is critical to ensure their optimal clinical application.

BET, SRC, and BCL2 family inhibitors are synergistic drug combinations with PARP inhibitors in ovarian cancer

BACKGROUND

Homologous recombination deficiencies (HRD) are present in approximately half of epithelial ovarian cancers, for which PARP inhibitors (PARPi) are becoming a preferred treatment option. However, a considerable proportion of these carcinomas acquire resistance or harbour de novo resistance, posing a significant challenge to treatment.

METHODS

To identify new combinatorial therapeutics to overcome resistance to PARPi, we employed high-throughput conditional RNAi and drug screening of patient-derived ovarian cancer cells. To prioritise clinically relevant drug combinations, we integrated empirical validation with analysis of The Cancer Genome Atlas (TCGA) and Genomics of Drug Sensitivity in Cancer (GDSC) datasets to nominate candidate targets and drugs, reaching three main findings.

FINDINGS

Firstly, we found that the PARPi rucaparib enhanced the effect of BET inhibitors (CPI-203 & CPI-0610) irrespective of clinical subtype or HRD status. Additional drug combination screens identified that dasatinib, a non-receptor tyrosine kinase inhibitor, augmented the effects of rucaparib and BET inhibitors, proposing a potential broadly applicable triple-drug combination for high-grade serous and clear cell ovarian carcinomas. Secondly, rucaparib synergised with the BCL2 family inhibitor navitoclax, with preferential activity in ovarian carcinomas that harbour alterations in BRCA1/2, BARD1, or MSH2/6. Thirdly, we identified potentially antagonistic drug combinations between the PARPi rucaparib and vinca alkaloids, anthracyclines, and antimetabolites, cautioning their use in the clinic.

INTERPRETATION

These findings propose therapeutic strategies to address PARP inhibitor resistance using agents that are already approved or are in clinical development, with the potential for rapid translation to benefit a broad population of ovarian cancer patients.

PARP inhibition in treatment of pancreatic cancer

INTRODUCTION

Tumor control and survival of patients with metastatic pancreatic ductal adenocarcinoma (PDAC) has improved with more effective polychemotherapies. The identification of novel therapeutic targets is strongly needed in order to propose maintenance therapies that improve quality of life while maintaining tumor control.

AREAS COVERED

PDAC with mutations in homologous recombination repair genes such as BRCA are particularly sensitive to platinum agents. Recently, the potential role of poly(ADP-ribose) polymerase (PARP) inhibitors was suggested. The POLO study has shown that olaparib was efficient and well-tolerated as maintenance therapy in patients with germline BRCA1/2 mutation and a metastatic PDAC controlled after a platinum-based induction chemotherapy.

EXPERT OPINION

The demonstration of olaparib efficacy in patients with metastatic PDAC and BRCA germline mutation has paved the way for maintenance with a targeted therapy. Further studies are needed to assess; the potential role for PARPI in earlier forms of PDAC, those with somatic or more rare BRACness signatures, to overcome primary or secondary resistances to PARPi, and to combine them with other antitumoral agents.

Morphological and molecular heterogeneity of epithelial ovarian cancer: Therapeutic implications

Ovarian epithelial cancer (OEC) is the most lethal gynecologic malignancy. Despite current chemotherapeutic and surgical options, this high lethality can be attributed to multiple factors, including late-stage presentation. In order to optimize OEC treatment, it is important to highlight that it is composed of five main subtypes: high-grade serous ovarian carcinoma (HGSOC), low-grade serous ovarian carcinoma (LGSOC), endometrioid ovarian carcinoma (EOC), ovarian clear cell carcinoma (CCOC), and mucinous ovarian carcinoma (MOC). These subtypes differ in their precursor lesions, as well as in epidemiological, morphological, molecular and clinical features. OEC is one of the tumours in which most pathogenic germline mutations have been identified. Accordingly, up to 20% OC show alterations in BRCA1/2 genes, and also, although with a lower frequency, in other low penetrance genes associated with homologous recombination deficiency (HRD), mismatch repair genes (Lynch syndrome) and TP53. The most important prognostic factor is the 2014 FIGO staging, while older age is also associated with worse survival. HGSOC in all stages and CCC and MOC in advanced stages have the worse prognosis among histological types. Molecular markers have emerged as prognostic factors, particularly mutations in BRCA1/2, which are associated with a better outcome. Regarding treatment, whereas a proportion of HGSOC is sensible to platinum-based treatment and PARP inhibitors due to HRD, the rest of the histological types are relatively chemoresistant. New treatments based in specific molecular alterations are being tested in different histological types. In addition, immunotherapy could be an option, especially for EOC carrying mismatch repair deficiency or POLE mutations.

•

The five different histological types have different precursor lesions and epidemiological, morphological, genetic, epigenetic and clinical features.

•

Histological type is an important prognostic factor.

•

Drugs targeting homologous recombination deficiency have been approved for treatment.

•

The use of immunotherapy is limited due to lack of predictive biomarkers

Emerging drugs for the treatment of ovarian cancer: a focused review of PARP inhibitors

INTRODUCTION

Poly (ADP-ribose) polymerase (PARP) inhibitors have demonstrated significant anticancer activity in cancers harboring homologous recombination deficiency (HRD), exemplified by high grade serous ovarian cancer (HGSC). PARP inhibitors (PARPi) are being used in women with newly diagnosed ovarian cancer as well as in the recurrent setting. PARPi combination therapies are in development.

AREAS COVERED

This review discusses the treatment of ovarian cancer, key PARPi clinical trials, mechanisms of action of PARPi, and novel PARPi combination regimens under investigation. PubMed and ClinicalTrials.gov were searched for PARPi trials. Active development was confirmed via PharmaProjects.

EXPERT OPINION

PARPi have shown to improve progression-free survival (PFS) for women with HGSC as monotherapy in both frontline and recurrent maintenance settings and as monotherapy as treatment for recurrence. These benefits are greatest in HGSC with underlying HRD, in particular for those with deleterious BRCA mutations, and with the least benefit in cancers that are HR proficient (HRP) and BRCA wild-type (wt). Thus far, an improvement in overall survival has only been demonstrated in patients with BRCA mutated EOC treated with olaparib maintenance in the platinum sensitive recurrence setting. Novel combinations of PARPi are undergoing testing in an effort to increase PARPi efficacy in HRP or PARPi-resistant cancers.

The forefront of ovarian cancer therapy: update on PARP inhibitors

BACKGROUND

In recurrent ovarian cancer, poly(ADP-ribose) polymerase (PARP)-inhibiting agents have transformed the treatment of platinum-sensitive disease. New data support use of PARP inhibitors earlier in the treatment algorithm.

DESIGN

We review results from recent phase III trials evaluating PARP inhibitors as treatment and/or maintenance therapy for patients with newly diagnosed ovarian cancer. We discuss the efficacy and safety of these agents in the all-comer and biomarker-selected populations studied in clinical trials, and compare the strengths and limitations of the various trial designs. We also consider priorities for future research, with a particular focus on patient selection and future regimens for populations with high unmet need.

RESULTS

Four phase III trials (SOLO-1, PAOLA-1/ENGOT-OV25, PRIMA/ENGOT-OV26 and VELIA/GOG-3005) demonstrated remarkable improvements in progression-free survival with PARP inhibitor therapy (olaparib, niraparib or veliparib) for newly diagnosed ovarian cancer. Differences in trial design (treatment and/or maintenance setting; single agent or combination; bevacizumab or no bevacizumab), patient selection (surgical outcome, biomarker eligibility, prognosis) and primary analysis population (intention-to-treat, BRCA mutated or homologous recombination deficiency positive) affect the conclusions that can be drawn from these trials. Overall survival data are pending and there is limited experience regarding long-term safety.

CONCLUSIONS

PARP inhibitors play a pivotal role in the management of newly diagnosed ovarian cancer, which will affect subsequent treatment choices. Refinement of testing for patient selection and identification of regimens to treat populations that appear to benefit less from PARP inhibitors are a priority.

Therapeutic applications of PARP inhibitors in ovarian cancer

Ovarian cancer is the most lethal gynecologic malignancy with a high recurrence rate. Poly(ADP-ribose) polymerase inhibitors (PARPi) are one of the most active new therapies for treatment of ovarian cancer. These treatment modalities are based on the mechanisms of "synthetic lethal" and "PARP trapping", especially for patients with homologous recombination deficiencies, and they demonstrate a high survival advantage. However, resistance to PARPi is an emerging problem. Identifying potential biomarkers to monitor the resistance and developing drug combination strategies are effective ways to address PARPi resistance. This review introduces the mechanisms of anticancer activity of PARPi and the developmental history in clinical research. Moreover, this paper systematically analyzes the functions of PARP family proteins. Additionally, this work highlights the treatment prospects of the combination of immunotherapy and PARPi in ovarian cancer. Finally, we propose several novel technologies to overcome the limitations of current preclinical studies and utilize them to select potential targets for combined drug therapy and identify biomarkers of PARPi resistance in ovarian cancer.

Mechanistic understanding of cellular responses to genomic stress

Within the past half century we have learned of multiple pathways for repairing damaged DNA, based upon the intrinsic redundancy of information in its complementary double strands. Mechanistic details of these pathways have provided insights into environmental and endogenous threats to genomic stability. Studies on bacterial responses to ultraviolet light led to the discovery of excision repair, as well as the inducible SOS response to DNA damage. Similar responses in eukaryotes promote upregulation of error-prone translesion DNA polymerases. Recent advances in this burgeoning field include duplex DNA sequencing to provide strikingly accurate profiling of mutational signatures, analyses of gene expression patterns in single cells, CRISPR/Cas9 to generate changes at precise genomic positions, novel roles for RNA in gene expression and DNA repair, phase-separated aqueous environments for specialized cellular transactions, and DNA lesions as epigenetic signals for gene expression. The Environmental Mutagenesis and Genomics Society (EMGS), through the broad range of expertise in its membership, stands at the crossroad of basic understanding of mechanisms for genomic maintenance and the field of genetic toxicology, with the need for regulation of exposures to toxic substances. Our future challenges include devising strategies and technologies to identify individuals who are susceptible to specific genomic stresses, along with basic research on the underlying mechanisms of cellular stress responses that promote disease-causing mutations. As the science moves forward it should also be a responsibility for the EMGS to expand its outreach programs for the enlightenment and benefit of all humans and the biosphere. Environ. Mol. Mutagen. 61:25-33, 2020. © 2019 Wiley Periodicals, Inc.