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TPS784 Background: Patients(pts) with metastatic pancreatic cancer (PC) have a median survival of less than one year even with use of multiagent chemotherapy programs. Pancreatic tumors are composed of multiple cell types and a dense extracellular matrix that may support cancer cell proliferation and impede chemotherapy delivery. Cancer-associated fibroblasts (CAF’s) in the tumor microenvironment secrete pro-inflammatory factors and components of the extracellular matrix. In PC laboratory models, engagement of the vitamin D receptor (VDR) by VDR agonists shifts CAFs toward a more quiescent phenotype with reduced tumor growth and improved chemotherapy penetration (Sherman. Cell, 2014). Paricalcitol is a synthetic VDR agonist used in patients with secondary hyperparathyroidism due to chronic kidney disease. A prior pilot study evaluated IV paricalcitol with gemcitabine (G) and nab-paclitaxel (A) before surgical resection in patients with resectable PC (NCT02030860). Methods: Pts with previously-untreated metastatic PC will be enrolled in a two-stage study consisting of a safety run-in and a randomized phase 2 study (NCT03520790). In the run-in stage, 36 pts will be randomized 1:1:1 to G (1000 mg/m2) and A (125 mg/m2) given 3 weeks on and 1 week off plus: (a) paricalcitol 25mcg IV thrice weekly, (b) paricalcitol 16mcg oral daily, or (c) placebo oral daily. Grade 3/4 hypercalcemia or genitourinary stones will be considered dose limiting toxicities.Pts will undergo paired pre- and on-treatment tumor biopsies to examine pharmacodynamic (PD) markers by bulk and single cell RNA sequencing and multiplex immunofluoresence.Assuming safety and supportive PD assessments, the phase 2 study will randomize an additional 76 pts to two treatment arms with GA plus: (a) paricalcitol or (b) placebo.Paricalcitol formulation (IV or oral) will be determined based on data from the run-in stage.The primary endpoint of the phase 2 study is overall survival, with a total of 100 pts needed to identify a hazard ratio of 0.6 with 80% power and one-sided alpha of 0.10.Secondary endpoints include safety, response rate, and progression free survival.Trial funding provided by SU2C, CRUK,Lustgarten Foundation, and AACR. Clinical trial information: NCT03520790.

580 Background: Though studies indicate that the genomic profiles of ICC and ECC are distinct, the clinical features that differentiate them still remain to be well characterized. The purpose of this study was to further analyze these differences and patient treatment patterns in a multi-center cohort. Methods: A retrospective chart review was performed at 8 institutions on patients (pts) with ICC or ECC diagnosed after June 2009. Data on demographics, risk factors, treatments, pathology and overall survival (OS) were collected. Tumor genotyping results from CLIA-certified tissue assays were analyzed. Fisher’s exact, Wilcoxon rank sum and log-rank tests were used to compare sub-groups. Results: In a database of 737 pts with cholangiocarcinoma, 538(73%) had ICC and 199(27%) had ECC. Pts with ICC more often presented in later stages, had tumors > 5cm at resection (p < 0.0001) and had metastases to the liver, lymph nodes, lung and/or bone (p < 0.01). Pts with ICC more often received liver directed therapy, targeted therapy and multiple lines of systemic therapy and they more often enrolled in a clinical trial (all p < 0.01). Pts with ECC were more likely to be male, undergo surgery, receive adjuvant chemotherapy and/or chemoradiation (all p < 0.05). Mutation profiling performed in 381 (52%) pts (ICC/ECC = 301/80) showed that pts with ICC were more likely to have IDH1 mutations and FGFR2 fusions, whereas pts with ECC were more likely to have KRAS, APC, SMAD4, WNT, TGFb and TP53 mutations (all < 0.05). Factors that did not differ significantly between pts with ICC and ECC include race, rates of primary sclerosing cholangitis, median diagnosis CA19-9 levels and R1 resection rate. Median OS from diagnosis was 18.9 months in ICC and 17.3 months in ECC (p = 0.8471). Conclusions: While pts with ICC and ECC have some similarities in their clinical features, differences in metastases patterns and molecular profiling significantly impact their management such that pts with ICC receive more liver-directed therapy, targeted therapy and more lines of systemic therapy. Further prospective studies are needed as referral patterns to tertiary care centers may have impacted these results.

155 Background: Ang-2 is produced by endothelial cells, predominantly in tissues undergoing vascular remodeling. Current studies suggest that Ang-2 partially suppresses T cell activation by increasing PD-L1 expression and decreasing activation of monocytes. We demonstrated that high pre-treatment serum Ang-2 is associated with reduced overall survival in patients treated with PD-1 blockade. We therefore hypothesized that the combination of Ang-2 and PD-1 blockade may be effective for treatment of patients with advanced cancer. Methods: We initiated a phase 1b trial of the combination of pembrolizumab and trebananib, an Ang-1/2 neutralizing peptibody in advanced solid tumors. Treatment consisted of an induction phase of pembrolizumab 200 mg every 3 weeks and trebananib weekly (with an initial run-in dose escalation of 15-30 mg/kg) for 12 weeks followed by pembrolizumab alone for 2 years. Here we present the updated data in the fully enrolled CRC expansion cohort. Results: The study enrolled 18 microsatellite stable (MSS) CRC patients. There were no DLTs in the dose escalation phase, and 30mg/kg was deemed to be the MTD. This summary is based on 15 CRC patients treated with 30 mg/kg trebananib plus pembrolizumab. The most common treatment-related adverse events (AEs) were abdominal distension, diarrhea, limb edema, transaminitis, and proteinuria, each reported in 40% of the patients. As of September 2019 (median follow up of 10 months), 13 patients were off treatment and two were continuing. Eleven patients were off treatment due to disease progression and 2 due to unacceptable toxicities (grade 4 pneumonitis and grade 3 transaminitis). The response rate was 7% (1 partial response for 23.8+ months) and the disease control rate was 27%, with 4 stable disease for a median of 10 months (4-18 months). Median time to progression and overall survival were 2.8 months (90% CI: 1.5 to 8.1 months) and 9.0 months (90% CI: 2.6 months to ∞), respectively. Conclusions: The combination of pembrolizumab and trebananib is well tolerated and demonstrated promising activity in patients with heavily treated MSS CRC. Clinical trial information: NCT03239145.

Gastrointestinal toxicities are among the leading causes of immune-related adverse effects of checkpoint blockade. These adverse events can be severe enough to require interruption or withdrawal of immune checkpoint blockade therapy. Patients with immune-related adverse effects require early recognition with an evaluation to rule out alternative etiologies and effective management to minimize complications. This article reviews the gastrointestinal and hepatic toxicities of the antibodies that target immune checkpoints CTLA-4 and PD-1/PD-L1 and provides an approach to their diagnosis and management.

The advent of immune checkpoint inhibitors (ICIs) has changed the landscape of cancer treatment. Older adults represent the majority of cancer patients; however, direct data evaluating ICIs in this patient population is lacking. Aging is associated with changes in the immune system known as "immunosenescence" that could impact the efficacy and safety profile of ICIs. In this paper, we review aging-associated changes in the immune system as they may relate to cancer and immunotherapy, with mention of the effect of chronic viral infections and frailty. Furthermore, we summarize the current clinical evidence of ICI effectiveness and toxicity among older adults with cancer.

SUMMARY Biliary tract carcinoma is a rare malignancy. We performed a comprehensive analysis of published prospective clinical trials in advanced biliary tract carcinoma in an attempt to identify active regimens in this setting. We searched PubMed and abstracts presented at the American Society of Clinical Oncology, Gastrointestinal Cancer Symposium, European Society of Medical Oncology and European Cancer Organization conferences for clinical trials in this disease. We found 83 trials. The effect of gemcitabine on overall survival benefit showed a strong trend (p = 0.014) and an improvement in progression-free survival (p = 0.003). Gemcitabine-based regimens containing 5-fluorouracil showed a trend toward an improved overall survival (p = 0.047) relative to platinum agents. Our findings support gemcitabine as the chemotherapy backbone for the treatment of patients with cholangiocarcinoma. Gemcitabine plus 5-fluorouracil combinations warrant further investigations.

Despite advances in treatment modalities, colorectal cancer (CRC) still accounts for about half a million deaths yearly worldwide. The majority of metastatic CRC are unresectable, and of those who undergo resection, few are cured. Advances in chemotherapy and targeted therapy have improved survival, but options remain limited, making the case for incorporating novel modalities in CRC treatment paradigm. Our improved understanding of the tumor immune microenvironment had led to the development of novel immunotherapeutic agents that have been tested in clinical trials such as cancer vaccines. Cancer vaccines are designed to activate the effector immune cells in order to generate an immune response against tumors. Dendritic cell vaccines offer potential benefits for CRC patients but requires further evaluation. We reviewed the role of dendritic cells in the colorectal tumor microenvironment and dendritic cancer vaccine studies in colorectal cancer.

O1 IL-15 primes an mTOR-regulated gene-expression program to prolong anti-tumor capacity of human natural killer cells #### Andreas Lundqvist1, Vincent van Hoef1, Xiaonan Zhang1, Erik Wennerberg2, Julie Lorent1, Kristina Witt1, Laia Masvidal Sanz1, Shuo Liang1, Shannon Murray3, Ola Larsson1

290 Background: Use of immunotherapy has increased exponentially with survival benefit in many malignancies. As a result, suspected irAEs are commonly encountered, but lack of a gold standard for diagnosis puts patients at risk. We describe preliminary results of a QI project to improve accuracy of irAE diagnosis. Methods: Specialists at our institution created algorithms to define the likelihood of immune-related hepatitis, colitis, and pneumonitis based on clinical data, diagnostic results, and treatment response. Records of patients admitted from June-November 2018 with possible irAE were retrospectively reviewed by an oncology provider and an immunotoxicity specialist. A web-based tool automated irAE likelihood from clinical data based on the aglorithms. Reviewers could agree or disagree with the result and share their clinical impression. We evaluated concordance between providers and between provider and algorithm. Results: Of 65 patients, most had non-small-cell lung cancer (29%), melanoma (15%), or breast cancer (9%) and were treated with pembrolizumab (48%), nivolumab (23%), or ipilimumab/nivolumab (22%). There were 4 irAE-related deaths and 40 patients (71%) discontinued therapy for presumed toxicity. After 14 cases were excluded due to incomplete information, algorithms were applied to the remaining 51 cases (19 colitis, 8 hepatitis, 24 pneumonitis). The algorithm generated the likelihood of an irAE in 63% of reviews. Overall agreement with the algorithm was 86% (84-100% for individual algorithms), Kappa 0.8 (0.7-1.0). Overall concordance between reviewers was 76% (75-88%), Kappa of 0.7 (0.6- 0.8). Conclusions: While algorithm definitions and provider impressions were fairly consistent, cases lacking a generated likelihood suggest that some clinical scenarios are not addressed. Different interpretation of clinical information or varying experience with irAEs may explain inter-reviewer discordance, which underscores the importance of applying a standardized approach to irAE diagnosis across settings and experience levels. In the next improvement cycle, the algorithm will be refined to broaden algorithm scope, clarify criteria, and improve accuracy.

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: ICOS is a costimulatory molecule upregulated on activated T cells. JTX-2011 is an ICOS agonist antibody intended to stimulate primed CD4 T effector cells. JTX-2011 was assessed in pts with advanced solid tumors as monotherapy (mono) and combination (combo) with nivolumab (nivo) in the Phase I/II ICONIC trial (NCT02904226). Peripheral T cell phenotyping in ICONIC demonstrated emergence of an ICOS high (hi) subset of CD4 T cells associated with tumor reductions in mono and combo pts. In ex vivo studies, soluble JTX-2011 stimulated a polyfunctional cytokine response only in ICOS hi cells. Methods: Ad hoc flow cytometry phenotyping on PBMCs from a subset of pts with evaluable samples (n=50) was initiated retrospectively in early 2018 in ongoing pts, then prospectively on newly enrolled pts. Clinical characteristics and outcomes were analyzed, including unadjusted p-values for post-hoc statistical analyses. Phenotyping was also done on samples from pts treated with PD-1/L1 inhibitor (PD-1/L1i) mono collected outside of ICONIC. Results: Emergence of ICOS hi CD4 T effector cells (all FoxP3-, subset Tbet+ Ki67+) was observed in all pts with ≥30% target lesion tumor reduction by investigator assessment on mono and combo therapy (n=7). Emergence was seen in pts with stable target lesions (n=11/23) including loss of these cells with disease progression. ICOS hi cells were not seen in ICONIC pts with target lesion increase ≥20% (n=14), or in pts treated with PD-1/L1i mono, including responders. Emergence of ICOS hi CD4 T cells correlated with improved PFS and OS (Table). ICONIC Pt characteristicsICOS hi (N=18)ICOS low (N=32)≥3 prior therapies, n (%)13 (72.2)18 (56.3)Prior immunotherapy, n (%)6 (33.3)15 (46.9)Tumor type, n (%)Gastric n=9 (50), NSCLC n=3 (16.7), TNBC n=2 (11.1), Other n=4 (22.2)Gastric n=8 (25), NSCLC n=6 (18.8), TNBC n=4 (12.5), Other n=14 (43.8),Mono vs Combo, n (%)Mono n=2 (11.1), Combo n=16 (88.9)Mono n=11 (34.4), Combo n=21 (65.6)G3-4 treatment-related adverse events, n (%)1 (5.6)2 (6.3)Time on JTX-2011, median mths (range), p=0.00065.6 (1.45-18.4)1.41 (0.03-6.28)PFS, investigator and central imaging review, median mths, (investigator, p Conclusion: Emergence of a distinct ICOS hi population of peripheral CD4 T cells is associated with improved PFS and OS with JTX-2011 mono and combo therapy. Two JTX-2011 development paths are planned: (1) combo with agents that induce ICOS hi CD4 T cells; (2) use of potential putative biomarkers predictive of emergence of this T cell population and JTX-2011 response. Citation Format: Timothy Anthony Yap, Justin F. Gainor, Margaret K. Callahan, Gerald S. Falchook, Russell Kent Pachynski, Patricia LoRusso, Shivaani Kummar, Geoffrey Thomas Gibney, Howard A. Burris, Scott S. Tykodi, Osama E. Rahma, Tanguy Seiwert, Kyriakos P. Papadopoulos, Ellen Hooper, Christopher J. Harvey, Amanda Hanson, Sean Lacey, Rachel McComb, Courtney Hart, Haley Laken, Ty McClure, Elizabeth Trehu. Improved progression-free and overall survival (PFS/OS) in patients (pts) with emergence of JTX-2011 associated biomarker (ICOS high CD4 T cells) on the ICONIC trial [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 CT189.

e14172 Background: Management of Immune checkpoint inhibitors (ICIs) associated irAEs requires accurate diagnosis and severity measurement. However, outside of clinical trials, there is no clear definition of irAEs to guide treatment. Methods: We established a dedicated immune toxicity inpatient service (ITox) for patients admitted with irAEs using institution-developed guidelines adapted from NCCN and ASCO. We developed definitions for ICI associated hepatitis, colitis and pneumonitis and created algorithms for defining an irAEs as definite, likely, possible, or unlikely. Algorithm fields were completed twice, by two independent reviewers including medical oncology specialists and toxicity specialists (a pulmonologist or gastroenterologist) to evaluate the accuracy of the algorithm in defining irAEs. Results: From June to November 2018, 65 patients were admitted to iTox with suspected irAEs. Various cancers patients treated with ICI were included; with lung and head and neck cancers the most common (36.9%). Pembrolizumab was the most common ICI (47.7%). ICI in combination with non-checkpoint inhibitor treatment was used in 23 (37.7%) and concurrent radiation therapy in 5 patients (7.7%). Forty (71.4%) patients discontinued ICI due to toxicity. Fifty-one patients were evaluable with irAEs: colitis (19); pneumonitis (24) and hepatitis (8). Multiple irAEs were reported in 17 patients. When applied to clinical cases, our algorithms generated a toxicity definition in 63% of cases, with which reviewers agreed most of the time (84-100%) (Kappa 0.7-1.0). Concordance between the two reviewers was 75-87% (Kappa 0.55-0.82) (Table). Conclusions: Our algorithms generated irAEs definitions with fair inter-rater reliability. These findings have real-world implications; accurate diagnosis of irAEs is essential for proper management. Defining irAEs outside the clinical trial context remains an important challenge. [Table: see text]

e14160 Background: Ang-2 is produced by endothelial cells, predominantly in tissues undergoing vascular remodeling and in hypoxic microenvironments. Ang-2 partially suppresses T cell activation by increasing PD-L1 expression and decreasing monocyte activation. Our group demonstrated that high pre-treatment serum Ang-2 is associated with reduced overall survival (OS) in patients treated with PD-1 blockade. Methods: We initiated a phase 1b trial to evaluate the safety, efficacy, and immunological effect of the combination of pembrolizumab and trebananib, an Ang-1/2 neutralizing peptibody, in solid tumors. Treatment consisted of an induction phase of pembrolizumab 200 mg every 3 weeks and trebananib weekly (with an initial run-in dose escalation of 15-30 mg/kg) for 12 weeks followed by pembrolizumab alone for 2 years. Here we present the preliminary data in the fully enrolled CRC expansion cohort. Results: The study enrolled a total of 18 microsatellite stable (MSS) heavily pretreated CRC patients. There were no DLTs and 30mg/kg was deemed to be the MTD. This summary is based on 15 CRC patients treated with 30 mg/kg trebananib (3 in dose escalation, 12 in dose expansion) plus pembrolizumab. Nine patients (60%) were female and the median age was 51 years (43-63). The most common treatment-related adverse events (AEs) were abdominal distension, diarrhea, limb edema, transaminitis, and proteinuria (each reported in 40% of the patients). One grade 3 transaminitis and one grade 4 pneumonitis related to pembrolizumab were reported. As of the date of data retrieval, 11 patients were off treatment and four were continuing with a median follow-up of 6.1 months. The response rate was 7% (1 partial response for 14 months) and the disease control rate was 33% (4 stable disease with CEA trending down). Median time to progression and OS were 2.8 (90% CI: 1.5 to 4.9 months) and 11.4 months (90% CI: 2.6 months to ∞), respectively. Conclusions: The combination of pembrolizumab and trebananib is well tolerated and demonstrated promising activity in heavily pretreated MSS CRC. Paired biopsies and blood were collected for planned correlative immune analyses which will be presented at the meeting. Clinical trial information: NCT03239145.

2582 Background: Colitis is a frequent toxicity of ICI therapy but there is paucity of data on risk factors. Specific serological markers and genetic polymorphisms have been associated with inflammatory bowel disease (IBD) (ulcerative colitis, Crohn’s disease). However, the prevalence of these markers in pts with ICI colitis is unknown. We performed a pilot study to determine the prevalence of IBD-associated genetic and serologic biomarkers in pts with ICI colitis. Methods: Cancer pts with histologically confirmed ICI enteritis/colitis and no history of IBD underwent commercial IBD panel testing. The panel included 4 genetic markers ( ATG16L1, NXK2–3, ECM1, STAT3), 8 serological markers (anti-A4-Fla2, anti-A4-FlaX, anti-CBir1, anti-OmpC, ASCAIgA, ASCA-IgG, pANCA, ANCA), and 5 inflammatory markers (vascular endothelial growth factor [VEGF], intracellular adhesion molecule 1[ICAM-1], vascular cell adhesion molecule 1 [VCAM-1], C-reactive protein, serum amyloid A [SAA]). Clinical testing on serum samples was performed by Prometheus Laboratories (San Diego, CA). Results: Of 15 cancer pts with biopsy confirmed ICI colitis, 10 (67%) were homozygous for 1 or more of 4 genetic markers. The remaining 5 pts were all heterozygous for two or more of the genetic markers. One or more serologic markers associated with IBD were elevated in 7/15 (47%) pts. Serum reactivity was noted for ASCA-IgA (1/15, 7%), ASCA-IgG (1/15, 7%), anti-OmpC (3/15, 20%), anti-CBR IgG (2/15, 13%), anti-A4-FlaX (1/15, 7%), and ANCA (2/15, 13%). One or more inflammatory markers were elevated in 13/15 (88%) pts. Elevations in VEGF, VCAM-1, ICAM-1, and SAA were noted in 2 (13%), 8 (53%), 8 (53%), and 11 (73%) pts, respectively. Only 6 (40%) pts had elevations in CRP levels despite the presence of active inflammation on biopsy. The IBD panel was reported as being consistent with Crohn’s disease in 2 pts, ulcerative colitis in 1 pt and inconclusive for type but consistent with IBD in 1 pt. Conclusions: In this pilot study, all patients with ICI colitis, were either homozygous or heterozygous for two or more high risk IBD alleles. If validated, such testing may prospectively identify pts at risk for developing ICI colitis.

4526 Background: Approval of anti–PD-L1/anti–PD-1 CPI agents has changed the mUC tx landscape, but real-world (RW) tx patterns are not well described. Here, we describe pt characteristics, time on tx (TOT), tx-cycle distribution, relative dose intensity (RDI) and subsequent tx for pts receiving atezolizumab (atezo), nivolumab (nivo) or pembrolizumab (pembro) monotherapy. Methods: Pts diagnosed with mUC who completed atezo, nivo or pembro in the first-line (1L) or prior-platinum second-line and beyond (2L+) settings by April 30, 2018, were identified from the US-based Flatiron Health electronic health record–derived database. TOT was defined as time from first to last CPI administration + 1 cycle, tx cycles as number of CPI doses received during TOT and RDI as ratio of actual to planned dose per week to reflect any dose interruption. Results: RW data from pts receiving atezo, nivo and pembro were analyzed (Table). Up to 38% of pts had ECOG PS > 1. Median TOT ranged from 2.1-2.8 mo, with overlapping 95% CIs; mean TOT ranged from 2.7-4.1 mo. Over 50% of pts had ≤ 4 tx cycles. 21%-38% of pts did not have RDI within 95%-105% of the labeled dose. Most common subsequent txs were platinum-based chemotherapy combinations with gemcitabine or taxanes (post–1L CPI) and taxane monotherapy or other CPI monotherapy/combinations (post–2L+ CPI). Conclusions: Here, we present the largest analysis of RW CPI use in mUC to date. Overall, this unadjusted descriptive analysis showed relative comparability of pt and tx characteristics and TOT across CPI-treated groups. Insights into RW tx allow for an understanding of how clinical trial data translate to broader pt populations, including those with ECOG PS > 1, and may be useful for practitioners. [Table: see text]

49 Background: Pre-clinical and clinical evidence support immune effects of targeted radiation (RT) resulting in synergy with immune checkpoint therapy. However, prospective data are lacking in regards to safety, efficacy and immunologic impacts of different doses of RT given in conjunction with PD-L1 and CTLA-4 blockade. Methods: ETCTN 10021 is a multicenter randomized phase 2 study evaluating repeated low-dose fractionated RT (LDFRT) or hypofractionated RT (HFRT) in combination with PD-L1 and CTLA-4 inhibition in metastatic microsatellite-stable colorectal cancer (CRC) refractory to first-line chemotherapy, or non-small cell lung cancer progressive on prior PD-1 inhibition. The primary endpoint is objective response excluding irradiated lesions. Pre- and on-treatment biopsies were analyzed using multiplex immunofluorescence (IF) evaluating multiple immune markers. We report the prespecified analysis of the CRC cohort. Results: Twenty CRC patients were randomized, 19 of whom were treated with immunotherapy and RT, and 18 of whom were evaluable for response. Median lines of prior therapy were 4 (range 1-7). There were 16 patients with toxicity potentially related to treatment (84%), and 8 patients with possibly associated grade 3-5 toxicity (42%). Best response was stable disease in one patient with an abscopal out-of-field response who developed new lesions after HFRT and 4 cycles with decreasing overall disease burden. Correlative IF performed on 5 sample pairs revealed that HFRT, but not LDFRT, increased infiltration of CD8+, and CD8+/PD1+/Ki67+ T-cells in the RT field. Conclusions: We demonstrate the feasibility of a multicenter randomized study adding different RT regimens to PD-L1/CTLA-4 blockade. Toxicity was, in general, consistent with PD-L1/CTLA-4 inhibition with no significant RT-related toxicities noted. Although the best response of stable disease doesn’t support the use of PD-L1/CTLA-4 inhibition with HFRT or LDFRT in this population using these RT regimens and schedule, integrated biomarkers provide support that HFRT impacts the local immune microenvironment. Clinical trial information: NCT02888743.

154 Background: Immune checkpoint therapy has changed the treatment landscape for many malignancies. As these agents are rapidly being incorporated into clinical practice, a subset of patients appear to have an accelerated tumor growth rate (TGR) after treatment initiation, a phenomenon termed hyperprogressive disease (HPD). Methods: A systematic search of original articles published between January 2000 and June 2018 was performed using PubMed, Embase, and Web of Science. Studies were eligible for inclusion if they reported on HPD in adult patients with advanced solid malignancies treated with checkpoint inhibitors and provided a specific HPD definition. Abstracts from ASCO, ESMO, and IASLC meetings were also included. Prespecified outcomes of interest included criteria used to define HPD, incidence of HPD, and association between HPD with baseline clinical or molecular characteristics and survival outcomes. Results: Of 700 studies screened, 12 retrospective studies were eligible, 3 of which evaluated patients treated in the context of clinical trials. Lung cancer and melanoma were the most common of the diverse histologies represented. The most common treatment was anti-PD1/PD-L1 monotherapy. A variety of criteria were utilized to define HPD, including TGR, RECIST progression, and time to treatment failure. HPD incidence ranged from 2% to 29%, and the only clinical factor significantly associated with HPD in more than one study was increased age. MDM2/4 and EGFR alterations appear to be associated with a higher incidence of HPD. HPD was significantly associated with poor overall survival in 3 studies. Conclusions: It remains unclear whether HPD reflects worsening disease caused by immunotherapy or is simply a manifestation of unfavorable, treatment unresponsive disease biology. There is a need to establish a consensus definition for HPD, and to examine HPD in prospective cohorts with appropriate comparison arms.

381 Background: Atezo (anti–PD-L1) was the first immune checkpoint inhibitor approved for mUC. Here, we describe pt characteristics, time on tx (TOT) and distribution of tx cycles for pts receiving atezo in clinical practice, to complement data from clinical trial setting. Methods: Pts diagnosed with mUC who initiated atezo monotherapy in the first-line (1L) or second-line and beyond (2L+; prior platinum tx) settings on or before Jun 30, 2017, were identified from the US-based Flatiron Health electronic health record–derived database. Tx data were analyzed through Mar 31, 2018. TOT was defined as time from first to last atezo administration, plus 1 cycle length. Median TOT was calculated by tx line using the Kaplan-Meier method. Tx cycles were calculated by the number of atezo doses received during TOT. Corresponding results from global atezo clinical trials are presented. Results: Real-world data (RWD) from 312 pts (n = 102, 1L; n = 210, 2L+) met the study selection criteria (Table). Median TOT was 3 and 3.5 months in the 1L and 2L+ settings, respectively, with 95% CIs overlapping with the trial TOT data. A median of 4 cycles (IQR, 2-7, 1L; 2-9, 2L+) was administered in both settings. Conclusions: This is the first study of RW atezo use in mUC. The TOT with atezo observed in a US RW setting and the clinical setting (IMvigor210/IMvigor211) was similar. [Table: see text]

TPS467 Background: CIT has significant survival benefits across multiple tumor types, but durable response is experienced by only subsets of patients (pts). To extend clinical benefit to more pts, efficacious CIT combinations (combos) targeting multiple cancer immune escape mechanisms need to be identified. The MORPHEUS platform includes multiple ph Ib/II trials designed to identify early signals of safety and efficacy of CIT combos. Using a randomized trial design, multiple treatment (tx) arms are compared with a single control arm in each pt cohort. We present three GI-specific MORPHEUS trials, each assessing CIT combos that could concurrently enhance multiple aspects of the cancer immune response. Methods: The MORPHEUS trials described here are global, open-label, randomized, Ph Ib/II trials enrolling pts with pancreatic ductal adenocarcinoma (PDAC), gastric or gastroesophageal junction cancers or colorectal cancer (CRC). New arms with novel CIT combos (table) are opened as new txs become available, and arms with minimal efficacy or unacceptable toxicity are closed. Studies include multiple cohorts for pts receiving different lines of tx (1L and 2L PDAC and gastric; 3L CRC). Pts with loss of clinical benefit or unacceptable toxicity may be eligible to enroll in a different CIT combo arm. Primary endpoints include safety and investigator-assessed ORR (RECIST v1.1); secondary endpoints: PFS, OS, DCR and DOR. Clinical trial information: NCT03193190, NCT03281369, NCT03555149. [Table: see text]

TPS721 Background: Locally advanced rectal cancer (LARC) improvements have plateaued due to an inability to consistently deliver adjuvant therapy and effective novel therapies. Systematic testing of new chemotherapy and radiation sensitizers is needed to advance treatment outcomes. This NCTN multi-arm randomized phase II modular clinical trial platform utilizes TNT with parallel experimental arms (EA) in LARC. The EAs are not intended for direct comparison, but rather to test a variety of sensitizers or hypotheses in a consistent and homogenous high-risk patient (pt) population with correlative biomarkers. Success of any EA will be determined by achievement of pathologic endpoints compared to a control arm. Methods: The NRG-GI002 trial serves as a modular platform to assess novel sensitizers to neoadjuvant chemotherapy and/or chemoradiotherapy (chemoRT) in LARC. Eligibility includes LARC with any ONE of the following: distal location (cT3-4 ≤ 5 cm from anal verge, any N); bulky (any cT4 or tumor within 3 mm of the mesorectal fascia); high risk for metastatic disease (cN2); or not a candidate for sphincter-sparing surgical resection. After randomization, pts receive neoadjuvant FOLFOX x 4 mo→chemoRT (capecitabine with 50.4 Gy)→surgical resection 8-12 wks later. The first EA will assess activity of veliparib with standard chemoRT. Enrollment to this EA is complete (results anticipated late 2019). The second EA, testing pembrolizumab concurrently with and following chemoRT, is currently active, with several other EAs in development. Primary endpoint is demonstrated improvement in Neoadjuvant Rectal Cancer score for the EA v control representing a 20% relative risk reduction in DFS HR and 3-4% absolute OS improvement. Secondary endpoints include comparisons of OS, DFS, toxicity, pCR, cCR, therapy completion, negative surgical margins, sphincter preservation, sphincter function including QOL, and exploratory assessments of molecular and radiographic predictors of response and distant failure. Target accrual is 79 evaluable pts/arm with additional EAs added through protocol amendments. NCT02921256. Support: U10CA180868, -180822, UG1-189867, U24-196067; AbbVie, Merck. Clinical trial information: NCT02921256.

The eukaryotic translation initiation factor 4E (eIF4E) is a potent oncogene that is found to be dysregulated in 30% of human cancer, including colorectal carcinogenesis (CRC). ISIS 183750 is a second-generation antisense oligonucleotide (ASO) designed to inhibit the production of the eIF4E protein. In preclinical studies we found that EIF4e ASOs reduced expression of EIF4e mRNA and inhibited proliferation of colorectal carcinoma cells. An additive antiproliferative effect was observed in combination with irinotecan. We then performed a clinical trial evaluating this combination in patients with refractory cancer. No dose-limiting toxicities were seen but based on pharmacokinetic data and tolerability the dose of irinotecan was reduced to 160 mg/m(2) biweekly. Efficacy was evaluated in 15 patients with irinotecan-refractory colorectal cancer. The median time of disease control was 22.1 weeks. After ISIS 183750 treatment, peripheral blood levels of eIF4E mRNA were decreased in 13 of 19 patients. Matched pre- and posttreatment tumor biopsies showed decreased eIF4E mRNA levels in five of nine patients. In tumor tissue, the intracellular and stromal presence of ISIS 183750 was detected by IHC in all biopsied patients. Although there were no objective responses stable disease was seen in seven of 15 (47%) patients who were progressing before study entry, six of whom were stable at the time of the week 16 CT scan. We were also able to confirm through mandatory pre- and posttherapy tumor biopsies penetration of the ASO into the site of metastasis.

Immune checkpoint inhibitors have been identified as breakthrough treatment in melanoma given its dramatic response to PD-1/PD-L1 blockade. This is likely to extend to many other cancers as hundreds of clinical trials are being conducted or proposed using this exciting modality of therapy in a variety of malignancies. While immune checkpoint inhibitors have been extensively studied in melanoma and more recently in lung cancer, little is known regarding immune checkpoint blockade in other cancers. This review will focus on the tumor immune microenvironment, the expression of PD-1/PD-L1 and the effect of immune modulation using PD-1 or PD-L1 inhibitors in patients with head and neck, prostate, urothelial, renal, breast, gastrointestinal and lung cancers.

The incidence of pancreatic cancer has been increasing while its 5-year survival rate has not changed in decades. In the era of personalized medicine, immunotherapy has emerged as a promising treatment modality in a variety of malignancies, including pancreatic cancer. This review will discuss the unique pancreatic tumor microenvironment, including the cells and receptors that transform the pancreas from its normal architecture into a complex mix of suppressor immune cells and dense extracellular matrix that allows for the unrestricted growth of cancer cells. Next, we will highlight the recently completed immunotherapy clinical trials in pancreatic cancer. Finally, we will explore the on-going immunotherapy clinical trials and future directions of this engaging and changing field.

Poorly differentiated neuroendocrine tumors are uncommon tumors of the GI tract and often diagnosed without the identification of the primary site. Here, we describe a case of poorly differentiated neuroendocrine carcinoma of unknown primary that is diagnosed by bone marrow biopsy. A68-year-old male patient presented with worsening back pain, hypercalcemia, anemia, and altered mental status. Initially, imaging favored multiple myeloma. However, a bone marrow biopsy revealed morphologic and immunohistochemical features of neuroendocrine origin.

Peptide antigens have been administered by different approaches as cancer vaccine therapy, including direct injection or pulsed onto dendritic cells; however, the optimal delivery method is still debatable. In this study, we describe the immune response elicited by two vaccine approaches using the wild-type (wt) p53 vaccine.Twenty-one HLA-A2.1 patients with stage III, IV, or recurrent ovarian cancer overexpressing the p53 protein with no evidence of disease were treated in two cohorts. Arm A received SC wt p53:264-272 peptide admixed with Montanide and GM-CSF. Arm B received wt p53:264-272 peptide-pulsed dendritic cells IV. Interleukin-2 (IL-2) was administered to both cohorts in alternative cycles.Nine of 13 patients (69%) in arm A and 5 of 6 patients (83%) in arm B developed an immunologic response as determined by ELISPOT and tetramer assays. The vaccine caused no serious systemic side effects. IL-2 administration resulted in grade 3 and 4 toxicities in both arms and directly induced the expansion of T regulatory cells. The median overall survival was 40.8 and 29.6 months for arm A and B, respectively; the median progression-free survival was 4.2 and. 8.7 months, respectively.We found that using either vaccination approach generates comparable specific immune responses against the p53 peptide with minimal toxicity. Accordingly, our findings suggest that the use of less demanding SC approach may be as effective. Furthermore, the use of low-dose SC IL-2 as an adjuvant might have interfered with the immune response. Therefore, it may not be needed in future trials.

326 Background: The immune checkpoint inhibitors (ICIs) confer a risk of unique inflammatory immune-related adverse events (irAEs), which are highly distinct from the adverse events historically observed with cytotoxic therapy. To develop a strategy for easier identification and mitigation of irAEs, we sought to understand the frequency of ED visits and hospitalizations in 90 days following ICI start by implementing a rapid learning system (RLS). Methods: We convened an Immunotherapy Toxicities Management Committee with representatives from the Center for Immuno-Oncology, Quality and Patient Safety, and Informatics to draft a series of recommendations for the development of an irAE rapid learning system. The Committee requested an audit of all irAEs between June 2015 and April 2018 by drug, event type (clinical diagnosis), outcomes (including ED visits, hospitalization with length of stay, and death), and time-frame (days since beginning ICI course). An automated pipeline was created to merge structured data from the Electronic Health Record (Epic) and billing system (EPSi). This data was used to design a tool which consisted of an automated dashboard to monitor patient and enable interventions. Results: Over the course of 3 years, a total of 2,020 unique patients receiving ICIs were seen. 918 were treated with Pembrolizumab (45.4%), 768 with Nivolumab (38.0%), 234 with Atezolizumab (11.6%), 111 with Nivolumab & Ipilmumab (5.6%), 68 with Ipilimumab (3.4%), 9 with Durvalumab (0.4%), and 9 with Avelumab (0.4%). ED visits and hospitalization rates over 90 days were similar among the three most prescribed therapies, ranging from 332 unique patient events in the Pembrolizumab Cohort (36.1%) to 96 unique patient events in the Atezolizumab cohort (41.0%). Conclusions: The dashboard is effective tool to build a RLS for irAEs. The immediate output of this tool is using natural language processing (NLP) to distinguish between irAEs related ED visits and hospitalizations or regular disease progression, and measure the impact of interventions including (a) developing standardized algorithms for monitoring for irAEs, (b) designing an educational program for providers, and (c) developing an inpatient and outpatient immunotherapy toxicity management service.

TPS4134Background: Multiple cancers have been treated successfully with CIT; nonetheless, only subsets of pts experience durable response with CIT monotherapy. CIT combinations may therefore be nee...

3020Background: Colony stimulating factor 1 receptor (CSF-1R) signaling supports recruitment, development, and maintenance of immune suppressive macrophages within the tumor. Combining anti–CSF-1R ...

3001Background: Preclinical studies demonstrate synergistic antitumor activity of PD-1 blockade and varli, a CD27 agonist antibody. Ph1 results were previously presented from a Ph1/2 study assessin...

3000Background: ICOS is a costimulatory molecule expressed on the surface of activated T cells. JTX-2011 is an ICOS agonist designed to stimulate CD4 T effector (T eff) cells and deplete intratumor...

125 Background: Immune Checkpoint Inhibitors (ICIs) are used to treat patients with a wide spectrum of malignancies. Individuals enrolled in clinical trials are usually more fit compared to patients seen in everyday practice. Therefore, it is important to evaluate the safety profile of these agents in real-world data. In addition, it is not clear if the safety of these agents is similar across all age groups. Methods: We reviewed the FDA Adverse Event Reporting System (FAERS) for adverse events associated with the use of PD-1 inhibitors (nivolumab and pembrolizumab); PD-L1 inhibitor (atezolizumab); and CTLA-4 inhibitor (ipilimumab). Our analysis was restricted to reports that included only an ICI as a suspect agent. For each agent, we performed a descriptive analysis of hospitalization (HO) and death (DE) outcomes, as well as select adverse events of special interest (AESI). We compared the distribution of each outcome within age groups ( < 65 years; 67-75; > 75) using Mantel-Haenszel chi -quare test for trend. Results: A total of 23,586 safety reports were included in our analysis. 415 for atezolizumab, 10,026 for nivolumab, 4,808 for pembrolizumab, 6,339 for ipilimumab, and 1,988 for the combination nivolumab plus ipilimumab. Increased age was associated with a statistically significant trend of more hospitalizations for all drugs except for the combination nivolumab plus ipilimumab where hospitalization rate was high ( > 80%) but similar across all age groups. Prevalence of any of the AESI was higher as age increased for all drugs (p < 0.0001) except for atezolizumab (p 0.12) and combination nivolumab plus ipilimumab (p 0.488). Proportion of older patients who experienced death was higher for pembrolizumab (p < 0.001), ipilimumab (p 0.002), and combination nivolumab plus ipilimumab (p < 0.001). Conclusions: Our analysis suggests that among patients treated with ICI, older individuals receiving pembrolizumab, Nivolumab or ipilimumab were more likely to develop immune related AEs, and to be hospitalized. An increased rate of death with higher age was seen with the use of pembrolizumab, ipilimumab, and combination nivolumab + ipilimumab. Older patients treated with ICIs should be monitored carefully for treatment-related AEs.

TPS876 Background: Locally-advanced rectal cancer (LARC) improvements have plateaued due to an inability to consistently deliver adjuvant therapy and effective novel therapies. Systematic testing of new chemotherapy and radiation sensitizers are needed to advance treatment outcomes. This randomized phase II modular clinical trial platform utilizes Total Neoadjuvant Therapy (TNT) with parallel experimental arms (EA) in LARC. The EAs are not intended for direct comparison, but rather to test a variety of sensitizers or hypotheses in a consistent and homogenous high-risk patient (pt) population with correlative biomarkers. Success of any EA will be determined by achievement of pathologic endpoints compared to a control arm. Methods: This NCTN multi-arm randomized phase II trial serves as a modular platform to assess novel sensitizers to neoadjuvant chemotherapy and/or chemoradiotherapy (chemoRT) in LARC. Eligibility includes LARC with any ONE of the following criteria: distal location (cT3-4 ≤5cm from the anal verge, any N); bulky (any cT4 or tumor within 3mm of the mesorectal fascia); high risk for metastatic disease (cN2); or not a candidate for sphincter-sparing surgical resection. After randomization, all pts receive neoadjuvant FOLFOX x 4mo → chemoRT (capecitabine with 50.4Gy) → surgical resection 8-12 wks later. The first EA will assess the activity of veliparib with standard chemoRT. A second EA, testing pembrolizumab concurrently with and following chemoRT, is in development. Primary endpoint is a demonstrated improvement in Neoadjuvant Rectal Cancer (NAR) score for the EA vs control representing a 20% relative risk reduction in DFS HR and 3-4% absolute OS improvement. Secondary endpoints include comparisons of OS, DFS, toxicity, pCR, cCR, therapy completion, negative surgical margins, sphincter preservation, sphincter function including quality of life, and exploratory assessments of molecular and radiographic predictors of response and distant failure. Target accrual is 79 evaluable pts per arm with additional EAs added through protocol amendments. NCT02921256. Support: U10 CA-180868, -180822, UG-189867, U24CA196067; AbbVie Clinical trial information: NCT02921256..

269 Background: Cholangiocarcinoma (CC) is a fatal malignancy with an unmet treatment need. With the approval of immunotherapy for solid tumors with mismatch repair (MMR) deficiency, there is a renewed interest in MMR testing. Little is known about the incidence of MMR deficiency in CC or its correlation to survival, immune cell infiltration, PD-L1 and other proteins expressed in CC such as mesothelin. Methods: CC tumors were identified from patients treated at the University of Virginia from 2000-2014. Tissue microarrays (TMAs) were constructed of 3-4 cores from each tumor and were stained by immunohistochemistry for MMR genes (MLH1, PMS2, MSH2, MSH6), mesothelin, PD-L1 and immune cells. TMAs were scanned using the Leica SCN400 and analyzed using the Digital Image Hub software. Stain intensity thresholds for defining positive cells were determined by two users and recorded as an average of all cores from each tumor. Mesothelin and PD-L1 expression were measured as a percentage of positive tumor cells. Correlation with overall survival was assessed using log-rank tests and classification and regression trees, with p values < 0.05 considered significant. Results: Ninety-one tumors were analyzed: 24 intrahepatic, 33 hilar, and 34 distal. MMR deficiency was found in 20 tumors (22%). None of the MMR deficient tumors co-expressed PD-L1 (>1%), which was found in 15% of the remaining tumors. T cell infiltration (CD4, CD8 and FoxP3) did not differ between MMR deficient or proficient tumors. Patients with MMR deficiency had a trend towards worse survival compared to those with proficiency (median OS: 19.2 vs. 28.1 months, p = 0.07). MMR deficient tumors showed a lower mesothelin expression compared to MMR proficient tumors, median 8 vs. 129 positive cells per TMA (p = 0.08). Patients with MMR deficiency and low mesothelin expression had a worse outcome compared to patients with MMR proficiency and high mesothelin expression (median OS: 14.5 vs. 30.0 months, p = 0.05). Conclusions: Given the high rate of MMR deficiency, all CC tumors should be tested and may benefit from anti-PD-1 therapy. The poor prognosis of MMR deficient CC may be independent of T-cell infiltration and additional studies are needed to better characterize the genetic and molecular landscape of this subset of tumors.

Endoglin is an endothelial cell membrane receptor essential for angiogenesis and highly expressed on the vasculature of many tumor types, including hepatocellular carcinoma (HCC). TRC105 is a chimeric IgG1 anti-CD105 monoclonal antibody that inhibits angiogenesis and tumor growth by endothelial cell growth inhibition, ADCC and apoptosis, and complements VEGF inhibitors.The aim of this phase II study was to evaluate the efficacy of anti-endoglin therapy with TRC105 in patients with advanced HCC, post-sorafenib.Patients with HCC and compensated liver function (Childs-Pugh A/B7), ECOG 0/1, were enrolled to a single-arm, phase II study of TRC105 15 mg/kg IV every two weeks. Patients must have progressed on or been intolerant of prior sorafenib. A Simon optimal two-stage design was employed with a 50% four-month PFS target for progression to the second stage. Correlative biomarkers evaluated included DCE-MRI as well as plasma levels of angiogenic biomarkers and soluble CD105.A total accrual of 27 patients was planned. However, because of lack of efficacy and in accordance with the Simon two-stage design, 11 patients were enrolled. There were no grade 3/4 treatment-related toxicities. Most frequent toxicities were headache (G2; N = 3) and epistaxis (G1; N = 4). One patient had a confirmed partial response by standard RECIST criteria and biologic response on DCE-MRI but the four-month PFS was insufficient to proceed to the second stage of the study.TRC105 was well tolerated in this HCC population following sorafenib. Although there was evidence of clinical activity, this did not meet prespecified criteria to proceed to the second stage. TRC105 development in HCC continues as combination therapy with sorafenib.

Most patients with pancreatic ductal adenocarcinoma (PDAC) die within 5 years following resection plus adjuvant gemcitabine (Gem) from outgrowth of occult metastases. We hypothesized that inhibition of the KRAS pathway with the MEK inhibitor trametinib would inhibit the outgrowth of occult liver metastases in a preclinical model. Liver metastases harvested from two patients with PDAC (Tumors 608, 366) were implanted orthotopically in mice. Tumor cell lines were derived and transduced with lentiviruses encoding luciferase and injected into spleens of mice generating microscopic liver metastases. Growth kinetics of liver metastases were measured with bioluminescent imaging and time-to-progression (TTP), progression-free survival (PFS), and overall survival (OS) were determined. Trametinib (0.3 mg/kg BID) significantly prolonged OS versus control (Tumor 608: 114 vs. 43 days, p

Background The protein products of the early genes E6 and E7 in high-risk HPV types 16 and 18 have been implicated in the oncogenic capability of these viruses. Therefore, these peptides represent attractive vaccine therapy targets. Methods Thirty-two patients with advanced cervical cancer (HPV16 or 18 positive) were treated with HPV16 E6 (18–26) (Arm A) or HPV16 E7 (12–20) peptide (Arm B) pulsed on PBMCs in order to illicit immune response against the relevant peptide on both arms. These PBMCs were cultured for a short time (48 hours only) and in the presence of GM- CSF, accordingly, they were identified as “Pre-Immature Dentritic Cells”. Results 51Cr release assay and ELISPOT demonstrated evidence of specific immune response against the relevant peptide in 10/16 (63%) evaluable patients in arm A and 7/12 (58%) in arm B. HPV16 E6 was found to be homologous to HPV18 E6 in both vivo and vitro. The median overall survival (OS) and progression free survival (PFS) for the full cohort was 10.0 and 3.5 months, respectively. There were no RECIST responses in any patient. The majority of toxicities were grade I and II. Conclusions We demonstrated the feasibility and ability of Pre-Immature Dentritic Cells pulsed with HPV16 E6 (18–26) or HPV16 E7 (12–20) to induce a specific immune response against the relevant peptide despite the advanced disease of the cervical cancer patients treated on this trial. We believe that this observation deserves further investigations. Electronic supplementary material The online version of this article (doi:10.1186/s12967-014-0353-4) contains supplementary material, which is available to authorized users.

e15650 Background: Cholangiocarcinoma (CC) is a rapidly progressing malignancy with an unmet treatment need. Little is known about the CC tumor immune microenvironment or about relevant antigenic targets. We hypothesized that lack of T cell infiltration or PD-L1 expression may identify patients at high risk of death, and that mesothelin may be a relevant antigenic target. Methods: A retrospective analysis was conducted of CC tumors at the University of Virginia from 2000-2014. TMAs were constructed of 3-4 cores from each tumor and were stained by IHC for CD4 and CD8 tumor infiltrating lymphocytes (TILs), mesothelin and PD-L1. TMAs were scanned using the Leica SCN400 and analyzed using the Digital Image Hub software. Stain intensity thresholds for defining positive cells were determined by two users and recorded as an average of all cores from each tumor. Mesothelin and PD-L1 expression were measured as a percentage of positive tumor cells. TILs and protein expression were analyzed for association with overall survival, grouped as high or low expression based either on the median or the 33rdpercentile. Correlation with overall survival was assessed using a log rank test and a classification and regression tree with p-values < 0.05 being considered statistically significant. Results: Ninety-nine tumors were available for analysis: 26 intrahepatic, 37 hilar, and 36 distal. PD-L1 and mesothelin expression > 1% of tumor cells were found in 16% and 92% of tumors, respectively. CD4 and CD8 TILs were found in nearly all tumors (98% and 96%), with the majority showing intraepithelial CD4 and CD8 infiltration (73% and 68%). There were no significant associations between survival and PD-L1, mesothelin, or CD4 and CD8 infiltration. However when considered together, the group with low mesothelin/low CD8 (each below 33rdpercentile) had worse survival (9.1 months) compared to high mesothelin/high CD8 (25 months), high mesothelin/low CD8 (30.1 months) and low mesothelin/high CD8 (26.1 months), p = 0.015. Conclusions: CC tumors that lack CD8 infiltration and mesothelin expression have a poor prognosis. Mesothelin represents an attractive target in cholangiocarcinoma, opening the door for future immunotherapy for CC.

4125 Background: Pancreatic cancer (PC) is a challenging target for immunotherapy.Tumor-infiltrating lymphocytes (TILs) do not reach the PC cells in significant numbers due to the presence of stroma and a suppressive microenvironment. Neoadjuvant chemoradiation (CRT) can increase the presence of TILs in the PC microenvironment. We hypothesized that combination of CRT and pembrolizumab can lead to further increase in TILs and their activation. Methods: Patients with resectable or borderline resectable PC have been randomized 2:1 to the investigational treatment (Arm A) to receive pembrolizumab 200mg IV every 3 weeks on days 1, 22, and 43 during concurrent CRT with capecitabine (825 mg/m2 orally twice daily, Monday-Friday, on days of radiation only) and radiation (50.4 Gy in 28 fractions over 28 days) or Arm B to receive only concurrent CRT with capecitabine. Restaging CT scan or MRI is performed at 4-6 weeks after completion of neoadjuvant treatment, and patients with resectable disease will undergo surgical resection. Here we report the preliminary safety data based on 22 enrolled patients. Results: As of February 3-2017,22 patients have been enrolled (14 Arm A and 8 Arm B). 50% of the patients had resectable disease (7 arm A; 4 arm B) and the other 50% had borderline resectable disease (7 Arm A; 4 arm B). Post-neoadjuvant therapy, 6 patients had unresectable disease (3 on each arm), and 14 patients underwent surgery (10 arm A and 4 arm B). There were 7 grade 3 treatment-related toxicities in Arm A (5 patients): 2 grade 3 diarrhea attributed to CRT; 4 grade 3 lymphopenias attributed to pembrolizumab, CRT or the combination; and one patient had elevated alkaline phosphatase probably related to the combination that met the definition of DLT and resolved after holding the treatment and receiving steroids. There was only one grade 3 toxicity on Arm B: lymphopenia attributed to CRT. No grade 4 toxicities have been reported on either arm. There were no major surgical complications reported within 30 days post-surgery. Conclusions: The combination of CRT and pembrolizuamb is safe based on the presented data. Clinical trial information: NCT02305186.

e21544 Background: Immune checkpoint inhibitors (ICIs) have a promising activity in variety of malignancies however little is known regarding their efficacy and toxicity profile in older adults (≥65 yo). Accordingly, we performed a meta-analysis of published trials using anti-PD-1 or PD-L1 to define the activity of these agents in this subset of patients. Methods: We conducted a search using PubMed and Web of Science databases for randomized controlled trials (RCTs) of PD-1 and PD-L1 inhibitors including nivolumab (N), pembrolizumab (P), and atezolizumab (A). We then identified the studies that reported a subgroup analysis of overall survival (OS) based on an age cutoff. Results: We identified a total of 17 RCTs that compared N, P and A to chemotherapy or targeted therapy. Out of those trials only 9 reported hazard ratio (HR) based on age and were included in this meta-analysis. These trials treated a total of 5033 patients including 2315 patient ≥65 yo (46%). The overall estimated, random-effects hazard ratio (HR) for death was 0.69 with 95% CI of 0.63 -0.74 (p < 0.0001) in the general population favoring ICIs. Based on the selected trials, there was evidence of a 31% reduction in the hazard of death with PD1/PDL1 inhibitors compared with chemo/targeted therapy. This OS benefit persisted when the analysis was done based on disease type (NSCLC or others) or the drug target (PD-1 or PD-L1). Analysis based on age cutoff of 65 yo showed that the efficacy of PD-1 and PD-L1 inhibitors did not vary for older or younger patients. The overall estimated random-effects HR was 0.64 with 95% CI of 0.54 -0.76 in patients ≥65 yo vs. 0.68 with 95% CI of 0.61-0.75 in patients < 65 yo. Data regarding toxicity based on age was available only for 3 trials. The rate of grade 3-4 toxicities was comparable between the 2 groups (45-50% in patients ≥ 65 compared to 37.1-50% in patients < 65). Conclusions: PD-1 and PD-L1 inhibitors efficacy using N, P or A is comparable in older and younger adults when using an age cutoff of 65 years. Future ICIs trials should report efficacy and toxicity based on age.

240 Background: As seen in lung cancer, young patients with cancer can have different risk factors, presentation, and tumor genotype than older patients with the same disease. The clinical and molecular features of young patients with CCA have yet to be well characterized. Methods: Retrospective chart review was performed on patients with intrahepatic (ICC) or extrahepatic cholangiocarcinoma (ECC) across 5 institutions. Data on demographics, risk factors, treatments, pathology, and overall survival (OS) were collected. Tumor genotyping results from MGH SNaPShot and Foundation Medicine were analyzed. Log-rank tests and Kaplan-Meier survival curves were used for statistical analysis. Results: Of 567 patients analyzed, 134 (23.6%) were < 50 years old (yo) and 455 (80.2%) had ICC. When assessed for risk factors, younger patients ( < 50yo) were more likely to have primary sclerosing cholangitis (PSC) (p < 0.001) and less likely to have diabetes (p = 0.05), compared to older patients ( ≥ 50yo). Surgical resection rates were similar in younger vs older patients (41.9 vs 42.6%, p = 0.890), but younger patients had larger tumors (median size 7.1 vs 5.3cm p = 0.012). Younger patients were also more likely to receive palliative systemic chemotherapy (p < 0.001) and more lines of therapy (median, 2 vs 1 line, p < 0.001). Frequency of treatment with liver directed therapy did not differ between the two groups. Molecular testing was performed on 222/567 (39.1%) patients of which 84/134 (62.7%) were younger patients and 138/433 (31.9%) were older patients. FGFR aberrations were more common in younger patients versus older patients (17.6 vs. 5.7%, p = 0.002). Targeted therapy was given to 15/84 (17.9%) younger and 28/138 (20.3%) older patients based on results of mutational profiling. Finally, no significant difference was seen in OS between younger and older patients (22.9 vs 22.7 months, p = 0.89). Conclusions: Younger patients with CCA may have different risk factors, tumor biology, and tolerance of systemic therapy compared to older patients. Further study is needed as referral patterns to tertiary care centers and motivation of younger patients to seek tertiary care may impact these results.

Purpose: Phase I clinical trials are generally conducted to identify the maximum tolerated dose (MTD) or the biologically active dose (BAD) using a traditional dose-escalation design. This design may not be applied to cancer vaccines, given their unique mechanism of action. The FDA recently published “Guidance for Industry: Clinical Considerations for Therapeutic Cancer Vaccines.” However, many questions about the design of cancer vaccine studies remain unanswered. Experimental Design: We analyzed the toxicity profile in 239 phase I therapeutic cancer vaccine trials. We addressed the ability of dose escalation to determine the MTD or the BAD in trials that used a dose-escalation design. Results: The rate of grade 3/4 vaccine-related systemic toxicities was 1.25 adverse events per 100 patients and 2 per 1,000 vaccines. Only two of the 127 dose-escalation trials reported vaccine-related dose limiting toxicities, both of which used bacterial vector vaccines. Out of the 116 trials analyzed for the dose–immune response relationship, we found a statistically significant dose–immune response correlation only when the immune response was measured by antibodies (P < 0.001) or delayed type hypersensitivity (P < 0.05). However, the increase in cellular immune response did not appear further sustainable with the continued increase in dose. Conclusions: Our analysis suggests that the risks of serious toxicities with therapeutic cancer vaccines are extremely low and that toxicities do not correlate with dose levels. Accordingly, the conventional dose-escalation design is not suitable for cancer vaccines with few exceptions. Here, we propose an alternative design for therapeutic cancer vaccine development. Clin Cancer Res; 20(18); 4758–67. ©2014 AACR.

Despite major advances in the treatment of ovarian cancer over the past two decades, it is still an incurable disease and requires the development of better treatment strategies. In recent years, we have developed a greater understanding of tumor immunology and the interactions between tumors and the immune system. This has led to the emergence of cancer immunotherapy as the fourth treatment modality in cancer. In this article, we address the principles of immunotherapy and different approaches that have been investigated over the past decade and discuss the future of immune therapy in ovarian cancer.

Inhibition of angiogenesis is a target in the treatment of a variety of malignancies. Sorafenib is an oral inhibitor of multiple tyrosine kinases involved in tumor angiogenesis. A related case of ophthalmologic toxicity has been reported with another vascular endothelial growth factor receptor inhibitor, sunitinib. We report the first case of retinal tear possibly associated with sorafenib.