PARP Inhibitor Therapy Research Articles

Precision Oncology of High-Grade Ovarian Cancer Defined through Targeted Sequencing.

Simple SummaryOvarian cancer is a rare and deadly gynaecologic cancer, with a relatively large hereditary component. Genomic analysis of tumour material can potentially provide information regarding therapy and identify hereditary carriers and their families. The aim of our prospective study was to apply genomic characterization to tumour material from women with ovarian cancer to identify women that might benefit from PARP inhibitor therapy, as well as to detect and triage women to genetic counselling. We used next generation sequencing using a targeted panel to prospectively analyse 274 tumours and identified 50 with a BRCA1/2 pathogenic variant. Twenty patients received olaparib based on these results, and 16 previously unknown hereditary carriers were identified. In addition, in a subset examined by an extended sequencing panel, actionable mutations were found in 84/88 tumours. This study demonstrates that personalized medicine approaches can be useful for women with ovarian cancer and can help with therapy selection and identification of at risk families. Background: We examined whether molecular characterization of high-grade epithelial ovarian cancer can inform the diagnosis and/or identify potential actionable targets. Methods: All of the consecutively sequenced high-grade ovarian tumours with consent between 2014 until 2019 were included. A total of 274 tumours underwent next generation sequencing using a targeted panel. Results: Patients with high-grade ovarian epithelial cancer were consented to prospective molecular characterization. Clinical information was extracted from their medical record. Tumour DNA was subjected to sequencing, and selected patients received PARP inhibitor therapy. Conclusions: Tumours from 274 women were sequenced, including high-grade serous carcinoma (n = 252), clear cell carcinoma (n = 4), carcinosarcoma (n = 9), endometrioid carcinoma (n = 3), undifferentiated carcinoma (n = 1), and mixed tumours (n = 5). Genomic profiling did not influence histologic diagnosis. Mutations were identified in TP53, BRCA1, BRCA2, as well as additional homologous recombination repair pathway genes BARD1, ATR, CHEK2, PALB2, RAD51D, RAD50, SLX4, FANCA, RAD51C, and RAD54L. In addition, mutations in PTEN and CDKN2A were identified. Several somatic mutations with implications for germline testing were identified, including RMI1, STK11, and CDH1. Germline testing identified 16 previously unknown BRCA1/2 carriers. Finally, 20 patients were treated with the PARP inhibitor olaparib based on the sequencing results.

Preclinical Studies on the Effect of Rucaparib in Ovarian Cancer: Impact of BRCA2 Status.

Background: Approximately 50% of ovarian cancer patients harbour homologous recombination repair deficiencies. These deficiencies have been successfully targeted using poly (ADP-ribose) polymerase inhibitors (PARPi) particularly for patients harbouring BRCA1/2 mutations. The aim of this study is to assess the effects of the PARPi rucaparib in vitro using cell lines with BRCA2 mutations in comparison to those with BRCA2 wild type. Methods: Cell proliferation assays, RT-qPCR, immunofluorescence, annexin V/PI assays were used to assess the effects of rucaparib in vitro. Results: The BRCA2 mutant ovarian cancer cell line PEO1 exhibited higher PARP1 activity when treated with H2O2 compared to wild type cell lines. The migratory and proliferative capacity of PEO1 cells was compromised following treatment with rucaparib 10 µM compared to BRCA2 wild-type cell lines via a mechanism involving the mTOR pathway. Rucaparib treatment significantly increased DNA damage primarily in PEO1 cells and SKOV3 cells compared with wild type. Conclusions: Appropriate identification of robust predictive biomarkers for homologous recombination deficiency using ‘liquid’ biopsies would facilitate the identification of patients suitable for PARPi therapy. Preliminary efforts to undertake such testing are described here. This study also demonstrates the mechanisms of action of rucaparib (PARPi) which may involve elements of the mTOR pathway.

Adherence to PARP inhibitor therapy among women with ovarian cancer

Objective:The objective of this study was to evaluate medical adherence for patients with ovarian cancer who initiated treatment with a PARP inhibitor therapy, and to identify factors associated with nonadherence. Methods:We used the MarketScan Database to identify ovarian cancer patients who initiated PARP inhibitor therapy between January 1, 2008 and December 31, 2017. The primary outcome was adherence defined as ≥ 80% proportion of days covered (PDC). A secondary outcome included adherence assessed using the medication possession ratio (MPR). Multivariable logistic regression analysis was performed to assess relation between PDC and explanatory variables. Sensitivity analysis was performed to evaluate impact of dose-adjustments and toxicity-related delays on adherence. Results:Among 170,976 patients diagnosed with ovarian cancer, 151 patients met inclusion criteria. The median time from diagnosis to initiating therapy was 33 months. Overall, 40 (26.5%) were non-adherent based on a PDC less than 80%. Non-adherent patients were more likely to receive niraparib and have a longer duration of therapy (p < 0.05). We found no significant impact of age, comorbidities, insurance plan, or year of PARP inhibitor initiation on non-adherence. In a sensitivity analysis to assess different definition of adherence, non-adherence ranged from 11.3% to 41.1%. When accounting for possible dose-adjustments, 21.2% of patients were non-adherent. Conclusion:This population based study of ovarian cancer patients found that a quarter of patients may be sub-optimally adherent to PARP inhibitor therapy. Future research should focus on identification of patients at risk for nonadherence and interventions to lower nonadherence among these patients.

764P Survey on the practical implementation of BRCA gene and HRD-testing and PARP-inhibitor management in Germany: A national NOGGO/JAGO-AGO intergroup study

Since the introduction of Poly (ADP-ribose) polymerase inhibitors (PARPi) the Breast Cancer gene (BRCA)-testing has evolved as a standard management in high grade ovarian cancer (EOC). The purpose of the study is to analyze the current implementation of BRCA testing and PARPi therapy for EOC in Germany.

1467P POLO: Long-term safety and tolerability of olaparib for patients with a germline BRCA mutation and metastatic pancreatic cancer

The phase III POLO trial (NCT02184195) compared maintenance PARP inhibitor therapy with olaparib (O) to placebo (P) in patients (pts) with a germline BRCA mutation and metastatic pancreatic cancer. We describe safety and tolerability results for pts with an overall survival (OS) of ≥ 2 years.

Targeting DNA Damage Repair Mechanisms in Pancreas Cancer.

Simple SummaryPancreatic cancer is a devastating malignant disease with a dismal prognosis and limited treatment options. Around 14% of pancreatic cancers harbour mutations in specific genes that are important to ensure appropriate DNA repair after damage, like the BRCA 1 and 2 genes. Recently, with olaparib a first treatment option for BRCA 1 and 2 mutated pancreatic cancer was approved. However, there is a relevant proportion of further genes involved in the DNA damage repair beyond BRCA1 and 2 that might benefit from such tailored therapeutic interventions like olaparib. Unfortunately, due to the lack of specific data, no general recommendations are currently available. Therefore, a representative panel of experts was assembled by the European Society of Digestive Oncology (ESDO) to assess the current knowledge and evaluate the significance to treat pancreatic cancer with mutations in DNA damage repair genes. The data-driven consensus recommendations of the ESDO expert panel aim to provide clinicians guidance for a state-of-the-art management.Impaired DNA damage repair (DDR) is increasingly recognised as a hallmark in pancreatic ductal adenocarcinoma (PDAC). It is estimated that around 14% of human PDACs harbour mutations in genes involved in DDR, including, amongst others, BRCA1/2, PALB2, ATM, MSH2, MSH6 and MLH1. Recently, DDR intervention by PARP inhibitor therapy has demonstrated effectiveness in germline BRCA1/2-mutated PDAC. Extending this outcome to the significant proportion of human PDACs with somatic or germline mutations in DDR genes beyond BRCA1/2 might be beneficial, but there is a lack of data, and consequently, no clear recommendations are provided in the field. Therefore, an expert panel was invited by the European Society of Digestive Oncology (ESDO) to assess the current knowledge and significance of DDR as a target in PDAC treatment. The aim of this virtual, international expert meeting was to elaborate a set of consensus recommendations on testing, diagnosis and treatment of PDAC patients with alterations in DDR pathways. Ahead of the meeting, experts completed a 27-question survey evaluating the key issues. The final recommendations herein should aid in facilitating clinical practice decisions on the management of DDR-deficient PDAC.

Therapeutic Potential of PARP Inhibitors in the Treatment of Gastrointestinal Cancers

Gastrointestinal (GI) malignancies are a major global health burden, with high mortality rates. The identification of novel therapeutic strategies is crucial to improve treatment and survival of patients. The poly (ADP-ribose) polymerase (PARP) enzymes involved in the DNA damage response (DDR) play major roles in the development, progression and treatment response of cancer, with PARP inhibitors (PARPi) currently used in the clinic for breast, ovarian, fallopian, primary peritoneal, pancreatic and prostate cancers with deficiencies in homologous recombination (HR) DNA repair. This article examines the current evidence for the role of the DDR PARP enzymes (PARP1, 2, 3 and 4) in the development, progression and treatment response of GI cancers. Furthermore, we discuss the role of HR status as a predictive biomarker of PARPi efficacy in GI cancer patients and examine the pre-clinical and clinical evidence for PARPi and cytotoxic therapy combination strategies in GI cancer. We also include an analysis of the genomic and transcriptomic landscape of the DDR PARP genes and key HR genes (BRCA1, BRCA2, ATM, RAD51, MRE11, PALB2) in GI patient tumours (n = 1744) using publicly available datasets to identify patients that may benefit from PARPi therapeutic approaches.

BRCAness as a Biomarker of Susceptibility to PARP Inhibitors in Glioblastoma Multiforme.

Glioblastoma multiforme (GBM) is the most common primary brain cancer. GBMs commonly acquire resistance to standard-of-care therapies. Among the novel means to sensitize GBM to DNA-damaging therapies, a promising strategy is to combine them with inhibitors of the DNA damage repair (DDR) machinery, such as inhibitors for poly(ADP-ribose) polymerase (PARP). PARP inhibitors (PARPis) have already shown efficacy and have received regulatory approval for breast, ovarian, prostate, and pancreatic cancer treatment. In these cancer types, after PARPi administration, patients carrying specific mutations in the breast cancer 1 (BRCA1) and 2 (BRCA2) suppressor genes have shown better response when compared to wild-type carriers. Mutated BRCA genes are infrequent in GBM tumors, but their cells can carry other genetic alterations that lead to the same phenotype collectively referred to as ‘BRCAness’. The most promising biomarkers of BRCAness in GBM are related to isocitrate dehydrogenases 1 and 2 (IDH1/2), epidermal growth factor receptor (EGFR), phosphatase and tensin homolog (PTEN), MYC proto-oncogene, and estrogen receptors beta (ERβ). BRCAness status identified by accurate biomarkers can ultimately predict responsiveness to PARPi therapy, thereby allowing patient selection for personalized treatment. This review discusses potential biomarkers of BRCAness for a ‘precision medicine’ of GBM patients.

THER-02. PARP Inhibitor Tolerability and Impact on Progression-Free Survival in Patients with High-Grade, Ovarian Carcinoma with Brain Metastasis: A Case-Series

Abstract Brain metastases secondary to ovarian carcinoma is an uncommon but increasing phenomenon. PARP inhibitors (PARPi) are increasingly used as an adjunctive treatment in patients with central nervous system metastases (CNS). Historically brain metastases has a historically poor prognosis. Five women with a mean age of 60.4 ± 7.6 years were included. All had stage IIIC/IV ovarian cancer and diagnosed with brain metastases at recurrence. Three underwent resection for oligometastatic disease followed by post-operative stereotactic radiosurgery (SRS), one had SRS without surgery, and one patient underwent whole brain radiotherapy for multiple metastases. Pathology was confirmed in those who were resected. Two patients had evidence of systemic disease in addition to CNS spread. Three women were BRCA1/2 Positive. Following initial radiotherapy, one patient received adjuvant chemotherapy followed by olaparib maintenance, one received 13 cycles of bevacizumab/olaparib, followed by olaparib maintenance. A third patient was treated with olaparib/bevacizumab and two patients received olaparib monotherapy, both of whom continued on therapy. All received olaparib therapy during their treatment and all had minor dose modifications due to side effects. Mean survival from initial cancer diagnosis was 62.4 ± 20.4 months. Mean duration of PARPi therapy was 27.6 ± 16.8 months. Mean survival following CNS recurrence was 22.8 ± 12 months. One patient is disease-free, two patients are alive with stable disease, one patient is alive but off treatment secondary to progression, and one patient is deceased secondary to progression of her brain metastases after being on PARP therapy for 18 months. The cohort remained highly functional across the trajectory of their disease with ECOG scores of 1 (n=4) or 0 (n=1). The results of this single institution retrospective evaluation suggest olaparib in combination with radiotherapy +/- bevacizumab is well tolerated and can provide additional benefit in patients with brain metastases secondary to ovarian carcinoma.

Comprehensive genomic profiling (CGP) via peripheral blood liquid biopsies identifies therapeutically relevant genomic alterations in tubo-ovarian and peritoneal cancer

Comprehensive genomic profiling (CGP) via peripheral blood liquid biopsies identifies therapeutically relevant genomic alterations in tubo-ovarian and peritoneal cancer

Overtreatment and excessive cost associated with primary versus secondary PARP inhibitor (PARPi) maintenance therapy for ovarian/peritoneal/fallopian tube cancer (EOC)

Objectives: To determine the efficacy and cost of primary olaparib or niraparib maintenance versus secondary olaparib or niraparib maintenance in platinum sensitive EOC. Methods: An institutional review board (IRB) approved single institution retrospective cohort study was performed in women with EOC to determine the efficacy and cost of primary or secondary maintenance PARPi therapy. We determined the costs of olaparib and niraparib therapy based on previously published costs of therapy and duration of therapy based on the Solo 1/ Solo 2 and Prima and Nova trials, respectively. Results: Among 40 patients treated with PARPi after 1 or 2 platinum chemotherapy there was no difference in overall survival (p=0.97) Among 166 women with stage III/IV germ-line BRCA mutated EOC who were followed >3 years following chemotherapy without PARPi therapy, 28.8% were disease free for more than 3 years (18.6% never recurred and 10.2% recurred >3 years after chemotherapy). Among 193 patients without a BRCA mutation 20.2% did not recur and 12 (6.2%) recurred more than 3 years after their chemotherapy. Primary olaparib maintenance therapy was significantly more expensive than secondary olaparib maintenance therapy by 260%. Primary niraparib maintenance therapy was slightly more expensive than secondary niraparib maintenance therapy by 4%, 51%, and 15% for BRCA mutated, HR deficient, and HR proficient patients, respectively. Notably, by eliminating the overtreatment of patients with primary PARPi therapy, the cost of delayed maintenance treatment for 100 women with EOC with BRCA mutations would be associated with a cost savings of $37,335,360 for olaparib and $7,335,360 for niraparib. Download : Download high-res image (89KB) Download : Download full-size image Conclusions: In this retrospective cohort of women with EOC, up to 29% percent of BRCA mutated patients may be over treated with primary PARPi maintenance therapy with significantly increased treatment costs.

Room for growth: Real-world maintenance and treatment PARP inhibitor use in BRCAm ovarian cancer patients

Objectives: Significant clinical benefit has been demonstrated for poly-ADP ribose polymerase inhibitors (PARPi) in the maintenance and treatment settings for BRCA mutation (BRCAm) carriers with ovarian cancer (OC). We examined the institutional experience of real-world PARPi use in patients (pts) with BRCAm OC. Methods: This was a retrospective series at an urban academic institution with two satellite sites. Pts were identified by ICD-10 codes corresponding to germline BRCA1/2 mutations and cross-checked by our institutional record of patients with OC. Pts were included if they had a diagnosis of OC with BRCAm and either received post-surgical treatment at our institution or had well-documented records of OC treatment. PARPi eligibility was determined at the time of initial diagnosis and each recurrence if a PARPi was FDA approved at that given time for that line of therapy as maintenance or treatment for each pt or if they underwent a clinical trial for PARPi. Outcome of interest was the number of eligible pts who did and did not receive PARPi therapy. Results: There were 120 BRCAm OC pts diagnosed between 1/1997 and 4/2020 with a median age of diagnosis of 53 (IQR 46-60.25). Of those, 95 (79%) were advanced stage and 67 (56%) underwent primary debulking. Fifty-two (43%) pts received only initial chemotherapy without recurrence at the time of our study with median follow-up of 64 months (range 1-298 months). Overall, 55 (44%) received a PARPi during their OC treatment course: 15 (13%), maintenance; and 44 (37%), treatment (Table 1). Sixty-six pts never received PARPi; of these patients, 14 (21%) never received a PARPi even though they were FDA-eligible during their treatment course. Of those, 12/66 (18%) were eligible for a maintenance PARPi, and 6/66 (9%) were eligible for treatment PARPi. Of these 14 FDA-eligible pts, five were deemed to be too ill for PARPi treatment, one refused, and the rest did not have documented reasons. The highest adherence to FDA eligibility was in the frontline maintenance setting, where 10/16 (63%) eligible pts underwent appropriate therapy. Of 10 pts that received PARPi after prior PARPi therapy, 5 received treatment for recurrence after prior PARPi for maintenance indications. Download : Download high-res image (108KB) Download : Download full-size image Conclusions: A fifth of BRCAm pts eligible for PARPi in their OC treatment course did not receive a PARPi. Studies addressing PARPi as treatment for recurrence after prior PARPi use in the maintenance setting are needed to better understand utility in this setting in BRCAm carriers. Increased education to ensure all BRCAm carriers receive a PARPi in their treatment course is needed. This is particularly important in the frontline maintenance setting where significant long term benefit has been reported.

Comprehensive genomic profiling (CGP) via peripheral blood liquid biopsies identifies therapeutically relevant genomic alterations in tubo-ovarian and peritoneal cancer

<h3>Objectives:</h3> Analysis of circulating tumor DNA (ctDNA) extracted from peripheral blood liquid biopsies is a less-invasive alternative to traditional solid tumor tissue testing. In this study, we analyzed a large cohort of liquid biopsies collected from advanced tubo-ovarian and peritoneal cancer patients to determine the clinical utility and landscape of potentially actionable genomic alterations. <h3>Methods:</h3> CGP by a hybrid-capture based sequencing assay was performed on blood samples from 574 patients with primary ovarian, fallopian tube, or peritoneal cancer. Short variant alterations, rearrangements, and copy number gains were interrogated across exons from 70 genes and introns from 7 genes; gene deletions were not evaluated. Microsatellite instability (MSI) was also assessed by the assay. An additional cohort assayed by an expanded gene panel and an analysis of paired liquid and tissue samples will be presented. <h3>Results:</h3> A total of 527 ovarian primary, 36 fallopian tube primary, and 11 peritoneal primary cancers were analyzed. Patients had a median age of 68 years (range 22-89+). There were 202 serous carcinomas, 7 carcinosarcomas, 7 clear cell carcinomas, 6 endometrioid carcinomas, 4 mucinous carcinomas, 1 carcinoma of mixed histology, and the remainder of the cases (n=347) had no specified histologic subtype. A total of 508 (89%) patients had at least 1 genomic alteration detected by the assay. The most frequently altered genes were <i>TP53</i> (74%) consistent with high-grade carcinomas, <i>CHEK2</i> (24%), <i>ATM</i> (14%), <i>BRCA1</i> (7%), <i>NF1</i> (7%), <i>PIK3CA</i> (6%), <i>BRCA2</i> (5%), and <i>KRAS</i> (5%). Patients often harbored more than one alteration in <i>TP53, CHEK2,</i> and <i>ATM</i> (48%, 22%, and 16% of altered cases respectively). Alterations in <i>BRCA1/2</i> were detected in a total of 71 patients (12.3%). 8/71 cases (11.3%) had multiple alterations in either <i>BRCA1</i> or <i>BRCA2,</i> and these alterations were consistent with known reversion mechanisms that restored <i>BRCA1/2</i> function and conferred resistance to PARP inhibitors (PARPi). Follow-up was available for one of these patients, who had <i>BRCA2</i> alterations and had received 10 months of PARPi therapy prior to the collection of their liquid biopsy. A second patient showed acquisition of a second, likely reversion <i>BRCA1</i> alteration on their liquid biopsy from a solid-tissue CGP test performed 22 months prior. Rearrangements in genes associated with approved targeted therapies were detected in <i>FGFR2</i> (n=3), <i>RET</i> (n=1), <i>ROS1</i> (n=1), and <i>ALK</i> (n=1). Other potentially targetable genes altered in this cohort included <i>ERBB2</i> (1%), <i>BRAF</i> (1%), and <i>PALB2</i> (1%). Additionally, one case was found to be MSI-high. <h3>Conclusions:</h3> CGP via liquid biopsies identified actionable alterations in metastatic or recurrent ovarian, fallopian tube, and peritoneal carcinomas across various histologic subtypes. The mutational landscape included alterations that supported the tissue diagnosis as well as potentially targetable alterations by both FDA-approved and investigational agents in clinical trials, inlcuding <i>BRCA1/2</i> mutations that conferred sensitivity and/or explained resistance to PARPi therapy. These results support the clinical utility and integration of liquid biopsy in guiding the treatment of advanced tubo-ovarian and peritoneal cancers.

Characterization of patients with BRCA mutated ovarian cancer who are eligible versus not eligible for PARP inhibitor maintenance therapy: exploratory analysis of the VELIA study

<h3>Objectives:</h3> Previous phase 3 trials of front-line maintenance with the PARP inhibitors (PARPi) olaparib and niraparib only included patients (pts) with complete (CR) or partial (PR) response following front-line chemotherapy (CT); both agents were adopted as standard of care (SOC) in these pts. This prevented the systematic study of all pts who are eligible for PARPi maintenance therapy after front-line CT or to predict their responses. The phase 3 VELIA study (NCT02470585) added veliparib (VEL) to front-line CT at diagnosis, followed by VEL maintenance in the absence of progressive disease (PD), permitting treatment of a broader cohort of pts. This exploratory analysis evaluated baseline characteristics associated with first-line CT response, to understand if predictive variables exist that could identify those who would be eligible vs ineligible for SOC PARPi maintenance. <h3>Methods:</h3> Pts with untreated Stage III/IV ovarian cancer were randomized to carboplatin/paclitaxel (CP) + placebo (PBO) followed by PBO maintenance (control arm), CP + VEL followed by PBO maintenance (VEL combination only), or CP + VEL followed by VEL maintenance (VEL throughout). Pts without progression after combination treatment transitioned to assigned maintenance therapy. In this exploratory analysis, pts with germline or somatic <i>BRCA</i> mutations (BRCAm) were grouped as maintenance eligible (ME; with CR/PR or non-PD with surgical complete resection) or maintenance not eligible (MNE; with stable disease/progression/non-CR/non-PD). Progression-free survival (PFS) in pts starting maintenance was measured from initiation of maintenance treatment. <h3>Results:</h3> Of 1,140 randomized pts, 298 had germline or somatic <i>BRCA</i>m; of these, 278 could be classified according to maintenance eligibility. MNE pts (n=56) were distributed equally among the control, VEL combination only, and VEL throughout arms (21%, 19%, and 21% of evaluable pts, respectively). MNE subgroups were enriched for advanced disease (18-39% of MNE subgroups vs 13-19% of ME subgroups had Stage IV disease) and less favorable performance status (41-67% MNE vs 20-40% of ME pts had ECOG performance status ≥1). For ME pts (n=222), median PFS from initiation of maintenance was not reached in the VEL throughout arm vs 19.7 months in the control arm (HR 0.29, 95% CI 0.16-0.52, Figure). For MNE pts, median PFS was 16.4 months in the VEL throughout arm and 18.9 months in the control arm (HR 1.331, 95% CI 0.52-3.44); however, sample sizes (n=18 and n=16, respectively) limit a meaningful analysis of PFS in these pts. <h3>Conclusions:</h3> The results of this exploratory analysis suggest that VEL has robust efficacy in pts with BRCA-mutated tumors eligible for SOC PARPi maintenance. Baseline characteristics of advanced disease and less favorable performance status were more common in MNE pts than ME pts. Molecular characterization is ongoing to identify mechanisms of sensitivity that predict eligibility for, and response to, PARPi therapy.

Homologous recombination deficient endometrial serous carcinoma: implications for PARPi therapy

<h3>Objectives:</h3> Endometrial serous carcinoma (EMSC) is an aggressive variant of uterine cancer with limited therapeutic options. We analyzed the genomics of the largest EMSC cohort to date (n=2,159) to determine the extent of homologous recombination deficiency (HRD) and potential for targeted therapies. <h3>Methods:</h3> EMSC was assayed via hybrid capture-based comprehensive genomic profiling. HRD status was determined using genome wide loss of heterozygosity (gLOH) scores with validated methods for PARP inhibitor effectiveness in ovarian carcinoma. gLOH-high was defined as a score of ≥16%, similar to previously described for ovarian carcinomas. Tumor mutational burden (TMB) was determined on 0.8Mbp of sequenced DNA, and TMB-high was defined as ≥10mut/Mb using an FDA-approved companion diagnostic cutoff for pembrolizumab in patients with unresectable or metastatic solid tumor based on the KEYNOTE-158 trial. Microsatellite instability (MSI) was determined on 95 loci. Clinicopathological and genomic data was centrally re-reviewed. <h3>Results:</h3> EMSC is characterized by <i>TP53</i> mutations (92%), microsatellite stability (99%), low tumor mutational burden (96%), and less frequent recurrent alterations in <i>PIK3CA</i> (35%), <i>PPP2R1A</i> (25%), <i>CCNE1</i> (19%), <i>ERBB2</i> (17%), <i>FBXW7</i> (17%) and <i>MYC</i> (12%). Evidence for HRD via high gLOH was identified in 21% of EMSC. There was no difference in age, MSI and TMB-high status between gLOH-high vs gLOH-low EMSC. However, alterations in <i>BRCA1/2</i> and HRD genes as a group were significantly enriched in gLOH-high EMSC (14% vs 2% and 23% vs 9%, both p<1E-8). gLOH-high EMSC exhibited significantly higher frequency of solid, pseudo-endometrioid or transitional-like (i.e. SET) variant morphology (52% vs 24%, p<0.05). Genomic ancestry calling revealed similar ancestry prevalence in HRD vs. non-HRD subgroups; however, in EMSC patients of African descent, there was an overall higher prevalence of <i>CCNE1</i> amplification (26%) and lower prevalence of <i>PIK3CA</i> (24%) and <i>PPP2R1A</i> (18%) alterations compared with patients of non-African descent (p<0.05). Finally, EMSC exhibited significantly higher frequency of gLOH-high (21% vs 8%, p=19E-24) as well as different genomic signatures (MSI-H 1% vs 28%; TMB-high 4% vs 33%, and distinct alteration frequencies of 134 genes, all p<0.05) compared with endometrioid-type endometrial carcinomas (n=2,346). <h3>Conclusions:</h3> EMSC has overall distinct genomic signatures compared to endometrioid endometrial carcinomas with a significant proportion of gLOH-high EMSC, compatible with HRD. Our study provides the framework for future studies to test the susceptibility of EMSC to PARP inhibitor therapy in a molecularly defined EMSC subgroup with evidence for HRD.

Acquired RAD51C Promoter Methylation Loss Causes PARP Inhibitor Resistance in High-Grade Serous Ovarian Carcinoma.

In high-grade serous ovarian carcinoma (HGSC), deleterious mutations in DNA repair gene RAD51C are established drivers of defective homologous recombination and are emerging biomarkers of PARP inhibitor (PARPi) sensitivity. RAD51C promoter methylation (meRAD51C) is detected at similar frequencies to mutations, yet its effects on PARPi responses remain unresolved.In this study, three HGSC patient-derived xenograft (PDX) models with methylation at most or all examined CpG sites in the RAD51C promoter show responses to PARPi. Both complete and heterogeneous methylation patterns were associated with RAD51C gene silencing and homologous recombination deficiency (HRD). PDX models lost meRAD51C following treatment with PARPi rucaparib or niraparib, where a single unmethylated copy of RAD51C was sufficient to drive PARPi resistance. Genomic copy number profiling of one of the PDX models using SNP arrays revealed that this resistance was acquired independently in two genetically distinct lineages.In a cohort of 12 patients with RAD51C-methylated HGSC, various patterns of meRAD51C were associated with genomic "scarring," indicative of HRD history, but exhibited no clear correlations with clinical outcome. Differences in methylation stability under treatment pressure were also observed between patients, where one HGSC was found to maintain meRAD51C after six lines of therapy (four platinum-based), whereas another HGSC sample was found to have heterozygous meRAD51C and elevated RAD51C gene expression (relative to homozygous meRAD51C controls) after only neoadjuvant chemotherapy.As meRAD51C loss in a single gene copy was sufficient to cause PARPi resistance in PDX, methylation zygosity should be carefully assessed in previously treated patients when considering PARPi therapy. SIGNIFICANCE: Homozygous RAD51C methylation is a positive predictive biomarker for sensitivity to PARP inhibitors, whereas a single unmethylated gene copy is sufficient to confer resistance.

Abstract CT115: Phase I trial of the triplet berzosertib (M6620, VX-970), veliparib and cisplatin (BVP) in patients with advanced solid tumors

Abstract Background: Ataxia-telangiectasia-related (ATR) protein kinase is central to the repair of damaged DNA through the homologous recombination (HR) pathway. We conducted a phase I trial of cisplatin in combination with the ataxia-telangiectasia-related (ATR) protein kinase inhibitor berzosertib (M6620) and the poly (ADP-ribose) polymerase (PARP) 1/2 inhibitor veliparib, postulating that simultaneous PARP and ATR inhibition impairs DNA repair and induces a “BRCA null”-like phenotype which could potentiate the antitumor activity of cisplatin. We evaluated the safety, maximal tolerated dose (MTD) and preliminary anti-tumor activity of this treatment triplet. The study was conducted through the Experimental Therapeutics Clinical Trials Network (ETCTN). Methods: This open label trial used a 3+3 design. Cisplatin and berzosertib were each administered intravenously on separate, sequential days for two continuous weeks [day (D) 1 and 8; D2 and 9 respectively], together with veliparib orally twice daily during IV therapy and for 24 hours after (D1-3 and 8-10) in 21-day cycles. Prior platinum and PARP inhibitor therapy were permitted. Tumor expression of DNA damage repair (DDR) biomarkers was assessed at the MTD using validated, quantitative immunofluorescence assays. Results: Fifty-three patients (pts) enrolled, 46 pts evaluable for response. The MTD and RP2D dose is cisplatin 40 mg/m2 D1 and D8, berzosertib 210 mg/m2 D2 and D9, and veliparib 200mg BID (D1-3, D8-10). Three patients achieved a confirmed partial response (PR; 5.6%). A further 2 patients had an unconfirmed PR (breast carcinoma, -30%; HGS carcinoma, -36%). Four responders (3 PR and 1 uPR) received prior platinum. Median time on study: 4 cycles (range 1-25). Genomic data was available on four pts achieving a response: ovarian cancer (BRCA-wildtype, ATM unknown; 25 cycles), breast carcinoma (ATM mutation; 14 cycles), SCC of the tongue (Chek2 mutation; 20 cycles), and HGS carcinoma (ATM/BRIP1 mutation; 4 cycles). Twenty-six pts (56.5%) had stable disease. Thirty-five patients (66.0%) required dose reduction in at least 1 agent, most commonly veliparib (25; 47.2%). Most common grade 3 and 4 adverse events were related to myelosuppression: anemia (20; 37.7%), thrombocytopenia (17; 32.1%), leukopenia (13; 24.5%), neutropenia (12; 22.6%), and lymphopenia (11; 20.8%). Ongoing pharmacodynamic analyses of tumor biopsies collected on C1D1 (post-veliparib/cisplatin) and C1D9 (post-veliparib/cisplatin/M6620) have demonstrated a combination-induced increase in RAD51, indicative of replication stress. Conclusions: The BVP combination shows anti-tumor activity in HR-compromised tumors and M6620 further increases the DDR response elicited by combination cisplatin/veliparib. Citation Format: Geraldine O'Sullivan Coyne, Khanh T. Do, Shivaani Kummar, Naoko Takebe, Sarina Piha-Paul, Richard Piekarz, Deborah Wilsker, Brandon Miller, Katherine Ferry-Galow, Ralph Parchment, Lamin Juwara DNP, Mary Jane Ong, Arjun Mittra, James H. Doroshow, Alice P. Chen. Phase I trial of the triplet berzosertib (M6620, VX-970), veliparib and cisplatin (BVP) in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT115.

Abstract 2061: Investigation of PALB2 mutation &amp; correlation with immunotherapy biomarker in Chinese non-small cell lung cancer patients

Abstract Background: PALB2, a gene in the homologous recombination repair (HRR) pathway, has been shown to be associated with the efficacy of platinum based chemotherapy, immunotherapy and PARP inhibitor therapy in several tumors. In addition, the role of germline PALB2 pathogenic variants as a major susceptibility gene has been reported in breast, ovarian, and pancreatic cancers. However, the PALB2 characteristics, its correlation with immunogenic marker, and the predictive value of immunotherapy in non-small cell lung cancer (NSCLC) was unknown. Methods: Tumor tissue samples from Chinese NSCLC were analyzed using next generation sequencing (NGS) (panel on 381/733-gene). TMB was defined as total number of somatic non-synonymous mutations in coding region. MSI was evaluated by NGS of 500 known MSI loci. PD-L1 expression was evaluated using immunohistochemistry (Dako 22C3). Two independent cohorts (the OAK and POPLAR study cohort) with data from 429 patients, and one cohort (Rizvi2018.NSCLC.240.NGS cohort) with data from 240 patients with advanced NSCLC, were used to analyze the prognostic effect of PALB2 on immunotherapy. Result: Genetic mutation of 5227 NSCLC patients were analyzed using NGS, of which 162 (3.1%) harbored germline PALB2 mutation (PALB2gmut) and 87 (1.66%) harbored somatic PALB2 mutation (PALB2smut). In NSCLC patients with PALB2gmut, the most frequently mutated genes were TP53 (65%), followed by CYP2C19 (51%), DPYD (45%), RAC1 (45%), VEGFA (44%), EGFR (43%), MGMT (42%) and CD74 (40%). The mutation frequency of TP53 was highest in NSCLC with PALB2smut (64%), followed by CYP2C19 (47%), UGT1A1 (38%), RAC1 (36%), VEGFA (36%), CD74 (36%), EGFR (30%), and LRP1B (30%). PALB2smut (14.52 Muts/Mb) was associated with higher TMB (P &amp;lt; 0.001) than PALB wild-type (PALB2wt) (6.15 Muts/Mb). But there was no significant difference on TMB between PALB2gmut (6.45 Muts/Mb) and PALB2wt (6.15 Muts/Mb) (P=0.64). There was no difference in PD-L1 expression among PALB2gmut, PALB2smut, and PALB2wt. No correlation was found with PD-L1 expression. In Rizvi2018.NSCLC.240.NGS cohort, there was no difference on progression-free survival (PFS) (HR =1.06, P=0.93) between PALB2 mutation (3.15 months) and PALB2wt (3.17 months). The OAK and POPLAR study cohort of NSCLC patients showed that there was no difference on overall survival (OS) (HR =1.1, P=0.75) between PALB2 mutation (10.38 months) and PALB2wt (11.07 months). Conclusions: These findings suggest that PALB2 may not be used as a biomarker for determining prognosis on immunotherapy in NSCLC. Citation Format: Xiangyang Cheng, Yating Zheng, Wenzhuan Xie, Mengli Huang. Investigation of PALB2 mutation &amp; correlation with immunotherapy biomarker in Chinese non-small cell lung cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2061.

Abstract 2206: Investigation of DNA damage repair mutated characteristics and correlation with immunogenic biomarker in Chinese head and neck cancer patients

Abstract Background: DNA damage repair (DDR) pathway have been reported in several cancer, and known as a predictive biomarker of platinum-based chemotherapy, PARP inhibitor therapy, radiotherapy, and immunotherapy. However, the predictive value and mutated characteristics of DDR in patients with head and neck cancer (HNC) is still uncertain. The purpose of this study is to assess the frequency of DDR mutations, and the correlation between DDR mutations and immunogenic biomarker such as tumor mutation burden (TMB), microsatellite instability (MSI) and PD-L1 expression in Chinese HNC patients. Methods: Genomic profiling of DNA was performed through a next-generation sequencing (NGS) (panel on 381/733-gene) on tissue from Chinese patients with head and neck cancer between January 23, 2017 and April 10 2020. TMB was defined as total number of somatic non-synonymous mutations in coding region. MSI was evaluated by NGS of 500 known MSI loci. PD-L1 expression was determined by immunohistochemistry staining using Dako 22C3. Germline or somatic mutations of 35 DDR genes were classified as DDR gene mutations. Result: Genetic mutation of 319 HNC patients were analyzed using NGS, of which 32 (10.03%) harbored alterations in DDR genes. The most frequently mutated DDR genes were BRCA2 (3.23%), followed by FANCA (2.02%), BRCA1 (1.61%), RAD51 (0.81%), RAD50 (0.81%), PMS2 (0.81%), and PLAB2 (0.81%). The frequency of KMT2C, CD274, FBXW7, APC, NOTCH1, PDCD1LG2, RB1, LRP1B, and JAK2 mutations was higher in DDR mutations (DDRmut) than in DDR wild-type (DDRwt) patients. PD-L1 status analysis was performed in 265 HNC patients, including 24 DDRmut patients and 241 DDRwt patients. But there was no significant difference on PD-L1 expression between DDRmut t and DDRwt (P=0.93). 310 HNC patients (including 31 DDRmut patients and 279 DDRwt patients) could be evaluated for TMB, the results showed that DDRmut (10.13Muts/Mb) was associated with higher TMB than DDRwt (5.65Muts/Mb) (P = 0.0031). Of the 308 HNC patients (including 31 DDRmut patients and 277 DDRwt), only 3 (0.97%) were diagnosed as MSI-H, including 2 (6.45%) patients with DDRmut and 1 (0.36%) patient with DDRwt. Conclusions: The DDR pathway genes alteration characteristics was presented in Chinese HNC patients, and was associated with a higher TMB level. These findings provide a theoretical basis for future investigation of clinical therapy in DDR mutated Chinese HNC patients. Citation Format: Yong Chen, Yan Wang, Yating Zheng, Wenzhuan Xie, Mengli Huang. Investigation of DNA damage repair mutated characteristics and correlation with immunogenic biomarker in Chinese head and neck cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2206.

Abstract 2245: Analysis of PALB2 in Chinese hepato-bilio-pancreaticcancer and correlation with immunogenic biomarker

Abstract Background: The role of germline PALB2 variants as a major susceptibility gene has been reported in breast, ovarian, and pancreatic cancers. But the PALB2 characteristics in hepato-bilio-pancreatic cancers, which include hepatic carcinoma (LIHC), biliary tract cancer (BTC), and pancreatic Carcinoma (PAAD), and its correlation with immunogenic marker was unknown. Methods: Tumor tissue samples from Chinese hepato-bilio-pancreatic cancer patients were analyzed using next generation sequencing (panel on 381/733-gene). TMB was defined as total number of somatic non-synonymous mutations in coding region. MSI was evaluated by NGS of 500 known MSI loci. PD-L1 expression was evaluated using immunohistochemistry (SP142). Results: The PALB2 mutation frequency in hepato-bilio-pancreatic cancers was 4.19% (190/4531), among 4.49% (93/2073) of LIHC, 4.17% (63/1511) of BTC, and 3.59% (34/947) of PAAD. The germline PALB2 mutation (PALB2gmut) and somatic PALB2 mutation (PALB2smut) frequency was 2.67% (121/4531) and 1.52% (69/4531) in hepato-bilio-pancreatic cancers, among 2.41% (50/2073) and 2.07% (43/2073) of LIHC, 3.04% (46/1511) and 1.13% (17/1511) of BTC, and 2.64% (25/947) and 0.95% (9/947) of PAAD. The mutation frequency of TP53 was highest in LIHC with PALB2gmut (64%), which is consistent with LIHC patients with PALB2smut (72%). In BTC patients, the most frequently mutated gene was TP53 (54%) in patients with PALB2gmut and MGMT (65%) in patients with PALB2smut. The gene with the highest frequency of mutations in PAAD patients with PALB2gmut is KRAS (84%), which is consistent with PAAD patients with PALB2smut (89%). There was no difference in PD-L1 expression among PALB2gmut, PALB2smut and PALB wild-type (PALB2wt) in any of the tumors mentioned above (P&amp;gt;0.05). In LIHC, PALB2smut has a higher TMB than PALB2wt (P=0.0003). The same phenomenon has also been observed in BTC (P=0.0014) and PAAD (P=0.0017). But there was no significant difference on TMB between PALB2gmut and PALB2wt (P=0.45 of LIHC, P= 0.21 of BTC, P=0.42 of PAAD). In PAAD, the ratio of MSI-H in PALB2smut patients was significantly higher than that in PALB2wt patients (P&amp;lt;0.001), while in LIHC and BTC, the ratio of MSI-H in PALB2smut showed no significant benefit, but showed a higher trend (P=0.074, P=0.095). However, in all three types of tumors, there was no significant difference on MSI-H ratio between PALB2gmut and PALB2wt (P&amp;gt;0.5). Conclusions: We found that PALBgmut was more frequent in all three tumors. However, PALBsmut are associated with higher TMB and have a higher MSI-H ratio. These findings provide a theoretical basis for the future clinical study of PALB2 in predicting the efficacy of immunotherapy and PARP inhibitor therapy in Chinese hepato-bilio-pancreatic cancer patients. Citation Format: Li Ou, Yating Zheng, Wenzhuan Xie, Mengli Huang. Analysis of PALB2 in Chinese hepato-bilio-pancreaticcancer and correlation with immunogenic biomarker [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2245.