The Cancer Journal

Poly(ADP-Ribose) Polymerase Inhibitor Inhibition in Ovarian Cancer

Abstract The emergence of clinical trial data for poly(ADP-ribose) polymerase inhibitors (PARPi), in BRCA-associated ovarian cancer (epithelial ovarian cancer [EOC]) in 2009 (Lancet 2010;376:245–251) unleashed a rapid series of additional asset development and clinical trial activation across all lines of EOC treatment, ultimately leading to 8 new approvals of 3 different PARPi in EOC since 2014. Monotherapy iPARPi were approved as frontline maintenance treatment for all patients with EOC who respond to platinum-based chemotherapy irrespective of biomarker (niraparib) and for BRCA-associated cancers (olaparib) (https://www.azpicentral.com/lynparza_tb/lynparza_tb.pdf#page=1; https://www.accessdata.fda.gov/drugsatfda_docs/label/2020/208447s015s017lbledt.pdf). Combination of olaparib and bevacizumab was approved as maintenance for patients in response to platinum-based and bevacizumab containing frontline therapy whose tumor is characterized as homologous recombination deficient and as approved test by the Food and Drug Administration, inclusive of BRCA-associated cancers (N Engl J Med 2019;381:2416–2428). Niraparib, olaparib, and rucaparib were also approved as maintenance treatment following response to platinum-based therapy in the recurrent setting irrespective of biomarker (https://www.azpicentral.com/lynparza_tb/lynparza_tb.pdf#page=1; https://www.accessdata.fda.gov/drugsatfda_docs/label/2020/208447s015s017lbledt.pdf; https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/209115s003lbl.pdf). All 3 PARPi were also approved as treatment in lieu of chemotherapy for patients with BRCA-associated cancers in third line and beyond (https://www.azpicentral.com/lynparza_tb/lynparza_tb.pdf#page=1;https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/209115s003lbl.pdf) and platinum-sensitive homologous recombination deficient in the fourth line and beyond (https://www.accessdata.fda.gov/drugsatfda_docs/label/2020/208447s015s017lbledt.pdf), as well as the National Comprehensive Cancer Network listed in combination with bevacizumab for treatment of patients with platinum-sensitive recurrent disease (https://www.nccn.org/professionals/physician_gls/pdf/ovarian.pdf). Ongoing clinical trials in all lines of treatment are evaluating combinations of therapies to improve efficacy among biomarker negative tumors as well as overcome acquired PARPi resistance due to prior use.

Integrated, Integral, and Exploratory Biomarkers in the Development of Poly(ADP-Ribose) Polymerase Inhibitors

Abstract In this article, we highlight biomarkers for poly(ADP-ribose) polymerase inhibitor (PARPi) sensitivity and resistance and discuss their implications for the clinic. We review the predictive role of a range of DNA repair genes, genomic scars, mutational signatures, and functional assays available or in development. The biomarkers used for patient selection in the specific Food and Drug Administration–approved indications for breast, ovarian, prostate, and pancreatic cancer vary across tumor type and likely depend on disease-specific DNA repair deficiencies but also the specifics of the individual clinical trials that were conducted. Mutations in genes involved in homologous recombination and/or replication fork protection are synthetic lethal with PARPi. Cancers with homologous recombination deficiency exhibit high genomic instability, characterized by genome-wide loss of heterozygosity, among other genomic aberrations. Next-generation sequencing can identify multiple patterns of genomic changes including copy number variations, single-nucleotide variations, insertions/deletions, and structural variations rearrangements characteristic of homologous recombination deficiency. Clinical trial evidence supports the use of BRCA mutation testing for patient selection, and for ovarian cancer, there are 3 commercial assays available that additionally incorporate genomic instability for identifying subgroups of patients that derive different magnitudes of benefit from PARPi therapy. Finally, we summarize new strategies for extending the benefit of PARPi therapy toward broader populations of patients through the use of novel biomarkers. Ultimately, design of a composite biomarker test combining multiple mutational signatures or development of a dynamic assay for functional assessments of homologous recombination may help improve the test accuracy for future patient stratification.

Poly(ADP-Ribose) Polymerase Inhibitor Combination Therapy

Abstract The introduction of poly(ADP-ribose) polymerase (PARP) inhibitors has led to significant improvements in outcome for several cancer types, most notably high-grade serous ovarian cancer. However, in general, benefit is restricted to tumors characterized by either BRCA1/2 mutation or homologous recombination deficiency. Combination therapy offers the potential to overcome innate and acquired PARP inhibitor resistance by either working synergistically with PARP inhibitors or by targeting the homologous recombination repair pathway through an alternate strategy, to restore homologous recombination deficiency. Several biological agents have been studied in combination with PARP inhibitors, including inhibitors of vascular endothelial growth factor (vascular endothelial growth factor; bevacizumab, cediranib), AKT (capivasertib), PI3K inhibitors (buparlisib, alpelisib), epidermal growth factor receptor and BET inhibitors. In general, PARP inhibitor and biological agent combinations are well tolerated, and early data suggest that they are clinically effective in both BRCA1/2 mutant and wild-type cancers. In this review, we discuss multiple clinical trials that are underway examining the antitumor activity of the most promising combination strategies.

The Principles and Practice of PARP Inhibitor Therapy

The Clinical Challenges, Trials, and Errors of Combatting Poly(ADP-Ribose) Polymerase Inhibitors Resistance

Abstract The use of poly(ADP-ribose) polymerase inhibitor (PARPi) exploits synthetic lethality in solid tumors with homologous recombination repair (HRR) defects. Significant clinical benefit has been established in breast and ovarian cancers harboring BRCA1/2 mutations, as well as tumors harboring characteristics of “BRCAness.” However, the durability of treatment responses is limited, and emerging data have demonstrated the clinical challenge of PARPi resistance. With the expanding use of PARPi, the significance of PARP therapy in patients pretreated with PARPi remains in need of significant further investigation. Molecular mechanisms contributing to this phenomenon include restoration of HRR function, replication fork stabilization, BRCA1/2 reversion mutations, and epigenetic changes. Current studies are evaluating the utility of combination therapies of PARPi with cell cycle checkpoint inhibitors, antiangiogenic agents, phosphatidylinositol 3-kinase/AKT pathway inhibitors, MEK inhibitors, and epigenetic modifiers to overcome this resistance. In this review, we address the mechanisms of PARPi resistance supported by preclinical models, examine current clinical trials applying combination therapy to overcome PARPi resistance, and discuss future directions to enhance the clinical efficacy of PARPi.

With Our Powers Combined

Abstract The use of poly(ADP-ribose) polymerase inhibitors and immune checkpoint inhibitor therapies has seen substantial clinical success in oncology therapeutic development. Although multiple agents within these classes have achieved regulatory approval globally—in several malignancies in early and advanced stages—drug resistance remains an issue. Building on preclinical evidence, several early trials and late-phase studies are underway. This review explores the therapeutic potential of combination poly(ADP-ribose) polymerase inhibitors and immune checkpoint inhibitor therapy in solid tumors, including the scientific and therapeutic rationale, available clinical evidence, and considerations for future trial and biomarker development across different malignancies using ovarian and other solid cancer subtypes as key examples.

Disparities in Gynecologic Cancers

Abstract Gynecologic cancer disparities have different trends by cancer type and by sociodemographic/economic factors. We highlight disparities in the United States arising due to poor delivery of cancer care across the continuum from primary prevention, detection, and diagnosis through treatment and identify opportunities to eliminate/reduce disparities to achieve cancer health equity. Our review documents the persistent racial and ethnic disparities in cervical, ovarian, and uterine cancer outcomes, with Black patients experiencing the worst outcomes, and notes literature investigating social determinants of health, particularly access to care. Although timely delivery of screening and diagnostic evaluation is of paramount importance for cervical cancer, efforts for ovarian and uterine cancer need to focus on timely recognition of symptoms, diagnostic evaluation, and delivery of guideline-concordant cancer treatment, including tumor biomarker and somatic/germline genetic testing.