Mutations In DNA Repair Pathways Research Articles

Abstract 7582: Descriptive analysis of patients with mCRPC and liver metastases receiving alpha and beta PSMA targeted radionuclide therapy (PSMA-TRT)

Abstract Introduction: Predictors of outcomes after PSMA-TRT are still being established. Liver metastases (mets) have been associated with poor response. Mutations in genes encoding DNA damage repair (DDR) and TP53 affect radiosensitivity. Here we describe a cohort of patients with mCRPC and liver metastases treated on clinical trials of PSMA-TRT. Methods: 39 patients with liver mets were enrolled on phase I/II PSMA-TRT studies between Jan 2006 to Apr 2022. Patients received alpha therapy (225Ac-J591), beta therapy (fractionated 177Lu-PSMA-617, single-dose and fractionated 177Lu-J591) or a combination of both (225Ac-591 and 177Lu-PSMA-I&T). All patients included in this analysis had CT imaging; patients enrolled after 2017 had PSMA-PET imaging. 15 patients also had genomic analysis completed. Results: Median age was 69 (range 55-93), PSA 85.7 (2.45-9614). 39 (100%) bone mets, 33 (84.6%) LN, 9 (23.1%) lung. 22 (56.4%) greater than 1 ARPI, 23 (59.0%) greater thanc 1 chemo, 13 (33.3%) sip-T, 7 (17.9%) Ra-223, 4 (10.2%) prior TRT (with concurrent liver mets). Of the 19 with both CT and PSMA PET, 18 (94.7%) were identified on PSMA PET (including 8 PET only), 10 (55.6%) on CT (1 CT only, i.e. non-PSMA PET avid). Median whole body PSMA-imaging score (PSMA-IS) was 4 (range 1-4), with 7 (17.9%) 1-2 and 32 (82.1%) 3-4. 9 (23.0%) received alpha-TRT, 26 (66.7%) beta-TRT, and 4 (10.3%) combo-TRT. Somatic or germline analysis was completed in 15 (38.5%) of 39 patients. 8 (53.3%) had mutations in DNA repair pathways (3 in BRCA2, 3 in CHEK 2, 1 in FANC, 1 in MSH2). 7 (46.7%) had mutations in TP53. 31 patients (79.5%) had PSA decline, with 15 (38.5%) achieving PSA 50. 26 (66.7%) had baseline CTC measured; 19 (73.0%) had detectable CTC at baseline. Of these 19, 3 (15.8%) converted to undetectable after therapy and 2 (10.5%) converted to favorable CTC. PSA50 rate in alpha-TRT was 4 (44.4%), beta-TRT 8 (30.7%), combo-TRT 3 (75%). PSA50 in patients with PSMA-IS 1-2 was 1 (14.2%) compared to 14 (43.9%) in PSMA-IS 3-4. 3 (37.5%) of 8 patients with mutDDR achieved PSA50, compared to 3 (42.9%) with mutTP53. Conclusions: This dataset adds to the collective literature of two subgroups of patients with mCRPC receiving TRT: those with liver disease and those with mutations in DNA repair pathways. The results of this study suggest higher rates of response in patients receiving alpha therapy, either alone or in combination with beta therapy, and in patients with high radiotracer uptake on PSMA-PET, based on PSMA-imaging score of 3 or 4. Genomic alterations in DRR proteins did not have clear implications. Citation Format: Samuel Ruder, Michael Sun, Andres Ricaurte Fajardo, Jones Nauseef, Zachary Davidson, Joseph Thomas, Sandra Huicochea Castellanos, Ana Molina, Cora Sternberg, Amie Patel, Escarleth Fernandez, Sarah Yuan, Edward Fung, Vasilios Avlonitis, Elisabeth O'Dwyer, David Nanus, Joseph Osborne, Neil Bander, Scott Tagawa. Descriptive analysis of patients with mCRPC and liver metastases receiving alpha and beta PSMA targeted radionuclide therapy (PSMA-TRT) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7582.

Abstract B138: Pharmacodynamics-driven phase 2 trial of talazoparib in patients with advanced solid tumors and aberrations in genes involved in DNA damage response

Abstract Background: Talazoparib is a poly (ADP-ribose) polymerase inhibitor (PARPi) with increased trapping of PARP-DNA complexes compared to other PARPi in clinical development. Talazoparib has single-agent synthetic lethality in BRCA1/2- and PTEN-deficient cell lines, has potent antitumor activity in animal models of tumors harboring mutations in DNA repair pathways, and has FDA-approved indications in advanced BRCA-mutated and HER2-negative breast cancer and in homologous recombination repair gene-mutated metastatic castration-resistant prostate cancer in combination with enzalutamide. This pilot study evaluated the pharmacodynamic (PD) effects of talazoparib on DNA damage response (DDR) markers in tumor biopsy tissue in both patients (pts) who are PARPi-naïve and pts who have received prior PARPi other than talazoparib to investigate for potential differential PARPi PD responses in DNA replication stress. Methods: We are conducting a multicenter phase 2 trial in adult pts with eligible deleterious germline or somatic mutations in BRCA1/2 or genes involved in DDR including ATM, ARID1A, IDH1, BAP1, ATR, CHK2, and PALB2. Pts were enrolled and assessed in two cohorts: 1) pts who were PARPi-naïve, and 2) pts who were treated with and had documented progression on a PARPi other than talazoparib. Talazoparib is administered orally at a dose of 1000 µg/day (D) in 28 D cycles (C). The primary objective is determining the replication stress PD effect of talazoparib as evaluated by activation of Rad51 combined with a lack of γH2AX activation. Paired tumor biopsies (baseline and C2D1) will be analyzed for DDR markers (γH2AX, pNBS1, and Rad51) by IFA. Responses and adverse events (AEs) are defined by RECIST 1.1 and CTCAE v5.0, respectively. Results: The PARPi-naïve cohort had 15 pts enrolled with a median age of 58 years (range 38-76) and median prior lines of systemic therapy of 2 (range 1-5). The PARPi-treated cohort had 8 pts enrolled with a median age of 72 years (range 35-85) and median prior lines of systemic treatment of 5.5 (range 1-10). A total of 11 sets of pre-treatment and post-treatment tumor biopsies have been received to date and analyses of DDR markers are ongoing. Of 11 pts in the PARPi-naïve cohort evaluable for response, 6 pts had stable disease (SD) as best response with 2 pts (nasal cavity cancer with ARID1A alteration, bile duct cancer with IDH1 alteration) who received talazoparib for ≥ 6 C. Of 7 pts in the PARPi-treated cohort evaluable for response, 4 pts had SD as best response. Treatment-related AEs of ≥ grade 2 with ≥ 5% incidence included anemia (n=10, 43.5%), leukopenia (n=7, 30.4%), lymphopenia (n=6, 26.1%), thrombocytopenia (n=6, 26.1%), and neutropenia (n=4, 17.4%). Conclusions: Study enrollment and analyses of PD DDR markers in paired tumor biopsies are both ongoing with data to be presented at the conference. No responses have been observed to date, which may be due to prior therapies, tumor histologies, mutational selection or dose delivered with further characterization anticipated via PD DDR marker data. Citation Format: Brian Ko, Geraldine H O'Sullivan Coyne, Abdul Rafeh Naqash, Thomas J George, David DeRemer, Larry Rubinstein, Jennifer Zlott, Deborah Wilsker, Donna Ketchum, Stephanie Runkle, Katherine V Ferry-Galow, Ralph E Parchment, Naoko Takebe, Sarah Shin, Andrea R Voth, Jiuping Ji, S. Percy Ivy, James H Doroshow, Alice P Chen. Pharmacodynamics-driven phase 2 trial of talazoparib in patients with advanced solid tumors and aberrations in genes involved in DNA damage response [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B138.

Perceptions of emerging PARP inhibitor (PARPi) data among practicing oncologists in prostate cancer.

546 Background: Studies suggest that PARPi agents work best in cancers, including metastatic castration-resistant prostate cancer (mCRPC), that have mutations in DNA repair pathways regulated by homologous recombination repair ( HRR) genes . The first PARPis for prostate cancer (olaparib for HRR-mutated and rucaparib for BRCA-mutated CRPC) were approved in 2020. Two recent trials, TALAPRO-2 and PROpel, evaluate PARPis plus an androgen receptor pathway inhibitor for patients both with and without genetic mutations were presented at ASCO GU 2023. This study aimed to determine oncologists’ perceptions of these new data. Methods: In April 2023, US-based oncologists were invited to attend one of two meetings to discuss data from ASCO GU 2023. Demographics were collected in an online survey, and perceptions of the TALAPRO-2 and PROpel trials were captured via audience response system technology at the meetings. Results: Across the two meetings, 115 oncologists were surveyed; 99 oncologists (86%) indicated that they manage patients with prostate cancer. Of these, 74% reported that they either very often or always test for HRR mutations, and the majority are testing at initial diagnosis of metastatic disease. Prior to reviewing trial updates, 84% of oncologists reported olaparib as their preferred PARPi, and the top factors driving their preferences are efficacy (83%) and safety/tolerability (63%). Perceptions of the trial updates are reported in Table 1. A subset of oncologists were also asked their treatment preferences for patients with mCRPC before and after the trial updates. Altogether, there was a 41% increase in physicians who would use talazoparib plus enzalutamide in an ATM-mutated patient after progression on docetaxel. They were also more likely to report (35%) a preference for this combination for a BRCA1-mutated patient after progression on abiraterone acetate. Additionally, there was a 27% increase in physicians who would use olaparib plus abiraterone acetate in an HRR-wild type patient after enzalutamide. Conclusions: Overall, these data show that clinical updates regarding PARPi agents have an impact on practicing oncologists. However, further exploration of genetic testing practices among oncologists and the impact of emerging data on real-world practice is needed.[Table: see text]

Abstract B033: LP-184, a tumor site activated small molecule therapeutic, is synthetically lethal in pancreatic cancers with DNA damage repair defects

Abstract Biomarker-based therapeutic strategies associated with increased efficacy, manageable toxicity and extended disease-free survival are urgently needed in pancreatic cancer (PaCa). 15-20% of PaCa carry mutations in DNA repair pathways (BRCA1/BRCA2/PALB2/RAD51/ATR/ATM/FANCD2). Additionally, mutations in nucleotide excision repair (NER) genes (ERCC2/3/4/5/6) have been reported in ~5% of PaCa. LP-184 is an acylfulvene analog that is converted to an active alkylating agent in the strict dependency on the oxidoreductase, prostaglandin reductase 1 (PTGR1). LP-184 induced tumor cell kill is enhanced in the presence of DNA damage repair (DDR) defects. Mutation or expression driven TC-NER and/or HR deficiency is expected to predispose PaCa cells to increased sensitivity to LP-184. To test the idea of LP-184 activity in DNA repair-deficient tumors, we evaluated the anti-tumor effects of LP-184 in mouse subcutaneous PDX models harboring pathogenic frameshift mutations in ATR (CTG-1522 model) or BRCA1 (CTG-1643 model) representing HR deficiency in PaCa. Two cycles of LP-184 treatment in CTG-1522 resulted in 140% tumor growth inhibition (TGI), relative to 80% TGI with gemcitabine in this FOLFIRONOX non-responder. Similarly, complete and durable tumor regression with 112% TGI was observed in CTG-1643 with single agent LP-184. There was <5% body weight loss and no significant hematological toxicity in both these models during or after LP-184 treatment. In selected PaCa models, we determined LP-184 efficacy to be synergistic in combination with multiple treatment modalities including standard of care agent gemcitabine, and ERCC3 degrader spironolactone in vitro, and with radiation therapy (RT) in vivo. Overall Bliss synergy scores (score > 10 indicates synergy) of 12.37 for LP-184 + gemcitabine in Capan-1, and 14.08, 16.47 and 15.52 for LP-184 + spironolactone in Capan-1 (BRCA2 loss), Hs766t (ATR mutant) and Panc03.27 cell lines respectively were achieved. Taking advantage of the transcriptional regulation underlying the NRF2 mediated anti-oxidant response pathway, we reasoned that induction of PTGR1 expression, a downstream NRF2 target gene, in irradiated PaCa tumors would thereafter poise them for LP-184 treatment. Indeed, we found that Panc03.27 xenograft tumors treated with 3 mg/kg i.p. LP-184 + 4 Gy RT once weekly for 3 weeks were significantly smaller than those receiving LP-184 alone or RT alone, thus capitalizing on the opportunity to increase PTGR1 expression (and linked LP-184 anti-tumor cytotoxicity) selectively in irradiated tumors. Increased PTGR1 expression has emerged as a promising biomarker for LP-184 cytotoxicity. Moreover, LP-184 can become synthetically lethal in multiple contexts when combined with genetic or pharmacologic DDR pathway aberrations, or with RT. Based on these properties, we anticipate that LP-184 will extend therapeutic opportunities to a large subset of PaCa patients. Citation Format: Aditya Kulkarni, Diana Restifo, Troy Dos Santos, Dusica Cvetkovic, Joseph McDermott, Kishor Bhatia, Panna Sharma, Charlie Ma, Igor Astsaturov. LP-184, a tumor site activated small molecule therapeutic, is synthetically lethal in pancreatic cancers with DNA damage repair defects [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr B033.

487P Randomized phase II study of trabectedin/olaparib compared to physician’s choice in subjects with previously treated advanced or recurrent solid tumors harboring DNA repair deficiencies

Genomic aberrations affecting the repair of DNA double-strand breaks (DSB) by homologous recombination (HR) are found in various cancers and result in sensitivity to inhibitors of the DNA repair enzyme PARP1. Trabectedin induces DNA DSB and PARP1 activation and may thus increase the effect of PARP inhibitors in HR-deficient cancers. Whole-exome/genome sequencing (WES/WGS) can identify mutations in DNA repair pathways and mutational signatures generated by these aberrations.

Emerging Role of PARP Inhibitors in Metastatic Prostate Cancer.

We highlight the clinical development of Poly (ADP-Ribose) polymerase (PARP) inhibitors in prostate cancer. Approximately 10 to 30% of metastatic prostate cancer patients carry germline or somatic mutations in DNA repair pathways. BRCA2 is the most commonly mutated gene in DNA damage repair pathways. Because of its critical function in homologous recombination repair (HRR) machinery, deleterious BRCA2 mutation enables synthetic lethality to a PARP inhibitor. Olaparib demonstrated clinical benefit in patients with deleterious mutations in HRR-related genes and most clearly in patients with BRCA2 mutations. Olaparib received the US FDA approval or mCRPC patients with a qualifying HRR gene mutation in May 2020. Rucaparib received an accelerated FDA approval for patients with BRCA1- or BRCA2-mutated mCRPC based on 43% objective response rate in a phase II study. To expand the application of a PARP inhibitor, several trials have evaluated various combination strategies with an androgen receptor signaling inhibitor, immunotherapy, radium-223, and others. While no PARP inhibitor combination regimen has been approved, promising data from a PARP inhibitor and an ASI combination have been reported. PARP inhibitor represents a standard treatment for patient with mCRPC with germline or somatic mutations in BRCA2 and other HRR pathway genes.

Niraparib Shows Superior Tissue Distribution and Efficacy in a Prostate Cancer Bone Metastasis Model Compared with Other PARP Inhibitors

Patients with prostate cancer whose tumors bear deleterious mutations in DNA-repair pathways often respond to PARP inhibitors. Studies were conducted to compare the activity of several PARP inhibitors in vitro and their tissue exposure and in vivo efficacy in mice bearing PC-3M-luc-C6 prostate tumors grown subcutaneously or in bone. Niraparib, olaparib, rucaparib, and talazoparib were compared in proliferation assays, using several prostate tumor cell lines and in a cell-free PARP-trapping assay. PC-3M-luc-C6 cells were approximately 12- to 20-fold more sensitive to PARP inhibition than other prostate tumor lines, suggesting that these cells bear a DNA damage repair defect. The tissue exposure and efficacy of these PARP inhibitors were evaluated in vivo in PC-3M-luc-C6 subcutaneous and bone metastasis tumor models. A steady-state pharmacokinetic study in PC-3M-luc-C6 tumor-bearing mice showed that all of the PARP inhibitors had favorable subcutaneous tumor exposure, but niraparib was differentiated by superior bone marrow exposure compared with the other drugs. In a PC-3M-luc-C6 subcutaneous tumor efficacy study, niraparib, olaparib, and talazoparib inhibited tumor growth and increased survival to a similar degree. In contrast, in the PC-3M-luc-C6 bone metastasis model, niraparib showed the most potent inhibition of bone tumor growth compared with the other therapies (67% vs. 40%-45% on day 17), and the best survival improvement over vehicle control [hazard ratio (HR), 0.28 vs. HR, 0.46-0.59] and over other therapies (HR, 1.68-2.16). These results show that niraparib has superior bone marrow exposure and greater inhibition of tumor growth in bone, compared with olaparib, rucaparib, and talazoparib.

A classification based on tumor-stroma ratio and tumor budding for patients with muscle-invasive bladder cancer

Background Tumor-stroma ratio (TSR) and tumor budding (TB) play important roles in muscle-invasive bladder cancer (MIBC). We developed a rating system (TSR-TB type) based on the morphological evaluation of TSR and TB for predicting patient outcome and using individualized care. Research design and methods TSR and TB were assessed in publicly accessible MIBC tumor slides from the TCGA database. MIBC patients were classified as low stromal type or high stromal type based on TSR, and high stromal type was further classified as compartmentalized stromal type or mixed stromal type based on TB. Results TSR-TB type was an independent adverse prognostic factor for OS in MIBC (P<0.001). Low stromal type had a greater prognosis than the other subtypes (P<0.001) and were enriched for FGFR3 mutations (P=0.001), which could be susceptible to targeted therapy. The mixed stromal type was distinguished by increased M2 macrophage penetration (P<0.001), anti-tumor immune activity, DNA repair pathway mutations, and poor survival. GSEA showed that certain cancer-related pathways, such as mitotic spindle, PI3K-AKT-MTOR signaling, and the G2M checkpoint, were hyperactivated in high stromal type (all FDR<0.05). Furthermore, mixed stromal type demonstrated enhanced activation of epithelial mesenchymal transformation (EMT), inflammatory response, KRAS signaling, and angiogenesis (all FDR<0.05). Conclusion TSR and TB-based MIBC classification coincides with patient survival and molecular alterations. The identified subtypes may have important implications for individualized MIBC therapy.

GENOMICS OF PROSTATE CANCER: CLINICAL UTILITY AND CHALLENGES.

The studying of prostate cancer genomics is important for understanding prostate cancer biology, it can provide clinically relevant stratification into subtypes, the development of new prognostic and predictive markers in the context of precision medicine, and the development of new targeted therapies. Recent studies have provided detailed insight into genomics, epigenomics and proteomics of prostate cancer, both primary and metastatic castration-resistant (mCRPC). Many mutations have been discovered, both those that occur early in the carcinogenesis and progression as well as those responsible for the resistance to therapy occurring later under the influence of treatment. A large number of characteristic mutated signaling pathways has been identified, e.g. the mutations in DNA repair pathway were found in 23% of mCRPC, which suggests potential response to PARP inhibitors. Multifocality and intralesional genomic heterogeneity of prostate cancer make the clinical application of genomics complicated. Although a great progress was made in understanding prostate cancer genomic, and clinical studies related to its routine application are ongoing, prostate cancer genomics still needs to find its standard wide routine application in patients with prostate cancer.

Integration of Mutational Signature Analysis with 3D Chromatin Data Unveils Differential AID-Related Mutagenesis in Indolent Lymphomas.

Activation-induced deaminase (AID) is required for somatic hypermutation in immunoglobulin genes, but also induces off-target mutations. Follicular lymphoma (FL) and chronic lymphocytic leukemia (CLL), the most frequent types of indolent B-cell tumors, are exposed to AID activity during lymphomagenesis. We designed a workflow integrating de novo mutational signatures extraction and fitting of COSMIC (Catalogue Of Somatic Mutations In Cancer) signatures, with tridimensional chromatin conformation data (Hi-C). We applied the workflow to exome sequencing data from lymphoma samples. In 33 FL and 30 CLL samples, 42% and 34% of the contextual mutations could be traced to a known AID motif. We demonstrate that both CLL and FL share mutational processes dominated by spontaneous deamination, failures in DNA repair, and AID activity. The processes had equiproportional distribution across active and nonactive chromatin compartments in CLL. In contrast, canonical AID activity and failures in DNA repair pathways in FL were significantly higher within the active chromatin compartment. Analysis of DNA repair genes revealed a higher prevalence of base excision repair gene mutations (p = 0.02) in FL than CLL. These data indicate that AID activity drives the genetic landscapes of FL and CLL. However, the final result of AID-induced mutagenesis differs between these lymphomas depending on chromatin compartmentalization and mutations in DNA repair pathways.

Abstract PO-036: LP184, a novel alkylating agent, is highly effective in pancreatic cancers with DNA damage repair defects

Abstract Biomarker-based chemotherapy with increased efficacy and prolonged disease-free survival are urgently needed in pancreatic cancer (PDAC). A 15-20% subset of PDAC tumors carry mutations in DNA repair pathway (BRCA1/BRCA2/PALB2/RAD51/ATM/FANCD2). Additionally, mutations in nucleotide excision repair (NER) genes (ERCC2/3/4/5/6) have been reported in ~5% of PDAC. LP184 is a novel synthetic small molecule acylfulvene analog. Using precise synthetic chemistry, we determined that only a negative enantiomer of LP184 is converted to an active alkylating agent in the strict dependency on oxidoreductase, prostaglandin reductase 1 (PTGR1). By computational analyses, we demonstrate a strong positive correlation of LP184 sensitivity with PTGR1 transcript levels (r=0.89, p&amp;lt;10−15) in a broad panel of cancer cell lines. Once activated by PTGR1, highly reactive LP-184 nucleophile creates covalent DNA adducts that are selectively repaired via Nucleotide Excision Repair (NER) mechanism coupled to transcription (TC-NER) and/or homologous recombination (HR). We reasoned that mutation or expression driven TC-NER and HR deficiency would predispose PDAC cells to increased sensitivity to LP184. To test the idea of LP184 activity in DNA repair-deficient tumors, we evaluated LP184 chemosensitivity in genetically defined PDAC models in vitro, ex vivo, and in xenografts. Testing in six different pancreatic cancer cell lines (Capan-1, CFPAC-1, Panc1, MiaPaCa2, Panc03.27 and BxPC-3) resulted in very potent inhibition with LP184 IC50 values ranging from 114 to 182 nM. In this cell line panel, LP184 sensitivity correlated negatively with transcript levels of an NER pathway gene ERCC8 (r = -0.94). In comparison to these PDAC cell lines, a normal pancreatic epithelial cell line HPNE was 3-6 times less sensitive to LP184 (IC50 670 nM). Ex vivo cultures of 4 out of 5 low-passage patient-derived xenografts with HR deficiency showed nanomolar sensitivity to LP184 with IC50s ranging from 45 to 270 nM. These tumor graft models which were at least 6 times less sensitive to olaparib in the same assay. Depletion of ERCC4 enhanced sensitivity to LP184 about 2-fold relative to the parental cell line. To define PTGR1 as a biomarker for LP184 activity, we used CRISPR/Cas9-mediated gene editing to deplete PTGR1 expression. We found PTGR1-null Capan-1 cell line-derived xenografts were poorly sensitive to LP184, whereas PTGR1-expressing xenografts showed near complete tumor regression in all LP184 treated animals with 109% tumor growth inhibition relative to the control group in this study. Furthermore, PTGR1 depleted cells were completely resistant to LP184 in vitro. Our preclinical data demonstrate that PDAC models carrying a range of DNA repair pathway mutations are highly sensitive to LP-184 in vitro and in vivo. Increased PTGR1 expression is a validated biomarker for LP184 cytotoxicity, and is the exclusive convertase of LP184 to an active alkylator drug. We anticipate LP184 will extend the therapeutic opportunities to a large subset of PDAC patients carrying these genetic alterations. Citation Format: Diana Restifo, Aditya Kulkarni, Caleb Schimke, Joseph McDermott, Umesh Kathad, Kishor Bhatia, Panna Sharma, Igor Astsaturov. LP184, a novel alkylating agent, is highly effective in pancreatic cancers with DNA damage repair defects [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-036.

A phase 2, two-stage study of mirvetuximab soravtansine (IMGN853) in combination with pembrolizumab in patients with microsatellite stable (MSS) endometrial cancer (EC).

TPS5611 Background: Folate receptor-alpha (FRα) is expressed on endometrial cancer (EC) cells and is associated with poor prognosis. Mirvetuximab soravtansine (ImmunoGen), an antibody drug conjugate (ADC) comprising a FRα-binding antibody, cleavable linker, and the tubulin-disrupting maytansinoid DM4, showed tolerability and single agent activity in a Phase 1 study with dose expansion in FRα+ advanced/recurrent EC (NCT01609556) and also when combined with chemotherapy, bevacizumab as well as pembrolizumab (NCT02606305). In addition to having direct target-mediated cytotoxicity, ADCs also stimulate the local tumor immune microenvironment. Mirvetuximab soravtansine has been shown to activate monocytes and promote phagocytosis of mirvetuximab-treated FRα-positive tumor cells through a mechanism of Fc-FcγR interaction. Further, the combination of ADCs with immune checkpoint inhibitors (ICI) can overcome primary resistance to immunotherapy in murine models. Given the low response of MSS endometrial cancers to PD-1 blockade, we hypothesized that addition of mirvetuximab may enhance response of these tumors to immunotherapy. Methods: This is a Phase 2, single cohort study of mirvetuximab soravtansine with pembrolizumab in recurrent or persistent EC. Patients must have advanced or recurrent MSS serous endometrial cancer with at least 1 and up to 3 prior lines of therapy. Confirmation of FRα expression (with PS2+ staining intensity in ≥ 50% of cells, performed centrally at Ventana Medical Systems, Inc) is required. Prior receipt of ICI is excluded. Patients will receive the combination of mirvetuximab soravtansine 6 mg/kg AIBW IV and pembrolizumab 200 mg IV administered every 21 days. The co-primary endpoint is progression-free survival at 6 months (PFS6) and objective response rate (ORR) by RECIST 1.1. Translational objectives include assessment of tumor infiltrating lymphocytes (TILs), expression of immune checkpoint markers, and whole exome sequencing (WES) for DNA repair pathway mutations, neoantigens, and polymorphisms in immunologically relevant genes. Statistical considerations are for a Simon two-stage optimal design with 16 patients in Stage 1 and 19 patients in Stage 2, to a total of 35. Prespecified activity for the first stage of accrual was met, and second stage accrual began November 2020. Clinical trial information: NCT03835819.

Abstract 2338: Comparison of genomic alterations in lung cancer specimens from high and low radon zones: Search for a genomic fingerprint

Abstract Introduction: Radon-222 (Rn) is a radioactive gas found in rocks and soil. It emits alpha particles that cause dsDNA breaks and increases potential for carcinogenesis. Rn is the 2nd leading cause of lung cancer in the US after smoking, with EPA estimates of &amp;gt;15000 deaths. A significant portion of land in US has high Rn soil levels; ‘action level' for indoor Rn mitigation is &amp;gt;4pci/L. Rhode Island (RI) contains several high Rn areas. We hypothesize that specific cellular and molecular mechanisms play a role in the neoplastic potential of Rn, detectable as signature genetic profiles. Our aim is to identify molecular patterns in patients (pts) from high Rn zones, by evaluating next generation sequencing (NGS) based assays in advanced lung cancer pts. Methods: Using a commercially available NGS assay, we retrospectively analyzed genomic DNA alterations in 324 genes from FFPE specimens of 159 stage IV lung cancer pts treated at Lifespan Cancer Institute at Brown University from 2014- 2019. Based on EPA Rn maps, we identified counties in RI with high indoor Rn levels (&amp;gt;4 pci/L), and compared the gene mutation patterns with those residing in low Rn areas (&amp;lt;4 pci/L). Results: Of the 159 pts (median age= 58), 35 (22%) belonged to high Rn and 124 (78%) to low Rn zones. Both groups had predominantly adenocarcinoma histology and high smoking prevalence (75-80%). Most prevalent genomic alterations in both cohorts were TP53, KRAS and CDKN2A mutations. In the high Rn group, we identified more frequent recurrent mutations in two DNA repair genes: ATM (11% in high Rn vs 1% in low Rn areas, p=0.00086) and CHEK2 (6% vs 0%, respectively, p=0.047). We then classified all detected genomic alterations into major pathways implicated in lung carcinogenesis; DNA repair, cell cycle, tyrosine kinase, and apoptosis. The only observed statistically significant difference in the frequency of mutations was for the DNA repair pathway (29% in high Rn vs 13% in low Rn, p=0.038). Conclusion: To our knowledge, this is the first report of a novel and mechanistically unique insight into the pathobiology of Rn induced lung cancer. Our observations suggest that Rn induced dsDNA breaks may constitute an oncogenic hit in cells which are unable to efficiently repair them because of DNA repair pathway mutations (particularly ATM and CHEK2). We are further testing this “second hit” hypothesis in a larger nationwide dataset comparing NGS profiles of lung cancers from low and high Rn areas in the US. Top 10 mutated genes in High and Low Radon groups (rank; frequency, %)High RnLow RnP value1. TP53 (63)1. TP53 (70)0.422. KRAS (26)2. KRAS (28)0.833. CDKN2A (23)3. CDKN2A (24)0.994. RB1 (17)4. RB1 (20)0.815. EGFR (14)7. EGFR (10)0.546. CDKN2B (14)6. CDKN2B (15)0.997. STK11 (11)5. STK11 (19)0.338. RBM10 (11)-. RBM10 (3)0.07-. SMARCA4 (3)8. SMARCA4 (8)0.469. NF1 (11)9. NF1 (7)0.4910. ATM (11)-. ATM (1)0.008-. MYC (6)10. MYC (5)0.99 Citation Format: Hina Khan, Harish Saiganesh, Adam J. Olszewski, Christopher G. Azzoli, Howard Safran. Comparison of genomic alterations in lung cancer specimens from high and low radon zones: Search for a genomic fingerprint [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2338.

1979TiP - Randomized phase II study of trabectedin/olaparib compared to physician’s choice in subjects with previously treated advanced or recurrent solid tumors harboring dna repair deficiencies

BackgroundGenomic aberrations affecting the repair of DNA double-strand breaks by homologous recombination (HR) are found in various cancers and result in sensitivity to inhibitors of the DNA repair enzyme poly (ADP-ribose) polymerase (PARP). DNA double-strand breaks and activation of PARP can be induced by trabectedin, a cytotoxic agent used in soft-tissue sarcoma. In HR-deficient cancers that depend on PARP activity, trabectedin may thus increase the effect of PARP inhibitors such as olaparib. Next-generation sequencing techniques allow rapid identification of mutations in DNA repair pathways and mutational signatures that are generated by these aberrations. Trial designWe present a randomized phase II trial comparing a combination of trabectedin and olaparib with treatment of physician’s choice in adult patients with advanced or metastatic tumors with genomic imprints of defective HR DNA repair (“BRCAness”), as determined by whole-exome or genome sequencing. A dedicated BRCAness score incorporates germline and somatic mutations in HR-relevant genes, mutational signatures, and measures of genomic instability; scores equal or above 3 allow for inclusion. Main exclusion criteria are hematologic and primary brain cancers, progressive/symptomatic brain metastases, ECOG PS>1, severe organ insufficiencies, and prior treatment with a PARP inhibitor. Patients are randomized 1:1 to treatment with trabectedin (day 1) and olaparib (days 1-21) in a 21-day cycle vs. physician’s choice, both until disease progression. Cross-over upon disease progression is allowed. The primary endpoint is disease control (including CR, PR and SD according to RECIST v1.1) after 16 weeks. Secondary endpoints are tumor response, PFS, OS and quality of life. Efficacy evaluation involves a 2-group comparison between treatment arms in 102 patients. The statistical test used is a one-sided test of differences in disease control rates (alpha = 0.025). An interim analysis for futility will be conducted after 30% of patients are evaluable for the primary endpoint. The trial is active within the German Cancer Consortium, and thus far nine patients have been randomized. Clinical trial identificationEudraCT: 2017-001755-31; NCT03127215. Legal entity responsible for the studyHeidelberg University Hospital, Heidelberg, Germany. FundingAstraZeneca, ParmaMar and German Cancer Research Center (DKFZ). DisclosureC.E. Heilig: Honoraria (self), Travel / Accommodation / Expenses: PharmaMar; Travel / Accommodation / Expenses: Teva; Honoraria (institution), Travel / Accommodation / Expenses: Lilly; Travel / Accommodation / Expenses: Celgene; Travel / Accommodation / Expenses: Novartis. H. Kopp: Advisory / Consultancy: BMS; Advisory / Consultancy, Travel / Accommodation / Expenses: Merck-MSD; Advisory / Consultancy: Sanofi; Advisory / Consultancy, Travel / Accommodation / Expenses: Roche; Travel / Accommodation / Expenses: Novartis; Travel / Accommodation / Expenses: Boehringer-Ingelheim. K.H. Metzeler: Honoraria (self), Advisory / Consultancy, Research grant / Funding (self), Travel / Accommodation / Expenses: Celgene; Advisory / Consultancy: Novartis; Advisory / Consultancy: Jazz; Research grant / Funding (institution): Agios. S. Richter: Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: PharmaMar; Research grant / Funding (institution): AstraZeneca; Research grant / Funding (self), Travel / Accommodation / Expenses: Lilly. B. Hermes: Travel / Accommodation / Expenses: PharmaMar; Research grant / Funding (institution): MSD; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): BMS; Research grant / Funding (institution): Bayer; Research grant / Funding (institution): Roche; Research grant / Funding (institution): Lilly. N. von Bubnoff: Honoraria (self): AstraZeneca; Honoraria (self): Amgen; Honoraria (self), Advisory / Consultancy, Research grant / Funding (self): Novartis; Honoraria (self): BMS. T. Kindler: Advisory / Consultancy: Novartis; Travel / Accommodation / Expenses: PharmaMar. J. Siveke: Advisory / Consultancy: Baxalta; Advisory / Consultancy, Research grant / Funding (self), Travel / Accommodation / Expenses: Celgene; Advisory / Consultancy, Travel / Accommodation / Expenses: Shire; Advisory / Consultancy, Travel / Accommodation / Expenses: Roche; Research grant / Funding (self), Travel / Accommodation / Expenses: BMS. S. Wagner: Advisory / Consultancy: Takeda. S. Ochsenreither: Honoraria (self), Advisory / Consultancy: MSD; Honoraria (self), Advisory / Consultancy: Merck; Honoraria (self), Advisory / Consultancy: Ipsen; Honoraria (self), Advisory / Consultancy: BMS; Advisory / Consultancy: AstraZeneca. B. Brors: Research grant / Funding (institution): SAP. D. Jäger: Advisory / Consultancy: Amgen; Advisory / Consultancy: Bayer; Advisory / Consultancy: CureVac; Advisory / Consultancy: Definiens; Advisory / Consultancy: Roche; Advisory / Consultancy: BMS. C. Von Kalle: Advisory / Consultancy: Roche; Advisory / Consultancy: Genentech; Advisory / Consultancy: Novartis; Advisory / Consultancy: Pfizer; Shareholder / Stockholder / Stock options: Genewerk. H. Glimm: Honoraria (self), Research grant / Funding (self): Bayer. S. Fröhling: Honoraria (self), Travel / Accommodation / Expenses: Amgen; Honoraria (self), Travel / Accommodation / Expenses: PharmaMar; Honoraria (self), Travel / Accommodation / Expenses: Lilly; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: Roche; Advisory / Consultancy: Bayer. R.F. Schlenk: Speaker Bureau / Expert testimony: Pfizer; Speaker Bureau / Expert testimony: Novartis; Research grant / Funding (institution): Pfizer; Speaker Bureau / Expert testimony, Research grant / Funding (institution), Travel / Accommodation / Expenses: Daiichi Synkyo. All other authors have declared no conflicts of interest.

P1.14-47 ctDNA NGS for Guiding Crizotinib Treatment in ALK-Rearranged Advanced NSCLC Patients (Pts)

FISH and IHC are commonly used and the golden standard for testing ALK rearrangement. However, they provide no information on fusion types or mutation status of other genes, which could be important prognostic factors. In addition, a tissue biopsy is not always applicable/preferred by pts. 43 ALK-rearranged treatment naïve advanced NSCLC pts were included. ALK-rearrangement was confirmed by ctDNA NGS with a panel of 59 tumor-related genes in 25 pts (ctDNA arm) and by IHC/FISH/tissue NGS in 18 pts (control arm). All pts received crizotinib as first-line therapy. PFS was estimated using Kaplan-Meier method and compared using log-rank test. On average, Pts in ctDNA arm were significantly older at diagnosis than pts in the control arm (56 vs. 45, p = 0.02), indicating the preferability of ctDNA NGS in elderly pts. Though older, pts in ctDNA arm had a similar mPFS with pts in the control arm (8 vs. 10 mo, p = 0.9). ALK fusion types in ctDNA arm and their associated statistics were listed in Table 1. Concomitant mutations were identified in 15 genes in 9 pathways. Frequently mutated pathways include p53 (in 8 pts) and DNA repair pathways (in 3 pts). Mutations in DNA repair pathway (5 vs. 10 mo, p = 0.06), high frequency of EML4-ALK (≥1.5%) (6 mo vs. NR, p = 0.06), and bone metastasis (6 vs. NR, p = 0.05) were associated with shorter mPFS.Table 1ALK fusion types and associated statisticssALK fusion types# of pts(Median) age at diagnosis (year)(m)PFS (mo)Average # of mutations per ptV11152101.5V3106162.8V2160-1V5'165-1V714932DCTN1-ALK147-2 Open table in a new tab Information on ALK fusion types, concomitant mutations, and mutation frequencies provided by NGS could be valuable prognostic factors and deserves further investigation. ctDNA NGS could be used as an effective alternative to identify ALK+ pts, especially for elderly pts, when tissue biopsy is inapplicable or not preferred.

Germline BRCA1/2 Mutation Status Is Not Associated with Differential Radiation Responsiveness in Patients with Locally Advanced Breast Cancer

Women with germline mutations in DNA repair pathways are at an increased risk of developing breast cancer. We posit that tumors arising in these patients may also be more sensitive to radiotherapy and, therefore, patients may experience improved locoregional relapse-free survival (LRRFS) and overall survival (OS) following adjuvant radiotherapy as compared to patients without DNA repair pathway mutations. Thus, we aimed to assess radiation responsiveness in a cohort of patients with locally advanced, stage III breast cancer who have undergone genetic testing. We evaluated the records of 754 women with stage III de novo primary breast cancer treated with surgery and adjuvant radiotherapy who all underwent genetic testing at our institution from 1993 to 2018. Mutations were categorized as pathogenic variant, variant of unknown significance (VUS), or negative. The Kaplan-Meier method was used to estimate the LRRFS and OS from the time of surgery. The median age at diagnosis was 43 years (range, 19-81). Median follow-up time was 5.0 years (interquartile range, 2.6-8.1 years). All patients were treated with adjuvant breast/chest wall and regional lymph node irradiation with photon/electron radiotherapy. A total of 108 (14.3%) of patients with stage III breast cancer had a pathogenic variant mutation in BRCA1/2 or a VUS; 646 (85.6%) had germline mutation testing that was negative for a BRCA1/2 mutation. There was no statistically significant difference in 10-year LRRFS (93% in both cohorts; p>0.99) or 10-year OS (78% for BRCA1/2 pathogenic variant or VUS vs. 76% for BRCA1/2 mutation-negative; p=0.61). Perturbations in ATM, CHEK2, MLH, MSH2/6, MUTYH, PALB2, RAD50/51, and/or TP53 and outcomes will also be evaluated in this single-institution cohort. Herein we report on the largest cohort of women with locally advanced breast cancer treated with adjuvant radiotherapy at a single institution who have undergone germline BRCA1/2 testing. Our findings suggest that responses to adjuvant radiotherapy in women with germline BRCA1/2 mutations is similar to patients with sporadic breast cancer. Further investigation regarding differential radiation responsiveness based on somatic BRCA1/2 testing may be warranted in given strong preclinical data demonstrating increased radioresponsiveness in cancers with deficiencies in homologous recombination repair.

An Analysis of Patients with DNA Repair Pathway Mutations Treated with a PARP Inhibitor.

Molecular analysis has revealed four subtypes of pancreatic ductal adenocarcinoma (PDAC). One subtype identified for the presence of DNA damage repair deficiency can be targeted therapeutically with the poly (ADP-ribose) polymerase (PARP) inhibitor olaparib. We performed a single institution retrospective analysis of treatment response in patients with PDAC treated with olaparib who have DNA damage repair deficiency mutations. Patients with germline or somatic mutations involving the DNA repair pathway were identified and treated with olaparib. The primary objective was to examine the objective response rate (ORR). The secondary objectives were assessing tolerability, overall survival, and change in cancer antigen 19-9. Quantitative texture analysis (QTA) was evaluated from CT scans to explore imaging biomarkers. Thirteen individuals with metastatic PDAC were treated with Olaparib. The ORR to Olaparib was 23%. Median overall survival (OS) was 16.47 months. Four of seven patients with BRCA mutations had an effect on RAD51 binding, with a median OS of 24.60 months. Exploratory analysis of index lesions using QTA revealed correlations between lesion texture and OS (hepatic lesion tumor texture correlation coefficient [CC], 0.683, p = .042) and time on olaparib (primary pancreatic lesion tumor texture CC, 0.778, p = .023). In individuals with metastatic PDAC who have mutations involved in DNA repair, Olaparib may provide clinical benefit. BRCA mutations affecting RAD51 binding domains translated to improved median OS. QTA of individual tumors may allow for additional information that predicts outcomes to treatment with PARP inhibitors. Pursuing germline and somatic DNA sequencing in individuals with pancreatic ductal adenocarcinoma may yield abnormalities in DNA repair pathways. These individuals may receive benefit with poly (ADP-ribose) polymerase (PARP) inhibition. Radiomics and deep sequencing analysis may yet uncover additional information that may predict outcome to treatment with PARP inhibitors.

Homologous recombination and DNA repair mutations in patients treated with carboplatin and nab-paclitaxel for metastatic non-small cell lung cancer

ObjectivesChemotherapy remains a cornerstone treatment in non-small cell lung cancer either in combination with checkpoint inhibitors or as subsequent therapy. Identifying molecular predictors of response allows for optimal treatment selection. We performed genomic analysis on tumor samples of patients treated with carboplatin and nab-paclitaxel as part of a phase II trial to evaluate the prognostic and predictive value of mutations in DNA repair pathway in patients treated with this regimen. Materials and methodsNext-generation sequencing libraries were produced using a capture-based targeted panel covering the coding exons of 278 genes on patients treated on clinical trial NCT00729612. Overall survival (OS) and progression-free survival (PFS) were assessed as part of the clinical outcomes and correlated with mutation analysis. ResultsOf 63 patients enrolled, 25 patients had sufficient and acceptable DNA isolated from archival tumor samples for targeted sequencing. The most commonly altered pathways included DNA repair (DR) including Fanconi anemia and homologous recombination, JAK-STAT signaling, IGF-1, mTOR, and MAPK-ERK. Four patients with mutations in homologous recombination mutations had a shorter PFS (hazard ratio [HR] = 4.54, 95% CI 1.2, 17.1, p = 0.026) and OS (HR = 6.3, 95% CI 1.8, 21.3, p = 0.003). ConclusionIn this analysis of patients with predominantly squamous cell non-small cell lung cancer treated with carboplatin and nab-paclitaxel in a phase II trial, patients with mutations in homologous recombination pathways had shorter overall and progression-free survival. Validation on additional datasets of patients treated with platinum-based chemotherapy and immunotherapy combinations is warranted.

Outcomes after adjuvant radiotherapy in breast cancer patients with and without germline mutations: A large, single-institutional experience.

1502 Background: Women with germline mutations in DNA repair pathways are at an increased risk of developing breast cancer. We posit that tumors arising in these patients may be more sensitive to radiotherapy and, therefore, patients may experience improved locoregional control and survival outcomes following adjuvant radiotherapy as compared to patients without DNA repair pathway mutations. Methods: We evaluated the records of 2,221 women with stage 0-III de novo primary breast cancer treated with surgery and adjuvant radiotherapy who all underwent genetic testing at our institution from 1993 to 2018. Mutations were categorized as pathogenic variant, variant of unknown significance (VUS), or negative. The Kaplan-Meier method was used to estimate the locoregional recurrence rate (LRR), rate of distant metastasis (DM), disease-free survival (DSS), and overall survival (OS) from the time of surgery. Results: The median age at diagnosis was 45 years (range 19-84). Median follow-up time was 7 years (95% confidence interval 6.6-7.4). Among 1,960 patients with evaluable radiation records, 752 (38.4%) received breast only radiation, 12 (0.6%) received chest wall only radiation, and 1,196 (61.0%) received breast/chest wall and regional nodal radiation. A total of 255 (11.4%) and 162 (7.3%) patients had a pathogenic variant mutation and a VUS only, respectively. Pathogenic variant and VUS in BRCA1/2 mutations were detected in 216 (9.7%) and 82 (3.7%) patients, respectively. Perturbations in ATM, CHEK2, MLH, MSH2/6, MUTYH, PALB2, RAD50/51, and/or TP53 were detected in 71% (85/119) of patients who tested positive for a non- BRCA1/2 pathogenic variant or VUS. On univariate analysis, there was no significant association between BRCA1/2 mutation status or any genetic mutation and rate of LRR or DM, DSS, or OS ( p &gt; 0.10 for all). Clinicopathological features including advanced stage and lymphovascular invasion were associated with higher cumulative incidence of LRR and DM as well as shorter DFS and OS ( p &lt; 0.01 for all). Conclusions: Herein we report on the largest cohort of women with breast cancer treated with adjuvant radiotherapy at a single institution who have undergone germline testing. Our findings suggest that the overall prognosis of breast cancer treated with adjuvant radiotherapy in patients with germline BRCA1/2 or other genetic predisposition is similar to patients with sporadic breast cancer. Further investigation to evaluate acute or late toxicities and secondary cancers as a result of radiotherapy is warranted.

DNA repair pathway alterations and correlation with immunotherapy response.

e14150 Background: Over the past decade, a better understanding of cancer biology has led to a revolution in immunotherapy. Checkpoint inhibitors (ICI), bispecific antibodies and agonistic agents have shown benefit in cancer treatment. Unfortunately, not all patients benefit and, despite the advances achieved in discovering markers of response, the selection of patients can still be challenging in everyday practice. Methods: We conducted a retrospective analysis of potential prognostic and predictive factors of survival in a cohort of 186 patients enrolled into Phase I Trials testing immunotherapeutic agents at our institution. We computed univariate and multivariate analysis (MVA) of demographics, clinical and molecular characteristics to assess their prognostic and predictive potential of clinical benefit (defined as achieving Complete or Partial Response (CR/PR) as best response or disease stabilization lasting &gt; 120 days) and survival. Molecular testing included Next Generation Sequencing (NGS - Oncomine Comprehensive Assay) grouped in DNA repair, Transcription regulation, Signal Transduction and Cell-Cell interaction pathways. Results: A total of 186 patients (Male/Female: 81/105; median age 61yo) received treatment with either immune checkpoint inhibitors (122 (65,6%)), checkpoint agonists (37 (19.9%)); bispecific antibodies (19 (10.21%) or other immunotherapies (8 (4.29%)) between November 2015 and July 2018. Royal Marsden Score (RMH) was assessed and correlated with progression free survival and overall survival in the total cohort. Median Overall Survival (mOS) was 422 days (CI95%: 345-500 days), 387 (CI95%: 297-478 days), 235 (CI95%: 131-338 days), and 167 (CI95% 64-270 days) for RMH 0, 1, 2 and 3, respectively (p = 0.007). Among 57 patients with NGS results, those with pathogenic mutations in DNA repair pathways (n = 26) showed a trend towards a higher response rate (69% vs 30% p = 0.064) and clinical benefit (65% vs 35%; p = 0.034). Conclusions: Alterations in DNA repair pathways are a potential predictor of benefit of immunotherapy and warrants further studies. A larger cohort of patients is currently being explored in our center to further validate these findings.