DNA damage response in breast cancer and its significant role in guiding novel precise therapies.

DNA damage response (DDR) deficiency has been one of the emerging targets in treating breast cancer in recent years. On the one hand, DDR coordinates cell cycle and signal transduction, whose dysfunction may lead to cell apoptosis, genomic instability, and tumor development. Conversely, DDR deficiency is an intrinsic feature of tumors that underlies their response to treatments that inflict DNA damage. In this review, we systematically explore various mechanisms of DDR, the rationale and research advances in DDR-targeted drugs in breast cancer, and discuss the challenges in its clinical applications. Notably, poly (ADP-ribose) polymerase (PARP) inhibitors have demonstrated favorable efficacy and safety in breast cancer with high homogenous recombination deficiency (HRD) status in a series of clinical trials. Moreover, several studies on novel DDR-related molecules are actively exploring to target tumors that become resistant to PARP inhibition. Before further clinical application of new regimens or drugs, novel and standardized biomarkers are needed to develop for accurately characterizing the benefit population and predicting efficacy. Despite the promising efficacy of DDR-related treatments, challenges of off-target toxicity and drug resistance need to be addressed. Strategies to overcome drug resistance await further exploration on DDR mechanisms, and combined targeted drugs or immunotherapy will hopefully provide more precise or combined strategies and expand potential responsive populations.

Stability Indicating Assay Method for the Quantitative Determination of Olaparib in Bulk and Pharmaceutical Dosage Form.

Objectives: Olaparib is an orally active poly (ADP-ribose) PARP (polymerases) inhibitor known to destroy cancer cells with BRCA1 or BRCA2 deficiency. An authentic, fast, distinct, and reliable reverse phase-high performance liquid chromatography (RP-HPLC) method was developed and promptly validated in tablet formulations for olaparib estimation. Materials and Methods: The proposed method focuses on the separation of olaparib in reverse phase mode using a Waters symmetry C18 (150 x 4.6 mm, 5 µm) analytical column with a flow rate of 1.0 mL/min and the injection volume was kept at 20 µL. The optimized mobile phase consists of ammonium acetate buffer (pH adjusted to 3.5 by glacial acetic acid): methanol in the ratio of 50:50 v/v. Results: The eluents were measured at 254 nm and the retention time for the drug encircled was about 4.32 min. The stress degradation studies of olaparib were conducted under acidic, alkaline, oxidative, photolytic and thermal conditions to demonstrate the stability of the drug. The regression value of 0.998 showed that the developed method was linear over the range of 80 µg/mL to 120 µg/mL. The developed RP-HPLC method is accurate and precise. The method was statistically validated as per International Conference on Harmonization guidelines. Conclusion: The proposed method is suitable and can be applied for the quantitative estimation of olaparib without any interference of the excipients used in the drug formulations.

Comprehensive Analysis of Adverse Events Induced by PARP Inhibitors Using JADER and Time to Onset.

Poly (ADP-ribose) polymerase (PARP) inhibitors are effective against breast cancer susceptibility gene (BRCA) mutations. Clinical trials have reported hematologic toxicity and gastrointestinal symptoms as class effects of PARP inhibitors. However, information on adverse events (AEs) in a Japanese clinical cohort is currently lacking. In this study, we conducted a comprehensive survey of the AEs of two PARP inhibitors, olaparib and niraparib, using the Japanese Adverse Reaction Reporting (JADER) database provided by the Pharmaceuticals and Medical Devices Agency (PMDA). Moreover, we also analyzed the course and time to the onset of AEs. Signals were detected for 15 and 11 AEs for olaparib and niraparib, respectively. Most occurred within the first month of treatment with either agent. These results may indicate the importance of early response and monitoring after beginning PARP inhibitor therapy. The results of this study may be useful for managing side effects and suggesting supportive care for patients using PARP inhibitors in the future.

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.

Management of breast cancer patients with BRCA gene mutations in Lebanon of the Middle East: perspectives and challenges.

BACKGROUND: This commentary explores and discusses the challenges oncologists face in diagnosing and managing breast cancer patients with BRCA gene mutations in Lebanon and the Middle East. METHODS: Key opinion leaders shared their recommendations to achieve better patient outcomes and satisfaction based on evidence-based medicine and their clinical experience in BRCA management. RESULTS: Challenges associated with BRCA management can be divided into four main levels: physicians, patients, test, and treatment factors. More genetic counselors are to be identified given their important role in the management of individuals with BRCA gene mutations. CONCLUSION: Genetic counseling, continuing education, infrastructure, testing, expertise, and financial support are needed to fulfill the unmet needs in the management of BRCA mutation carriers.

The systemic treatment of recurrent ovarian cancer revisited.

Treatment approaches for relapsed ovarian cancer have evolved over the past decade from a calendar-based decision tree to a patient-oriented biologically driven algorithm. Nowadays, platinum-based chemotherapy should be offered to all patients with a reasonable chance of responding to this therapy. The treatment-free interval for platinum is only one of many factors affecting patients' eligibility for platinum re-treatment. Bevacizumab increases the response to chemotherapy irrespective of the cytotoxic regimen and can be valuable in patients with an urgent need for symptom relief (e.g. pleural effusion, ascites). For patients with recurrent high-grade ovarian cancer, which responds to platinum-based treatment, maintenance therapy with a poly(ADP-ribose) polymerase inhibitor can be offered, regardless of the BRCA mutation status. Here we review contemporary decision-making processes in the systemic treatment of relapsed ovarian cancer.

Case Report: BAP1 Mutation and RAD21 Amplification as Predictive Biomarkers to PARP Inhibitor in Metastatic Intrahepatic Cholangiocarcinoma.

INTRODUCTION: Intrahepatic cholangiocarcinoma (ICC) is a rare hepatobiliary cancer characterized by a poor prognosis and a limited response to conventional therapies. Currently chemotherapy is the only therapeutic option for patients with Stage IV ICC. Due to the poor response rate, there is an urgent need to identify novel molecular targets to develop novel effective therapies. Precision oncology tests utilizing targeted next-generation sequencing (NGS) platforms have rapidly entered into clinical practice. Profiling the genome and transcriptome of cancer to identify potentially targetable oncogenic pathways may guide the clinical care of the patient. CASE PRESENTATION: We present a 56-year-old male patient affected with metastatic ICC, whose cancer underwent several precision oncology tests by different NGS platforms. A novel BAP1 mutation (splice site c.581-17_585del22) and a RAD21 amplification were identified by a commercial available platform on a metastatic lesion. No germline BAP1 mutations were identified. Several lines of evidences indicate that PARP inhibitor administration might be an effective treatment in presence of BAP1 and/or RAD21 alterations since both BAP1 and RAD21 are involved in the DNA repair pathway, BAP1 interacts with BRCA1 and BRCA1-mediated DNA repair pathway alterations enhance the sensitivity to PARP inhibitor administration. In this case, after failing conventional therapies, patient was treated with PARP inhibitor olaparib. The patient had a partial response according to RECIST criteria with an overall survival of 37.2 months from the time of diagnosis of his ICC. Following 11.0 months on olaparib treatment, sustained stable disease control is ongoing. The patient is still being treated with olaparib and no significant toxicity has been reported. CONCLUSION: These findings have clinical relevance since we have shown PARP inhibitor as a potential treatment for ICC patients harboring BAP1 deletion and RAD21 amplification. We have also highlighted the utility of NGS platforms to identify targetable mutations within a cancer.

Poly (ADP-Ribose) Polymerase Inhibitor Treatment as a Novel Therapy Attenuating Renal Ischemia-Reperfusion Injury.

Intrarenal robust inflammatory response following ischemia-reperfusion injury (IRI) is a major factor in the pathogenesis of renal injury in ischemic acute kidney injury (AKI). Although numerous studies have investigated various agents of immune modulation or suppression for ischemic AKI, few showed reproducible effects. We hypothesized that poly (ADP-ribose) polymerase (PARP) inhibitor may favorably change post-ischemic intrarenal immunologic micromilieu by reducing damage-associated molecular pattern (DAMP) signals and improve renal outcome in ischemic AKI. The effects of JPI-289 (a PARP inhibitor) on early renal injury in a murine IRI model and hypoxic HK-2 cell model were investigated. Bilateral IRI surgery was performed in three groups of 9-week-old male C57BL/6 mice (control, JPI-289 50 mg/kg, and JPI-289 100 mg/kg; n = 9-10 in each group). Saline or JPI-289 was intraperitoneally injected. Renal function deterioration was significantly attenuated in the JPI-289 treatment groups in a dose-dependent manner. Inflammatory cell infiltration and proinflammatory cytokine/chemokine expressions in the post-ischemic kidneys were also attenuated by JPI-289 treatment. JPI-289 treatment at 0.5 and 0.75 µg/ml facilitated the proliferation of hypoxic HK-2 cells. PARP inhibition with JPI-289 treatment showed favorable effects in ischemic AKI by attenuating intrarenal inflammatory cascade in a murine model and facilitating proliferation of hypoxic HK-2 cells.

Targeting DNA damage response pathway: recent progress of PARP inhibitors in cancer therapy / 中国药理学通报

Genomic instability is one of the most pervasive characteristics of cancer cells,and DNA damage response (DDR) pathway plays a crucial role in genomic stability.The DDR pathway is a complex signaling network,which involves cell DNA repair,apoptosis and cell cycle regulation.Deficiencies in these repair pathways can result in several different genetic disorders,including cancer.Targeted therapy based on inhibiting the DDR pathway in cancers offers a novel therapy strategy for patients with tumors lacking specific DDR functions.Many small-mole-cule compounds targeting DDR pathway are typically developed for solid cancer therapy.The poly (ADP-ribose) polymerase (PARP) inhibitor is a kind of DDR inhibitors which exploits the principle of synthetic lethality to selectively kill cancer cells.This review highlights the molecular mechanisms of PARP inhibitor action,the progress of PARP inhibitors in cancer therapy,drug resistance and the challenge of PARP inhibitor in the future.