Abstract: Purpose: Malignant mesothelioma (MM) arising in the peritoneal cavity is a rare neoplasm characterized by peritoneal progression and for which there are limited therapeutic options. We evaluated the peritoneal progression-free and overall survival (PFS and OS, respectively) for patients with peritoneal MM after surgical resection and regional chemotherapy. Patients and Methods: Forty-nine patients (28 males, 21 females; median age, 47 years; range, 16 to 76 years) with MM underwent laparotomy, tumor resection, continuous hyperthermic peritoneal perfusion with cisplatin (median dose 250 mg/m 2 ), and a single postoperative intraperitoneal dwell of fluorouracil and paclitaxel (n = 35) on protocols approved by the Institutional Review Board. Standard techniques for actuarial analyses of potential prognostic variables (Kaplan-Meier method with two-tailed log-rank test and Cox proportional hazards model) were performed. Results: At a median potential follow-up of 28.3 months, median actuarial PFS is 17 months and actuarial OS is 92 months. Factors associated with improved PFS and OS by the Cox proportional hazards model were a history of previous debulking surgery, absence of deep tissue invasion, minimal residual disease after surgical resection (OS only), and age younger than 60 years (OS only). Conclusion: Surgical resection and regional chemotherapy for MM results in durable PFS and OS. Favorable outcome is associated with age, tumor biology (selection of patients with a history of previous debulking), lack of invasive tumor growth, and minimal residual disease after tumor resection.

Abstract: We investigated the combination of lymphodepleting chemotherapy followed by the adoptive transfer of autologous tumor reactive lymphocytes for the treatment of patients with refractory metastatic melanoma. Patients and Methods Thirty-five patients with metastatic melanoma, all but one with disease refractory to treatment with high-dose interleukin (IL) -2 and many with progressive disease after chemotherapy, underwent lymphodepleting conditioning with two days of cyclophosphamide (60 mg/kg) followed by five days of fludarabine (25 mg/m 2 ). On the day following the final dose of fludarabine, all patients received cell infusion with autologous tumor-reactive, rapidly expanded tumor infiltrating lymphocyte cultures and high-dose IL-2 therapy. Results Eighteen (51%) of 35 treated patients experienced objective clinical responses including three ongoing complete responses and 15 partial responses with a mean duration of 11.5 ± 2.2 months. Sites of regression included metastases to lung, liver, lymph nodes, brain, and cutaneous and subcutaneous tissues. Toxicities of treatment included the expected hematologic toxicities of chemotherapy including neutropenia, thrombocytopenia, and lymphopenia, the transient toxicities of high-dose IL-2 therapy, two patients who developed Pneumocystis pneumonia and one patient who developed an Epstein-Barr virus–related lymphoproliferation. Conclusion Lymphodepleting chemotherapy followed by the transfer of highly avid antitumor lymphocytes can mediate significant tumor regression in heavily pretreated patients with IL-2 refractory metastatic melanoma.

Abstract: The identification of many tumor-associated epitopes as nonmutated “self” Ags led to the hypothesis that the induction of large numbers of self/tumor Ag-specific T cells would be prevented because of central and peripheral tolerance. We report in this study on vaccination efforts in 95 HLA-A*0201 patients at high risk for recurrence of malignant melanoma who received prolonged immunization with the “anchor-modified” synthetic peptide, gp100209–217(210M). Vaccination using this altered peptide immunogen was highly effective at inducing large numbers of self/tumor-Ag reactive T cells in virtually every patient tested, with levels as high as 42% of all CD8+ T cells assessed by tetramer analysis. From 1 to 10% of all CD8+ cells were tumor-Ag reactive in 44% of patients and levels & gt;10% were generated in 17% of patients. These studies were substantiated using the ELISPOT assay and a bulk cytokine release assay. Although our data regarding “tumor escape” were inconclusive, some patients had growing tumors that expressed Ag and HLA-A*0201 in the presence of high levels of antitumor T cells. There was no difference in the levels of antitumor Ag-specific T cells in patients who recurred compared with those that remained disease-free. Thus, the mere presence of profoundly expanded numbers of vaccine-induced, self/tumor Ag-specific T cells cannot by themselves be used as a “surrogate marker” for vaccine efficacy. Further, the induction of even high levels of antitumor T cells may be insufficient to alter tumor progression.

Abstract: Previously, we reported our experience treating 14 patients with metastatic melanoma using a fully human antibody to cytotoxic T-lymphocyte antigen-4 (anti–CTLA-4) in conjunction with peptide vaccination. We have now treated 56 patients to evaluate two different dose schedules of anti–CTLA-4 and to explore the relationship between autoimmunity and tumor regression. Patients and Methods A total of 56 patients with progressive stage IV melanoma were enrolled onto the study. All had Karnofsky performance status ≥ 60% with no prior history of autoimmunity. Twenty-nine patients received 3 mg/kg anti–CTLA-4 every 3 weeks, whereas 27 received 3 mg/kg as their initial dose with subsequent doses reduced to 1 mg/kg every 3 weeks. In both cohorts patients received concomitant vaccination with two modified HLA-A*0201-restricted peptides from the gp100 melanoma-associated antigen, gp100:209-217(210M) and gp100:280-288(288V). Results Two patients achieved a complete response (ongoing at 30 and 31 months, respectively) and five patients achieved a partial response (durations of 4, 6, 25+, 26+, and 34+ months, respectively), for an overall objective response rate of 13%. Tumor regression was seen in lung, liver, brain, lymph nodes, and subcutaneous sites. Of 14 patients with grade 3/4 autoimmune toxicity, five (36%) experienced a clinical response compared with only two responses in the 42 patients (5%) with no autoimmune toxicity (P = .008). There were no significant differences in response rate or toxicity between the two dose schedules. Conclusion Administration of anti–CTLA-4 monoclonal antibody plus peptide vaccination can cause durable objective responses, which correlate with the induction of autoimmunity, in patients with metastatic melanoma.

Abstract: PURPOSE: A strain of Salmonella typhimurium (VNP20009), attenuated by chromosomal deletion of the purI and msbB genes, was found to target to tumor and inhibit tumor growth in mice. These findings led to the present phase I study of the intravenous infusion of VNP20009 to patients with metastatic cancer. PATIENTS AND METHODS: In cohorts consisting of three to six patients, 24 patients with metastatic melanoma and one patient with metastatic renal cell carcinoma received 30-minute intravenous bolus infusions containing 10 6 to 10 9 cfu/m 2 of VNP20009. Patients were evaluated for dose-related toxicities, selective replication within tumors, and antitumor effects. RESULTS: The maximum-tolerated dose was 3 × 10 8 cfu/m 2 . Dose-limiting toxicity was observed in patients receiving 1 × 10 9 cfu/m 2 , which included thrombocytopenia, anemia, persistent bacteremia, hyperbilirubinemia, diarrhea, vomiting, nausea, elevated alkaline phosphatase, and hypophosphatemia. VNP20009 induced a dose-related increase in the circulation of proinflammatory cytokines, such as interleukin (IL)-1β, tumor necrosis factor alpha, IL-6, and IL-12. Focal tumor colonization was observed in two patients receiving 1 × 10 9 cfu/m 2 and in one patient receiving 3 × 10 8 cfu/m 2 . None of the patients experienced objective tumor regression, including those patients with colonized tumors. CONCLUSION: The VNP20009 strain of Salmonella typhimurium can be safely administered to patients, and at the highest tolerated dose, some tumor colonization was observed. No antitumor effects were seen, and additional studies are required to reduce dose-related toxicity and improve tumor localization.

Abstract: TPS499 Background: PC carries a poor prognosis. F has improved overall survival (OS) compared to G leading to its use as a 1st line treatment for patients (pts) with advanced PC. Similarly, the combination of G and A has demonstrated OS benefit. No data exists for G/A in the 2nd line setting. Many oncologists continue to sequence F treatment followed upon disease progression by G/A for pts with advanced PC with good performance status. N is a chimeric monoclonal IgG1 antibody recognizing an aberrantly glycosylated MUC5AC specific to GI tumors. Its mechanism of action is through ADCC. An IHC based companion diagnostic assay is utilized to select pts whose tumors express the target (approx. 65-70%). A prior study administering N to pts with advanced PC refractory to chemotherapy was well tolerated with disease stabilization and prolongation of OS. Furthermore 2 of 5 pts receiving the combination of G+N following progression on F remain alive at 10 and 12 months respectively. Methods: The primary objective of this phase 2.5 study is to determine if the combination of N and G plus A can improve the OS for pts who have PC over G plus A alone in the post F setting. The trial is a 2-arm randomized 1:1 multi-institution trial of N plus G and A vs. G and A. Eligible pts would be expected to have an estimated 4.5 to 4.8 month median OS with G alone, but this may be enhanced somewhat with the addition of A. The goal is to determine if the use of N along with G and A will result in pts having an increased median OS of 8 months vs. an estimated 5 months without N. Kaplan-Meier curves and a two-tailed log-rank test will be the primary analysis methods. All pts must have tissue positive for the MUC5AC variant (≥20% by IHC). Because N has been established to be safe when given with G alone but not with the combination of G and A, stopping rules for safety will be adhered to for the first 6 pts randomized to G/A plus N. Enrollment to the study has commenced. Correlative studies will utilize both PBMCs and serum for immune monitoring. Frequency, phenotype and function of different immune cells (including CD8+ T cells, CD4+ T cells, Tregs and MDSCs) will be analyzed. Clinical trial information: NCT01834235.

Abstract: 240 Background: NPC-1C (NEO102) is a novel chimeric monoclonal antibody that recognizes a variant form of MUC5AC expressed specifically by human pancreatic (P) and colorectal (CC) tumors. The mechanism of action is through Antibody-dependent cell-mediated cytotoxicity (ADCC). We are presenting results of dose escalation and preplanned expansion cohort of NEO-102. Methods: This is a Phase Ib/IIa, open label, multicenter clinical trial and expansion cohort of NEO102. Patients are preselected based on an Immunuhistochemistry (IHC) companion diagnostic assay. Antigen expression cut off was set at 20% expression. NEO102 was administered every 2 weeks IV with tumor assessments every 8 weeks. The primary objective was to determine safety and tolerability of NEO102. Secondary objectives include overall survival, clinical benefit, pharmacokinetics and explore the immunologic correlates. Results: Twenty-six patients (3 pancreatic and 23 colon cancer) are evaluable for toxicity and response. Median age is 55 (32 - 68) years, 14 are male. Two dose limiting toxicities were experienced at 4.0 mg/kg: grade 3 hyperbilirubinemia (n=4) and grade 3 anemia (n=1). The maximum tolerated dose (MTD) and recommended phase-2 dose (RP2D) was established at 3.0 mg/kg. Of 12 patients evaluated for response, 5 demonstrated stable disease by RECIST (42%; 4 CC, 1 P) after the first course (Day 57) and 1 PC had SD after the second course (Day 114). OS is 4.5+ months (1+ - 13.5+), median duration of treatment of 74+ days (36-133). Of those screened, 60-70% tumors were IHC positive. Immune correlates (including cytokine profile, HAMA) will be presented. Conclusions: Treatment with NEO102 is well tolerated with a manageable safety profile. RP2D is 3.0 mg/kg. Preliminary results with NEO102 have demonstrated signs of clinical activity based on stabilization of disease in heavily pretreated patients with PC and CC. A Phase II study of NEO102 monotherapy in pancreatic and colon cancer is now enrolling patients. In addition, a combination study using NEO102 with cytotoxic chemotherapy in metastatic pancreatic cancer is underway. Clinical trial information: NCT01040000.

Abstract: Introduction: Chimeric antigen receptor (CAR) T cells targeting either CD19 or CD22 have yielded striking complete remission (CR) rates of 70%-90% in patients with relapsed/refractory B-cell acute lymphoblastic leukemia (ALL), but CD19 negative and CD22 low relapse limits the curative potential of these single-antigen CAR T cell approaches. We hypothesized that a bivalent CAR-T construct that can target CD19 and/or CD22 would prevent antigen negative/low relapse. Here we present the combined single institution experience to date of pediatric and adult patients with R/R ALL treated with this novel bispecific CAR. Methods: We conducted parallel Phase I clinical trials of CD19/CD22 bispecific CAR T cells in pediatric and adult patients with relapsed/refractory ALL. We utilized lentiviral transduction of a bivalent CAR construct incorporating the fmc63 CD19 and m971 CD22 single chain variable fragments (scFvs) and a 41BB costimulatory endodomain. After lymphodepletion with fludarabine and cyclophosphamide, patients were infused with fresh or cryopreserved CAR T cells manufactured using a 7-11 day process. Two dose levels were tested during dose escalation: Dose level 1 was 1x106 CAR T cells/kg and dose level 2 was 3x106 cells/kg. Primary objectives assessed the ability to successfully manufacture CAR19/22 CAR T cells and safety while response at Day 28 post-infusion was a secondary objective. Blood, bone marrow and cerebrospinal fluid samples were obtained at protocol defined intervals for correlative biology studies. Results: Nineteen patients have been enrolled (10 pediatric; 9 adult) with a median age of 23 years (range, 2-68) and median of 4 (range, 2-11) prior lines of leukemia-directed therapy. Ten patients received prior HCT, 9 were treated with prior Blinatumomab, 3 with prior CD19 directed CAR T cells and 4 with prior Inotuzumab. Fourteen patients (8 pediatric, 6 adult) have been infused to date with CD19/CD22 bispecific CAR T cells; 7 were treated at dose level 1 (DL1) and 7 at dose level 2 (DL2). Successful manufacturing of cells at target dose levels was achieved in all patients. Twelve patients have reached day 28 and are included in the safety and response analysis presented here. Nine of 12 (75%) experienced cytokine release syndrome (CRS) and 2/12 (17%) developed immune-effector cell neurotoxicity syndrome (ICANS). The CRS and ICANS were all grade 1 or 2 across both dose levels and across pediatric and adult patients except for one adult with high disease burden who experienced grade 4 CRS and grade 4 ICANS, both of which were reversible. No differences in toxicities were seen across the patient age spectrum and there were no cases of treatment-related mortality within 28 days following CAR T infusion. Eleven of 12 (92%) patients achieved a CR, 10 of whom achieved CR at day 28 and one with a PR of extramedullary disease at day 28 which improved to CR by day 180 without further leukemia-directed intervention. One patient had primary progressive disease prior to day 28. Peak CAR expansion as detected by peripheral blood flow cytometry reached a median level of 11.13% (DL1) and 29.1% (DL2) CAR T of CD3+ cells with a range of 0.7-22.54% and 3.8-86.96%, respectively. To date, 3 patients (1 pediatric and 2 adult patients) have relapsed, all with retention of CD19. Post-remission practice differed across pediatric and adult patients; Six pediatric patients reaching day 28 underwent consolidative hematopoietic cell transplantation (HCT) whereas no adult patients received subsequent HCT. One patient died from complications post HCT while in remission. Therefore, the overall survival for all infused patients was 92% with a median follow-up of 9.5 months from time of infusion (range, 1-20). Conclusion: The combined pediatric and adult phase I trials of bispecific CD19/CD22 targeting CAR T cells in relapsed/refractory ALL demonstrates safety and tolerability at two dose levels. Expanded accrual at dose level 2 is ongoing and clinical outcomes will be updated. This work additionally demonstrates feasibility of delivering unified B-ALL CAR T cell therapy across age boundaries. Multi-parametric CyTOF studies permitting CAR T cell phenotyping in conjunction with single cell TCR tracking, proteomics, epigenomics and cytokine profiling are ongoing and will be used to further characterize persisting CAR T cells and define inter-product and inter-patient variability. Disclosures Muffly: Pfizer: Consultancy; KITE: Consultancy; Adaptive: Research Funding. Majzner:Xyphos Inc.: Consultancy; Lyell Immunopharma: Consultancy. Feldman:Octane Biotech, Inc.: Employment; Personalized Medicine Initiative Science: Membership on an entity's Board of Directors or advisory committees. Miklos:Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Juno: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Becton Dickinson: Research Funding; Miltenyi Biotech: Membership on an entity's Board of Directors or advisory committees; Precision Bioscience: Membership on an entity's Board of Directors or advisory committees; AlloGene: Membership on an entity's Board of Directors or advisory committees. Mackall:Obsidian: Research Funding; Lyell: Consultancy, Equity Ownership, Other: Founder, Research Funding; Nektar: Other: Scientific Advisory Board; PACT: Other: Scientific Advisory Board; Bryologyx: Other: Scientific Advisory Board; Vor: Other: Scientific Advisory Board; Roche: Other: Scientific Advisory Board; Adaptimmune LLC: Other: Scientific Advisory Board; Glaxo-Smith-Kline: Other: Scientific Advisory Board; Allogene: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Apricity Health: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Unum Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

Abstract: 2531 Background: NEO201 is a humanized IgG1 monoclonal antibody generated against tumor-associated antigens from colorectal cancer which binds specifically to tumor-associated CEACAM-5 and CEACAM-6 variants without binding CECAM 5/6 on normal epithelial tissues. NEO-201 reactivity is positive in the majority of adenocarcinomas including colon (85%), pancreas (86%), lung (79%), and breast (53%). Preclinical data showed that NEO-201 exerts anti-tumor activity through antibody dependent cellular cytotoxicity and complement dependent cytotoxicity. Here we present outcomes from a phase I trial of NEO-201 in advanced solid tumors (NCT03476681). Methods: This was a classic 3+3 dose escalation trial, with cohort expansion at the RP2D. NEO-201 was administered intravenously every two weeks in a 28-day cycle. The primary objective was to assess the MTD/RP2D of NEO-201 in patients with advanced solid tumors. The secondary objective was to assess the preliminary antitumor activity and exploratory objectives assessed pharmacokinetics and the effect of NEO-201 administration on immunologic parameters and possible relationships with response. Of 17 patients enrolled, 11 had colorectal, 4 had pancreatic and 2 had breast cancer. 4 patients received NEO-201 at dose level (DL) 1 (1 mg/kg), 6 patients at DL 1.5 (1.5 mg/kg) and 7 patients at dose DL 2 (2 mg/kg). Results: At the time of data cutoff, all patients had discontinued therapy. 11 of 14 evaluable patients discontinued due to disease progression and 3 patients discontinued due to DLT (grade 4 febrile neutropenia and prolonged neutropenia, each in 1/6 patients at DL2, and grade 3 febrile neutropenia in 1/6 patients at DL 1.5). Most common grade 3/4 toxicities were neutropenia (94%), white blood cell decrease (59%), lymphocyte decrease (29%), and febrile neutropenia (24%). Protocol was modified to allow administration of G-CSF and based on safety and PK data the RP2D was established as 1.5mg/Kg. Median number of doses received was 4.7. 13 subjects were able to undergo disease assessment after two cycles. The best response observed was stable disease (SD) in 5/9 evaluable patients with colorectal cancer. Minor CA-19-9 reductions were observed in two pancreatic cancer patients at DL 1.5. Correlative endpoints revealed that all patients enrolled in the trial expressed NEO-201 target antigen on their tumor tissue. Analysis of soluble factors in serum revealed that a high level of soluble MICA at baseline was correlated with a downregulation of NK cell activation markers and progressive disease. Unexpectedly, flow cytometry showed that NEO-201 also binds to circulating T regulatory cells and depleted these cells especially in patients with SD. Conclusions: NEO-201 was safe and well tolerated at the MTD of 1.5 mg/kg. Depletion of T regulatory cells suggests that the combination of NEO-201 with immune checkpoint inhibitor should be tested in future clinical trials. Clinical trial information: NCT03476681.