PARP Inhibitors for BRCA1/2 mutation-associated and BRCA-like malignancies

Poly(ADP-ribose)polymerase inhibitors (PARPis) have shown promising activity in patients with BRCA1/2 mutation-associated (BRCA1/2(MUT+)) ovarian and breast cancers. Accumulating evidence suggests that PARPi may have a wider application in the treatment of sporadic high-grade serous ovarian cancer, and cancers defective in DNA repair pathways, such as prostate, endometrial, and pancreatic cancers. Several PARPis are currently in phase 1/2 clinical investigation, with registration trials now being designed. Olaparib, one of the most studied PARPis, has demonstrated activity in BRCA1/2(MUT+) and BRCA-like sporadic ovarian and breast cancers, and looks promising in prostate and pancreatic cancers. Understanding more about the molecular abnormalities involved in BRCA-like tumors, exploring novel therapeutic trial strategies and drug combinations, and defining potential predictive biomarkers, is critical to rapidly advancing the field of PARPi therapy and improve clinical outcomes.

Investigational agents in development for the treatment of ovarian cancer

Although significant success has been achieved in the treatment of advanced and recurrent ovarian cancer, there is clearly room for improvement. The use of targeted agents in this patient population has the promise to provide improved survival and quality of life. There are a myriad of relevant pathways under exploration in all settings of ovarian cancer. Clinical trial data are accumulating for antiangiogenic therapy, including vascular endothelial growth factor (VEGF)-specific inhibitors and multiple angiogenic signaling target inhibitors, as well as poly-ADP-ribose polymerase (PARP) inhibitors. Other types of tumorigenic pathway inhibitors, including those that target phosphatidylinositol-3-kinase (PI3K), mammalian target of rapamycin (mTOR), protein kinase B (AKT), Src, folate receptor alpha, and insulin-like growth factor-1 receptor (IGF-1R) pathways are in earlier phases of development for ovarian cancer. Attempts to target the epidermal growth factor receptor (EGFR) of ovarian tumors have been met with limited success; however, newer agents that inhibit this pathway show promise. Finally, with recognition of the role of Wee-1 in p53-deficient tumors, an inhibitor of this tyrosine kinase is being evaluated in recurrent ovarian cancer. The logistical challenge is to determine the optimal timing and proper combinations of novel agents independently as well as concomitantly with conventional chemotherapeutics. Reported results have been modest; however, our growing understanding of these pathways will be potentially reflected in greater impact on response and survival.

Olaparib, PARP1 inhibitor in ovarian cancer

INTRODUCTION

Ovarian cancer is the most important cause of gynecological cancer-related mortality. Conventional treatments for advanced or recurrent disease offer limited results in terms of long-term responses and survival. Researches have recently focused on target therapies, which represent a new, promising, therapeutic approach, able to maximizing tumor kill and minimizing toxicity. The family of polyadenosine diphosphate-ribose polymerase (PARP) inhibitors is currently one of the most hopeful and investigated alternatives.

AREAS COVERED

Preclinical and clinical studies of Olaparib , the most investigated PARP inhibitor in ovarian cancer, are analyzed and discussed. Data were obtained by searching for all English peer-reviewed articles on Medline, on Cochrane Database and all on-going Phase I and II studies registered on National Cancer Institute Clinical Trials; also any related abstracts recently presented on Olaparib at major international congresses will be included.

EXPERT OPINION

Bad prognosis and drug resistance usually affect ovarian cancer. Recent trends toward the knowledge of molecular-specific pathways have produced new target drugs. PARP inhibition mediated by Olaparib in BRCA1 (breast cancer 1) and BRCA2 (breast cancer 2)-mutated and in sporadic ovarian cancer represents a promising field of investigation. Further studies are needed to confirm initial exciting results.

BRCAness: finding the Achilles heel in ovarian cancer

Ovarian cancer is the leading cause of death among gynecological cancers. It exhibits great heterogeneity in tumor biology and treatment response. Germline mutations of DNA repair genes BRCA1/2 are the fundamental defects in hereditary ovarian cancer that expresses a distinct phenotype of high response rates to platinum agents, improved disease-free intervals and survival rates, and high-grade serous histology. The term "BRCAness" describes the phenotypic traits that some sporadic ovarian tumors share with tumors in BRCA1/2 germline mutation carriers and reflects similar causative molecular abnormalities. BRCA pathway studies and molecular profiling reveal BRCA-related defects in almost half of the cases of ovarian cancer. BRCA-like tumors are particularly sensitive to DNA-damaging agents (e.g., platinum agents) because of inadequate BRCA-mediated DNA repair mechanisms, such as nucleotide-excision repair and homologous recombination (HR). Additional inhibition of other DNA repair pathways leads to synthetic lethality in HR-deficient cells; this has been employed in the treatment of BRCA-like ovarian tumors with poly(ADP-ribose) polymerase inhibitors with promising results. This article presents a comprehensive review of the relevant literature on the role of BRCAness in ovarian cancer with respect to BRCA function, methods of BRCA epigenetic defect detection and molecular profiling, and the implications of BRCA dysfunction in the treatment of ovarian cancer.

The role of targeted therapy in ovarian cancer

Ovarian cancer is the second most common gynaecological malignancy and the leading cause of death from gynaecological cancer. Although in some cases treatment is initially effective, there is a considerable risk of disease recurrence and resistance to therapy. Therapies targeting molecular alterations in tumours offer the promise of significantly improved treatment. So far, the most promising targeted agents are angiogenesis inhibitors and PARP inhibitors. Here, we review the various targeted therapeutic approaches under clinical investigation in phase I and II trials of ovarian cancer and the challenges facing their future success in the clinic.