Blogs

Scientific Highlights for Thursday, Nov. 10, 2022

TCR T CELL THERAPY TARGETING NEOANTIGENS IN SOLID TUMORS

1478. A Phase I study of personalized adoptive TCR T cell therapy in patients with solid tumors: safety, efficacy, and T cell trafficking to tumors of non-virally gene edited T cells.

Stephanie Mandl (PACT Pharma, United States) presented on a Phase I study of NeoTCR-P1, a personalized autologous T cell therapy for treatment of solid tumors. Neoantigen-specific T cell receptors (neoTCRs) were isolated and cloned from patients’ circulating CD8 T cells and inserted into an autologous cell product by non-viral genome engineering and then infused back into the patients. Patients were infused with cell products containing one, two, or three unique TCRs. Of 88 eligible patients, over 50,000 neoantigens were predicted, over 120,000 neoantigen-HLA regents were produced, and over 900 unique neoTCRs were identified. 16 patients were infused with NeoTCR-P1 T cells (NeoTCR-P1), and four of the 16 were also treated with IL-2. 11 patients had microsatellite stable-colorectal cancer, two had breast cancer, one had ovarian cancer, one had melanoma, and one had non-small cell lung cancer (NSCLC). Two patients experienced toxicities related to NeoTCR-P1 infusions. Five patients had stable disease at day 28 post-infusion, across tumor types. Administration of IL-2 increased persistence and efficacy of neo TCR T cells. Eight tumors underwent biopsy after infusion. Targeted neoantigens were detected in seven post-treatment biopsies and represented 15 of 22 targets. This study provides early proof-of-concept of personalized TCR T cell therapies. NeoTCR-P1 was safe, and the transgenic cells were able to traffic to tumor. Future programs are in progress to increase the efficacy and durability of NeoTCR T cells.

SOLUBLE LAG-3 PROTEIN IMPROVES EFFICACY OF PEMBROLIZUMAB FOR FIRST-LINE TREATMENT OF NON-SMALL CELL LUNG CANCER

1470.  Combining the antigen-presenting cell activator eftilagimod alpha (soluble LAG-3) and pembrolizumab: efficacy results from the 1st line non-small cell lung cancer cohort of TACTI-002 (Phase II)

Wade Iams (Vanderbilt Ingram Cancer Center, United States) presented data from the first-line non-small cell lung cancer (NSCLC) cohort of TACTI-002, a phase II trial of eftilagimod alpha (efti) and pembrolizumab. Efti, soluble LAG-3, is a first-in class compound and an MHCII agonist. Efti stimulates APC priming upstream of cytotoxic T cell killing, thus it was hypothized that efti could increase the efficacy of pembrolizumab (pembro). The primary endpoint of the study was overall response rate. 114 treatment-naïve patients representing a range of PD-L1 histologies (TPS <50% in 75% of patients) received efti + pembro. The overall response rate was 40.4%. A moderate step-wise improvement in response rate was associated with increasing levels of PD-L1 expression, though the most favorable response was observed ina  patient with TPS < 1%. Response rate was similar in squamous v non-squamous tumors. Responses were durable: responses were ongoing in 24 patients, and median duration of response, while still maturing, is currently 22 months. Progression free survival rate is also maturing, and it is currently at 6.6 months. Increased PFS is also associated with tumor PD-L1 score. Rate of immune-related events is similar to pembrolizumab monotherapy for NSCLC (approximately 5%). Levels of circulating CXCL10 and IFN-gamma, biomarkers of TH1 cytotoxicity, exhibit an increase from baseline levels to treatment, specifically after initial administration of Efti. These data indicate that efti+ pembro is an effective and tolerable regimen for first-line treatment of NSCLC, and other studies investigating efti+pembro for other disease states are in progress.

OXIDATIVE DAMAGE TO TELOMERES OF T CELLS IN THE TUMOR MICROENVIRONMENT

408. Neutralizing oxidative damage at telomeres prevents T cell dysfunction and improves adoptive cell therapy

Dayana Rivadeneira (University of Pittsburgh, United States) reported on a study on the effects of reactive oxygen species (ROS)-induced DNA damage at the telomeres affected the activity of tumor-infiltrating lymphocytes (TILs). It was previously shown that ROS from mitochondria damage telomeric DNA, causing telomere fragility and decreased cytokine production. Telomeric FISH assays of TILs from B16 mouse melanoma tumors indicated that DNA damage accumulates in the telomeres of exhausted T cells, but the telomeres do not shorten. A photosensitizer strategy was developed and used to create targeted singlet oxidative damage to telomeres specifically damaged. Developed photosensitizer stragety to induce ox damage to telomeres. Mouse models expressing the damage system exhibited suppression of T cell expansion, increased expression of PD-1, and loss of cytokine production. When the ROS scavenger TRF1 was fused with GPX1 and targeted to telomeres, telomere fragility decreased, and tumor size decreased. Although there was no change to PD-1 levels, CD39 levels decreased, and T cells expressed higher levels of cytokines, indicating improved T cell functionality. These data indicate that oxidative stress plays a role in T cell dysfunction in the tumor microenvironment. Protecting T cell telomeres from oxidative damage preserves T cell function and has the potential improve patient response to immunotherapy.

EXAMINING PHENOTYPIC HETEROGENEITY OF INTRATUMORAL MYELOID CELLS IN IMMUNE CHECKPOINT-RESPONSIVE AND NON-RESPONSIVE TUMORS

505. High-dimensional analyses of intratumoral myeloid cells highlights presence of distinct myeloid cell phenotypes in immune checkpoint-sensitive and resistant tumors

Swetha Anandhan (The University of Texas MD Anderson Cancer Center, United States) presented comparative analyses of intratumoral myeloid cell subsets to identify the phenotype of immunosuppressive myeloid cells and to identify potential combination strategies to improve patient response to immune checkpoint blockade therapy (ICT). Previous work has shown that myeloid cells are present at high levels in the stroma of many tumor types that are ICT non-responsive, suggesting specific subsets and abundance and myeloid cells play a role in tumor response to ICT. Myeloid cells in orthotopic mouse models of ICT responsive (B16F10 melanoma) and ICT non-responsive (MT4 pancreatic) tumors pre and post ICT were analyzed via single cell RNA sequencing. Macrophages and neutrophils were found at two-fold higher levels in ICT non-responsive (MT4) tumors compared to ICT-responsive (B16F10) tumors. Distinct phenotypic myeloid subsets were identified in melanoma and pancreatic tumor. Three subsets were abundant in pancreatic tumors and corresponded to immunosuppression. The remaining subset was present in melanoma tumors and exhibited an antigen presenting cell-like phenotype. In general, myeloid cells in tumors exhibit high levels of heterogeneity dependent on type. Myeloid cells from melanoma tumors exhibit upregulation of proinflammatory pathways that promote T cell activity, and myeloid cells from pancreatic tumors exhibit upregulation of anti-inflammatory pathways that inhibit T cell activity. scRNAseq of tumor and stromal cells from MT4 and human pancreatic tumors indicate that cancer associated fibroblasts (CAFs) from pancreatic tumors express elevated levels of TNF Stimulating Gene 6 (TSG-6), an anti-inflammatory molecule, that inhibits a pro-inflammatory phenotype and promotes an anti-inflammatory phenotype in myeloid cells. Blocking TSG-6 with monoclonal antibody improves survival and response to ICT in mice with pancreatic tumors by decreasing immunosuppressive myeloid cells and increasing abundance of CD8 T cells. These data support a model in which TSG-6, expressed at high levels by CAFs, promotes an immunosuppressive phenotype in myeloid cells in the tumor. Analyses of patient data are ongoing, with the goal to develop CAF- and TSG-6-targeting therapies in humans.

IDENTIFYING PUBLIC NEOANTIGENS FROM DRIVER MUTATIONS

218. Immunogenic landscape and therapeutic targeting of mutant NRAS ”public” neoantigens

Inaki Etxeberria (Memorial Sloan Kettering Cancer Center, United States) presented work to identify shared, cancer-specific public neoantigens derived from mutated driver genes and to identify therapeutic targets for these neoantigens. This study focused on recurrent mutations at the NRAS (Q61) hotspot; most tumors that harbor NRAS mutations respond poorly to current immunotherapies and are associated with poor outcomes. An immunopeptidomic screen to identify common driver mutations associated with HLA alleles, and T cell receptors (TCRs) for the neoantigen were retrieved and verified. The three most common NRAS(Q61) substitutions – R, K, and L- are processed and presented by HLA-A*01, which is expressed in about 25% of North Americans. NRAS Q61R-specific T cells exhibited immunogenic responses in about 60% of patients studied, NRAS Q61K-specific T cells in 30% of patients, and NRAS Q61L-specific T cells in 60% of patients. 18 T cell receptors (TCRs) were retrieved from patient samples and functionally validated for specifically recognizing NRAS Q61 public neoantigens. All patient-derived TCRs exhibit high-affinity for the public neoantigens. Furthermore, a subset TCR candidates demonstrate “cross-protection” towards multiple NRAS Q61 mutated variants, indicating that these cross-protective receptors can potentially provide therapeutic coverage for more than 90% of NRAS mutations. Treatment with ipilimumab/nivolumab increases the levels of circulating NeoAg-specific T cells (Q61R) – levels of TCR in circulation increase after treatment. This study provides proof-of-concept that NRAS(Q61) driver mutations can give rise to public neoantigens that can be studied across patients, and tumor types and can be targeted through T cell receptors.

EFFICACY OF CD70-TARGETING CAR-T CELLS FOR CLEAR CELL RENAL CARCINOMA

558. CTX130 allogeneic CRISPR-Cas9–engineered chimeric antigen receptor (CAR) T cells in patients with advanced clear cell renal cell carcinoma: Results from the phase 1 COBALT-RCC study

Sumanta Pal (City of Hope Comprehensive Cancer Center, United States) presented results from the COBALT-RCC study, a phase I dose-escalation study of CTX130, a CD-70 targeting allogeneic CAR T cell therapy for clear cell renal cell carcinoma (ccRCC). CD70 is transiently expressed on lymphocytes and antigen presenting cells and expressed at high levels in cRCC tumors. Previous studies indicate CTX130 is effective in inhibiting tumor growth in renal cell carcinoma xenograft models. 14 patients with stage IV metastatic, unresectable disease with a median of three prior treatments (range: 1-6) received infusion of CTX130 in a dose escalation study. Median CD70 expression level on the tumors was 100% (range, 1-100%). CAR T cell expansion occurred across all dose levels, and higher CAR T exposure and disease control was observed. 7 (50%) of patients experienced grade 1-2 cytokine release syndrome (CRS), and none experienced CRS >= grade 3. No patients experienced neurotoxicity. Acceptable safety levels were observed over all dose levels. One patient achieved a durable complete remission maintained over 18 months, and 9 (68.2%) of patients exhibited stable disease (SD). SD is ongoing for over 7.8 months in one patient. Disease control rate was 77%. CTX130, CD-70 CAR-T cells for ccRCC, show a favorable toxicity profile and promising anti-tumor activity. The durable CR achieved in one patient is the first complete response to CAR T cell therapy in patients with relapsed or refractory solid tumors. This study provide proof-of concept for the use of CD-70 targeting CART cells to treat ccRC and other CD-70-expressing solid malignancies.

ACTIVATING INNATE AND ADAPTIVE IMMUNITY TO TREAT METASTASES

782. Intratumoral sotigalimab with pembrolizumab activates antigen-presenting cells and induces local and distant anti-tumor responses in first-line metastatic melanoma: results of a phase I/II study

Salah-Eddine Bentebibel (The University of Texas MD Anderson Cancer Center, United States) presented results from an ongoing phase I/II study of intratumoral sotigalimab, a humanized IgG1 CD40 agonist antibody, in combination with pembrolizumab for checkpoint inhibitor-naïve metastatic melanoma. CD40, a member of the TNF receptor family, is expressed on macrophages, dendritic cells, and B cells. Previous work indicates that locally injecting immunostimulatory agents can trigger anti-tumor immunity at locations throughout the body, thus intratumoral injections of sotigalimab could potentially enhance response to immune checkpoint inhibitors at both local and distal lesions. 32 patients were enrolled in the study. No study discontinuations or deaths occurred due to treatment-related adverse events. Six patients (18%) experienced grade 3 immune related adverse events, but no immunosuppressive therapy was needed. The overall response rate (ORR) was 47% in distal lesions, and disease control rate was 69%. ORR with the recommended phase two dose of 10 mg sotigalimab was 50%. Clinical responses were observed in PD-L1-positive and -negative tumors. Analyses of peripheral blood samples and tumor biopsies indicate that sotigalimab engaged the CD40 pathway and increased expression of genes associated with antigen presentation. Multiplex imaging indicated activation of dendritic cells and macrophages at local and distal sites in patients who responded to therapy, suggesting that activation of antigen presenting cells may overcome resistance to anti-PD-1 therapy. Patients who responded to combination therapy exhibited an increase in CD8+ T cell infiltration, proliferation, and clonality compared to non-responders. T cell receptor sequencing of responders indicated that T cell clonality had increased and new clones were shared between distant and local sites. The data indicate that treatment with sotigalimab + pembrolizumab for metastatic melanoma is well-tolerated and activates the innate and adaptive immune systems at local and distant lesions.

SYNERGISTIC EFFECT OF IL-2 AND IL-12 ON MODELS OF LUNG CANCER

1087. Addition of IL-2 overcomes lung tumor resistance to IL-12 by coordinating cytotoxic and regulatory T cell responses

Brendan Horton (Massachusetts Institute of Technology) reported on the development of a model of IL-12-resistant lung cancer. An orthotopic murine lung cancer model to implant tumors at different locations. Previous studies indicate that different T cell responses are partially based on site of tumor growth. For example, KP murine lung tumors are resistant to a combination immune checkpoint blockade (ICB) of anti-CTLA-4 and -PD-L1. When the same tumor cells are inoculated subcutaneously to the flank, the tumor responds to ICB. Other work has established that differences in T cell activity in tumors are established during T cell priming in the lymph nodes. When T cells from lung tumors vs flank tumors were sorted, T cells from the flank tumor expressed high level of granzyme, while T cells from the lung expanded and proliferated but dysfunctional. Transcriptomic profiling of the cells indicated higher levels of cytokine receptor IL-2 alpha and IL-12 in flank tumors, and receptor expression was lower in the lungs. IL-12 is a potent differentiator of T cells and stimulates tumor regression in most mouse models of cancer. Extended half-life IL-12 fused to murine serum albumin (IL12-MSA) induced tumor control and increased survival of mice with flank tumors but provided no benefit to mice with metastatic lung tumors Combining IL-2 with IL-12 produced a synergistic response, extending the survival of mice with metastatic lung tumors. Response to IL12-MSA in flank tumors was associated with expansion and differentiation of CD8 T cells in the tumor-draining lymph node (TdLN) and depletion of regulatory T cells (Treg) from the tumor microenvironment. In contrast, T cell expansion and activation was not observed in lung tumors. CD8 T cells and Treg cells in the lung tumor also exhibited lower binding activity to IL12-MSA, but this decreased binding activity was abrogated with the addition of IL-2. These findings indicate that IL-2 stimulates increased expression of IL-12 receptors on T cells, sensitizing the T cell response to IL-12 through CD8+ T cell activation and inhibition of Treg cells. Further study of this mouse model will provide more insights to the biological mechanisms of IL-12 response and resistance.

HIGH ENDOTHELIAL VENULES ARE IMPORTANT FOR THE RECRUITMENT AND ACTIVATION OF T CELLS TO THE TUMOR AND LYMPH NODES

507. High endothelial venules control the journey of stem-like CD8+ T cells from lymph node to tumor during cancer immunotherapy with combined anti-PD-1 plus anti-CTLA-4 antibodies

Lucas Blanchard (CNRS-IPBS, University of Toulouse, France) presented a study of high endothelial venules (HEVs) and their role in the generation and migration of stem-like CD8+ T cells during spontaneous anti-tumor immunity and cancer immunotherapy. The CD62L and CD62P pathways were identified as being necessary for tumor-associated HEVs to capture circulating Cd8 T cells, and T cells express CD62L and other chemokines to facilitate their interaction with HEVs and recruitment to the tumor. Using mouse syngeneic tumor models, HEV function was blocked in vivo using antibodies targeting HEVs. Blocking HEV lymphocyte trafficking resulted in fewer CD8+ T cells in the tumor and reduced expansion of TCF-1+ stem-like CD8+ T cells in tumor-draining lymph nodes. Combined PD-L1 + CTLA-4 immune checkpoint blockade expanded stem like CD8 T cells in tumor-draining lymph nodes and the tumor, suggesting HEVs play an important role in the response to checkpoint blockade. These data suggest that HEVs play important dual roles in the anti-tumor response by stimulating the recruitment and activation of stem-like CD8+ T cells in tumor draining lymph nodes, and by promoting the entry of stem-like CD8+ T cells into the tumor. These findings provide new insights on the mechanisms and importance of lymphatic structures in the anti-tumor immune response during checkpoint blockade therapy.