PARP Inhibitor Olaparib Research Articles

MP27-10 CLINICAL UTILITY OF NEXT-GENERATION SEQUENCING FOR PROSTATE CANCER IN THE CONTEXT OF A CHANGING TREATMENT LANDSCAPE

You have accessJournal of UrologyCME1 May 2022MP27-10 CLINICAL UTILITY OF NEXT-GENERATION SEQUENCING FOR PROSTATE CANCER IN THE CONTEXT OF A CHANGING TREATMENT LANDSCAPE Jacqueline R. Griffin, Tomi Jun, Sunny Guin, Bobby Chi-Hung Liaw, Vaibhav G. Patel, Che-Kai Tsao, Michael R. Rossi, Rong Chen, Xiang Zhou, Feras Hantash, and William K. Oh Jacqueline R. GriffinJacqueline R. Griffin More articles by this author , Tomi JunTomi Jun More articles by this author , Sunny GuinSunny Guin More articles by this author , Bobby Chi-Hung LiawBobby Chi-Hung Liaw More articles by this author , Vaibhav G. PatelVaibhav G. Patel More articles by this author , Che-Kai TsaoChe-Kai Tsao More articles by this author , Michael R. RossiMichael R. Rossi More articles by this author , Rong ChenRong Chen More articles by this author , Xiang ZhouXiang Zhou More articles by this author , Feras HantashFeras Hantash More articles by this author , and William K. OhWilliam K. Oh More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002570.10AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: The clinical utility of next-generation sequencing (NGS) depends on the availability of sequencing-directed therapies (SDT). There were no FDA-approved SDTs in prostate cancer (PCa) until 2020, when PARP inhibitors olaparib and rucaparib were approved for tumors bearing homologous recombination repair (HRR) genes. We assessed the clinical utility of NGS in PCa before and after the approval of these agents in a single academic medical center. METHODS: For PCa patients seen at Mount Sinai Hospital (New York, NY: 2018–2021) receiving NGS (161-gene Sema4 Signal Solid Tumor Panel), data were extracted from Mount Sinai electronic medical record using a proprietary automated pipeline with limited manual curation (Sema4 PRODB). The primary outcome was clinical utility in metastatic PCa, defined as proportion of metastatic PCa patients receiving SDT. Secondary outcomes included time-to-next-treatment (TTNT, time from SDT start to the start of next systemic therapy) and the proportion of patients with clinically actionable (as of 9/2021) alterations, defined as either Tier 1 (FDA-approved treatments in prostate cancer) or Tier 2 (either off-label or investigational agents). RESULTS: Of 332 PCa patients; 51% (N=170) were sequenced 2020 or later. Median age at diagnosis was 65 (IQR 12). Of which, 39% (N=129) were localized and 61% (N=203) metastatic. We identified 167 actionable alterations in 125 patients (38% of cohort). Of actionable alterations, 31% (N=51) were Tier 1 and 69% (N=116) Tier 2. Of the 44 patients with Tier 1 alterations, 8 (18%) received SDT (all received olaparib). Proportion of metastatic patients receiving olaparib increased from 1% (2/145) before 2020 to 10% (6/58) during or after 2020 (p=0.008). Of the 36 patients not receiving olaparib: 20 were sequenced before FDA approval and treated with an alternative systemic therapy; 8 had localized disease and were not eligible; 8 had limited follow-up or unknown treatment status. For those who received olaparib, the median TTNT was 5 months. CONCLUSIONS: Clinical utility of NGS was linked to treatment landscape. Increases in NGS test volume and olaparib use coincided with approval of PARP inhibitors for HRR-mutated PCa patients. Notably, NGS was used to match patients to off-label/investigational olaparib before its FDA approval. Source of Funding: Sema4 © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e453 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Jacqueline R. Griffin More articles by this author Tomi Jun More articles by this author Sunny Guin More articles by this author Bobby Chi-Hung Liaw More articles by this author Vaibhav G. Patel More articles by this author Che-Kai Tsao More articles by this author Michael R. Rossi More articles by this author Rong Chen More articles by this author Xiang Zhou More articles by this author Feras Hantash More articles by this author William K. Oh More articles by this author Expand All Advertisement PDF DownloadLoading ...

57TiP SOLTI-1910: Predicting olaparib sensitivity in patients with unresectable locally advanced/metastatic HER2-negative breast cancer with BRCA1/2, PALB2, RAD51C/D mutations or HRD by the RAD51 test: RADIOLA trial

The OlympiAD trial evaluated the PARP inhibitor (PARPi) olaparib versus a non-platinum standard chemotherapy in HER2-negative metastatic breast cancer (MBC) patients with a germline BRCA1/2 (gBRCA) mutation. Olaparib resulted in improved progression-free survival (PFS) and doubled the response rate vs chemotherapy. Nevertheless, the response rate to PARPi is »60% in the gBRCA1/2 population with MBC (current approval), suggesting a limited positive predictive value of gBRCA1/2 status. Moreover, patients with other relevant Homologous Recombination Repair defects (HRD) such as PALB2 or RAD51C/D mutation carriers, or HRD epigenetic silencing, are not captured with a gBRCA analysis.

PARP inhibitor olaparib enhances the efficacy of radiotherapy on XRCC2-deficient colorectal cancer cells

The use of PARP inhibitors in combination with radiotherapy is a promising strategy to locally enhance DNA damage in tumors. Loss of XRCC2 compromises DNA damage repairs, and induced DNA damage burdens may increase the reliance on PARP-dependent DNA repairs of cancer cells to render cell susceptibility to PARP inhibitor therapy. Here we tested the hypothesis that XRCC2 loss sensitizes colorectal cancer (CRC) to PARP inhibitor in combination with radiotherapy (RT). We show that high levels of XRCC2 or PARP1 in LARC patients were significantly associated with poor overall survival (OS). Co-expression analyses found that low levels of PARP1 and XRCC2 were associated with better OS. Our in vitro experiments indicated that olaparib+IR led to reduced clonogenic survival, more DNA damage, and longer durations of cell cycle arrest and senescence in XRCC2-deficient cells relative to wild-type cells. Furthermore, our mouse xenograft experiments indicated that RT + olaparib had greater anti-tumor effects and led to long-term remission in mice with XRCC2-deficient tumors. These findings suggest that XRCC2-deficient CRC acquires high sensitivity to PARP inhibition after IR treatment and supports the clinical development for the use of olaparib as a radiosensitizer for treatment of XRCC2-deficient CRC.

Anti-CD37 radioimmunotherapy with 177Lu-NNV003 synergizes with the PARP inhibitor olaparib in treatment of non-Hodgkin's lymphoma in vitro.

Background and purposePARP inhibitors have been shown to increase the efficacy of radiotherapy in preclinical models. Radioimmunotherapy results in selective radiation cytotoxicity of targeted tumour cells. Here we investigate the combined effect of anti-CD37 β-emitting 177Lu-NNV003 radioimmunotherapy and the PARP inhibitor olaparib, and gene expression profiles in CD37 positive non-Hodgkin’s lymphoma cell lines.Materials and methodsThe combined effect of 177Lu-NNV003 and olaparib was studied in seven cell lines using a fixed-ratio ray design, and combination index was calculated for each combination concentration. mRNA was extracted before and after treatment with the drug combination. After RNA-sequencing, hierarchical clustering was performed on basal gene expression profiles and on differentially expressed genes after combination treatment from baseline. Functional gene annotation analysis of significant differentially expressed genes after combination treatment was performed to identify enriched biological processes.ResultsThe combination of olaparib and 177Lu-NNV003 was synergistic in four of seven cell lines, antagonistic in one and both synergistic and antagonistic (conditionally synergistic) in two, depending on the concentration ratio between olaparib and 177Lu-NNV003. Cells treated with the combination significantly overexpressed genes in the TP53 signalling pathway. However, cluster analysis did not identify gene clusters that correlate with the sensitivity of cells to single agent or combination treatment.ConclusionThe cytotoxic effect of the combination of the PARP inhibitor olaparib and the β-emitting radioimmunoconjugate 177Lu-NNV003 was synergistic in the majority of tested lymphoma cell lines.

Inhibition of PARP Potentiates Immune Checkpoint Therapy through miR-513/PD-L1 Pathway in Hepatocellular Carcinoma.

Background The DNA repair enzyme poly(ADP-ribose) polymerase (PARP) is involved in DNA damage repair and cell death. However, the association between PARP's biological activities and the immune microenvironment in hepatocellular carcinoma (HCC) is unclear. The present study will explore whether combining a PARP inhibitor with anti-PD1 might improve the anti-HCC impact and explain how it works. Method The PARP inhibitor olaparib was screened out of 867 drugs through Cell Counting Kit 8 (CCK-8) assay. The expression of PARP was verified through the TCGA and TISIDB databases. The impacts exerted by PARP inhibitor olaparib to HCC cells were assessed via wound healing, Transwell, and proliferation assay. In vivo, experiments were performed in a C57BL/6 mouse model to evaluate the function of PARP inhibitor olaparib combination with anti-PD1 in HCC and mice tumors were further detected by immunohistochemically staining. Result Olaparib was selected as the research object on the basis of drug screening. The results of the TCGA and Human Protein Atlas databases revealed that PARP was significantly upregulated in carcinoma cell cluster of HCC tissues compared to normal tissues. Higher expression of PARP showed a poorer prognosis based on Kaplan-Meier Plotter. qRT-PCR experiments confirmed that olaparib could increase PD-L1 expression through inhibiting miR-513 in HCC cells. In vivo, experiment confirmed that the combination of olaparib and anti-PD1 could enhance the immunotherapy effect of HCC. Conclusion The present study reveals that inhibition of PARP potentiates immune checkpoint therapy through the miR-513/PD-L1 pathway in HCC and the combination of PARP inhibitor olaparib and anti-PD1 is beneficial to HCC therapy.

The Anti-ROR1 Monoclonal Antibody Zilovertamab Inhibits the Proliferation of Ovarian and Endometrial Cancer Cells.

The non-canonical Wnt signalling receptor ROR1 is aberrantly expressed in numerous cancers, including ovarian and endometrial cancer. We previously reported that silencing ROR1 could inhibit the proliferation and metastatic potential of ovarian and endometrial cancer cells in vitro. Zilovertamab is an ROR1-targeting humanised monoclonal antibody, with demonstrated safety and efficacy in clinical trials of several ROR1-related malignancies. The aim of this study was to investigate the potential of zilovertamab alone, or in combination with commonly utilised gynaecological cancer therapies (cisplatin, paclitaxel and the PARP inhibitor—Olaparib) on high-grade serous ovarian cancer (HGSOC), including models of platinum resistance and homologous recombination deficiency (CaOV3, CaOV3CisR, PEO1 and PEO4) and endometrial cancer (EC) cell lines (Ishikawa and KLE). The effect of zilovertamab (at 25 µg/mL or 50 µg/mL) +/− agents was investigated using the IncuCyte S3 Live Cell imaging system. Zilovertamab alone inhibited the proliferation of HGSOC and EC cells in vitro, including in models of platinum resistance and homologous recombination deficiency. In general, the addition of commonly used chemotherapies to a fixed dose of zilovertamab did not enhance the observed anti-proliferative activity. This study supports the potential of zilovertamab, or other ROR1-targeting therapies, for treating women with HGSOC and EC.

Zafirlukast Induces VHL- and HIF-2α-Dependent Oxidative Cell Death in 786-O Clear Cell Renal Carcinoma Cells.

Mutations in the Von Hippel–Lindau (VHL) gene are the driving force in many forms of clear cell renal cell carcinoma (ccRCC) and promote hypoxia-inducible factor (HIF)-dependent tumor proliferation, metastasis and angiogenesis. Despite the progress that has already been made, ccRCC generally remain resistant to conventional therapies and ccRCC patients suffer from metastasis and acquired resistance, highlighting the need for novel therapeutic options. Cysteinyl leukotriene receptor 1 (CysLTR1) antagonists, like zafirlukast, are administered in bronchial asthma to control eicosanoid signaling. Intriguingly, long-term use of zafirlukast decreases cancer risk and leukotriene receptor antagonists inhibit tumor growth, but the mechanisms still remain unexplored. Therefore, we aim to understand the mechanisms of zafirlukast-mediated cell death in ccRCC cells. We show that zafirlukast induces VHL-dependent and TNFα-independent non-apoptotic and non-necroptotic cell death in ccRCC cells. Cell death triggered by zafirlukast could be rescued with antioxidants and the PARP-1 inhibitor Olaparib, and additionally relies on HIF-2α. Finally, MG-132-mediated proteasome inhibition sensitized VHL wild-type cells to zafirlukast-induced cell death and inhibition of HIF-2α rescued zafirlukast- and MG-132-triggered cell death. Together, these results highlight the importance of VHL, HIF and proteasomal degradation in zafirlukast-induced oxidative cell death with potentially novel therapeutic implications for ccRCC.

PARP inhibitors chemopotentiate and synergize with cisplatin to inhibit bladder cancer cell survival and tumor growth

BackgroundManagement of bladder cancer (BLCA) has not changed significantly in the past few decades, with platinum agent chemotherapy being used in most cases. Chemotherapy reduces tumor recurrence after resection, but debilitating toxicities render a large percentage of patients ineligible. Recently approved immunotherapy can improve outcomes in only a third of metastatic BLCA patients. Therefore, more options for therapy are needed. In this study, we explored the efficacy of PARP inhibitors (PARPi) as single agents or as combinations with platinum therapy.MethodsWe treated BLCA cells with PARPi (olaparib, niraparib, rucaparib, veliparib, or talazoparib) alone or as the combination of cisplatin with PARPi. We then measured their survival, proliferation, apoptosis, as well as their ability to form colonies. BLCA xenografts in male SCID mice were treated similarly, followed by the assessment of their growth, proliferation, and apoptosis.ResultsPARPi niraparib and talazoparib were effective in reducing BLCA cell survival as single agents. Combinations of Cisplatin with talazoparib and niraparib effectively reduced the survival of BLCA cells, while veliparib was not effective even at high concentrations. In vivo, the combinations of cisplatin with niraparib, rucaparib, or talazoparib reduced BLCA xenograft growth significantly.ConclusionsWe provide evidence that PARPi can be effective against BLCA as single agents or as combinatorial therapy with cisplatin.

ATR Inhibitor AZD6738 (Ceralasertib) Exerts Antitumor Activity as a Monotherapy and in Combination with Chemotherapy and the PARP Inhibitor Olaparib.

This detailed preclinical investigation, including pharmacokinetics/pharmacodynamics and dose-schedule optimizations, of AZD6738/ceralasertib alone and in combination with chemotherapy or PARP inhibitors can inform ongoing clinical efforts to treat cancer with ATR inhibitors.

In vivo anti-tumor effect of PARP inhibition in IDH1/2 mutant MDS/AML resistant to targeted inhibitors of mutant IDH1/2.

Treatment options for patients with relapsed/ refractory acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) are scarce. Recurring mutations, such as mutations in isocitrate dehydrogenase-1 and −2 (IDH1/2) are found in subsets of AML and MDS, are therapeutically targeted by mutant enzyme-specific small molecule inhibitors (IDHmi). IDH mutations induce diverse metabolic and epigenetic changes that drive malignant transformation. IDHmi alone are not curative and resistance commonly develops, underscoring the importance of alternate therapeutic options. We were first to report that IDH1/2 mutations induce a homologous recombination (HR) defect which confers sensitivity to poly (ADP)-ribose polymerase inhibitors (PARPi). Here, we show that the PARPi olaparib is effective against primary patient-derived IDH1/2-mutant AML/ MDS xeno-grafts (PDXs). Olaparib efficiently reduced overall engraftment and leukemia-initiating cell frequency as evident in serial transplantation assays in IDH1/2-mutant but not -wildtype AML/MDS PDXs. Importantly, we show that olaparib is effective in both IDHmi-naïve and -resistant AML PDXs, critical given the high relapse and refractoriness rates to IDHmi. Our pre-clinical studies provide a strong rationale for the translation of PARP inhibition to patients with IDH1/2-mutant AML/ MDS, providing an additional line of therapy for patients who do not respond to or relapse after targeted mutant IDH inhibition.

Tumor Intrinsic PD-L1 Promotes DNA Repair in Distinct Cancers and Suppresses PARP Inhibitor-Induced Synthetic Lethality.

PD-L1 upregulates BRCA1-mediated homologous recombination, and PD-L1-deficient tumors exhibit BRCAness by manifesting synthetic lethality in response to PARP inhibitors, revealing an exploitable therapeutic vulnerability and a candidate treatment response biomarker. See related commentary by Hanks, p. 2069.

CAMP-Mediated Autophagy Promotes Cell Survival via ROS-Induced Activation of PARP1: Implications for Treatment of Acute Lymphoblastic Leukemia.

PARP1 inhibitors augment the DNA damage-induced killing of ALL cells by limiting the opposing effects of cAMP-mediated autophagy, which involves ROS-induced PARP1 activation and depletion of cellular NAD levels.

DNA Repair Enzyme Poly(ADP-Ribose) Polymerase 1/2 (PARP1/2)-Targeted Nuclear Imaging and Radiotherapy.

Simple SummaryIn parallel to the successful clinical implementation of PARP1/2 inhibitors as anti-cancer drugs, which interfere with the DNA repair machinery, these small molecule agents have also gained attention as vehicles for molecular imaging and radiotherapy. In this review article, we summarize the development and preclinical evaluation of radioactively-labelled PARP inhibitors for positron emission tomography (PET) for many applications, such as selecting patients for PARP inhibitor treatment, response prediction or monitoring, and diagnosis of tumors. We report on early clinical studies that show safety and feasibility of PARP-imaging in humans. In addition, we summarize the latest developments in the field of PARP-targeted radiotherapy, where PARP inhibitors are studied as vehicles to deposit highly cytotoxic radioisotopes in close proximity to the DNA of tumor cells. Lastly, we look at synthetic strategies for PARP-targeted imaging and therapy agents that are compatible with large scale production and clinical translation. Since it was discovered that many tumor types are vulnerable to inhibition of the DNA repair machinery, research towards efficient and selective inhibitors has accelerated. Amongst other enzymes, poly(ADP-ribose)-polymerase 1 (PARP1) was identified as a key player in this process, which resulted in the development of selective PARP inhibitors (PARPi) as anti-cancer drugs. Most small molecule PARPi’s exhibit high affinity for both PARP1 and PARP2. PARPi are under clinical investigation for mono- and combination therapy in several cancer types and five PARPi are now clinically approved. In parallel, radiolabeled PARPi have emerged for non-invasive imaging of PARP1 expression. PARP imaging agents have been suggested as companion diagnostics, patient selection, and treatment monitoring tools to improve the outcome of PARPi therapy, but also as stand-alone diagnostics. We give a comprehensive overview over the preclinical development of PARP imaging agents, which are mostly based on the PARPi olaparib, rucaparib, and recently also talazoparib. We also report on the current status of clinical translation, which involves a growing number of early phase trials. Additionally, this work provides an insight into promising approaches of PARP-targeted radiotherapy based on Auger and α-emitting isotopes. Furthermore, the review covers synthetic strategies for PARP-targeted imaging and therapy agents that are compatible with large scale production and clinical translation.

Genetic medicine is accelerating in Japan

BackgroundIn 2018, BRACAnalysis® was covered by medical insurance in Japan as a companion diagnostic test for the poly ADP-ribose polymerase inhibitor olaparib. In April 2020, eligibility for BRCA1/2 genetic testing was expanded to the diagnosis of hereditary breast and ovarian cancer syndrome, and medical management including prophylactic surgery and surveillance were covered by public insurance for BRCA1/2 mutation carriers who developed breast or ovarian cancer. The amount of BRCA1/2 genetic testing has been increasing recently, but the number of subjects and the impact of testing for patients’ outcomes remain unclear.Patients and methodsThis study explored the potential number of patients who will be eligible for new insurance coverage for BRCA1/2 genetic testing. We analyzed 868 patients from 938 surgeries between January 2014 and September 2020 from our database.ResultsOverall, 372 patients (43%) were eligible for new insurance coverage for BRCA1/2 genetic testing. The most common category was family history of breast or ovarian cancer within third-degree relatives. We found that 202 patients (23%) had family history of breast or ovarian cancer. In addition, the progression-free survival was significantly lower in triple-negative breast cancer patients aged 60 years or younger compared with the other patients (P = 0.0005).ConclusionThe genetic medicine for primary breast cancer patients with BRCA1/2 germline mutation is accelerating rapidly in Japan. Therefore, establishing a system for the genetic medicine would be urgent.

Clinical utility of next-generation sequencing for prostate cancer in the context of a changing treatment landscape.

112 Background: Next-generation sequencing (NGS) is increasingly common in clinical practice, but its clinical utility may depend on the availability of sequencing-directed therapies (SDT). There were no FDA-approved SDTs in prostate cancer (PCa) until 2020, when PARP inhibitors olaparib and rucaparib were approved for tumors bearing alterations in certain homologous recombination repair (HRR) genes. We assessed the clinical utility of NGS in PCa before and after the approval of these agents in a single academic medical center. Methods: This was a retrospective single-center study including all PCa patients seen at Mount Sinai Hospital (New York, NY) between 2018–2021 who received NGS via the 161-gene Sema4 Signal Solid Tumor Panel. Clinical data were extracted from the Mount Sinai electronic medical record using a proprietary automated pipeline with limited manual curation (Sema4 PRODB). The primary outcome was clinical utility in metastatic PCa, defined as the proportion of metastatic PCa patients who received SDT. Secondary outcomes included time-to-next-treatment (TTNT, defined as time from SDT start to the start of next systemic therapy) and the proportion of patients with clinically actionable (as of 9/2021) alterations, defined as either Tier 1 (associated with FDA-approved treatments in prostate cancer) or Tier 2 (associated with either off-label or investigational agents). Results: The cohort consisted of 332 PCa patients; 51% (N = 170) were sequenced in 2020 or later. The median age at diagnosis was 65 (IQR 12). The most advanced stage documented was localized for 39% (N = 129) and metastatic for 61% (N = 203). Overall, 167 actionable alterations were identified in 125 patients (38% of cohort). Of the actionable alterations, 31% (N = 51) were Tier 1 and 69% (N = 116) were Tier 2. Of the 44 patients with Tier 1 alterations, 8 (18%) received SDT (all received olaparib). The proportion of metastatic patients receiving olaparib increased from 1% (2/145) before 2020 to 10% (6/58) during or after 2020 (p = 0.008). Of the 36 patients not receiving olaparib: 20 were sequenced before FDA approval and were treated with an alternative systemic therapy; 8 had localized disease and were not eligible; 8 had limited follow-up or unknown treatment status. For those who received olaparib, median TTNT was 5 months. Conclusions: In this single-center retrospective cohort, clinical utility of NGS was linked to treatment landscape. Increases in NGS test volume and olaparib use coincided with the approval of PARP inhibitors for patients with HRR-mutated prostate cancers. Notably, NGS was used to match patients to off-label/ investigational olaparib before its FDA approval.[Table: see text]

Targeting resistant prostate cancer, with or without DNA repair defects, using the combination of ceralasertib (ATR inhibitor) and olaparib (the TRAP trial).

88 Background: Men with metastatic, castration resistant prostate cancer (mCRPC) harboring DNA repair defects (̃20%) achieve a radiographic progression free survival of 7.4 months with PARP inhibitors (PARPi). Preclinical studies combining a PARPi (olaparib) and DNA damage checkpoint inhibitor (ATR inhibitor, ceralasertib) show synergy, providing the rationale to test this combination in men with mCRPC, including where single agent olaparib has been shown to be active. Methods: Two cohorts were accrued to a trial combining ceralasertib with olaparib in men a) with or b) without DNA repair defects. All patients progressed on ≥1 prior mCRPC therapy with no prior PARPi or platinum chemotherapy. The primary endpoint was disease response (confirmed PSA decline ≥50% and/or RECIST response), while disease progression was defined per Prostate Cancer Working Group 3 definition. Each cohort is analyzed independently for disease endpoints, while both groups were combined for toxicity assessments. Results: The 12 person DNA repair-deficient (DRDef) cohort allowed patients with germline BRCA2 loss (n = 4), somatic BRCA2 loss (n = 1) and ATM loss (n = 1 germline, n = 5 somatic and n = 1 somatic with unknown germline). 35 men without BRCA2/BRCA1 or ATM genomic loss were accrued to the DNA repair-proficient (DRPro) cohort. These men had next-generation sequencing (NGS) on contemporary biopsies (prior to enrolment without intervening therapy, 12), prior NGS on metastatic tissue (10), prior NGS on primary prostatic tissue (n = 3), or cell-free analyses (5). Five patients have incomplete cell-free analyses. At data cutoff (October 2021), in the DRDef cohort, the response rate by confirmed ≥50% PSA decline was 4/10 (40%) including 3 of 4 BRCA2 patients, and another is awaiting sufficient follow up; 1 of 6 ATM-deficient patients responded and another is awaiting sufficient follow up. All 4 DRDef responders remain on therapy (median of 8 months). For patients in the DRPro cohort who have completed therapy and response assessment (n = 21), 3 responded, one with a duration of 12 months, two with 6 months. An updated analysis will be presented. Conclusions: This analysis suggests potential activity of the doublet for DRDef (BRCA2 mainly) and DRPro mCRPC. Ongoing biomarker analysis (e.g. ATM IHC, contemporaneous cell-free DNA analysis rather than archived tissue) may help guide selection of patients most likely to benefit. Clinical trial information: NCT03787680.

Impact of provider education on prostate cancer genetic counseling referrals.

59 Background: Guidelines recommend germline genetic not only for men with advanced and metastatic prostate cancer but also those with NCCN-high risk disease. Many men harboring germline DNA repair defects would not have met criteria for testing under previous guidelines (Nicolosi et al, JAMA Oncol 2019). Knowledge of germline mutations is pertinent due to recent regulatory approval of PARP inhibitors olaparib and rucaparib and guides screening for first-degree relatives who are at increased risk for other cancers (Pritchard et al, NEJM 2016). Knowledge gaps for germline genetic testing have been previously described (Loeb et al, Cancer Treat Res Commun 2020). Through a series of educational sessions, we sought to increase utilization of appropriate genetic services for men with prostate cancer. Methods: Starting March 2021, virtual educational presentations were held for nurse navigators, urologists, and medical oncologists throughout our large community-based healthcare system. Surveys were distributed following each presentation to measure clinicians’ perception of their knowledge regarding prostate cancer genetics referrals on a five-step scale. Prostate cancer patient referral data was measured from September 2020 to August 2021, six months prior to and after the presentations. Results: Self-reported understanding of prostate cancer genetics referral practices following the educational presentations increased by an average of 1.7/5 steps (2.5 to 4.2/5) for physicians and 1.4/5 steps (2.9 to 4.1/5) for nurse navigators. From March to August 2021, there were 107 genetic referrals for prostate cancer (average 17.8 referrals/month) compared to 49 referrals from September 2020 to February 2021 (8.2 referrals/month). Conclusions: Prostate cancer genetics referrals increased 118% following educational presentations to urologists, medical oncologists, and nurse navigators. This correlates with an improvement in self-reported knowledge gaps. Provider education interventions may improve access to genetic services for men with prostate cancer. The increase in referrals likely does not account for all patients meeting criteria for germline testing. Work is ongoing to calculate the number of referrals as a proportion of the eligible population.[Table: see text]

Abstract ES5-2: Optimizing the management of early stage TNBC

Abstract The recent approvals of the immunotherapeutic agent pembrolizumab, the antibody-drug conjugate sacituzumab govitecan and the PARP inhibitors olaparib and talazoparib for select patients with metastatic triple negative breast cancer (TNBC) have spurred interest in evaluating these and other novel agents in patients with earlier stage disease. For the last several decades, a standard approach to treating early stage TNBC was to administer neoadjuvant chemotherapy, most often an anthracycline/taxane-based regimen. Pathologic complete response (pCR) rates generally ranged 30-40%. Trials such as CALGB 40603, GeparSixto and BrighTNess demonstrated that the addition of carboplatin to an anthracycline and taxane based chemotherapy could increase the pCR rates (53-58%). At the most recent ESMO conference, the BrighTNess investigators reported that the addition of carboplatin improved event free survival (EFS) after a median follow-up of 4.5 years. For patients not experiencing a pCR, the Create-X trial showed benefit of capecitabine in the adjuvant setting.As of August 2021, there is a new standard for treating early stage TNBC. Specifically, based on the KEYNOTE-522 trial, pembrolizumab, in combination with chemotherapy, is FDA approved for this indication. KEYNOTE-522 enrolled over 1170 stage 2-3 TNBC patients and randomized them to chemotherapy +/- pembrolizumab. The most recent report showed the trial met it’s co-primary endpoints of improved pCR (63% vs 56%) and EFS (84.5% vs 76.8%) after a median follow-up of 39 months. Importantly, the benefit was regardless of the PD-L1 status of the patient’s tumor. With the approval of pembrolizumab comes a number of questions: 1) which patients should receive this regimen which is associated with immune-related toxicities, some of which are lifelong, 2) what is the optimal chemotherapy backbone, 3) is a full year of pembrolizumab required and 4) are there other biomarkers to be explored that may predict response to therapy or the development of toxicity? Other studies either have or are evaluating other targeted agents in the preoperative setting for early stage TNBC. In a small study of 20 BRCA mutation carriers treated preoperatively with single agent talazoparib, investigators reported a pCR rate of 53%. A study looking at sacituzumab monotherapy in the preoperative setting has completed accrual and the results are awaited. These two trials begin to address the question of whether we can identify an “achilles” heel in TNBC and if so, will targeting it improve patient outcomes. Good correlative studies that provide improved understanding of the impact of these therapies on the TNBC microenvironment will help inform the next generation of trials; likely combination therapies.There is also the question of adjuvant therapy, particularly for those that do not experience a pCR with preoperative therapy. As stated above, the CREATE-X trial supports the use of capecitabine in patients with residual disease, however EA1131 demonstrated that outcomes are still poor for this population. More recently, for patients with BRCA-mutated cancers, the OlympiA trial showed benefit to a year of adjuvant olaparib. There is also growing interest in whether patients with residual disease who are at highest risk for recurrence can be identified using technologies looking for cell-free DNA to find those with minimal residual disease. Historically we’ve thought about TNBC for what it’s not – it is not ER, PR or HER2 positive. With multiple studies now showing benefit of specific agents in TNBC, the next several years will provide an opportunity to more extensively dissect triple negative tumors and their. microenvironment. This will allow us to learn what TNBC “is”, and which of likely multiple different therapeutic strategies will be best applied to which patients. Citation Format: E Mittendorf. Optimizing the management of early stage TNBC [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr ES5-2.

Abstract PL2: Triple Negative Breast Cancer - Pitfalls and Progress

Abstract Triple negative breast cancer (TNBC), lacking expression of the hormone receptors (estrogen/ER, progesterone/PR) and without amplification or overexpression of HER2, is defined by what it isn’t, which fails to reflect the potential for targetability and improved outcomes now emerging. In spite of recent advances, TNBC continues to carry the worst prognosis of all the clinical subtypes, has the fewest therapeutic options, and affects young women and women of color most, so improving therapy in this subtype is among the biggest challenges in breast cancer oncology. Epidemiologic studies confirm the unique biology of the basal-like subtype, which comprises the majority of TNBC, its unique risk factors and metastatic patterns. However, TNBC (and the basal-like intrinsic subtype) molecular and immunologic heterogeneity is becoming clearer, as are the implications of this heterogeneity on treatment response and outcome. For example, the presence of tumor infiltrating lymphocytes (TILS) is consistently associated with better outcomes in nonmetastatic TNBC. Prognosis in this subtype, as with all other subtypes, is driven not only by biology but also by clinical variables. Unlike hormone receptor-positive, there are no effective genomic prognostic assays for TNBC, however as with all breast cancer clinical subtypes, small node-negative breast cancers do well and may not need chemotherapy. However these are the minority; in the remainder of early TNBC, standard chemotherapy includes both anthracyclines and taxanes, with some evidence of benefit of the incorporation of platinums. There have been advances for patients with nonmetastastic TNBC in the past few years. For example, in all but the smallest node-negative tumors, the use of the neoadjuvant, or preoperative, approach improves surgical outcomes and allows risk stratification based on pathologic response. In patients treated with neoadjuvant chemotherapy with residual disease at surgery, adjuvant capecitabine improves relapse and survival. In those with germline mutations of BRCA1 or 2, the addition of adjuvant PARP inhibition in intermediate and high risk TNBC improved outcomes. Immune checkpoint inhibition (ICI) added to neoadjuvant chemotherapy improves pathologic response to therapy, and more recently the ICI pembrolizumab has also been shown to improve relapse-free survival. In metastatic disease, ICI improves outcome when added to chemotherapy in first-line treatment of PDL1-positive TNBC, and the PARP inhibitors olaparib and talazoparib offer a non-chemotherapy option for those with germline BRCA1, BRCA2, or PALB2. However it remains true that metastatic TNBC remains dependent on chemotherapy-based treatment options. The antibody-drug conjugate (ADC) sacituzumab govitecan is an example of ways to deliver cytotoxic chemotherapy more safely and effectively, and has become a standard 2nd line or later option with examination of this ADC and others in earlier settings ongoing. Efforts to define TNBC in therapeutically targetable ways have not yet resulted in the goal of redefining this entity according to tumor and immune targets, but with greater biologic understanding and ongoing clinical and translational efforts, it is likely the term “triple negative” will become obsolete in the future. Citation Format: LA Carey. Triple Negative Breast Cancer - Pitfalls and Progress [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PL2.

Abstract P1-08-22: The role of DAXX as a critical growth regulator of triple negative breast cancer

Abstract Background: Triple negative breast cancer (TNBC) is a heterogeneous disease that frequently presents at a metastatic stage or upon initial early stage diagnosis, and may recur quickly. Treatment options are limited outside of cytotoxic chemotherapy in the adjuvant or metastatic setting and there is an immediate need to identify and validate novel biomarkers that predict sensitivity to chemotherapy. Previously, it was shown that the pro-apoptotic protein DAXX is required for paclitaxel-mediated breast cancer cell death. Based on these data and our recent discoveries that DAXX is a potent inhibitor of breast cancer stem cells in ER+ breast cancer (Peiffer et al., Cancer Res. 2019; Peiffer et al., NPJ Breast Cancer. 2020), we next explored the role of DAXX in TNBC. We found that high DAXX expression in TNBC cells regulates cell proliferation and activities of PARP-1 and JNK; two pathways required for cell death. The goals of the current work were to investigate the mechanism by which DAXX regulates proliferation at the level of PARP-1 and/or JNK and test if DAXX expression predicts sensitivity to carboplatin, paclitaxel, doxorubicin, the PARP-1 inhibitor olaparib, or the JNK inhibitor SP600125 in TNBC cells. Methods: Proliferation and cell cycle analysis were performed in three TNBC cell lines (MDA-MB-231, BT549, and MDA-MB-468) under DAXX expression and depletion conditions using an siRNA approach. Sensitivity to carboplatin, paclitaxel, and doxorubicin was determined by measuring proliferation in a dose-dependent manner. PARP-1 activity was assessed by detecting global protein PARylation levels using Western blotting. JNK activation was analyzed by measuring phosphorylated JNK levels. A JNK inhibitor (SP600125) was used to determine if JNK signaling was responsible for restricting cell proliferation and if DAXX was required for the elevated JNK activity. Olaparib was used to assess the role of PARP-1 activation in DAXX-depleted cells. Results: The TNBC cell lines expressed high levels of DAXX. Depletion of DAXX increased cell proliferation by promoting cell cycle progression through the S-phase. The consequence of this increased cell proliferation was decreased sensitivity to carboplatin and paclitaxel, but not to doxorubicin. Mechanistically, at least one chemotherapeutic agent, carboplatin induced JNK activation and DAXX was required for the increased JNK activity. The JNK inhibitor (SP600125) partially reversed resistance to carboplatin in DAXX-depleted cells. Additionally, genetic knockdown of DAXX resulted in elevated PARP-1 activity as measured by global PARylation of proteins. PARP-1 blockade using olaparib also partially reversed resistance to carboplatin in DAXX-depleted cells. Conclusions: These results suggest that DAXX is a critical growth regulator and predictor of response to carboplatin and paclitaxel in triple negative breast cancer cells. DAXX is necessary to activate the JNK pathway in response to carboplatin and it is this carboplatin-mediated JNK signaling that inhibits cell proliferation. Furthermore, DAXX limits PARP-1 activity and is necessary for increased sensitivity to carboplatin or paclitaxel. Data herein support assessing DAXX expression in triple negative tumors to determine if high DAXX expression predicts increased sensitivity to carboplatin, paclitaxel, and if DAXX-low expressing TNBC cells require addition of a JNK or PARP-1 inhibitor. Citation Format: Clodia Osipo, Debra Wyatt, Michelle Fernandez, Daniel S Peiffer, Kathy S Albain. The role of DAXX as a critical growth regulator of triple negative breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-08-22.