PARPi Therapy Research Articles

STK39-mediated amplification of γ-H2A.X promotes homologous recombination and contributes to PARP inhibitor resistance.

The phosphorylation of histone H2A.X into γH2A.X is a crucial early event in the DNA damage response, marking DNA damage sites and initiating repair processes. While ATM kinase is traditionally recognized as the primary mediator of H2A.X phosphorylation, our study identifies serine/threonine kinase 39 (STK39) as a novel enhancer of this critical signaling pathway. We demonstrate that after DNA damage, STK39 undergoes phosphorylation by the ATM kinase, facilitating its interaction with the Mre11-Rad50-Nbs1 complex and subsequent recruitment to chromatin. This recruitment enables STK39 to further phosphorylate H2A.X, thus amplifying γH2A.X production and promoting homologous recombination repair. Notably, we observe a significant upregulation of STK39 in pancreatic adenocarcinoma (PAAD) tissues, correlating with heightened resistance to PARPi therapy. Furthermore, we demonstrate the synergistic efficacy of combining STK39 inhibition with PARP inhibitors in suppressing and reversing PAAD growth. This study not only provides new insights into the molecular dynamics of H2A.X phosphorylation but also highlights the therapeutic potential of targeting STK39 to enhance PARPi sensitivity in PAAD (created with BioRender).

Efficacy of PARP inhibitor therapy after targeted BRAF/MEK failure in advanced melanoma

Modern advancements in targeted therapy and immunotherapy have significantly improved survival outcomes for advanced melanoma; however, there remains a need for novel approaches to overcome disease progression and treatment resistance. In recent years, PARPi therapy has shown great promise both as a single regimen and in combination with other therapeutics in melanoma. Here, we describe three unique cases of advanced BRAF V600 mutated melanoma that progressed on targeted BRAF/MEK agents that subsequently exhibited partial to near-complete responses to combinatory PARPi and BRAF/MEK inhibitors. This highlights both a potential synergy underlying this combinatory approach and its efficacy as a treatment option for patients with advanced melanoma refractory to targeted and/or immunotherapies. Prospective clinical trials are needed to explore this synergic effect in larger melanoma cohorts to investigate this combination for treating refractory advanced melanoma.

Impact of homologous recombination repair/BReast CAncer (BRCA) gene alterations on survival in a real-world setting of metastatic prostate cancer.

To investigate alterations of homologous recombination repair (HRR) and especially BReast CAncer 1/2 (BRCA1/2) gene on overall survival (OS). Moreover, to explore the effect of inhibition of poly(ADP-ribose)-polymerase (PARPi) as systemic therapy for metastatic castration-resistant prostate cancer (mCRPC). Of all HRR-screened patients with metastatic prostate cancer, baseline characteristics were sampled. Kaplan-Meier estimates and multivariable Cox regression models predicted the effect of HRR/BRCA1/2 alterations on OS. Of 196 eligible patients, 61 (31%) harboured any HRR and 40 (20%) BRCA1/2 alterations. Of HRR alterations, 40 (66%) vs six (10%) vs five (8.2%) vs four (6.6%) vs two (3.3%) vs four (6.6%) were BRCA1/2 vs Ataxia-telangiectasia mutated kinase (ATM) vs checkpoint kinase 2 (CHEK2) vs cyclin-dependent kinase 12 (CDK12) vs Fanconi anaemia complementation Group A (FANCA) vs positive for other mutations. Of these, 30% received a PARPi. OS differed significantly between HRR-positive vs -negative patients. Specifically in hormone-sensitive prostate cancer, the median OS was 63 (HRR positive) vs 57 (BRCA1/2 positive) vs 113 months (HRR negative) (P ≤ 0.01). In mCRPC, OS was 42 (HRR positive) vs 41 (BRCA1/2 positive) vs 70 months (HRR negative) (P ≤ 0.01). HRR and BRCA1/2 alterations were associated with worse OS after multivariable adjustment. Finally, patients with mCRPC with BRCA1/2 mutation treated without PARPi harboured worse OS than patients with BRCA1/2 mutation and PARPi therapy (median OS: 33 vs 48 months, P < 0.03). Incidence of HRR alteration in a clinical real-world setting is high when using blood- and tissue-based tests. Patients with HRR/BRCA alterations have worse outcomes resulting in significant OS differences between HRR/BRCA-positive patients with mCRPC with and without PARPi usage vs HRR/BRCA-negative patients.

DNA damage targeted therapy for advanced breast cancer.

Breast cancer (BC) is the most prevalent malignancy affecting women worldwide, including Portugal. While the majority of BC cases are sporadic, hereditary forms account for 5-10% of cases. The most common inherited mutations associated with BC are germline mutations in the BReast CAncer (BRCA) 1/2 gene (gBRCA1/2). They are found in approximately 5-6% of BC patients and are inherited in an autosomal dominant manner, primarily affecting younger women. Pathogenic variants within BRCA1/2 genes elevate the risk of both breast and ovarian cancers and give rise to distinct clinical phenotypes. BRCA proteins play a key role in maintaining genome integrity by facilitating the repair of double-strand breaks through the homologous recombination (HR) pathway. Therefore, any mutation that impairs the function of BRCA proteins can result in the accumulation of DNA damage, genomic instability, and potentially contribute to cancer development and progression. Testing for gBRCA1/2 status is relevant for treatment planning, as it can provide insights into the likely response to therapy involving platinum-based chemotherapy and poly[adenosine diphosphate (ADP)-ribose] polymerase inhibitors (PARPi). The aim of this review was to investigate the impact of HR deficiency in BC, focusing on BRCA mutations and their impact on the modulation of responses to platinum and PARPi therapy, and to share the experience of Unidade Local de Saúde Santa Maria in the management of metastatic BC patients with DNA damage targeted therapy, including those with the Portuguese c.156_157insAlu BRCA2 founder mutation.

2P Integrated analysis of DNA and RNA revealed PARPi resistant mechanism of ovarian cancer: A paired tissue analysis of pre and post PARPi therapy

2P Integrated analysis of DNA and RNA revealed PARPi resistant mechanism of ovarian cancer: A paired tissue analysis of pre and post PARPi therapy

Abstract CT203: Multi-omic analysis of serial biopsies to inform biomarkers of sensitivity to olaparib and durvalumab in patients with metastatic BRCA-wildtype triple negative breast cancer (mTNBC)

Abstract Background: The phase 2 Adaptive Multi-Drug Treatment of Evolving Cancers (AMTEC) trial (NCT03801369) evaluated the efficacy of the combination of the PARP inhibitor Olaparib (Ola) and the PD-L1 inhibitor Durvalumab (Durva) in participants with BRCA-wildtype mTNBC. The combination was found to be effective with a median progression free survival (mPFS) of 5.5 months (AACR 2022). Here we report on updated biomarker analyses from paired biopsies (Bx) pre- and on-Ola therapy from 14 AMTEC participants. Methods: AMTEC participants undergo a pre-Ola Bx (Bx1), then one (28-day) cycle of Ola monotherapy with a repeat on-Ola Bx (Bx2) before adding Durva to Ola. Multi-omic profiling of DNA, RNA, and protein signals in Bx1 and Bx2 using Deep candidate gene sequencing, RNAseq, Nanostring Digital Spatial Profiling (DSP), and multiplex immunohistochemistry (mIHC) was correlated with clinical outcomes to identify predictors of Ola + Durva sensitivity, and adaptive resistance to PARPi therapy. Results: We identified over 30 biomarkers, with the optimal predictive value arising from Bx2. Key potential biomarkers were confirmed in an independent test set. Markers of good prognosis: • Basal Immune Activated (BLIA)/Basal Immune Suppressed (BLIS subtype) - A BLIA subtype on Bx2 was associated with a mPFS of 7.36 months compared to 1.71 months for BLIS/Luminal androgen receptor subtypes (p=0.001) • Multi-omic immune composite - A positive immune consensus signature (RNA, DSP, mIHC) on Bx2 was associated with a mPFS of 7.36 months compared to 2.29 months (p=0.005) • B cell activation signature - We developed a novel B-cell RNA activation signature that was highly predictive of response in Bx2, with mPFS of 8.54 and 1.04 months in signature-positive and signature-negative tumors, respectively (p=0.0004) Markers of poor prognosis: • AKT/MAPK pathway - AKT pathway gene mutations in Bx2 with concomitant protein phosphorylation of pathway members correlated with a shorter mPFS of 2.4 months compared to 7.13 months for no pathway mutation/activation (p=0.03). MAPK pathway protein phosphorylation in Bx2 was a negative prognostic factor, with mPFS of 2.17 months (p=0.004) • Angiogenesis - An upregulated Hallmark of Cancer angiogenesis RNA signature on Bx2 was associated with a shorter mPFS of 1.94 months compared to 7.95 months with no angiogenesis upregulation (p=0.0009) The following markers did not show significant association with survival outcomes on AMTEC: • PD-L1 positivity by IHC (defined as &amp;gt;1% Tumor Proportion Score, 22C3 antibody) • Tumor mutational burden • HRD, as measured by Rad51 foci or by mutations in HR pathway members Conclusions: Findings highlight the value of paired Bxs to identify predictive biomarkers of PARPi + immune checkpoint inhibitor sensitivity. The striking predictive value of the BLIA/BLIS signature warrants evaluation in a larger trial. Emerging resistance mechanisms justify AMTEC trial expansion to include PARPi + MEKi or PARPi + AKTi in biomarker selected patients, which is now in progress. Citation Format: Zahi I. Mitri, Allison L. Creason, Jayne M. Stommel, Daniel Bottomly, Jeong Youn Lim, SMMART Clinical Trials Program, Christopher L. Corless, Shannon McWeeney, Gordon B. Mills. Multi-omic analysis of serial biopsies to inform biomarkers of sensitivity to olaparib and durvalumab in patients with metastatic BRCA-wildtype triple negative breast cancer (mTNBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT203.

Frequency of peripheral PD-1+regulatory T cells is associated with treatment responses to PARP inhibitor maintenance in patients with epithelial ovarian cancer.

Poly (adenosine diphosphate [ADP]-ribose) polymerase inhibitors (PARPis) are becoming the standard of care for epithelial ovarian cancer (EOC). Recently, clinical trials of triple maintenance therapy (PARPi+anti-angiogenic agent+anti-PD-1/L1) are actively ongoing. Here, we investigated the immunological effects of PARPi or triple maintenance therapy on T cells and their impact on clinical responses. We collected serial blood from EOC patients receiving PARPi therapy (cohort 1: PARPi, n = 49; cohort 2: olaparib+bevacizumab+pembrolizumab, n = 31). Peripheral T cells were analyzed using flow cytometry and compared according to the PARPi response. Progression-free survival (PFS) was assessed according to prognostic biomarkers identified in a comparative analysis. Regulatory T cells (Tregs) were suppressed by PARPi therapy, whereas PD-1 was not significantly changed. Short PFS group exhibited a higher percentage of baseline PD-1+Tregs than long PFS group, and the patients with high percentage of PD-1+Tregs before treatment showed poor PFS in cohort 1. However, the expression of PD-1 on Tregs significantly decreased after receiving triple maintenance therapy, and the reduction in PD-1+Tregs was associated with superior PFS in cohort 2 (P = 0.0078). PARPi suppresses Tregs, but does not affect PD-1 expression. Adding anti-PD-1 to PARPi decreases PD-1+Tregs, which have negative prognostic value for PARPi monotherapy.

Phase III MIRASOL (GOG 3045/ENGOT-ov55) study: Initial report of mirvetuximab soravtansine vs. investigator's choice of chemotherapy in platinum-resistant, advanced high-grade epithelial ovarian, primary peritoneal, or fallopian tube cancers with high folate receptor-alpha expression.

LBA5507 Background: Mirvetuximab soravtansine (MIRV), an antibody drug conjugate targeting FRα, demonstrated clinically meaningful antitumor activity in a single arm trial reported previously (Matulonis, JCO 2023). MIRASOL is a randomized phase 3 trial to confirm the efficacy of MIRV vs standard-of-care chemotherapy in patients (pts) with PROC. Methods: 453 PROC pts with high FRα expression (Roche FOLR1 Assay) with 1-3 priors were randomized 1:1 to MIRV 6 mg/kg, adjusted ideal body weight, Day 1 of a 21-day cycle or IC: paclitaxel, pegylated liposomal doxorubicin, or topotecan. The primary efficacy endpoint was progression-free survival (PFS) by investigator (INV) with key secondary endpoints ORR, overall survival (OS), and patient-reported outcomes in hierarchical order; other endpoints included safety and tolerability. Blinded independent central review (BICR) for PFS and ORR were sensitivity analyses. Results: With a data cutoff of March 6, 2023, 227 pts were randomized to the MIRV arm; 226 to the IC arm. Median follow-up was 13.1 months. Baseline characteristics were well balanced across arms; 14% of pts had one, 39% two, and 47% three prior lines of therapy; 62% received prior bev; and 55% received prior PARPi therapy. The study met its primary and key secondary endpoints with statistically significant results in PFS (INV), ORR (INV), and OS (Table). In the bev-pretreated subset (n=281), PFS HR was 0.64 (0.492, 0.842) and OS HR was 0.74 (0.535, 1.036); in the bev-naïve subset (n=172), PFS HR was 0.66 (0.459, 0.942) and OS HR was 0.51 (0.306, 0.860). The adverse event (AE) profile of MIRV was consistent with prior reports: predominantly low-grade ocular (MIRV vs IC all grade 56% vs 9%; grade 3+ 14% vs 0%) and gastrointestinal events (MIRV vs IC all grade 70% vs 66%; grade 3+ 13% vs 15%). Compared with IC, MIRV was associated with lower rates of grade 3+ treatment-emergent AEs (42% vs 54%), serious AEs (24% vs 33%), and discontinuations due to TEAEs (9% vs 16%). Fourteen percent of pts on the MIRV arm remained on study drug vs 3% on the IC arm. Conclusion: MIRV is the first treatment to demonstrate a PFS and OS benefit in PROC compared to IC. The efficacy data, along with the well-characterized safety profile, position MIRV as a new, standard of care for pts with FRα positive PROC. Clinical trial information: NCT04209855 .[Table: see text]

Using chemotherapy response by KELIM score to predict response to first line maintenance PARP inhibitor therapy in non-BRCA mutant/homologous recombination deficiency (HRD) unknown high grade serous ovarian cancer (HGSOC).

e17547 Background: Maintenance PARP inhibitor therapy after response to first line chemotherapy is now standard of care in advanced HGSOC. Niraparib is available to all patients based on the PRIMA trial data; however, the progression free survival (PFS) benefit for patients without BRCA mutations or homologous recombination deficiency (HRD) is limited. Funded HRD testing is not accessible in many countries. Patient selection for PARPi therapy in non-BRCA mutant HGSOC is challenging. The calculated CA-125 ELIMination of Rate Constant K (KELIM) score is a mathematical model developed to evaluate CA-125 kinetics during chemotherapy. KELIM has been shown to correlate with chemosensitivity, with scores ≥1 associated with better clinical outcomes. This project aims to use real-world patient data to assess if surrogate markers, such as KELIM score and/or pathological chemotherapy response score, can predict response to 1st line maintenance PARPi in the absence of funded HRD testing. Methods: A retrospective review of non-BRCA mutant HGSOC cases on first line maintenance PARPi therapy at BC Cancer, Canada between April 2020 and June 2022. Only cases confirmed to be non-BRCA mutant (by both germline and tumour testing) were included in the study. Data collection was through electronic medical records and included patient demographics, chemotherapy intent (neoadjuvant vs. adjuvant), pathological (p) chemotherapy response score (CRS), progression-free survival (PFS) defined as start of niraparib to radiological evidence of disease progression. PFS analysis was performed in all patients provided 1 full cycle had been completed. The rate of not progressing at 12 months (PFS12) was calculated. KELIM score was calculated from at least 3 CA125 values taken within 100 days from the chemotherapy start date and using a validated calculation software. Results: 70 patients met the full eligibility criteria for analysis. All patients received niraparib as PARPi therapy. Mean age was 67 years and 40 patients (57%) were ≥ 65 years. Most patients were FIGO stage 3C at presentation (56%). Median number of niraparib cycles was 10 (range 1-28). 35/70 patients (50%) had disease progression at time of data analysis with a median follow-up of 13.2 months. 59 patients had evaluable KELIM scores. pCRS was not associated with any statistically significant differences in PFS. Patients with KELIM scores ≥1 had a trend to greater PFS from niraparib vs. those with KELIM &lt;1 with median PFS of 15 months vs. 8.3 months respectively ( p=0.06). PFS12 rate was higher at 64% with KELIM scores ≥1 vs. 43% with KELIM &lt;1; ( p=0.18). Conclusions: We show that KELIM score could be a useful tool to predict PARP inhibitor response and aid clinical decision-making by oncologists and patients in the real world setting where HRD testing is unfunded.

Detection of homologous recombination deficiency (HRD) using a novel genomic and epigenomic liquid biopsy assay in patients with breast cancer.

556 Background: Homologous recombination and repair (HRR) deficiency (HRD) is characterized by genomic instability associated with dysfunction in BRCA1/2 or other HRR genes. Patients with breast cancer harboring an HRD phenotype with or without HRR mutations have derived clinical benefit from PARPi therapy. We have previously shown that GuardantINFINITY, a novel genomic and epigenomic liquid biopsy assay, can identify HRR SNVs, indels, rearrangements, copy number loss, reversions, and BRCA1 promoter methylation for patient selection and resistance monitoring, a major challenge for PARPi treatment. Here, we present a method of predicting HRD status by cfDNA using GuardantINFINITY in patients with advanced breast cancer. Methods: We developed a probabilistic genomic model to predict HRD status, inferred from genome-wide somatic SNV, indel, and CNV signatures indicative of BRCA1/2 deficiency, including large-scale state transitions (LST), whole-genome tumor loss of heterozygosity (LOH), telomeric allelic imbalance (TAI). A second probabilistic model, based on targeted measurements of genomic and epigenetic changes was learned from a subset of clinical samples to enhance the genomic model. The model was trained and tested on a cohort of over 12,000 GuardantOMNI and GuardantINFINITY clinical breast cancer samples to assess the sensitivity of accurately detecting deficiency in select HRR-genes ( BRCA1/2, PALB2, RAD51D). The aggregated predictive model was validated on an independent cohort of breast cancer samples. Results: The model based on genomic and epigenetic signals identified HRR-gene deficiency in a breast cancer cohort with a estimated 95% LoD of 22.5% tumor fraction and an AUC of 0.75 across all tumor fractions, an improvement in sensitivity over when only the genomic model is used (AUC of 0.7, 95% LoD of 28%). Specificity remained high for both models (100%, n = 83) in cancer free samples. Application of this model in a cohort of 1,101 patients with unselected breast cancer identified 390 patients with an HRD phenotype, of whom 192 patients had a known HRR-gene mutation. Of the 201 patients with a known pathogenic mutation in an HRR gene, 49 also had co-occurring LoH in the same gene, indicating biallelic loss. Conclusions: In this analysis, we demonstrate that a probabilistic model of genomic and methylation predictors can detect HRD status in patients with breast cancer from cfDNA using GuardantINFINITY. Additional analytical and clinical studies to further evaluate this model are ongoing. With HRD prediction, GuardantINFINITY provides a comprehensive minimally-invasive solution for PARPi and DNA damage treatment selection, longitudinal monitoring, and an exploratory platform for investigating epigenetic signals that may underpin resistance.

Use of PARPi among patients with HER2+ve MBC: Results from a real world dataset.

e13044 Background: Among individuals with germline mutations in BRCA1/ BRCA2 genes, life-time risk of developing breast cancer is approximately 50%. The majority of these cancers are HER2-ve with a low frequency of HER2+ve breast cancer (2.1%-10% in pts with BRCA1 mutations and 6.8%-13% of pts with BRCA2 mutations) with co-occurrence of BRCA mutation and HER2+ve status being a poor prognostic factor. PARPi have been shown in phase III trials to be effective in HER2-ve BRCA mutation MBC. The objective of this retrospective analysis was to look at the prognostic outcome associated with use of PARPi among pts with HER2 +ve BRCA mutated MBC in the real-world setting. Methods: We utilized a federated network of de-identified health data representing approximately 107 million pt lives available through the TriNetX Research Network. We identified patients with MBC who were treated with PARPi, and pts were assumed to have BRCA mutated MBC if they were recorded with a PARPi. Overall survival (OS) was computed using the Kaplan Meier product limit method. Pts with MBC were defined as having HER2+ve status if they received an anti-HER2 therapy after metastasis, HR+ve if they received endocrine therapy after metatstasis, and triple negative (TNBC) if they did not receive anti-HER2 therapy or endocrine therapy. Results: 1369pts with MBC were treated with PARPi, of whom 77.9%received olaparib. Mean age of pts was 57ys. 546(39.9%), 521(38.1%) and 73(5.3%) pts had TNBC, HR+ve/HER2-ve, and HER2+ve MBC, respectively. Among pts with HER2+ve disease, 35.2% and 74.0% had HR-ve and HR+ve MBC, respectively. Median time to use of PARPi was 7.1m, 15.1m, and 24.0m among pts with TNBC, HR+ve/HER2-ve, and HER2 +ve MBC respectively. Median OS was 44.4m, 47.0m, and 46.7m among pts with TNBC, HR+ve/HER2-ve and HER2+ve MBC respectively. Among pts with HER2+ve disease, median OS was 74.5m and 31.5m among pts with HR+ve and HER-ve disease, respectively (HR=0.27, p=0.0001). 321(23.4%) pts had brain metastases of whom 36.8%, 36.4% and 8.1% had TNBC, HR+ve/HER2-ve and HER2+ve MBC respectively. Among pts with HER2+ve MBC,38.3% received anti HER2 therapy before PARPi, 24.7% received anti HER2 therapy after PARPi and 37.0% received PARPi and anti HER2 therapy concurrently. Among pts with HER2+ve disease, median OS was 44.4m among those who received anti -HER2 therapy on or before PARPi and 93.8m among those who received anti-HER2 therapy after PARPi (HR 0.83, p=0.64).Among pts with brain metastases, median OS was 23.9m, 40.0m and 40.2m among pts with TNBC, HR+ve/HER-ve and HER2+ve MBC respectively. Conclusions: To our knowledge this is the first real world data set to report on the prognostic outcome of pts with HER2+ve BRCA mutated MBC. When PARPi inhibitors are given median OS is similar among the three subtypes of breast cancer. Although not significant, there appears to be a trend towards improved OS with earlier use of PARPi among patients with HER2+ve BRCA mutated MBC.

Identification of novel actionable SNVs using targeted comprehensive genome profiling in patients with sarcoma.

e23520 Background: The utility of comprehensive genome profiling is not well validated in early-stage sarcoma. The 5-year survival rate for metastatic sarcoma is less than 20%. The application of comprehensive Next Generation Sequencing (NGS) on tumor DNA has led to the identification of a multitude of actionable alterations in oncogenes &amp; tumor suppressor genes alongside the detection of immunotherapy markers like microsatellite instability, tumor mutational burden, and homologous recombinant deficiency. Methods: We retrospectively analyzed ccfDNA and gDNA in 13 sarcoma patients by targeted Next Generation Sequencing (NGS) using OncoIndx proprietary gene panel that targets exonic regions of 600 cancer-related genes. Illumina-compatible libraries were prepared by the target hybridization method and sequenced on Nextseq 2000 platform in a pair-end fashion. Variant calling was performed using an indigenously developed bioinformatics pipeline. Results: Here we report for the first time the identification of several, novel mutations in rare sarcomas such as IDH2R140W (in epithelioid hemangioendothelioma), CTNNB1D32V (in undifferentiated small round cell sarcoma) and DDR2M754I (in osteosarcoma). Furthermore, we observed, JAK1 amplification and BRAF-GUSBP1 fusion in osteosarcoma and a sarcomatoid carcinoma case, respectively. JAK1 amplification and DDR2M754I were found in the same patient. The IDH2 mutation and JAK1 amplification could find potential applications for JAK1 and IDH2 inhibitors respectively. Similarly, cancers having DDR2 mutations are known to respond to multikinase inhibitors such as Imatinib and Dasatinib, thus making a strong case for the potential repurposing of these drugs in sarcomas. ~93% of patients demonstrated genome-wide instabilities as evidenced by LOH, LST, TAI, and high TMB. Homologous Recombinant deficiency was found in 66.7% of patients. Although this is a small patient population, the high HRD+ percentages point to the underappreciated importance of HRD testing in sarcoma and herald the use of PARPi therapy for sarcoma. Conclusions: We identified several actionable mutations in rare sarcoma cases. These findings highlight the power of comprehensive genome profiling like the OncoIndx panel and warrant further studies on the role of IDH2, JAK1, and BRAF fusion in sarcomas. Moreover, they also present a strong potential case for repurposing of TKI such as Imatinib and Dasatinib in sarcomas.

PARP inhibitor olaparib induced differential protein expression in cervical cancer cells

PARP inhibitors are a potential class of chemotherapeutic drugs but PARP inhibitor response has not been explored systematically. We lack a specific understanding of the subset of the proteome preferentially modified in various cancers by PARP inhibitors. Implications of PARP inhibitor and PARP1 in cervical cancer treatment and resistance are not fully elucidated. We conducted a mass spectrometry-based proteomic analysis of cervical cancer Hela cells treated with olaparib. We aimed to identify the alteration in the protein signaling pathway induced by PARP inhibitors beyond the DNA damage response pathway. Our data demonstrate a significant reduction in PARP activity and enhanced cell death after olaparib treatment. We further observed articulated proteomic changes with a significant enrichment of proteins in diverse cellular processes. The differentially expressed proteins were predominantly associated with RNA metabolism, mRNA splicing, processing, and RNA binding. Our data also identified proteins that could probably contribute to survival mechanisms resulting in resistance to PARP inhibitors. Hence, we put forth the overview of proteomic changes induced by PARP inhibitor olaparib in cervical cancer cells. This study highlights the significant proteins modified during PARP inhibition and thus could be a probable target for combination therapies with PARP inhibitors in cervical cancer. Significance•This study provides the overview of proteomic changes induced by PARP inhibitor olaparib in cervical cancer Hela cells.•We demonstrated that Olaparib inhibited PARP1 activity in Hela cells in a dose-dependent manner while no change was observed in the expression of PARP1.•PARP inhibition potentially regulated the RNA metabolism, RNA binding proteins, metastasis-related genes, mitochondrial proteins, transcription factors and regulators, and ubiquitination proteins.•We also identified increased expression of tumor-promoting and drug resistance proteins that could contribute to the resistance mechanism to PARPi therapy.•This approach will be helpful to generate insights into precision oncology for personalized treatment and generate data repositories for future artificial intelligence-based research.

The BRCAness Landscape of Cancer

BRCAness refers to the damaged homologous recombination (HR) function due to the defects in HR-involved non-BRCA1/2 genes. BRCAness is the important marker for the use of synthetic lethal-based PARP inhibitor therapy in breast and ovarian cancer treatment. The success provides an opportunity of applying PARP inhibitor therapy to treat other cancer types with BRCAness features. However, systematic knowledge is lack for BRCAness in different cancer types beyond breast and ovarian cancer. We performed a comprehensive characterization for 40 BRCAness-related genes in 33 cancer types with over 10,000 cancer cases, including pathogenic variation, homozygotic deletion, promoter hypermethylation, gene expression, and clinical correlation of BRCAness in each cancer type. Using BRCA1/BRCA2 mutated breast and ovarian cancer as the control, we observed that BRCAness is widely present in multiple cancer types. Based on the sum of the BRCAneass features in each cancer type, we identified the following 21 cancer types as the potential targets for PARPi therapy: adrenocortical carcinoma, bladder urothelial carcinoma, brain lower grade glioma, colon adenocarcinoma, esophageal carcinoma, head and neck squamous carcinoma, kidney chromophobe, kidney renal clear cell carcinoma, kidney renal papillary cell carcinoma, liver hepatocellular carcinoma, lung adenocarcinoma, lung squamous cell carcinoma, mesothelioma, rectum adenocarcinoma, pancreatic adenocarcinoma, prostate adenocarcinoma, sarcoma, skin cutaneous melanoma, stomach adenocarcinoma, uterine carcinosarcoma, and uterine corpus endometrial carcinoma.

Frequency of homologous recombination deficiency in a large community-based cohort of epithelial ovarian cancer cases (597)

Frequency of homologous recombination deficiency in a large community-based cohort of epithelial ovarian cancer cases (597)

PARPi post PARPi: Clarity from the Clearity real world experience (164)

<b>Objectives:</b> To describe clinical characteristics and oncologic outcomes in patients who received PARPi after prior PARPi failures. <b>Methods:</b> Patients with ovarian cancer who received PARPi after progression on prior PARPi therapy were identified in the Clearity Foundation Data Repository. Contingency tables of PARPi received, therapy line, and treatment response after first and second PARPi exposure, germline, and somatic testing were analyzed and compared using the Chi-square test. Time-to-event curves of time-to-next-therapy (TTNT) were generated and compared using the log-rank test. Findings with p<0.05 were considered significant. <b>Results:</b> Twenty unique patients comprised the cohort. Thirteen patients (65%) had <i>BRCA1</i> or <i>BRCA2</i> mutations diagnosed by germline or tumor testing. Four additional patients had genomic alterations in <i>HRR</i> genes. PARPi received included olaparib, rucaparib, veliparib, niraparib, and talazoparib, with olaparib most frequently received. Thirteen patients (65%) had a primary platinum-sensitive recurrence, and seven patients (35%) had platinum-resistant disease with a primary course of therapy. Patients received a median number of two therapy lines prior to 1^st PARPi exposure. Patients received a median number of five therapy lines prior to 2^nd PARPi exposure. Patients without a <i>BRCA</i> mutation were significantly more likely to be treated with a PARPi in combination with another drug (i.e., chemotherapy, anti-VEGF agent, immunotherapy, or small molecule TKI) than patients with a <i>BRCA</i> mutation at 1^st PARPi exposure (71% vs 23%, p=0.04) and 2^nd PARPi exposure (100% vs 46.2%, p=0.02). There was a significantly higher clinical benefit rate (CBR) to 1^st PARPi compared to 2^nd in the entire cohort (70% vs 25%, p<0.01). Those with <i>BRCA</i> mutations had a significantly higher CBR with 1^st PARPi exposure compared to those without BRCA mutations (85 vs 43%, p=0.04). However, CBR with 2^nd PARPi exposure was not significantly different between those with <i>BRCA</i> mutations and those without <i>BRCA</i> mutations (15% vs 43%, p=0.2). Median TTNT after 2^nd PARPi exposure did not differ between those with <i>BRCA</i> mutations and those without (HR: 4.8 [95% CI: 2.4-7.1] vs 3.4 [95% CI: 2.8-4.0] months) (Figure 1). Within the <i>BRCA</i> mutated cohort, median TTNT with 2^nd PARPi exposure was significantly shorter than TTNT with 1^st PARPi exposure (4.8 [95% CI: 2.4-7.1] versus 8.9 [95% CI: 2.9-14.9] months; HR: 4.6 [95% CI: 1.6-13.1], log-rank p=0.004). There was no significant difference in median TTNT for patients without <i>BRCA</i> mutations with 2^nd PARPi exposure compared to 1^st PARPi exposure (3.4 [95% CI: 2.8-4.0] vs 4.7 [95%CI 0.6-8.7] months). <b>Conclusions:</b> We did not find a clinical benefit to second PARPi exposure after prior PARPi failure, regardless of <i>BRCA</i> mutation status. Patients without a <i>BRCA</i> mutation were much more likely to receive PARPi in combination with another agent in real-world use, despite established clinical benefits.

A Systematic Review and Meta-Analysis on the Prognostic Value of BRCA Mutations, Homologous Recombination Gene Mutations, and Homologous Recombination Deficiencies in Cancer.

Patients with BRCA1/2 mutations (BRCAm), loss-of-function mutations in other homologous recombination repair (HRRm) genes, or tumors that are homologous recombination deficiency positivity (HRD+) demonstrate a robust response to PARPi therapy. We conducted a systematic literature review and meta-analysis to evaluate the prognostic value of BRCAm, HRRm, and HRD+ on overall survival (OS) among those treated by chemotherapy or targeted therapy other than PARPi across tumor types. A total of 135 eligible studies were included. Breast cancer (BC) patients with BRCA1/2m had a similar overall survival (OS) to those with wild-type BRCA1/2 (BRCA1/2 wt) across 18 studies. Ovarian cancer (OC) patients with BRCA1/2m had a significantly longer OS than those with BRCA1/2 wt across 24 studies reporting BRCA1m and BRCA2m, with an HR of 0.7 (0.6–0.8). Less OS data were reported for other tumors: 6 studies for BRCA2m compared with BRCA2 wt in prostate cancer with an HR of 1.9 (1.1–3.2) and 2 studies for BRCA1/2m compared with BRCA1/2 wt in pancreatic cancer with an HR of 1.5 (0.8–3.1). Only 4 studies reported HRD+ by either BRCA m or genomic instability score (GIS) ≥ 42 and OS by HRD status. The HR was 0.67 (0.43–1.02) for OS with HRD+ vs. HRD−. A total of 15 studies reported the association between HRRm and OS of cancers in which one or more HRR genes were examined. The HR was 1.0 (0.7–1.4) comparing patients with HRRm to those with HRR wild-type across tumors. Our findings are useful in improving the precision and efficacy of treatment selection in clinical oncology.

Hematological disorders after salvage PARPi treatment for ovarian cancer: Cytogenetic and molecular defects and clinical outcomes.

Inhibitors of poly(ADP-ribose) polymerase (PARPi) are increasingly employed as salvage therapy in epithelial ovarian cancer (EOC), but cytotoxic drug exposure along with PARP inhibition may favor development of hematological disorders. In our study, of 182 women with EOC treated with PARPi, 16 (8.7%) developed therapy-related myeloid neoplasms (t-MNs), with 12 cases of myelodysplasia and 4 of acute myeloid leukemia. All experienced persistent cytopenia after PARPi discontinuation. Seven patients had del(5q)/-5 and/or del(7q)/-7, nine had a complex karyotype and TP53 mutations, recently reported as risk factor for t-MNs in EOC post-PARPi, were found in 12 out of 13 tested patients. Four patients had a rapid and fatal outcome, one had stable disease, eleven underwent induction therapy, followed by allogeneic hematopoietic cell transplantation in seven. Three of these 11 patients experienced refractory disease, and 8 had complete remission. During a 6.8months (range 2.3-49) median observation time, 3 out of 16 patients were alive, with one surviving patient free of both solid and hematological tumors. Ten patients died because of leukemia, two because of transplant-related events, one from heart failure. Five more patients experienced persistent cell blood count abnormalities following PARPi discontinuation, without reaching MDS diagnostic criteria. A customized Myelo-panel showed clonal hematopoiesis in all five patients. These findings confirm the actual risk of t-MNs in EOC patients after chemotherapy and prolonged PARPi therapy. The management of these patients is complex and outcomes are extremely poor. Careful diagnostic procedures are strongly recommended whenever unusual cytopenias develop in patients receiving PARPi therapy.

Homologous recombination repair deficiency (HRD) testing in newly diagnosed advanced-stage epithelial ovarian cancer: A Belgian expert opinion.

Ovarian cancer (OC) has a poor prognosis as most patients present with non-specific symptoms and the disease is mostly diagnosed at advanced stages. Approximately 90% of cases are classified as epithelial OC (EOC), a category comprising histologically and molecularly distinct tumours. Identifying reliable biomarkers and employing personalised therapies in OC subgroups is crucial for battling the disease. EOCs are often characterised by homologous recombination repair deficiency (HRD), frequently caused by inactivation of the breast cancer susceptibility (BRCA) genes. These findings have led to the development of poly- (adenosine diphosphate [ADP])- ribose polymerase inhibitors (PARPi), which are synthetically lethal to HRD tumour cells. Both patients with HRD and non-HRD tumours can benefit from PARPi therapy in the recurrent setting. Moreover, recent phase III trials in patients with newly diagnosed advanced-stage OC have demonstrated greater clinical benefit from PARPi in treating HRD than non-HRD tumours. These findings offer new opportunities for the use of PARPi as maintenance therapy after first-line chemotherapy based on the presence of HRD. In the current article, we provide recommendations for HRD testing and treatment of patients with newly diagnosed advanced-stage EOC.

Abstract 3249: Targeting polyploid giant cancer cells to overcome resistance to PARP inhibitors in ovarian cancer

Abstract PARP inhibitors (PARPi) offer major clinical benefit for patients with ovarian or other cancers, especially those with deficiencies in the homologous recombination DNA repair pathway. However, most patients with advanced cancer eventually acquire resistance to PARPi, and the mechanisms by which tumors escape PARPi therapy are still not fully understood. Here, we report that treatment with the PARPi olaparib induces the formation of polyploid giant cancer cells (PGCCs) in ovarian and breast cancer cell lines (Hey, SKOV3, MCF-7), three human high-grade serous cancer (HGSC)-derived organoids, and HGSC patient-derived xenografts. Live-cell fluorescence time-lapse tracking of ovarian cancer cells labeled with FUCCI (fluorescent ubiquitination cell-cycle indicator) or histone H2B-mCherry/α-tubulin-EGFP revealed that PGCCs primarily developed from the endoreplication of diploid cancer cells after exposure to sublethal concentrations of olaparib. PGCCs exhibited markers of senescent cells; however, they were able to escape senescence to generate mitotically competent daughter cells via budding, multipolar mitosis, and acytokinetic mitosis following olaparib withdrawal. PGCCs and derived daughter cells conferred resistance to olaparib-induced cytotoxicity, which could be blocked by the anti-progesterone drug mifepristone. Whole transcriptome analysis by RNA sequencing of ovarian cancer cell lines and ovarian cancer-derived organoids showed activation of a senescence-associated secretory phenotype with upregulated cytokines and chemokines and downregulation of MYC signaling in PGCCs. Mifepristone/olaparib combination therapy significantly mitigated tumor growth in patient-derived xenograft models with acquired resistance to olaparib. Thus, targeting of PGCCs may represent a promising approach to overcome PARPi resistance in recurrent ovarian cancer. Citation Format: Xudong Zhang, Jun Yao, Xiaoran Li, Na Niu, Yan Liu, Anil K. Sood, Jinsong Liu. Targeting polyploid giant cancer cells to overcome resistance to PARP inhibitors in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3249.