EVIDENCE OF IMMUNOEDITING IN PANCREATIC CARCINOMA PRESENTED
LB005: High quality neoantigens are immunoedited in long term survivors of pancreatic cancer
Marta Luksza, PhD (Icahn School of Medicine at Mount Sinai), and colleagues investigated the hypothesized mechanism of immunoediting in pancreatic cancer. This proposal suggests that the immune system kills immunogenic tumor clones, selecting less immunogenic clones to survive over time; however, clinical evidence of this phenomenon has been limited.
The group evaluated tumors from long (n=9) and short-term (n=6) survivors of pancreatic ductal carcinoma to determine the immunogenicity of tumor clones. Long-term survivors had higher levels of T cell infiltration in tumors than patients with shorter survival. Over time, these T cell-infiltrated tumors became less immunogenic, evidenced by fewer neoantigens and neoantigens of lower quality. The group also showed that tumors in long-term survivors eventually become enriched in self-like mutations, indicating that the immune system could successfully eradiate non-self clones. The decreased clonal heterogeneity observed in long-term survivors also indicated that these patients’ immune systems were able to effectively eradicate newly-arising clones. This study thus provides valuable immunological insight into a very difficult-to-treat tumor.
COMBINATION OF PD1-IL2V IMMUNOCYTOKINE AND ANTI-PD-L1 SHOWS BENEFIT IN PRECLINICAL PANCREATIC TUMORS
71: The immunocytokine PD1-IL2v overcomes immune checkpoint resistance, and combination with an anti-PD-L1 antibody further enhances its anti-tumor activity
Stephan Wullschleger, PhD (Swiss Institute for Experimental Cancer Research), discussed a preclinical investigation of the immunocytokine PD1-IL2v, a conjugate of an anti-PD-1 monoclonal antibody and an IL-2 variant. The variant is engineered to specifically activate effector T cells, rather than regulatory T cells. The agent was tested in murine PanNET neuroendocrine pancreatic tumors, which are resistant to immune checkpoint blockade.
Mice treated with the immunocytokine were able to mount a more effective anti-cancer response than those treated with anti-PD-1 and IL-2v as separate agents. Tumors treated with PD1-IL2v had increased effector T cell infiltration. However, these responding tumors eventually stabilized and relapsed, warranting investigation of these resistance mechanisms. There was an upregulation of PD-L1 on tumor vasculature post treatment, suggesting the addition of an anti-PD-L1 therapy to the immunocytokine treatment. This combination (immunocytokine plus anti-PD-L1) resulted in improved therapeutic outcomes and greater T cell function. The agent is under consideration for clinical trials based upon these results.
IMMUNOLOGICAL AND CLINICAL ACTIVITY ESTABLISHED WITH HER2/4-1BB BISPECIFIC
CT017: Clinical and biomarker activity of PRS-343, a bispecific fusion protein targeting 4-1BB and HER2, from a Phase 1 study in patients with advanced solid tumors (Study PRS-343-PCS_04_16)
Sarina Piha-Paul, MD (The University of Texas MD Anderson Cancer Center), presented a phase 1 trial of PRS-343, bispecific fusion protein that targets 4-1BB and HER2. The objective was to improve the therapeutic index of 4-1BB modulation. The clinical trial enrolled 78 patients with advanced solid tumors, 42 of whom were efficacy-evaluable.
The minimum dose of PRS-343 was 2.5 mg/kg. In the evaluable population, 1 CR, 4 PR and 17 SD were observed, which included a 43% ORR at 8 mg/kg and 25% ORR at 18 mg/kg. Common treatment-related adverse events included grade 3-4 infusion reaction in 8% of patients, and other common events included nausea, chills and vomiting. Across patients, dose-dependent increases in CD8+ T cell infiltration and soluble 4-1BB were noted. There was some indication of a better response in gastric and colorectal cancer patients. Cases presented included a patient with gastric cancer with a PR on treatment, who had high baseline HER2 expression and PD-L1-positivity; after treatment, this patient demonstrated a 5.7-fold increase in CD8+ T cell infiltration in tumors. Another patient with rectal cancer and a CR had baseline high HER2, microsatellite stability and low TMB, but experienced a 2-fold increase in CD8+ T cell infiltration. Signals of response were also noted in patients with HER2-low or immunologically cold tumors, indicating that PRS-343 is a potential therapeutic option for these difficult tumors.
SITC recently provided guidance for the development of biomarkers in immunotherapy, which can be viewed in the Journal for ImmunoTherapy of Cancer (JITC).
ARMED MSCS DEMONSTRATE BENEFIT IN PRECLINICAL MELANOMA
77: MSC loaded oncolytic virus and expressing immunomodulators have therapeutic efficacy in advanced melanomas
The therapeutic efficacy of armed Mesenchymal stem cells (MSCs) was investigated by Nobuhiko Kanaya, MD (Brigham and Women’s Hospital), and colleagues. These MSCs were engineered to deliver either oncolytic herpes simplex viruses (oHSVs) or the cytokine GM-CSF.
In vitro, MSC-oHSVs were able to kill PTEN-mutant melanoma cells. The combination of the two MSC agents (oHSV or GM-CSF armed) was then tested in a bilateral syngeneic tumor model. When the MSCs were intratumorally injected into one tumor, anti-cancer effects were seen in both the treated and untreated tumors, indicating an abscopal effect. When these treated mice were later re-challenged with the same tumor cells injected into the brain, all mice rejected tumor engraftment. Immune responses, including evidence of effector and central memory T cells, were observed with the treatment. Loading MSC with immunomodulatory agents may improve their efficacy for cancer treatment.
You can read about another approach to improving the efficacy of oncolytic virus therapies in this recent article in JITC.
IMMUNOLOGICAL AND CLINICAL IMPACT OF CD40 AGONISM INVESTIGATED IN PANCREATIC CANCER
CT005: T cell inflammation in the tumor microenvironment after agonist CD40 antibody: Clinical and translational results of a neoadjuvant clinical trial
Patients with resectable pancreatic cancer were treated with a CD40 agonistic antibody (selicrelumab) in a trial presented by Katelyn T. Byrne, PhD (University of Pennsylvania). Sixteen patients were enrolled and treated with selicrelumab with or without chemotherapy in a peri-operative approach, including neoadjuvant selicrelumab +/- chemotherapy and adjuvant chemotherapy and selicrelumab.
The toxicity profile was as expected, with only grade 1-2 cytokine release syndrome observed and other common higher-grade events including hyperglycemia and liver function test abnormalities. The median overall survival was 23.4 months, along with a median disease-free survival of 13.8 months. An in-depth investigation of the immunological effects of selicrelumab was also conducted. Selicrelumab-treated tumors were more often enriched with T cells than historical controls of tumors treated with chemotherapy/ chemoradiation or untreated tumors (82% selicrelumab, 23% chemotherapy/ chemoradiation, 37% untreated). Selicrelumab-treated patients had less fibrosis, fewer M2 macrophages, and increased activation of dendritic cells and T cells. The study provides evidence of immunological and potential clinical impact of CD40 agonism for pancreatic cancers.
IN-DEPTH ANALYSIS OF TILS IDENTIFIES TUMOR-SPECIFIC SUBPOPULATIONS
127: Single cell mapping of tumor infiltrating lymphocytes enables neoantigen-reactive T cell identification in metastatic human cancer
Frank J. Lowery III, PhD (National Cancer Institute), discussed the identification of tumor-reactive cells from amongst all tumor-infiltrating lymphocytes. The group used TCR sequencing and 5’ RNA sequencing to analyze TILs from ten tumor samples including several histologies, leveraging prior TCR neoantigen reactivity data in their analysis.
Several T cell phenotypic clusters were identified – for example, cells within the CD8-CCL3 cluster expressed CCL3 differentially relative to other groups. Clones that were primarily expanded in either the tumor or in peripheral blood were also identified. Known neoantigen-reactive TCRs were largely found within two clusters: CD4-IL6ST and CD8-CCL3. This prompted investigation of additional TCRs in these clusters for their tumor reactivity and several new neoantigen-reactive TCR clonotypes were identified. The group also defined a signature of T cell neoantigen reactivity, which could prospectively identify neoantigen-reactive T cells, indicating a potential way to improve the efficacy of TIL therapy in the future.
DUAL-TARGETED CAR T RESULTS IN 80% CRR IN EARLY TRIAL
CT007: CD19/CD20 bispecific chimeric antigen receptor (CAR) in naïve/memory T-cells for the treatment of relapsed or refractory B-cell lymphomas
A first-in-human investigation of CD19/CD20 bispecific CAR T therapy was presented by Sanaz Noelle Ghafouri, MD (University of California, Los Angeles). Naïve/memory T cells were modified with a bispecific CD19/CD20 CAR and infused into patients with multiply relapsed B cell lymphomas. Five patients were included in this analysis, at CAR T doses of 50x106 (n=4) and 200x106 (n=1).
Four patients exhibited a complete response with this therapy, all of which are ongoing (from 2 to 14 months’ follow-up). All patients experienced only grade 1 cytokine release syndrome, and no neurotoxicity events were observed. No dose-limiting toxicities occurred. CAR T peak expansion was observed at day 14. The one non-responding patient had CD19- and CD20-negative relapse at day 14 after CAR T infusion, despite demonstrating CD19/CD20-positive disease at enrollment. This led investigators to hypothesize that this pre-existing CD19/CD20-negative clone expanded after marker-positive disease was eliminated with treatment. Results from additional patients and follow-up will help determine the role of dual-targeted CAR T therapy for hematologic malignancies.
SITC’s clinical practice guideline on management of cell therapy adverse events can be found in JITC.
EXTENDED FOLLOW-UP SHOWS CONTINUED BENEFIT OF LIFILEUCEL FOR ADVANCED MELANOMA
CT008: Lifileucel (LN-144), a cryopreserved autologous tumor infiltrating lymphocyte (TIL) therapy in patients with advanced (unresectable or metastatic) melanoma: durable duration of response at 28 month follow up
Jason Alan Chesney, MD, PhD (University of Louisville), presented extended follow-up results of the C-144-01 trial, investigating lifileucel for the treatment of patients with advanced melanoma. These results included patients in cohort 2 of the study, who received cryopreserved, second-generation tumor-infiltrating lymphocyte (TIL) products. This report includes a median 28-month follow-up for the 66 enrolled patients.
Patients had received a prior average of 3.3 therapies, and all patients were previously exposed to anti-PD-1, 80% to anti-CTLA-4, and 23% to BRAFi/MEKi. Non-myeloablative cyclophosphamide/fludarabine lymphodepletion was employed prior to a single lifileucel infusion and patients received up to 6 doses of supportive high-dose IL-2. Responses to the therapy included 3 CR and 21 PR, for an overall response rate of 36.4% by investigator assessment. Median time to response was 1.4 months and median duration of response was not yet reached. The investigators did not find any major characteristics of the product that correlated with patient outcomes, nor any new safety signals. Therapy with lifileucel may thus be a promising option for patients with pretreated melanoma.
PROMISING PRECLINICAL EVALUATION OF B7-H6/CD3 BISPECIFIC FOR COLORECTAL CANCER
56: A novel B7-H6/CD3 bispecific IgG-like T cell engaging antibody for the treatment of colorectal cancer
Susanne Hipp, PhD (Boehringer Ingelheim), discussed the preclinical evaluation of a B7-H6/CD3 T cell engager. The agent is an IgG-like bispecific and was tested in vitro and in preclinical colorectal cancer (CRC) models. The investigators chose B7-H6 as a tumor antigen due to its high prevalence on CRC tumors as well as its restricted expression in normal tissues.
In vitro studies demonstrated dose-dependent T cell-mediated lysis of B7-H6-positive CRC cells, with EC50 values from 0.9-25 ng/mL. T cells co-cultured with the bispecific did not kill B7-H6-negative tumor cells. Xenograft mouse models reconstituted with human PBMCs or T cells were used for additional preclinical evaluation. Single intravenous doses of the bispecific at 0.5 mg/kg had anti-tumor effects, which were further pronounced with weekly dosing. After treatment, tumors showed increased T cell infiltration and upregulation of PD-1 on T cells and PD-L1 on tumor cells. The investigators are using these studies to support potential clinical development.
ROLE OF MACROPHAGES INVESTIGATED IN HCC
64: Characterization of molecular and spatial diversity of macrophages in hepatocellular carcinoma
The role of macrophages within the hepatocellular carcinoma (HCC) tumor microenvironment (TME) was discussed by Pauline Hamon, PhD (Icahn School of Medicine at Mount Sinai). The investigators evaluated the immune cells within the TME from 26 HCC samples (7 treatment-naïve, 19 treated with anti-PD-1) with single-cell RNA sequencing and multiplex immunohistochemistry.
While Kupffer cells are common throughout normal liver tissue, the group found a lack of these cells within the TME. Rather, the macrophage populations within the HCC TME fell into three categories, based on their expression of FOLR2, SPP1 and TREM2. FOLR2-expressing macrophages were more common in untreated than treated tumors, and in tumors that had low T cell infiltration. On the other hand, SPP1 and TREM2 macrophages were found in tumors with high T cell infiltration. Additionally, SPP1 macrophages were enriched in responding patients. Further analysis using physically-interacting cell sequencing showed that HCC samples were enriched for immunosuppressive macrophages, though further data is needed. The role of macrophages may therefore be important to improve the immune responsiveness of HCC.
Read more about the impact of macrophages in cancer development and treatment in this recent review in JITC.
STUDY INVESTIGATES IMMUNOLOGICAL EFFECTS OF INTRATUMORAL THERAPY AND IMMUNE CHECKPOINT BLOCKADE
CT032: CMP-001 demonstrates improved response in noninflamed anti-PD-1 refractory melanoma and response is associated with serum CXCL10
Jason John Luke, MD (University of Pittsburgh), discussed the combination of pembrolizumab and CMP-001, a CpG-A oligonucleotide TLR9 agonist, as treatment for advanced melanoma. All patients had either stable or progressive disease after prior anti-PD-1 treatment. Combination treatment was given to 159 patients, and another 40 patients were treated with only CMP-001. CMP-001 was administered intratumorally, while pembrolizumab was given intravenously.
A numerically greater increase in serum CXCL10 was noted in responding patients compared to non-responders after combination treatment, with 18.8-fold increases in responders, 9.9-fold with stable disease, and 6.15-fold with progressive disease. No baseline patient characteristics correlated with response. However, greater changes from pre- to on-treatment in certain tumor markers correlated with response, including type 1 interferons, IFN-gamma signature and CD8+ T cell infiltration. Increased inflammation was noted in both injected and non-injected tumor lesions, evidenced by increased PD-L1 expression and CD8+ T cell infiltration. This study therefore sheds light on the immunological effects of intratumoral therapies.
The impact of many factors on the efficacy of intratumoral therapy was discussed in a recent article in JITC.
TARGETING MUC1* MAY BE AN EFFECTIVE CAR T APPROACH
57: First-in-human CAR T targets MUC1 transmembrane cleavage product
Cynthia Bamdad, PhD (Minerva Biotechnologies), described a novel CAR T product that is targeted to a cleavage product of MUC1, known as MUC1*. It is the “transmembrane portion that remains after MUC1 is enzymatically cleaved and the bulky tandem repeat domain is shed from the cell surface.” Targeting an epitope on this form of MUC1 in the tumor microenvironment helps to increase the tumor specificity of the CAR T therapy.
IND-enabling studies showed that the antibody used to develop the CAR had high levels of binding to tumor tissues such as breast, ovarian, pancreatic and lung, without appreciable binding to normal tissue. Likewise, MUC1*-positive tumor cells were effectively killed in vitro by the CAR product, while MUC1*-negative cells, or cells expressing only full-length MUC1, were not. NSG murine studies demonstrated effective tumor eradication with a corresponding increase in CAR T expansion. Early clinical results of the therapy in patients with metastatic breast cancer have shown effective CAR T expansion and evidence of anti-tumor efficacy, and the trial is still ongoing. Further work is also in progress to develop CAR T therapies that are more resistant to exhaustion, using the CAR-1XX approach. These studies showed that CAR-1XX were better able to eradicate heterogeneous tumors and may further improve the success of this therapy.
MACROPHAGES WITH HER2 CAR DEMONSTRATE PRECLINICAL EFFICACY
63: Chimeric antigen receptor macrophages (CAR-M) induce anti-tumor immunity and synergize with T cell checkpoint inhibitors in pre-clinical solid tumor models
Macrophages bearing chimeric antigen receptors (CAR-M) were investigated by Stefano Pierini, PhD (Carisma Therapeutics), and colleagues, in order to explore their potential to treat solid tumors. The CAR-M in this study was engineered with an anti-HER2 CAR.
Transduction of the macrophages polarized them toward an M1 phenotype. In vitro studies showed dose-dependent killing of HER2+ tumor cells by the CAR-Ms, but non-transduced macrophages were not able to phagocytose the cancer cells. The CAR-M were also able to boost T cell activation through upregulation of MHC I and II and increasing antigen cross-presentation. The agent was then tested in immunocompetent mouse models with CT26-HER2+ tumors. CAR-M treated mice showed decreased tumor growth, improved survival, and increased tumor immune infiltration including tumor antigen reactive T cells. Responding mice were also resistant to re-challenge with HER2-negative tumors. Local administration of CAR-M in HER2+ tumors also led to responses in contralateral, untreated, HER2-negative tumors, indicating systemic immune responses. Finally, the combination of CAR-M and anti-PD-1 therapy was able to eliminate PD-1-resistant murine tumors as well. The CAR-M agent is currently entering early-stage clinical trials in solid tumors.