CD22 CAR T cells demonstrate high response rates and safety in pediatric and adult B-ALL: Phase 1b results

Chimeric antigen receptor (CAR) T cells targeting CD22 (CD22-CAR) provide a therapeutic option for patients with CD22+ malignancies with progression after CD19-directed therapies. Using on-site, automated, closed-loop manufacturing, we conducted parallel Phase 1b clinical trials investigating a humanized CD22-CAR with 41BB costimulatory domain in children and adults with heavily treated, relapsed/refractory (r/r) B-ALL. Of 19 patients enrolled, 18 had successful CD22-CAR manufacturing, and 16 patients were infused. High grade (3-4) cytokine release syndrome (CRS) and immune effector-cell-associated neurotoxicity syndrome (ICANS) each occurred in only one patient; however, three patients experienced immune-effector-cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS). Twelve of 16 patients (75%) achieved CR with an overall 56% MRD-negative CR rate. Duration of response was overall limited (median 77 days), and CD22 expression was downregulated in 4/12 (33%) available samples at relapse. In summary, we demonstrate that closed-loop manufacturing of CD22-CAR T cells is feasible and is associated with a favorable safety profile and high CR rates in pediatric and adult r/r B-ALL, a cohort with limited CD22-CAR reporting.

HLH-like toxicities predict poor survival after the use of tisagenlecleucel in children and young adults with B-ALL

Chimeric antigen receptor-associated hemophagocytic lymphohistiocytosis (HLH)-like toxicities (LTs) involving hyperferritinemia, multiorgan dysfunction, coagulopathy, and/or hemophagocytosis are described as occurring in a subset of patients with cytokine release syndrome (CRS). Case series report poor outcomes for those with B-cell acute lymphoblastic leukemia (B-ALL) who develop HLH-LTs, although larger outcomes analyses of children and young adults (CAYAs) with B-ALL who develop these toxicities after the administration of commercially available tisagenlecleucel are not described. Using a multi-institutional database of 185 CAYAs with B-ALL, we conducted a retrospective cohort study including groups that developed HLH-LTs, high-grade (HG) CRS without HLH-LTs, or no to low-grade (NLG) CRS without HLH-LTs. Primary objectives included characterizing the incidence, outcomes, and preinfusion factors associated with HLH-LTs. Among 185 CAYAs infused with tisagenlecleucel, 26 (14.1%) met the criteria for HLH-LTs. One-year overall survival and relapse-free survival were 25.7% and 4.7%, respectively, in those with HLH-LTs compared with 80.1% and 57.6%, respectively, in those without. In multivariable analysis for death, meeting criteria for HLH-LTs carried a hazard ratio of 4.61 (95% confidence interval, 2.41-8.83), controlling for disease burden, age, and sex. Patients who developed HLH-LTs had higher pretisagenlecleucel disease burden, ferritin, and C-reactive protein levels and lower platelet and absolute neutrophil counts than patients with HG- or NLG-CRS without HLH-LTs. Overall, CAYAs with B-ALL who developed HLH-LTs after tisagenlecleucel experienced high rates of relapse and nonrelapse mortality, indicating the urgent need for further investigations into prevention and optimal management of patients who develop HLH-LTs after tisagenlecleucel.

Abstract 959: Immune signatures of GD2 CAR T cell activity in H3K27M+ diffuse midline glioma patients

Introduction: H3K27M-mutated diffuse intrinsic pontine glioma (DIPG) and spinal cord diffuse midline glioma (DMG) are universally lethal central nervous system (CNS) tumors in children and young adults. We previously demonstrated safety and activity of GD2.41BB.z chimeric antigen receptor T cells (CAR-Ts) at dose level 1, 1x106 GD2 CAR-T/kg (Majzner/Ramakrishna et al. Nature 2022) and reported results of dose level 2, 3x106 GD2 CAR-T/kg (Majzner et al. AACR 2022). Here, we present in depth high-dimensional analyses to define the immune states that contribute to CAR-T activity in patients.

Methods: Thirteen patients (10 DIPG/3 spinal DMG; 4-30 years old; 7F/6M) were enrolled in this GD2 CAR-T phase 1 clinical trial (NCT04196413). GD2 CAR-Ts were administered to 12/13 enrolled patients. In the first cohort, CAR-Ts were administered initially intravenously (IV), followed by serial intracerebroventricular infusions (ICV; range 0-11 infusions/patient). Patient GD2 CAR-T product, peripheral blood, and cerebrospinal fluid (CSF) samples were evaluated for CAR-T expansion (qPCR; flow cytometry), cytokine signatures (Multiplex Luminex), and immune cell profiles (single cell RNA-sequencing). Data were analyzed in the context of clinical trajectory and patient response.

Results: 10/12 infused subjects demonstrated clinical and/or radiographic benefit, with less systemic toxicity following ICV compared to IV infusion. CAR-T expansion was noted in the periphery and CSF of all treated patients and following serial ICV infusions. In peripheral blood, cytokine concentrations, including IFN-gamma, IL6, and CXCL9, were higher after IV compared to ICV CAR-T infusions, correlating with increased systemic inflammation. Conversely in CSF, cytokine concentrations, such as CCL2 and CXCL9, were higher following ICV compared to IV CAR-T infusions. Transcriptomic analysis was conducted on 576,199 single cells from 91 samples, including GD2 CAR-T products and patient CSF. This is the largest CAR-T dataset in CNS tumors. Patient CSF samples were dominated by T cell and myeloid populations. After IV CAR-T infusion, patient CSF exhibited an increased fraction of regulatory T cells and suppressive myeloid populations from baseline. These immune suppressive cells reduced after ICV infusion. Ongoing analyses are underway to explore the relation of these immune populations to patient response.

Conclusions: H3K27M-mutated DIPG/DMG patients demonstrate continued clinical response with serial ICV GD2 CAR-T infusions, with heterogeneity in the durability of response across patients. In-depth correlative analyses profile distinct immune populations and demonstrate population shifts depending on route of administration and over the course of treatment. Key findings from these data will allow for iterative improvement in CAR-T therapies for H3K27M+ DIPG/DMG patients, providing hope to shift the paradigm of this fatal disease.

Citation Format: Sneha Ramakrishna, Zinaida Good, Moksha Desai, Daniel Zamler, Rebecca Mancusi, Jasia Mahdi, Robbie Majzner, Liora Schultz, Rebecca Richards, Jennifer Kamens, Valentin Barsan, Cynthia Campen, Sonia Partap, Zachary Ehlinger, Warren Reynolds, Yiyun Chen, Mark P. Hamilton, Jennifer Moon, Christina Baggott, Michael Kunicki, Michelle Fujimoto, Amy Li, Sneha Jariwala, Sharon Mavroukakis, Emily Egeler, Ashley Jacobs, Courtney Erickson, Karen Yamabe-Kwong, Snehit Prabhu, Kara Davis, Steve Feldman, Bita Sahaf, Crystal L. Mackall, Michelle Monje. Immune signatures of GD2 CAR T cell activity in H3K27M+ diffuse midline glioma patients [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 959.

Outcomes After Nonresponse and Relapse Post-Tisagenlecleucel in Children, Adolescents, and Young Adults With B-Cell Acute Lymphoblastic Leukemia

PURPOSE

Nonresponse and relapse after CD19-chimeric antigen receptor (CAR) T-cell therapy continue to challenge survival outcomes. Phase II landmark data from the ELIANA trial demonstrated nonresponse and relapse rates of 14.5% and 28%, respectively, whereas use in the real-world setting showed nonresponse and relapse rates of 15% and 37%. Outcome analyses describing fate after post-CAR nonresponse and relapse remain limited. Here, we aim to establish survival outcomes after nonresponse and both CD19+ and CD19- relapses and explore treatment variables associated with inferior survival.

METHODS

We conducted a retrospective multi-institutional study of 80 children and young adults with B-cell acute lymphoblastic leukemia experiencing nonresponse (n = 23) or relapse (n = 57) after tisagenlecleucel. We analyze associations between baseline characteristics and these outcomes and establish survival rates and salvage approaches.

RESULTS

The overall survival (OS) at 12 months was 19% across nonresponders (n = 23; 95% CI, 7 to 50). Ninety-five percent of patients with nonresponse had high preinfusion disease burden. Among 156 morphologic responders, the cumulative incidence of relapse was 37% (95% CI, 30 to 47) at 12 months (CD19+; 21% [15 to 29], CD19-; 16% [11 to 24], median follow-up; 380 days). Across 57 patients experiencing relapse, the OS was 52% (95% CI, 38 to 71) at 12 months after time of relapse. Notably, CD19- relapse was associated with significantly decreased OS as compared with patients who relapsed with conserved CD19 expression (CD19- 12-month OS; 30% [14 to 66], CD19+ 12-month OS; 68% [49 to 92], P = .0068). Inotuzumab, CAR reinfusion, and chemotherapy were used as postrelapse salvage therapy with greatest frequency, yet high variability in treatment sequencing and responses limits efficacy analysis across salvage approaches.

CONCLUSION

We describe poor survival across patients experiencing nonresponse to tisagenlecleucel. In the post-tisagenlecleucel relapse setting, patients can be salvaged; however, CD19- relapse is distinctly associated with decreased survival outcomes.

Effect of a MUC5AC Antibody (NPC-1C) Administered With Second-Line Gemcitabine and Nab-Paclitaxel on the Survival of Patients With Advanced Pancreatic Ductal Adenocarcinoma: A Randomized Clinical Trial

IMPORTANCE

Treatment options are limited for patients with advanced pancreatic ductal adenocarcinoma (PDAC) beyond first-line 5-fluorouracil, leucovorin, irinotecan, and oxaliplatin (FOLFIRINOX), with such individuals commonly being treated with gemcitabine and nab-paclitaxel.

OBJECTIVE

To determine whether NPC-1C, an antibody directed against MUC5AC, might increase the efficacy of second-line gemcitabine and nab-paclitaxel in patients with advanced PDAC.

DESIGN, SETTING, AND PARTICIPANTS

This multicenter, randomized phase II clinical trial enrolled patients with advanced PDAC between April 2014 and March 2017 whose disease had progressed on first-line FOLFIRINOX. Eligible patients had tumors with at least 20 MUC5AC staining by centralized immunohistochemistry review. Statistical analysis was performed from April to May 2022.

INTERVENTIONS

Patients were randomly assigned to receive gemcitabine (1000 mg/m2) and nab-paclitaxel (125 mg/m2) administered intravenously on days 1, 8, and 15 of every 4-week cycle, with or without intravenous NPC-1C 1.5 mg/kg every 2 weeks.

MAIN OUTCOMES AND MEASURES

The primary end point was overall survival (OS). Secondary end points were progression-free survival (PFS), objective response rate (ORR), and safety. Pretreatment clinical variables were explored with Cox proportional hazards analysis.

RESULTS

A total of 78 patients (median [range] age, 62 [36-78] years; 32 [41%] women; 9 [12%] Black; 66 [85%] White) received second-line treatment with gemcitabine plus nab-paclitaxel (n = 40) or gemcitabine plus nab-paclitaxel and NPC-1C (n = 38). Median OS was 6.6 months (95% CI, 4.7-8.4 months) with gemcitabine plus nab-paclitaxel vs 5.0 months (95% CI, 3.3-6.5 months; P = .22) with gemcitabine plus nab-paclitaxel and NPC-1C. Median PFS was 2.7 months (95% CI, 1.9-4.1 months) with gemcitabine plus nab-paclitaxel vs 3.4 months (95% CI, 1.9-5.3 months; P = .80) with gemcitabine plus nab-paclitaxel and NPC-1C. The ORR was 3.1% (95% CI, 0.4%-19.7%) in the gemcitabine plus nab-paclitaxel and NPC-1C group and 2.9% (95% CI, 0.4%-18.7%) in the gemcitabine plus nab-paclitaxel group. No differences in toxicity were observed between groups, except that grade 3 or greater anemia occurred more frequently in patients treated with gemcitabine plus nab-paclitaxel and NPC-1C than gemcitabine plus nab-paclitaxel (39% [15 of 38] vs 10% [4 of 40]; P = .003). The frequency of chemotherapy dose reductions was similar in both groups (65% vs 74%; P = .47). Lower performance status, hypoalbuminemia, PDAC diagnosis less than or equal to 18 months before trial enrollment, lymphocyte-to-monocyte ratio less than 2.8, and CA19-9 greater than 2000 IU/mL were independently associated with poorer survival.

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial of advanced PDAC, NPC-1C did not enhance the efficacy of gemcitabine/nab-paclitaxel. These data provide a benchmark for future trials investigating second-line treatment of PDAC.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01834235.

Abstract CT001: Major tumor regressions in H3K27M-mutated diffuse midline glioma (DMG) following sequential intravenous (IV) and intracerebroventricular (ICV) delivery of GD2-CAR T cells

Background: H3K27M-mutated DMGs are universally lethal central nervous system tumors that express high levels of the disialoganglioside GD2. IV administered GD2-CAR T cells (GD2-CART) regress DMG in preclinical models, and locoregionally delivered CARs demonstrate enhanced activity in xenograft models of brain tumors.

Methods: NCT04196413 is a 3+3 Phase I dose escalation trial testing GD2-CART in patients with H3K27M DMG, with dose-limiting toxicities (DLT) considered independently for DIPG and spinal DMG (sDMG). Arm A tested escalating doses of IV GD2-CART (DL1: 1e6 GD2-CART/kg; DL2=3e6 GD2-CART/kg) following lymphodepletion (LD). After the DLT period, patients with clinical and/or radiographic benefit were eligible for subsequent ICV GD2-CART (10-30e6 GD2-CART) administered via Ommaya catheter without LD every 4-8 weeks for a maximum of 12 doses. We previously reported early results from 4 patients treated on DL1, which demonstrated clinical activity and manageable toxicity. Here we provide updated results for DL1 and DL2.

Results: Thirteen subjects were enrolled and 11 treated [n=4 DL1 (3 DIPG/1 sDMG); n=9 DL2 (7 DIPG/2 sDMG)]. Two subjects were removed prior to treatment due to rapid progression. No DLTs were observed on DL1. Three subjects experienced DLT on DL2 (2 DIPG/1 sDMG) due to grade 4 cytokine release syndrome (CRS), successfully managed with tocilizumab, anakinra, and corticosteroids. CRS occurred earlier on DL2 vs. DL1 (Day 3 vs 7). On both dose levels, all subjects exhibited transient symptoms related to on-tumor inflammation, termed Tumor Inflammation-Associated Neurotoxicity (TIAN), which was successfully managed with anakinra and, in some cases, CSF drainage and dexamethasone. No DLT due to TIAN has occurred.

Ten patients have had adequate follow-up to assess benefit. Nine experienced radiographic and/or clinical benefit after IV infusion, and they received subsequent ICV GD2-CART infusions (median= 4 ICV infusions/pt, range 1-6). ICV infusions were not associated with high-grade CRS, although some subjects developed transient fever, headache, meningismus, nausea, and/or vomiting, and several subjects developed TIAN. Four patients continue to receive ICV infusions on study and have experienced continued clinical and radiographic benefit at 11+, 9.5+, 8+ and 7+ months following enrollment. A 31-year-old with sDMG has experienced a near-complete (>95%) reduction in tumor volume and a 17-year-old with DIPG experienced a near-complete (>98%) reduction in volume of a pontine tumor.

Conclusions: IV treatment of DIPG and sDMG with GD2-CART is safe at a dose of 1e6/kg, but associated with unacceptable rates of high-grade CRS at 3e6/kg. ICV GD2-CART without LD, administered following a previous course of IV GD2-CART with LD, has been well tolerated and has mediated impressive sustained clinical benefit in some patients with DIPG/sDMG. Given these findings, we are launching a new arm to assess safety and activity and to define the recommended phase 2 dose for ICV delivery of GD2-CART without LD. Patients are eligible for up to 12 ICV infusions of GD2-CART administered every 4-6 weeks. Clinical benefit will be formally assessed using patient-reported outcomes. GD2-CART has the potential to transform therapy for patients with H3K27M+ DIPG/sDMG.

Citation Format: Robbie G. Majzner, Jasia Mahdi, Sneha Ramakrishna, Shabnum Patel, Harshini Chinnasamy, Kristen Yeom, Liora Schultz, Valentin Barsan, Rebecca Richards, Cynthia Campen, Agnes Reschke, Angus Martin Shaw Toland, Christina Baggott, Sharon Mavroukakis, Emily Egeler, Jennifer Moon, Ashley Jacobs, Karen Yamabe-Kwong, Lindsey Rasmussen, Esther Nie, Sean Green, Michael Kunicki, Michelle Fujimoto, Zach Ehlinger, Warren Reynolds, Snehit Prabhu, Katherine E. Warren, Tim Cornell, Sonia Partap, Paul Fisher, Gerald Grant, Hannes Vogel, Bita Sahaf, Kara Davis, Steven Feldman, Michelle Monje, Crystal L. Mackall. Major tumor regressions in H3K27M-mutated diffuse midline glioma (DMG) following sequential intravenous (IV) and intracerebroventricular (ICV) delivery of GD2-CAR T cells [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 CT001.

DIPG-15. Major tumor regressions in H3K27M-mutated diffuse midline glioma (DMG) following sequential intravenous (IV) and intracerebroventricular (ICV) delivery of GD2-CAR T-cells

BACKGROUND: H3K27M-mutated DMGs express high levels of the disialoganglioside GD2 and GD2-CAR T-cells (GD2-CART) regress DMG in preclinical models. METHODS: NCT04196413 is a 3 + 3 Phase I dose escalation trial testing GD2-CART in patients with biopsy-proved H3K27M DMG, with dose-limiting toxicities (DLT) considered independently for DIPG and spinal DMG (sDMG). Arm A tested escalating doses of IV GD2-CART (DL1=1e6 GD2-CART/kg; DL2=3e6 GD2-CART/kg) following lymphodepletion (LD). After the DLT period, patients with clinical and/or radiographic benefit were eligible for subsequent ICV GD2-CART infusions (10-30e6 GD2-CART) administered via Ommaya without LD. RESULTS: Twelve subjects were treated after standard radiotherapy, 7 of whom began treatment at the time of progression [n=4 DL1 (3 DIPG/1 sDMG); n=8 DL2 (6 DIPG/2 sDMG)]. No DLTs were observed on DL1. Three subjects experienced DLT on DL2 (2 DIPG/1 sDMG) due to grade-4 cytokine release syndrome (CRS). On both dose levels, all subjects exhibited transient symptoms related to on-tumor inflammation, termed Tumor Inflammation-Associated Neurotoxicity (TIAN); no DLT due to TIAN has occurred. Ten subjects experienced radiographic and/or clinical benefit after IV infusion and received subsequent ICV infusions (median=4 ICV infusions/pt, range=1-7). ICV infusions were not associated with high-grade CRS. Four patients continue to receive ICV infusions on study and have experienced continued clinical and radiographic benefit, currently 7-11 months following enrollment. Two patients (one sDMG, one DIPG) have experienced near-complete (>95%) tumor volume reduction. CONCLUSIONS: IV treatment of DIPG and sDMG with GD2-CART is safe at a dose of 1e6/kg, but associated with frequent high-grade CRS at 3e6/kg. ICV GD2-CART has been well tolerated and has mediated impressive sustained clinical benefit in some patients with DIPG/sDMG. Given these findings, we are launching a new arm to assess safety and activity and to define the recommended phase 2 dose for ICV delivery of GD2-CART without LD.

Disease Burden Affects Outcomes in Pediatric and Young Adult B-Cell Lymphoblastic Leukemia After Commercial Tisagenlecleucel: A Pediatric Real-World Chimeric Antigen Receptor Consortium Report

PURPOSE

Tisagenlecleucel is a CD19-specific chimeric antigen receptor T-cell therapy, US Food and Drug Administration-approved for children, adolescents, and young adults (CAYA) with relapsed and/or refractory (RR) B-cell acute lymphoblastic leukemia (B-ALL). The US Food and Drug Administration registration for tisagenlecleucel was based on a complete response (CR) rate of 81%, 12-month overall survival (OS) of 76%, and event-free survival (EFS) of 50%. We report clinical outcomes and analyze covariates of outcomes after commercial tisagenlecleucel.

METHODS

We conducted a retrospective, multi-institutional study of CAYA with RR B-ALL across 15 US institutions, who underwent leukapheresis shipment to Novartis for commercial tisagenlecleucel. A total of 200 patients were included in an intent-to-treat response analysis, and 185 infused patients were analyzed for survival and toxicity.

RESULTS

Intent-to-treat analysis demonstrates a 79% morphologic CR rate (95% CI, 72 to 84). The infused cohort had an 85% CR (95% CI, 79 to 89) and 12-month OS of 72% and EFS of 50%, with 335 days of median follow-up. Notably, 48% of patients had low-disease burden (< 5% bone marrow lymphoblasts, no CNS3, or other extramedullary disease), or undetectable disease, pretisagenlecleucel. Univariate and multivariate analyses associate high-disease burden (HB, ≥ 5% bone marrow lymphoblasts, CNS3, or non-CNS extramedullary) with inferior outcomes, with a 12-month OS of 58% and EFS of 31% compared with low-disease burden (OS; 85%, EFS; 70%) and undetectable disease (OS; 95%, EFS; 72%; P < .0001 for OS and EFS). Grade ≥ 3 cytokine release syndrome and neurotoxicity rates were 21% and 7% overall and 35% and 9% in patients with HB, respectively.

CONCLUSION

Commercial tisagenlecleucel in CAYA RR B-ALL demonstrates efficacy and tolerability. This first analysis of commercial tisagenlecleucel stratified by disease burden identifies HB preinfusion to associate with inferior OS and EFS and increased toxicity.

GD2-CAR T cell therapy for H3K27M-mutated diffuse midline gliomas

Diffuse intrinsic pontine glioma (DIPG) and other H3K27M-mutated diffuse midline gliomas (DMGs) are universally lethal paediatric tumours of the central nervous system¹. We have previously shown that the disialoganglioside GD2 is highly expressed on H3K27M-mutated glioma cells and have demonstrated promising preclinical efficacy of GD2-directed chimeric antigen receptor (CAR) T cells², providing the rationale for a first-in-human phase I clinical trial (NCT04196413). Because CAR T cell-induced brainstem inflammation can result in obstructive hydrocephalus, increased intracranial pressure and dangerous tissue shifts, neurocritical care precautions were incorporated. Here we present the clinical experience from the first four patients with H3K27M-mutated DIPG or spinal cord DMG treated with GD2-CAR T cells at dose level 1 (1 × 10⁶ GD2-CAR T cells per kg administered intravenously). Patients who exhibited clinical benefit were eligible for subsequent GD2-CAR T cell infusions administered intracerebroventricularly³. Toxicity was largely related to the location of the tumour and was reversible with intensive supportive care. On-target, off-tumour toxicity was not observed. Three of four patients exhibited clinical and radiographic improvement. Pro-inflammatory cytokine levels were increased in the plasma and cerebrospinal fluid. Transcriptomic analyses of 65,598 single cells from CAR T cell products and cerebrospinal fluid elucidate heterogeneity in response between participants and administration routes. These early results underscore the promise of this therapeutic approach for patients with H3K27M-mutated DIPG or spinal cord DMG.

Tisagenlecleucel outcomes in relapsed/refractory extramedullary ALL: a Pediatric Real World CAR Consortium Report

Chimeric antigen receptor (CAR) T cells have transformed the therapeutic options for relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia. Data for CAR therapy in extramedullary (EM) involvement are limited. Retrospective data were abstracted from the Pediatric Real World CAR Consortium (PRWCC) of 184 infused patients from 15 US institutions. Response (complete response) rate, overall survival (OS), relapse-free survival (RFS), and duration of B-cell aplasia (BCA) in patients referred for tisagenlecleucel with EM disease (both central nervous system (CNS)3 and non-CNS EM) were compared with bone marrow (BM) only. Patients with CNS disease were further stratified for comparison. Outcomes are reported on 55 patients with EM disease before CAR therapy (CNS3, n = 40; non-CNS EM, n = 15). The median age at infusion in the CNS cohort was 10 years (range, <1-25 years), and in the non-CNS EM cohort it was 13 years (range, 2-26 years). In patients with CNS disease, 88% (35 of 40) achieved a complete response vs only 66% (10 of 15) with non-CNS EM disease. Patients with CNS disease (both with and without BM involvement) had 24-month OS outcomes comparable to those of non-CNS EM or BM only (P = .41). There was no difference in 12-month RFS between CNS, non-CNS EM, or BM-only patients (P = .92). No increased toxicity was seen with CNS or non-CNS EM disease (P = .3). Active CNS disease at time of infusion did not affect outcomes. Isolated CNS disease trended toward improved OS compared with combined CNS and BM (P = .12). R/R EM disease can be effectively treated with tisagenlecleucel; toxicity, relapse, and survival rates are comparable to those of patients with BM-only disease. Outcomes for isolated CNS relapse are encouraging.

Abstract CT031: GD2 CAR T cells mediate clinical activity and manageable toxicity in children and young adults with DIPG and H3K27M-mutated diffuse midline gliomas

Background: Diffuse intrinsic pontine glioma (DIPG) and other H3K27M-mutated diffuse midline gliomas (DMGs) are universally lethal central nervous system tumors. We previously discovered that the disialoganglioside GD2 is highly and homogenously expressed on H3K27M+ gliomas and demonstrated that GD2 CAR T cells are effective in preclinical models (Mount/Majzner et al., Nat Med, 2018).

Methods: Four subjects (3 DIPG, 1 spinal cord DMG; 4-25 yr; 1M/3F) were enrolled at DL1. Three subjects with H3K27M+ DIPG received 1e6 autologous GD2 CAR T cells/kg intravenously (IV) on study. One patient, a 25 y/o with spinal cord DMG, developed rapidly progressive disease after enrollment, resulting in complete paraparesis that led to removal from the study prior to cell infusion; she was treated on a single patient eIND with the same treatment regimen as DL1. We utilized a retroviral vector expressing a 14g2a.4-1BB.z CAR construct and an inducible iCasp9 safety switch. Manufacturing was performed in the Miltenyi Prodigy on CD4/CD8 enriched apheresis product. CAR T cells were cultured in the presence of dasatinib to improve T cell fitness (Weber et al., Science, 2021). An Ommaya reservoir was placed in all patients for monitoring of intracranial pressure (ICP).

Results: We generated GD2 CAR T cell products meeting release criteria for all four patients. All subjects received lymphodepletion with cyclophosphamide and fludarabine and remained inpatient for 14+ days after infusion. All patients developed cytokine release syndrome (Grade 1-3) manifested by fever, tachycardia and hypotension, beginning 6-7 days after infusion. Due to concern for tumoral edema and increased ICP, patients were managed with conservative fluid resuscitation, and early intervention with tocilizumab and anakinra +/- corticosteroids. Other toxicities included ICANS (Grade 1-2) and neurotoxicity mediated by inflammation in sites of disease which we have termed Tumor Inflammation-Associated Neurotoxicity (TIAN). TIAN most often manifested as worsening of existing deficits, but one patient developed symptoms of increased ICP which quickly resolved upon removal of CSF via the Ommaya. No evidence of on-target, off-tumor toxicity was observed in any patients. No dose-limiting toxicities occurred.CAR T cells trafficked to the CNS and were detected in both the CSF and peripheral blood. Inflammatory cytokines including IL-6 were elevated in the CSF and blood. 3/4 patients exhibited marked improvement or resolution of neurological deficits and some radiographic improvement. The patient treated on a single patient eIND exhibited a &gt;90% reduction in her spinal cord DMG tumor volume at two months post-infusion. Durability of the therapeutic benefit remains to be determined.

Conclusions: This is the first report of GD2 CAR T cell therapy for DIPG and spinal cord DMG. Toxicities are similar to other CAR T cells with additional, manageable complications due to inflammation at CNS sites of tumor. Treatment at DL1 demonstrated a tolerable safety profile and clear signs of T cell expansion and activity including clinical responses. This approach has the potential to transform therapy for patients with H3K27M+ DIPG/DMG. Further correlative studies, including single-cell RNAseq, longer-term outcomes and results from patients on subsequent dose levels will also be presented.

Citation Format: Robbie G. Majzner, Sneha Ramakrishna, Aaron Mochizuki, Shabnum Patel, Harshini Chinnasamy, Kristen Yeom, Liora Schultz, Rebecca Richards, Cynthia Campen, Agnes Reschke, Jasia Mahdi, Angus Martin Shaw Toland, Christina Baggott, Sharon Mavroukakis, Emily Egeler, Jennifer Moon, Kayla Landrum, Courtney Erickson, Lindsey Rasmussen, Valentin Barsan, John S. Tamaresis, Anne Cunniffe Marcy, Michael Kunicki, Michelle Fujimoto, Zach Ehlinger, Sreevidya Kurra, Timothy Cornell, Sonia Partap, Paul Fisher, Gerald Grant, Hannes Vogel, Bita Sahaf, Kara Davis, Steven Feldman, Crystal L. Mackall, Michelle Monje. GD2 CAR T cells mediate clinical activity and manageable toxicity in children and young adults with DIPG and H3K27M-mutated diffuse midline gliomas [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 CT031.

OMIC-11. SINGLE CELL RNA SEQUENCING FROM THE CSF OF SUBJECTS WITH H3K27M+ DIPG/DMG TREATED WITH GD2 CAR T-CELLULAR THERAPY

Introduction

We are conducting a Phase I clinical trial utilizing chimeric antigen receptor (CAR) T-cells targeting GD2 (NCT04196413) for H3K27M-mutant diffuse intrinsic pontine glioma (DIPG) and spinal cord diffuse midline glioma (DMG). Cerebrospinal fluid (CSF) is collected for correlative studies at the time of routine intracranial pressure monitoring via Ommaya catheter. Here we present single cell RNA-sequencing results from the first 3 subjects.

Methods

Single cell RNA-sequencing was performed utilizing 10X Genomics on cells isolated from CSF at various time points before and after CAR T-cell administration and on the CAR T-cell product. Output was aligned with Cell Ranger and analyzed in R.

Results

As detailed in the Majzner et al. abstract presented at this meeting, three of four subjects treated at dose-level one exhibited clear radiographic and/or clinical benefit. We have to date completed single cell RNA-sequencing for three of these four subjects (two with benefit, one without). After filtering out low-quality signals and doublets, 89,604 cells across 3 subjects were analyzed. Of these, 4,122 cells represent cells isolated from CSF and 85,482 cells represent CAR T-cell product. Two subjects who demonstrated clear clinical and radiographic improvement exhibited fewer S100A8⁺S100A9⁺ myeloid suppressor-cells and CD25⁺FOXP3⁺ regulatory T-cells in the CSF pre-infusion compared to the subject who did not derive a therapeutic response. In one subject with DIPG who demonstrated improvement, polyclonal CAR T-cells detectable in CSF at Day +14 demonstrated enrichment of CD8A, GZMA, GNLY and PDCD1 compared to the pre-infusion CAR T-cells by trajectory analysis, suggesting differentiation toward a cytotoxic phenotype; the same subject exhibited increasing numbers of S100A8⁺S100A9⁺ myeloid cells and CX3CR1⁺P2RY12⁺ microglia over time. Further analyses will be presented as data become available.

Conclusions

The presence of immunosuppressive myeloid populations, detectable in CSF, may correlate to clinical response in CAR T cell therapy for DIPG/DMG.

EPCT-14. GD2 CAR T-CELLS MEDIATE CLINICAL ACTIVITY AND MANAGEABLE TOXICITY IN CHILDREN AND YOUNG ADULTS WITH H3K27M-MUTATED DIPG AND SPINAL CORD DMG

Background

We previously discovered high expression of the disialoganglioside GD2 on H3K27M+ gliomas and demonstrated preclinical efficacy of intravenous (IV) GD2-targeted chimeric antigen receptor (CAR) T-cells in preclinical models of H3K27M-mutated diffuse intrinsic pontine glioma (DIPG) and diffuse midline gliomas (DMGs). We are now conducting a Phase I clinical trial (NCT04196413) of autologous GD2-targeting CAR T-cells for H3K27M+ DIPG and spinal cord DMG. Here we present the results of subjects treated at dose level 1 (DL1; 1 million GD2-CAR T-cells/kg IV).

Methods

Four patients (3 DIPG, 1 spinal DMG; ages 4–25; 1M/3F) were enrolled at DL1. Three subjects with H3K27M+ DIPG received 1e6 GD2-CAR T-cells/kg IV on study. One patient with spinal DMG enrolled but became ineligible after manufacturing and was treated on an eIND at DL1. An Ommaya reservoir was placed in all subjects for therapeutic monitoring of intracranial pressure. Subjects underwent lymphodepletion with fludarabine/cyclophosphamide and remained inpatient for at least two weeks post-infusion.

Results

All subjects developed cytokine release syndrome (Grade 1–3) manifested by fever, tachycardia and hypotension. Other toxicities included ICANS (Grade 1–2) and neurological symptoms/signs mediated by intratumoral inflammation which we have termed Tumor Inflammation-Associated Neurotoxicity (TIAN). No evidence of on-target, off-tumor toxicity was observed in any patients. No dose-limiting toxicities occurred. CAR T cells trafficked to the CNS and were detected in CSF and blood. 3/4 patients exhibited marked improvement or resolution of neurological deficits and radiographic improvement. The patient treated on an eIND exhibited &gt;90% reduction in spinal DMG volume but progressed by month 3. Re-treatment of this subject via intracerebroventricular administration resulted in a second reduction in spinal DMG volume by ~80%.

Conclusions

GD2-CAR T-cells at DL1 demonstrate a tolerable safety profile in patients with H3K27M+ DIPG/DMG with clear signs of T-cell expansion and activity including clinical responses.

Ensituximab (E) in patients (pts) with refractory metastatic colorectal cancer (mCRC): Results of a phase I/II clinical trial

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Background: E is an investigational, novel, chimeric monoclonal IgG1 antibody derived from an immunogenic neoantigen with sequence homology to MUC5AC that is preferentially expressed with exquisite specificity to pancreatic cancer and CRC. Its mechanism of action is via antibody-dependent cellular cytotoxicity (ADCC). The efficacy and safety of E was evaluated in a single-arm, open-label, phase 1/2 clinical trial of adult pts with refractory mCRC. Methods: Pts were selected based on > 20% expression of tumor antigen, as measured by immunohistochemistry. Based on phase 1 results, E was administered 3 mg/kg IV every 2 weeks until unacceptable toxicity or disease progression. Primary endpoint was overall survival (OS). Serum cytokine levels were analyzed at baseline, day 4, and day 15. E-mediated ADCC of CD16 genotype V/V, V/F, and F/F pt PBMCs was measured with an IN-111 release assay using the E target-expressing ASPC-1 pancreatic cancer cell line. Results: Fifty-seven and 63 pts were evaluable for OS and safety, respectively. Median OS was significantly longer than historical control: 6.8 vs 5.0 months (mo); p = 0.007; 95% CI: 5.39,8.02. Three pts were alive at end of study (21, 21, and 24 mo); 21 pts survived ≥ 12 mo. Pts had a median of 4 prior therapies (range 2-9); 25% had received regorafenib. Forty-seven pts were evaluable by RECIST, and 20 (43%) had stable disease of target lesions at end of first course (day 57). E was well tolerated, with < 2% grade 3 and no grade 4 toxicities. There were no trends in serum cytokine and chemokine levels. Analysis of 56 samples (8 V/V, 26 V/F, 17 F/F, and 5 undetermined) showed that V/V PBMCs had significantly higher E-mediated ADCC than PBMCs harboring other genotypes. No correlation between CD16 polymorphism and pt outcome was observed. Conclusions: E demonstrated excellent tolerability and encouraging OS in this heavily pretreated population. Correlative in vitro data suggest that E can mediate higher levels of ADCC activity in individuals with a V/V versus other genotypes. The lack of correlation between CD16 polymorphism and pt outcomes in this study suggests that other immune-related factors (under investigation) may impact the efficacy of E in vivo. Clinical trial information: NCT01040000.

A phase II therapeutic, open label, multi-center clinical trial of NPC-1C, a chimeric monoclonal antibody(mAb), in adults with chemotherapy refractory metastatic colorectal cancer (mCRC), initial results

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Background: NEO-102 is a novel chimeric mAb targeting a variant of MUC5AC with specificity to colorectal cancer. Its mechanism of action is through antibody dependent cellular cytotoxicity (ADCC). An earlier, phase I study, established the maximum tolerated dose at 3.0 mg/kg IV every 2 weeks with encouraging early signs of clinical activity. We report initial results of the subsequent phase II study. Methods: This is a single arm, open label multi-center clinical trial of NEO-102 in adults with mCRC pts who failed at least two lines of standard chemotherapy (C). An immunohistochemistry (IHC) based companion diagnostic assay was used to select eligible pts whose tumors express the target in > 20% of tumor cells. NEO-102 at 3.0 mg/kg IV was administered q 2 weeks until disease progression. The primary endpoint was OS. A minimum of 43 pts were needed assuming that treatment with NEO-102 will improve OS by 40% (7.0 months) using a one-sided significance level of 10% and 80% power for this study compared to historical control of 5 months. Additional objectives were to evaluate response rate as measured by RECIST criteria and analyze patient PBMCs for ADCC and immune cytokine profiling. Results: A total of 47 pts enrolled were evaluable. 26 pts were male and 35 pts were white. Twenty-four out of 47 pts (51%) remain alive as of September 2015 with an ongoing median OS of 7.0 months (Range 2-22 months). Of these heavily pre-treated pts, 42 were evaluable for response, 13 (31%) demonstrated stable disease by RECIST. Seven pts had more than 4 doses of treatment, maximum 13 doses. Grade 3 adverse events were anemia 1/47 (2%), hyperbilirubinemia 1/47 (2%), diarrhea 1/47 (2%), fatigue 1/47 (2%), headache 1/47 (2%), nausea 1/47 (2%) and vomiting 1/47 (2%). No grade 4 toxicities were reported. Conclusions: In the monotherapy phase 2 study of NEO 102 in patients with refractory mCRC preliminary results demonstrate excellent tolerability and encouraging OS. Updated OS and Progression Free Survival data will be presented at the ASCO 2016 GI Cancers symposium. Additional combination trials with NEO-102 and C are underway. Clinical trial information: NCT01040000.

A multicenter randomized phase II study of NPC-1C (N) in combination with gemcitabine (G) and nab-paclitaxel (A) versus G and A alone in patients with metastatic or locally advanced pancreatic cancer (PC) previously treated with folfirinox (F)

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.

A phase I/II multicenter study of the chimeric monoclonal antibody NEO102 (NPC-1C) in adults with refractory pancreatic (PC) and colorectal cancer (CC)

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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 CT415: A Phase I/IIA multicenter clinical trial of the chimeric monoclonal antibody NEO102 (NPC-1C) in adults with refractory pancreatic and colorectal cancer

Background:NPC-1C, (NEO-101 and NEO102, Precision Biologics, Inc) is a novel chimeric monoclonal antibody being developed as a treatment for pancreatic and colorectal cancers. NPC-1C recognizes a variant form of MUC5AC expressed specifically by human pancreatic and colorectal tumors. A Phase I trial of NEO-101 has been completed and reported previously. This Phase IIA study utilizes NEO-102, a glycoengineered form of NEO-101 with improved stability and decreased red cell agglutination.

Methods: This is a Phase Ib/IIa, open label, multicenter dose escalation clinical trial with Neo-102 for patients with refractory pancreatic and colorectal cancer. The primary objective is to determine safety, tolerability of escalating doses of NEO-102. Secondary objectives are to assess pharmacokinetics as well as immune response at each dose level, evaluate clinical benefit as measured by RECIST criteria and overall survival, and to explore the immunologic correlates associated with NEO-102. Analyses of patient peripheral blood mononuclear cells (PBMCs) for antibody-dependent cell-mediated cytotoxicity (ADCC) and immune cytokine profiling utilizing the Milliplex MAP Human Cytokine/Chemokine Panel are planned to assess for immunologic outcome, and for correlation with clinical benefit. Patients with histologically confirmed adenocarcinoma of the pancreas who have progressed after front line chemotherapy; or metastatic colorectal cancer who have progressed after at least 2 chemotherapy regimens; whose tumors express the target NEO-102 antigen as defined as ≥ 20% positive stain by NPC-1C immunohistochemistry (IHC) are eligible. Patients have good performance status (KPS ≥ 50%) and adequate hematologic, hepatic and renal function are eligible. Major exclusion criteria include uncontrolled brain metastases, ascites, or other uncontrolled medical illness. Dose escalation was performed in a standard 3+3 design at doses of 1.5mg/kg, 2 mg/kg, 3 mg/kg and 4 mg/kg.

Results: A total of 12 patients (2 pancreatic and 10 colon cancer) have been enrolled. Preplanned dose escalation to the 4 mg/kg dose has been completed and no dose limiting toxicity was observed. Median age is 58 years, 7 are male, median number of prior treatment regimens are 4+ (range 1+ to 8+) Treatment related AEs include grade 1 and 2 diarrhea, fatigue, mucositis, nausea, pruritus, epigastric pain, nasal congestion, insomnia, mouth ulcers, back pain, congestion, weight loss, chills facial flushing and fever, and grade 3 diarrhea and anemia. No severe adverse events (SAE) have been deemed to be drug related. Overall response rate includes 4 patients with PD and 5 patients have achieved SD and 3 patients are too early to evaluate. Median duration of treatment is 56+ days (Range 29 to131+). Conclusions: We have completed dose escalation with NEO-102, a first in man monoclonal antibody with a unique mechanism of action. Treatment is well tolerated with manageable safety profile. Due to encouraging preliminary clinical activity, as demonstrated by disease stabilization in a heavily pretreated population, a Phase II study of NEO-102 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.

Citation Format: Muhammad Shaalan Beg, Michael Morse, Sandip P. Patel, Sharon Mavroukakis, Melony Beatson, Philip M. Arlen, Nilofer S. Azad. A Phase I/IIA multicenter clinical trial of the chimeric monoclonal antibody NEO102 (NPC-1C) in adults with refractory pancreatic and colorectal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT415. doi:10.1158/1538-7445.AM2014-CT415

A phase Ib/IIa study of NEO-102: A therapeutic antibody to treat pancreatic and colorectal cancers

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Background: We have developed a chimeric monoclonal antibody (ab) that targets a variant of MUC5AC that is expressed specifically by human pancreatic (P) and colorectal (C) tumors with minimal reactivity to normal GI mucosa. In the phase (ph) I trial of the initial formulation NEO-101, 5/19 patients (pts) had stable disease (SD) after completing their 1st course of treatment (tx) (4 doses) and overall survival (OS) of >12 months (mos) observed in 3 C and 2 P pts despite disease progression on standard (std) of care tx regimens. The current study utilizes NEO-102, a glycoengineered form of NEO-101 with improved stability and decreased RBC agglutination. Methods: A Ph Ib/IIa open label, multi-center dose-escalation clinical trial with NEO-102 is enrolling pts with advanced P and C cancer refractory to std therapy. Primary objective: measure efficacy by analysis of CT scans pre- and post-therapy using RECIST criteria, OS, clinical laboratory tests, and physical examinations. Secondary objectives: a.determine safety and tolerability of escalating doses of NEO-102; b. assess pharmacokinetics (PK) and select immune responses to the ab at each dose level. Analyses of pt PBMCs for ADCC and immune cytokine profiling utilizing the Milliplex MAP Human Cytokine/Chemokine Panel are planned to assess for immunologic outcome, and for correlation with clinical benefit. Results: Safety analysis has been performed on 3 pts enrolled in the first cohort at the dose level of 1.5 mg/kg IV q2weeks. There were no dose limiting toxicities (DLT) observed. In this cohort, one of the pts is evaluable for SD at 4 mos. The other 2 pts are scheduled for restaging scans. Pts are currently being accrued at the 2 mg/kg dose level. Conclusions: Preliminary results with NEO-102 ab have demonstrated signs of clinical activity based on stabilization of disease in heavily pretreated pts with P and C cancer. Safety has been established at the 1.5 mg/kg dose level and patients are currently being accrued to the 2 mg/kg dose level. If no DLT is observed at the current dose level, we plan to escalate to 3mg/kg and 4mg/kg respectively. Immune biomarker analyses are underway to correlate PBMC ADCC and cytokine profile with tx response. Clinical trial information: NCT01040000.

Administration of a CD25-directed immunotoxin, LMB-2, to patients with metastatic melanoma induces a selective partial reduction in regulatory T cells in vivo

CD25+ CD4+ T regulatory (Treg) cells regulate peripheral self tolerance and possess the ability to suppress antitumor responses, which may in part explain the poor clinical response of cancer patients undergoing active immunization protocols. We have previously shown that in vitro incubation of human PBMC with LMB-2, a CD25-directed immunotoxin, significantly reduced CD25+ FOXP3+ CD4+ Treg cells without impairing the function of the remaining lymphocytes. In the current study, eight patients with metastatic melanoma were treated with LMB-2 followed by MART-1 and gp100-specific peptide vaccination. LMB-2 administration resulted in a preferential, transient reduction in mean circulating CD25+ CD4+ T cell number, from 83 +/- 16 cells/microl to a nadir of 17 +/- 5 cells/microl, a 79.1% reduction. FOXP3 analysis revealed a less robust depletion with mean FOXP3+ CD4+ Treg cell number decreasing from 74 +/- 15 cells/microl to 36 +/- 8 cells/microl, a 51.4% reduction. FOXP3+ CD4+ Treg cells that survived LMB-2-mediated cytotoxicity expressed little or no CD25. Similar to the peripheral blood, immunohistochemical analysis showed a 68.9% mean reduction in FOXP3+ CD4+ Treg cell frequency in evaluable lesions. Despite inducing a reduction in Treg cell numbers in vivo, LMB-2 therapy did not augment the immune response to cancer vaccination and no patient experienced an objective response or autoimmunity. These data demonstrate the capacity of a CD25-directed immunotoxin to selectively mediate a transient partial reduction in circulating and tumor-infiltrating Treg cells in vivo, and suggest that more comprehensive Treg cell elimination may be required to bolster antitumor responses in patients with metastatic melanoma.

Phase I study of the intravenous administration of attenuated Salmonella typhimurium to patients with metastatic melanoma

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 x 10(8) cfu/m(2). Dose-limiting toxicity was observed in patients receiving 1 x 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)-1beta, tumor necrosis factor alpha, IL-6, and IL-12. Focal tumor colonization was observed in two patients receiving 1 x 10(9) cfu/m(2) and in one patient receiving 3 x 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.

Phase I study of the intravenous administration of attenuated Salmonella typhimurium to patients with metastatic melanoma

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 x 10(8) cfu/m(2). Dose-limiting toxicity was observed in patients receiving 1 x 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)-1beta, tumor necrosis factor alpha, IL-6, and IL-12. Focal tumor colonization was observed in two patients receiving 1 x 10(9) cfu/m(2) and in one patient receiving 3 x 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.