Search

Introduction: In the setting of metastatic pancreatic adenocarcinoma (mPDAC), lower baseline plasma KRAS mutation levels have been associated with improved survival. While tissue-agnostic, plasma-based copy number instability (CNI) has been demonstrated as an early indicator of response to immunotherapy for some solid tumors, it has not been assessed for patients with mPDAC, nor in combination with KRAS mutations for patients receiving standard of care chemo/radiotherapy. Here we evaluate the combination of mutant KRAS (mKRAS) and CNI detection in plasma as a predictor of overall and progression-free survival (OS/PFS) in mPDAC patients who received standard of care therapy. Methods: Cell-free DNA was extracted from plasma and libraries prepared at baseline (Week 0) and weeks 8, 16 and 24 on therapy, and analyzed by next-generation sequencing (CNI) and droplet digital PCR (mKRAS). Descriptive statistics were computed for variables including CNI (score is a measure of circulating tumor DNA) and mKRAS variant allele fraction. Detection was defined as above the limit of detection (mKRAS=0.13%) and above the 95th percentile of the value in normal individuals (CNI=24). Therapy response was assessed by OS and PFS. Results: 196 plasma samples from 64 mPDAC patients were analyzed. When dichotomized as detectable vs undetectable, CNI alone was significantly associated with OS at all on-therapy timepoints but not baseline, whereas mKRAS was significantly associated with OS for all 4 timepoints (Table 1). Detection of both CNI and mKRAS in combination was strongly associated with worse OS at all timepoints, yielding the highest HR. Similar results were obtained when mKRAS and CNI were dichotomized at their respective median values or with PFS as the clinical endpoint. Conclusions: Combined CNI and mKRAS detection at baseline and on-therapy may provide a strong and early indication of worse prognosis for patients with mPDAC. Table 1. Association of CNI and mKRAS with Overall Survival (HazardRatio [95% CI], log-rank p-value) Timepoint CNI mKRAS CNI and KRAS Baseline/Week 0 1.54 [0.89-2.68], 0.1 2.05 [1.12-3.78], 0.02 2.50 [1.46-4.28], 0.0006 Week 8 1.78 [0.99-3.18], 0.05 2.21 [1.19-4.08], 0.01 9.81 [3.40-28.28], Citation Format: Samuele Cannas, Jacob E. Till, Kristine Kim, Michael J. LaRiviere, Charles M. Vollmer, Jennifer R. Eads, Thomas B. Karasic, Peter J. O'Dwyer, Charles J. Schneider, Ursina R. Teitelbaum, Kim A. Reiss Binder, Mark H. O'Hara, Douglas T. Ross, Kim McGregor, Kirsten Bornemann-Kolatzki, Ekkehard Schütz, Julia Beck, Erica L. Carpenter. Liquid biopsy signature combining copy number instability and mutant KRAS detection is associated with survival for patients with metastatic pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1043.

Immune checkpoint inhibitors have limited clinical activity in pancreatic cancer. Based on preclinical data, we hypothesized that hypofractionated radiation may cooperate with dual checkpoint inhibition in patients (Rech AJ, et al, Cancer Research, 2018). We therefore designed a phase 1 study to evaluate the safety and feasibility of two schedules of hypofractionated radiation with durvalumab (anti-PDL1) and tremelimumab (anti-CTLA-4) in patients with metastatic pancreatic, lung, and breast cancers and melanoma. Here, we present the data for pancreatic adenocarcinoma. Methods: Patients with metastatic pancreatic cancer treated with at least one prior line of therapy with measurable disease by RECIST in addition to an index lesion amenable to hypofractionated radiation were enrolled sequentially to two cohorts – cohort A evaluating 3 fractions of 8 Gy or cohort B evaluating 1 fraction of 17 Gy. Patients received 4 cycles of tremelimumab 1 mg/kg IV and durvalumab 20 mg/kg IV every 4 weeks for 4 doses followed by durvalumab 10 mg/kg IV every 2 weeks until progression. Radiation was given in week 2 of treatment. Patients were replaced if they did not receive week 5 of therapy on trial, but were included in safety/feasibility analysis. Blood and, when feasible, baseline and on-treatment biopsies were obtained for exploratory biomarker evaluation. Results: 10 patients were treated in cohort A and 21 patients in cohort B. All patients were included in the safety and feasibility assessment. Overall, treatment was well tolerated in both cohorts. The most common adverse events were grade 1 or 2 fatigue (A 30%, B 23.8%), diarrhea (A 10%, B 14.3%), pruritis (A 10%, B 14.3%), AST/ALT elevation and constipation (each A 10%, B 9.5%). Grade 3 diarrhea, elevated bilirubin, pneumonitis, and syncope were noted in 1 patient each, all in cohort B. Grade 5 pneumothorax occurred after baseline biopsy in 1 patient. Grade 2 hyperthyroidism (A) and pneumonitis (B) were noted each in 1 patient. 8 patients in cohort A and 13 patients in cohort B were evaluable for response. In cohort A, 50% of patients had stable disease as best response, and median overall survival was 4.9 months. In cohort B, 23.1% had PR and 30.8% had SD as best response and mOS was 5.2 months. Responses occurred more frequently when metastatic lung nodules were radiated – SD in 3/5 (60%) patients in cohort A, PR in 3/10 (30%) and SD in 4/10 (40%) patients in cohort B, compared to SD in 1/3 (33%) patients in cohort A and 0/3 (0%) patients in cohort B who underwent radiation to a liver lesion. Biomarker analysis will be presented. Conclusions: The combination of durvalumab, tremelimumab with hypofractionated radiation is safe and feasible in a refractory pancreatic adenocarcinoma patient population. Encouraging clinical activity warrants further evaluation, especially when hypofractionated radiation is delivered to lung nodules. Citation Format: Mark H. O'Hara, Adham S. Bear, Max M. Wattenberg, Ursina R. Teitelbaum, Kim A. Reiss, Thomas B. Karasic, Charles J. Schneider, Peter J. O'Dwyer, Edgar H. Ben-Josef, Andrzej P. Wojcieszynski, Amit H. Maity, Rosemarie H. Mick, Robert H. Vonderheide. Phase 1 study of hypofractionated radiation in combination with tremelimumab and durvalumab in refractory metastatic pancreatic adenocarcinoma [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 A016.

Up to 85% of patients with resectable pancreatic ductal adenocarcinoma (PDAC) experience metastatic relapse after curative intent surgery with many recurring early. Detection of such occult metastases (those thought to be below the level of detection of standard of care imaging at the time of resection) could steer patients to a different treatment course rather than delaying systemic therapy until after recovery from inappropriate surgery. Here we investigate the potential of pancreas-specific circulating cell-free DNA (cfDNA) as a biomarker for the detection of occult metastatic disease and as a prognostic biomarker. Blood specimens were collected from 53 patients (15 negative control healthy subjects, 11 positive control metastatic PDAC patients, and 27 resectable PDAC patients prior to resection), processed to plasma, and banked. Plasma cfDNA was extracted, quantified, treated with bisulfite, and used as template for PCR amplification of 9 marker loci that are uniquely unmethylated in DNA of pancreatic acinar or duct cells. Following deep sequencing of PCR products, the fraction of cfDNA molecules derived from the pancreas was determined and multiplied by the total cfDNA concentration to yield pancreas-specific cfDNA. Recurrence and survival data were abstracted from the medical record and receiver operator curve analysis was utilized to determine statistical significance. Metastases were categorized as overt (present at diagnosis), occult (discovered during or within 4 months of curative intent surgery), or two-year (discovered during or within two years of curative intent surgery). Pancreas-derived cfDNA was significant for the detection of occult or overt metastases in our full cohort (18 of 52 evaluable subjects) with an area under the curve (AUC) of 0.86 (95% Confidence Interval, 0.74-0.80) and 0.91 (0.83-1.00) for liver-specific occult or overt metastases (15 of 52). It was borderline significant for the detection of occult metastases in the resectable sub-cohort (7 of 27) with an AUC of 0.71 (0.47-0.96) but significant for the detection of occult liver-specific metastases (5 of 27) with an AUC of 0.79 (0.62-0.96). Further, detection of overt metastases or two-year metastases (28 of 50) was significant with an AUC of 0.85 (0.74-0.96). In the resectable sub-cohort, it was also significant for the detection of two-year metastases (17 of 25) with an AUC of 0.79 (0.60-0.97) and prognostic for 2-year overall survival (12 of 24) with an AUC of 0.81 (0.62-1.00) in the resectable sub-cohort. Liver-derived cfDNA was also analyzed and was always outperformed by pancreas-specific cfDNA. In this pilot cohort, enumeration of pancreas-specific cfDNA shows promise as biomarker of occult metastatic disease, two-year metastatic progression, and two-year overall survival in resectable PDAC. Further investigation of a larger cohort and potential combination with other known markers like CA19-9 and tumor size is underway; results for an additional ~40 patients will be available by the time of the meeting. Citation Format: Jacob E. Till, Roni Ben-Ami, Ruth Shemer, Kristine Kim, Aseel Abdalla, Samuele Cannas, Charles M. Vollmer, Mark H. O'Hara, Ben Z. Stanger, Yuval Dor, Erica L. Carpenter. Pancreas-specific circulating cell-free DNA for detection of occult metastases and prognosis in resectable pancreatic ductal adenocarcinoma [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 A030.

Chimeric antigen receptor (CAR) T cell immunotherapy is FDA approved for the treatment of a subset of B cell malignancies but has shown limited clinical success in solid tumor therapy. T cell exhaustion is an important factor involved in treatment failure, and can, in part, result from continuous stimulation of the CAR by tumor cells expressing the cognate antigen. To gain deeper understanding of CAR T cell exhaustion induced by chronic antigen exposure (CAE), we developed and validated a robust in vitro model, in which mesothelin-redirected CAR T cells (M5CAR) were continuously stimulated with mesothelin-expressing AsPC-1 pancreatic tumor cells such that tumor cells were never cleared, and we characterized these CAE CAR T cells by gene expression at population and single-cell levels, and by epigenetic analyses. CAE M5CAR T cells recapitulate the hallmarks of T cell exhaustion, including reduced proliferation, down-modulation of surface CAR, decreased cytokine production, and reduced cytotoxicity. In addition, CAR T cells undergoing CAE have a transcriptional signature and an epigenetic landscape consistent with exhaustion. Further, transcriptomic analysis revealed that CAE M5CAR T cells undergo a transition from T cells to a post-thymic NK-like T cell phenotype. This plasticity was confirmed by TCR lineage tracing and was also detected in CD19 CAR T cells analyzed from post-infusion blood from DLBCL patients and in M5CAR T cells infiltrating relapsed tumors derived from a xenograft NSG/AsPC-1 mouse model. The dysfunctional signature and the NK phenotype were further detected in vivo by transcriptomic analysis in Ly95 TCR-specific TILs infiltrating NY-ESO-1 tumors. Among the genes included in the dysfunctional signature, the transcription factors SOX4 and ID3 were identified as potential regulators of dysfunction by differential gene expression and pathway analyses. To determine their role in the establishment of a dysfunctional phenotype, we generated ID3KO.M5 and SOX4KO.M5 CAR T cells using CRISPR technology in primary human lymphocytes. The cytotoxic potential of the M5 CAR T cell product generated was not modified by the genetic disruption of the transcription factors. However, when CAR T cells were challenged with chronic antigen stimulation, KO CAR T cells showed a significant reduction of the dysfunctional signature and the NK-like T cell gene expression. Importantly, CAE KO CAR T cells exhibit improved cytotoxicity as compared to Mock.M5CAR T cells. In summary, we have developed a robust in vitro model that recapitulates the hallmarks of T cell exhaustion and that facilitated the identification of a gene signature defining CAR dysregulation, a T-to-NK-like-T cell transition as a novel feature of CAR T cell dysfunction and the transcription factors SOX4 and ID3 as key regulators of CAR T cell exhaustion. Citation Format: M. Angela Aznar, Charly R. Good, Shunichiro Kuramitsu, Parisa Samareh, Sangya Agarwal, Greg Donahue, Kenichi Ishiyama, Nils Wellhausen, Austin K. Rennels, Yujie Ma, Lifeng Tian, Sonia Guedan, Katherine A. Alexander, Zhen Zhang, Philipp C. Rommel, Nathan Singh, Karl M. Glastad, Max W. Richardson, Keisuke Watanabe, Janos L. Tanyi, Mark H. O’Hara, Marco Ruella, Simon F. Lacey, Edmund K. Moon, Stephen J. Schuster, Steven M. Albelda, Lewis L. Lanier, Regina M. Young, Shelley L. Berger, Carl H. June. Mechanisms of CAR T cell dysfunction and identification of transcription factors that drive the exhaustion phenotype [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3602.

Activating missense mutations within RAS oncogenes are among the most prevalent genomic alterations observed in human cancers and drive oncogenesis in the three most lethal tumor types. Emerging evidence suggests mutant KRAS (mKRAS) may be targeted immunologically, but mKRAS epitopes remain poorly defined. Here, we employ multi-omic approaches to characterize optimal HLA class I-restricted mKRAS epitopes. Using in silico epitope prediction, we identify candidate mKRAS G12 epitopes with high predicted binding affinity to prevalent HLA class I alleles. We utilize biochemical approaches to identify mKRAS epitopes with high measured binding affinity and stability to HLA-A*03:01, -A*11:01 and -B*07:02. Furthermore, we provide proteomic validation of epitope processing and presentation by these alleles. We report mKRAS G12V and G12R epitopes are immunogenic as evidenced by the isolation of mKRAS G12V- and G12R-specific TCRαβ from healthy donors. The transfer of mKRAS-TCRs to primary CD8+ T cells serves as sensitive probes to validate mKRAS epitope processing and presentation by tumor cells and confers cytotoxicity against mKRAS human tumor cell lines of various histologies. The kinetics of lytic activity correlate with measured TCR avidity and mKRAS/HLA class I complex abundance expressed on the tumor cell surface. Finally, the adoptive transfer of mKRAS-TCR engineered primary CD8+ T cells to NOD scid gamma mice leads to tumor eradication in an orthotopic mKRAS lung cancer model. This study validates mKRAS as a bona fide tumor neoantigen and supports strategies to identify recurrent driver alterations for immunological targeting. Based on this work, clinical studies targeting mKRAS in cancer patients using vaccines and adoptive T cell therapy are under active investigation. Citation Format: Adham S. Bear, Tatiana Blanchard, Mark H. O'Hara, John Scholler, Robert H. Vonderheide, Gerald P. Linette, Beatriz M. Carreno. Biochemical and functional characterization of mutant KRAS epitopes validates this oncoprotein for immunological targeting [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1899.

Deploying CD40 activation to stimulate T cell responses upstream of immune checkpoint molecules is a novel clinical opportunity for cancer immunotherapy. Despite numerous active clinical trials with agonistic CD40 monoclonal antibodies (mAb), biological treatment effects especially treatment-related modulation of the tumor microenvironment (TME), remain poorly understood. Here, we performed a neoadjuvant clinical trial of agonistic CD40 mAb (selicrelumab) administered intravenously with or without chemotherapy (gemcitabine and nab-paclitaxel) to 16 resectable patients with pancreatic ductal adenocarcinoma (PDAC) prior to surgery followed by adjuvant chemotherapy and CD40 mAb. The toxicity profile was acceptable, including only grade 1 or 2 cytokine release syndrome and expected toxicities from chemotherapy. Disease-free survival was 13.8 months (95% CI 2.9 - 24.8 months) and median overall survival was 23.4 months (95% CI 18.0 - 28.8), with 8 patients alive at a median of 20.0 months after surgery (follow-up range 12.2 to 34.8 months). Neoadjuvant selicrelumab induced major pharmacodynamic differences in the TME, as revealed by a multiplex imaging platform auditing the immune ecosystem, compared to resection specimens from PDAC patient previously untreated or given neoadjuvant chemotherapy/chemoradiotherapy only. For tumors resected after selicrelumab, 82% (9/11) were T-cell enriched, compared to 37% (38/104) (p=0.004) of untreated tumors and 23% (93/13) of chemotherapy/chemoradiation-treated tumors (p=0.012). Moreover, for selicrelumab tumors, tumor-associated fibrosis was less, “M2” macrophages were fewer, dendritic cells were more mature, and T cells were activated and proliferative, compared to the non-selicrelumab groups. In the periphery, CD8+ and CD4+ T cells were more activated and proliferative, and serum inflammatory cytokines CXCL10 and CCL22 increased after treatment. This study provides proof-of-concept in patients that agonistic CD40 mAb alters the TME, enhances T-cell infiltration, and modulates systemic inflammatory responses. These findings inform design of next-generation CD40 clinical trials. Citation Format: Katelyn T. Byrne, Courtney B. Betts, Rosemarie Mick, Shamilene Sivagnanam, David L. Bajor, Daniel A. Laheru, E. Gabriela Chiorean, Mark H. O'Hara, Shannon M. Liudahl, Craig Newcomb, Cécile Alanio, Ana P. Ferreira, Byung S. Park, Takuya Ohtani, Austin P. Huffman, Sara A. Väyrynen, Andressa Dias Costa, Judith C. Kaiser, Andreanne M. Lacroix, Colleen Redlinger, Martin Stern, Jonathan A. Nowak, E. John Wherry, Martin A. Cheever, Brian M. Wolpin, Emma E. Furth, Elizabeth M. Jaffee, Lisa M. Coussens, Robert H. Vonderheide. T cell inflammation in the tumor microenvironment after agonist CD40 antibody: Clinical and translational results of a neoadjuvant clinical trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT005.

Chimeric antigen receptor (CAR) T cell therapy has achieved remarkable success in hematological malignancies but remains largely ineffective in solid tumors. A major factor leading to the reduced efficacy of CAR T cell therapy is T cell dysfunction, and the mechanisms mediating this dysfunction are under investigation. Here we establish a robust model to study dysfunction of mesothelin-redirected CAR T cells in pancreatic cancer. Continuous antigen exposure results in hallmark features of exhaustion including reduced proliferation capacity and cytotoxicity, and severe defects in cytokine production. Here we identified a transcriptional signature at both population and single-cell levels in CAR T cells after continuous antigen exposure. In addition, TCR lineage tracing revealed a CD8+ T-to-NK-like T cell plasticity that results in reduced tumor cell killing. The transcription factors SOX4 and ID3 are specifically expressed in the dysfunctional CAR NK-like T cells and are predicted to be master regulators of the dysfunction gene expression signature and the post-thymic acquisition of an NK-like T cell fate. Finally, we identified the emergence of NK-like CAR T cells in a subset of patients after infusion of CAR T cells. The findings gleaned from this study shed light on the plasticity of human CAR T cells and suggest new approaches to improve the efficacy of CAR T cell therapy in solid tumors by preventing or revitalizing CAR T cell dysfunction. Citation Format: Charly R. Good, Shunichiro Kuramitsu, Parisa Samareh, Greg Donahue, Kenichi Ishiyama, Yujie Ma, Nils Wellhausen, Lifeng Tian, Sangya Agarwal, Sonia Guedan, M. Angela Aznar, Katherine A. Alexander, Zhen Zhang, Nathan Singh, Max W. Richardson, Keisuke Watanabe, Janos L. Tanyi, Mark H. O'Hara, Marco Ruella, Simon F. Lacey, Edmund K. Moon, Stephen J. Schuster, Steven M. Albelda, Lewis L. Lanier, Regina M. Young, Shelley L. Berger, Carl H. June. Induction of T cell dysfunction and NK-like T cell differentiation in vitro and in patients after CAR T cell treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 60.

Pathologic somatic gene mutations within the KRAS proto-oncogene occur in greater than 90% of pancreatic ductal adenocarcinomas (PDA). These mutations are often conserved involving the codon 12 position and most frequently result in G12D, G12V, or G12R transitions. Unfortunately, no mutant KRAS (mKRAS)-targeted therapies exist to date. We hypothesize conserved hot-spot KRAS mutations may serve as cancer neoantigens for targeted immune-based therapeutic approaches. Using a validated in silico epitope prediction pipeline, we identified mKRAS epitopes with predicted strong binding affinity to the highly prevalent MHC class I alleles HLA-A*03:01, HLA-A*11:01, and HLA-B*07:02. We then confirmed the processing, presentation, and binding of putative mKRAS epitopes using HPLC-tandem mass spectrometry and competitive peptide-binding assays. The immunogenicity of bona fide mKRAS epitopes was confirmed by the in vitro generation of mKRAS-specific CD8+ T cell responses using healthy donor blood samples that were restricted to HLA-A*03:01, -A*11:01, or -B*07:02 as determined by cytokine release assay and peptide/MHC multimer staining. Following T-cell receptor (TCR) sequencing, transgenic expression of mKRAS-specific TCRs on primary CD8+ T cells conferred cytotoxic potential against KRAS-mutated tumor cell lines expressing target HLA/mKRAS combinations. Importantly, mKRAS-specific CD8+ T cells did not cross-react with wild-type or alternatively mutated KRAS epitopes as measured by cytokine release or cytotoxicity assays. Based on these data, we initiated an adjuvant vaccine clinical study at the University of Pennsylvania Abramson Cancer Center targeting mKRAS in patients with resected PDA. The objective of this clinical study is to identify further mKRAS-specific TCR sequences for future adoptive T-cell therapy applications. To date, a total of 7 subjects have been enrolled, and 3 subjects have been vaccinated against targeted mKRAS short peptides utilizing a dendritic cell-based platform. Results from the first vaccinated subject have demonstrated the generation of a KRAS G12V-specific CD8+ T-cell response restricted to HLA-A*11:01 following vaccination with >10% mKRAS-specific T cells isolated following primary in vitro expansion of CD8+ T cells using antigen-pulsed dendritic cells as measured by peptide/MHC multimer staining. TCR sequencing has been completed and functional studies to validate antigen specificity and tumor cytotoxicity are in process. The results of these studies will serve to develop a widely applicable T-cell therapy for PDA patients, and will have implications for the large number of patients with other KRAS-mutated cancers. Citation Format: Adham S. Bear, Andrew J. Rech, Lee P. Richman, Mark H. O'Hara, Gerald P. Linette, Beatriz M. Carreno, Robert H. Vonderheide. Identification of T-cell receptors targeting mutant KRAS in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr B04.

CDX-1140 is an agonist CD40 mAb intended to promote priming of CD8+ effector T cells through activation of dendritic cells (DC), enhance macrophage tumoricidal activity, and mediate direct killing of CD40-expressing tumor cells. CDX-1140 is a human IgG2 mAb with Fc receptor independent activity and is synergistic with sCD40L, suggesting a potential to enhance CD40L-mediated immune activation. CDX-1140 has a broad dose-dependent activity that may achieve maximal agonist activity at doses that provide significant tumor penetration with minimal toxicities from systemic CD40 activation. CDX-301 (rhFLT3L) is a DC growth factor that markedly increases CD141+ DCs, including in the tumor microenvironment (TME). CD141+ DCs are critical for initiating anti-tumor immune responses and are often depleted within the TME. Preclinical studies have shown that treatment with CDX-301 synergizes with CD40 signaling to enhance anti-tumor immune responses, suggesting that combining CDX-1140 and CDX-301 could result in enhanced clinical benefit. CDX1140-01(NCT03329950) is a Phase I dose-escalation study of CDX-1140 as monotherapy or in combination with CDX-301 evaluating safety, PK, PD, and preliminary clinical activity in patients (pts) with refractory solid tumors and non-Hodgkin lymphoma. CDX-1140 is given iv q 4 weeks at doses from 0.01 to 3 mg/kg utilizing a 3+3 design (first 2 cohorts are single-pts). In combination cohorts (solid tumors only), CDX-301 at 75 μg/kg daily x 5 is administered sc prior to cycles 1 and 2 of escalating doses of CDX-1140 starting at 0.09 mg/kg. Tumor-specific expansion cohorts are planned to further explore the activity of monotherapy or combination treatment. To date, 18 pts across 10 tumor types have been dosed in CDX-1140 monotherapy cohorts with doses ranging from 0.01 to 0.72 mg/kg and without identification of an MTD. There has been one DLT (0.18 mg/kg): grade 3 pneumonitis and hypoxia. One pt (0.72 mg/kg) experienced grade 3 fatigue requiring hospitalization 48 hrs after the first infusion. There have been 3 additional grade 3 treatment-related adverse events: dyspnea (0.18 mg/kg), nausea (0.36 mg/kg), and vomiting (0.36 mg/kg). The first combination cohort (n=5) has been completed. In monotherapy and combination cohorts there have been no significant drug-related changes in liver function tests to date. CDX-1140 PK is quantifiable at doses ≥ 0.09 mg/kg and exposure appears dose proportional. Expected dose-dependent PD effects have shown activation of peripheral blood lymphocytes and increases in pro-inflammatory cytokines and chemokines. Combination with CDX-301 has shown enhanced cytokine responses. The data suggest that CDX-1140 has the expected biologic and safety profile predicted from preclinical studies and may achieve dose levels optimal for systemic exposure. The addition of CDX-301 may enhance the activity of CDX-1140. Citation Format: Rachel E. Sanborn, Nashat Y. Gabrail, Nina Bhardwaj, Michael S. Gordon, Mark O'Hara, Danny Khalil, Thomas Hawthorne, Richard Gedrich, Laura Vitale, Mark Rogalski, Tianshu Li, Tracey Rawls, Tibor Keler, Michael Yellin. First-in-human Phase I study of the CD40 agonist mAb CDX-1140 and in combination with CDX-301 (rhFLT3L) in patients with advanced cancers: Interim results [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-194.

Background: Checkpoint inhibitors such as anti-PD-1 are ineffective as single agents for patients (pts) with PDAC. Preclinical data suggest that chemotherapy with agonistic CD40 antibodies can be combined with anti-PD-1 to trigger effective T cell immunity. We conducted a multi-center, open label clinical trial to evaluate the combination of APX005M with nivo and standard chemotherapy (gem and NP). Herein, we report safety and efficacy from the ongoing study. Methods: Pts with previously untreated PDAC were enrolled in 4 cohorts: Gem/NP/APX005M 0.1 mg/kg (B1), Gem/NP/APX005M 0.3 mg/kg (B2), Gem/NP/Nivo/APX005M 0.1 mg/kg (C1) and Gem/NP/Nivo/APX005M 0.3 mg/kg (C2). Primary objectives were to evaluate safety and determine the recommended Phase II dose (RP2D) of APX005M. Secondary objectives included tumor response and immune pharmacodynamics. Analyses were performed on dose-limiting toxicity (DLT)-evaluable subjects, defined as receiving 1 dose of APX005M and ≥ 2 doses of gem/NP during Cycle 1 and remaining on study through Cycle 2 Day 1. Results: N=30 pts dosed; 24 DLT-evaluable (6 per cohort). Median follow up is 32.2 weeks. N=13 (54%) pts experienced an AE leading to discontinuation, and 10 (42%) pts experienced a treatment-related serious AE. Two DLTs were observed, 1 each in cohorts B2 and C1 (grade 3 and 4 febrile neutropenia, respectively). AE rates were similar across cohorts. Four (17%) subjects died (2 each in Cohorts B1 and C1) due to disease progression (n=2) and AE (n=2, sepsis and septic shock in the setting of neutropenia). Within the DLT-evaluable population, best overall responses included 14 (58%) PR (11 confirmed, 3 unconfirmed), 8 (33%) SD, 1 (4%) PD and 1 (4%) NE. Post-baseline tumor assessments were available for 2 of the 6 DLT-inevaluable pts (best overall responses of SD and confirmed PR). Multiplexed IHC analysis of baseline tumors revealed a low CD8 T cell and high macrophage infiltrate. Analysis of circulating mutant KRAS DNA showed marked and rapid decrease with therapy in some pts. Immune profiling of PBMCs at baseline and on-treatment by CyTOF revealed remodeling of the myeloid compartment in response to treatment, with rapid activation of dendritic cells in most pts. Conclusions: Gem/NP/APX005M ± nivo demonstrated manageable safety profiles and promising antitumor activity in untreated metastatic PDAC pts. APX005M 0.3 mg/kg was selected as the dose for a randomized Phase II study in which the primary endpoint is 1-year overall survival. Clinical trial information: NCT02482168. Citation Format: Mark H. O'Hara, Eileen M. O'Reilly, Mick Rosemarie, Gauri Varadhachary, Zev A. Wainberg, Andrew Ko, George A. Fisher, Osama Rahma, Jaclyn P. Lyman, Christopher R. Cabanski, Erica L. Carpenter, Travis Hollmann, Pier Federico Gherardini, Lacey Kitch, Cheryl Selinsky, Theresa LaVallee, Ovid C. Trifan, Ute Dugan, Vanessa M. Hubbard-Lucey, Robert H. Vonderheide. A Phase Ib study of CD40 agonistic monoclonal antibody APX005M together with gemcitabine (Gem) and nab-paclitaxel (NP) with or without nivolumab (Nivo) in untreated metastatic ductal pancreatic adenocarcinoma (PDAC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT004.

Background: PARP inhibitors have activity in multiple BRCA-related malignancies and have recently demonstrated dramatic efficacy as a maintenance strategy for platinum-sensitive ovarian cancer. Between 5-8% of patients with pancreatic cancer (PC) have a pathogenic mutation in BRCA1, BRCA2 or PALB2. Therefore, we initiated a single arm phase II clinical trial of maintenance monotherapy rucaparib in patients with advanced PC and a pathogenic germline or somatic BRCA or PALB2 mutation, whose cancer had not progressed following at least four months of platinum-based chemotherapy (NCT 03140670). Methods: Patients were enrolled and treated with rucaparib 600mg PO BID until disease progression or unacceptable toxicity. The primary endpoint is progression free survival (PFS). Patients have previously received >4 months of platinum-based chemotherapy without evidence of disease progression. However, patients with a medical contraindication to receiving the full four months of platinum have been permitted to enroll at the discretion of the primary investigator. Responses were determined using RECIST v1.1. Results: As of December 31st, 2018, we have enrolled 24 of the planned 42 patients, of which 19 are evaluable for PFS at the time of this interim analysis. For these patients, the mutational distribution includes: 13 germline BRCA2, 3 germline BRCA1, 2 germline PALB2, 1 somatic BRCA2. Patients were predominantly female (84.2%) with a median age of 61 years (range: 35-81). Patients had received a median of four months (range 0.5-32 months) of prior platinum therapy for advanced disease. All patients were evaluable for toxicity. Overall, treatment with rucaparib was well tolerated without dose limiting toxicities. The most common adverse events that were at least possibly related to treatment included nausea (grade 1, 41.6%; grade 2, 4.2%), dysgeusia (grade 1, 33.3%) and fatigue (grade 1, 25%). One patient required dose reduction for nausea. The median PFS was 9.1 months from the start of rucaparib therapy with an ORR of 36.8% (six PRs; one CR). Disease control rate (CR + PR + SD) was 89.5% for at least eight weeks. Two patients (10.5%) had progressive disease at first follow-up scan two months after beginning treatment. Eight patients have been on rucaparib for >6 months and two patients remain on treatment for >1 year (13 months and 15 months). The seven responding patients include those with germline BRCA2 mutations (4 patients), germline PALB2 mutations (2 patients) and somatic BRCA2 mutation (1 patient). Conclusions: Based on these early data, maintenance rucaparib following induction with platinum-based chemotherapy shows encouraging disease control with minimal toxicity in patients with platinum-sensitive advanced PC and a pathogenic mutation in BRCA1, BRCA2 or PALB2. Citation Format: Kim A. Reiss Binder, Rosemarie Mick, Mark O'Hara, Ursina Teitelbaum, Thomas Karasic, Charles Schneider, Peter J. O'Dwyer, Erica Carpenter, Austin Pantel, Mehran Makvandi, David Mankoff, Katherine Nathanson, Kara Maxwell, Stacy Cowden, Mary Jane Fuhrer, Janae Romeo, Gregory L. Beatty, Susan Domchek. A Phase II, single arm study of maintenance rucaparib in patients with platinum-sensitive advanced pancreatic cancer and a pathogenic germline or somatic mutation in BRCA1, BRCA2 or PALB2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT234.

A phase I study to evaluate the safety and feasibility of an intravenous infusion of autologous T cells transduced to express a chimeric antigen receptor directed against mesothelin (CART-meso) in patients with mesothelin expressing tumors is being conducted at the University of Pennsylvania. Here we report on the first five patients treated with CART-meso T cell infusion. Five patients with recurrent advanced stage cancers (two serous ovarian, two epithelial mesothelioma, and one pancreatic) who had received 4-12 prior regimens, were treated with a single infusion of CART-meso cells. Apheresed autologous T cells were transduced with a lentiviral vector expressing the CAR construct composed of an extracellular anti-mesothelin single chain variable fragment derived from mouse monoclonal antibody (SS1) fused to the intracellular signaling domains of 4-1BB (CD137) and TCRzeta. Each patient received a single dose of 1-3 × 10^7 CART-meso cells/m2. No lymphodepletion with chemotherapy was given prior to infusion. All subjects enrolled were successfully infused and there were no acute adverse events (AE) with infusion. To date, Grade 4 AEs have included sepsis(1), anemia(1), pleural effusions(1), tachypnea(1), dyspnea(1), and aspiration(1) and Grade 3 AEs have included sepsis(1), leukocytosis(2), DIC(1), tachycardia(1), dyspnea(1), hypotension(1), dusky extremities(1), fatigue(1), ascites(1), peritonitis(1), elevated LFTs(1), portal vein hypertension(1), and acute kidney injury(1). After infusion, CART-meso T cells were transiently detectable by PCR in the peripheral blood in all patients up to Day 21-28 after infusion. CART-meso cells were found to traffic to tumor sites within the peritoneum and liver, as well as to off-tumor on-target sites such as pericardial fluid, but without clinical toxicity of pericarditis. Expansion of CART-meso cells was also observed in the pleural fluid of one patient who had a known malignant pleural effusion. Cytokine profiling of the peripheral blood revealed elevations of IL-6 and VEGF with significant elevations seen in the one patient with malignant pleural effusion. No elevations in TNFα or IFNγ were found. Anti-tumor efficacy is suggested by the clearing of malignant cells in the pleural fluid of one patient on Day 21 and Day 26 after infusion, as well as radiological and clinical evidence of stable to decreased burden of disease in one patient. Patient follow-up for 1-3 months post infusion has revealed no evidence of long-term toxicities to date. These interim results suggest that intravenous infusion of CART-meso T cells without lymphodepletion is feasible and safe. In these five patients with metastatic mesothelin expressing cancers, the infusion was well tolerated with no off-tumor on-target toxicities. Laboratory and clinical findings suggest infused T cells are effective and functional. Citation Format: Janos L. Tanyi, Andrew R. Haas, Gregory L. Beatty, Mark A. Morgan, Caitlin J. Stashwick, Mark H. O'Hara, David L. Porter, Marcela V. Maus, Bruce L. Levine, Simon F. Lacey, Anne Marie Nelson, Maureen McGarvey, Naseem DS Kerr, Gabriela Plesa, Carl H. June. Safety and feasibility of chimeric antigen receptor modified T cells directed against mesothelin (CART-meso) in patients with mesothelin expressing cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT105. doi:10.1158/1538-7445.AM2015-CT105