Anti-PD-1 therapy triggers Tfh cell-dependent IL-4 release to boost CD8 T cell responses in tumor-draining lymph nodes

Anti-PD-1 therapy targets intratumoral CD8+ T cells to promote clinical responses in cancer patients. Recent evidence suggests an additional activity in the periphery, but the underlying mechanism is unclear. Here, we show that anti-PD-1 mAb enhances CD8+ T cell responses in tumor-draining lymph nodes by stimulating cytokine production in follicular helper T cells (Tfh). In two different models, anti-PD-1 mAb increased the activation and proliferation of tumor-specific T cells in lymph nodes. Surprisingly, anti-PD-1 mAb did not primarily target CD8+ T cells but instead stimulated IL-4 production by Tfh cells, the major population bound by anti-PD-1 mAb. Blocking IL-4 or inhibiting the Tfh master transcription factor BCL6 abrogated anti-PD-1 mAb activity in lymph nodes while injection of IL-4 complexes was sufficient to recapitulate anti-PD-1 mAb activity. A similar mechanism was observed in a vaccine model. Finally, nivolumab also boosted human Tfh cells in humanized mice. We propose that Tfh cells and IL-4 play a key role in the peripheral activity of anti-PD-1 mAb.

Abstract LB210: Preclinical development and evaluation of allogeneic CAR T cells targeting CD70 for the treatment of renal cell carcinoma

CD70 is highly expressed on renal cell carcinoma (RCC), with limited normal tissue expression, making it an attractive CAR T target for an immunogenic solid tumor indication. Here we generated and characterized a panel of anti-CD70 scFv-based CAR T cells. Despite the expression of CD70 on T cells, production of CAR T from a subset of scFvs with potent in vitro activity was achieved. Expression of CD70 CARs was found to mask CD70 detection in cis and provide protection from CD70 CAR T-mediated fratricide. Two unique classes of CAR T cells were identified with differing memory phenotype, activation status, and cytotoxic activity. Epitope mapping revealed CARs binding to the membrane distal region of the CD70 extracellular domain (ECD) fall into the more active and differentiated class, as compared to CARs binding the membrane proximal region of the CD70 ECD. CD70 CAR T cells were evaluated with rituximab-based off switches to provide control over CAR T function and displayed robust antitumor activity against RCC cell lines and patient-derived xenografts in mouse models. Tissue cross reactivity studies to evaluate off-target binding with two lead CARs showed membrane staining in rare tissue-resident lymphocytes, thus matching the known expression pattern of CD70. Expected findings related to T cell activation, and elimination of CD70-expressing cells were observed in a cynomolgus monkey CD3-CD70 bispecific toxicity study and included cytokine release and loss of cellularity in lymphoid tissues. Lastly, highly functional CD70 allogeneic CAR T cells were produced at large scale through elimination of the T cell receptor by TALEN® gene editing. Taken together, these efficacy and safety data support the evaluation of CD70 CAR T cells for the treatment of RCC and led to the advancement of an allogeneic CD70 CAR T candidate into Phase I clinical trials.

Citation Format: Siler Panowski, Surabhi Srinivasan, Nguyen Tan, Silvia Tacheva-Grigorova, Bryan Smith, Yvonne Mak, Hongxiu Ning, Jonathan Villanueva, Dinali Wijewarnasuriya, Shanshan Lang, Zea Melton, Adit Ghosh, Mathilde Dusseaux, Roman Galetto, Jonathan Heyen, Tao Sai, Thomas Van Blarcom, Javier Chaparro-Riggers, Barbra Sasu. Preclinical development and evaluation of allogeneic CAR T cells targeting CD70 for the treatment of renal cell carcinoma [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 LB210.

Preclinical Development and Evaluation of Allogeneic CAR T Cells Targeting CD70 for the Treatment of Renal Cell Carcinoma

CD70 is highly expressed in renal cell carcinoma (RCC), with limited expression in normal tissue, making it an attractive CAR T target for an immunogenic solid tumor indication. Here we generated and characterized a panel of anti-CD70 scFv-based CAR T cells. Despite the expression of CD70 on T cells, production of CAR T from a subset of scFvs with potent in vitro activity was achieved. Expression of CD70 CARs masked CD70 detection in cis and provide protection from CD70 CAR T-mediated fratricide. Two distinct classes of CAR T cells were identified with differing memory phenotype, activation status, and cytotoxic activity. Epitope mapping revealed that the two classes of CARs bind unique regions of CD70. CD70 CAR T cells displayed robust antitumor activity against RCC cell lines and patient-derived xenograft mouse models. Tissue cross-reactivity studies identified membrane staining in lymphocytes, thus matching the known expression pattern of CD70. In a cynomolgus monkey CD3-CD70 bispecific toxicity study, expected findings related to T cell activation and elimination of CD70-expressing cells were observed, including cytokine release and loss of cellularity in lymphoid tissues. Lastly, highly functional CD70 allogeneic CAR T cells were produced at large scale through elimination of the T cell receptor by TALEN-based gene editing. Taken together, these efficacy and safety data support the evaluation of CD70 CAR T cells for the treatment of RCC and has led to the advancement of an allogeneic CD70 CAR T candidate into phase I clinical trials.

Abstract 2326: Allo CAR T TM targeting CD70 for the treatment of renal cell carcinoma

Renal Cell Carcinoma (RCC) represents a substantial patient population, with 65,340 new cases estimated in the US in 2018. Patients with localized tumors undergo nephrectomy, however 30-40% of patients develop metastasis, with a 5-year median survival rate of only 11.6%. Current treatment for advanced disease improves overall survival, but disease relapse is common and additional treatments are needed. RCC is a highly T-cell infiltrated tumor type with responsiveness to Immuno-Oncology (IO) agents and thus it may be amenable to a T-cell based therapy. T cells can be genetically modified to express chimeric antigen receptors (CARs), and adoptive transfer of CAR T cells is showing great promise in hematologic malignancies. To translate this approach for RCC treatment, expression data were mined and CD70 was identified as an antigen expressed in a high proportion of patients with RCC, with limited normal tissue expression on a fraction of activated lymphocytes and subsets of dendritic cells. Since CD70 expression is present on activated T cells, targeting it with a CAR could lead to fratricide and T cell exhaustion. For this reason, screens were specifically designed to identify CARs that were less impacted by these issues and used to triage a large panel of CD70 CARs. Optimal CARs were successfully manufactured and demonstrated robust in vitro and in vivo anti-tumor activity against target cells expressing relevant levels of CD70. A large panel of single chain fragment variables (scFvs) that bind to CD70 were generated and formatted into second-generation 41BB-CD3zeta CARs. CARs were first screened in a Jurkat cell CD70-knockout assay and clones showing tonic signaling were eliminated. CD70 CAR T cells were generated with various scFvs and ranked based on transduction efficiency, phenotype, activation status and expansion. A subset of CD70 CAR T cells were moved into in vitro short and long-term cytotoxicity assays. Target cells expressing high, medium, and low levels of CD70 were utilized. Ability to kill cell lines with CD70 expression similar to that seen in primary tumors was used as criteria for candidate selection. CAR T were evaluated in multiple in vivo xenograft models and robust anti-tumor activity was observed. Some candidates performed better with CD70 knockout and some worked irrespective of knockout. To profile potential toxicity, a cyno toxicity study was conducted with one clone formatted as a CD70-CD3 bispecific antibody. No unexpected findings were observed. In the event of unexpected toxicity, CAR T cells were further engineered to contain an off-switch, by which CAR T are eliminated upon administration of Rituximab. Multiple off-switch CAR formats were evaluated, and optimal formats determined independently for each CAR. One CD70 CAR T was also successfully manufactured in a large-scale process. In summary, multiple CD70 CAR T have been profiled and a subset selected for further investigation as potential clinical candidates.

Citation Format: Siler Panowski, Surabhi Srinivasan, Silvia Tacheva-Grigorova, Nguyen Tan, Thomas Van Blarcom, Tao Sai, Jonathan Heyen, Niranjana Nagarajan, Mathilde Dusseaux, Roman Galetto, Barbra Sasu. Allo CAR T TM targeting CD70 for the treatment of renal cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2326.

Abstract 3751: Allogeneic EGFRvIII chimeric antigen receptor T cells for treatment of glioblastoma

Glioblastoma multiforme (GBM) is a highly aggressive form of brain tumors with a 5-year survival rate of less than 10%. Standard-of-care combining radiation therapy with temozolomide only yields a median survival of 14.6 months and more effective therapeutic options to extend patient lives are urgently needed. EGFR variant III (EGFRvIII) is a tumor specific mutant of EGFR found in 25-30% of GBM but not expressed in healthy tissues. EGFRvIII is formed by an in-frame deletion of exons 2-7 of the wild-type EGFR which leads to removal of 267 amino acids in the extracellular domain of the receptor. The truncated receptor loses its ability to bind ligands but acquires constitutive kinase activity. The lack of normal tissue expression makes EGFRvIII an ideal target for developing CAR T therapy. Most CAR T therapies in clinical development use the patients’ own T cells for CAR T manufacturing. Our approach is to develop an “off-the-shelf” CAR-T treatment for GBM using healthy donor T cells with the TCR (T-cell receptor) disrupted to prevent graft-versus-host disease. This allogeneic approach could circumvent challenges faced by some patients due to limited availability and quality of their own T cells and rapid progress of their diseases, and has the potential to reduce the high cost associated with autologous CART therapy. Using phage panning and hybridoma approaches, we generated a series of humanized and fully human EGFRvIII antibodies with a wide range of affinities. Recombinant EGFRvIII protein binding by Biacore and FACS assays using EGFRvIII and EGFR wild-type expressing cells demonstrated that these antibodies are highly specific for EGFRvIII. The antibodies were converted to ScFvs and cloned into a CAR vector. Subsequently, EGFRvIII CARs were transduced into primary human T cells for functional studies. We developed a series of assays to evaluate CAR expression, degranulation activity and target dependent cytotoxicity. Our goal is to select CAR candidate that is safe, persistent and has potent target dependent cytotoxicity.

Citation Format: Oi Kwan Wong, Mathilde Dusseaux, Jing-Tyan Ma, Melinda Au, Sophie Leduc, Joyce Chou, Jessica M. Yu, Marjorie Bateman, Thomas Pertel, Kevin C. Lindquist, Julianne Smith, Barbra Sasu, Shu-Hui Liu. Allogeneic EGFRvIII chimeric antigen receptor T cells for treatment of glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3751. doi:10.1158/1538-7445.AM2017-3751

MAIT cells detect and efficiently lyse bacterially-infected epithelial cells

Mucosal associated invariant T cells (MAIT) are innate T lymphocytes that detect a large variety of bacteria and yeasts. This recognition depends on the detection of microbial compounds presented by the evolutionarily conserved major-histocompatibility-complex (MHC) class I molecule, MR1. Here we show that MAIT cells display cytotoxic activity towards MR1 overexpressing non-hematopoietic cells cocultured with bacteria. The NK receptor, CD161, highly expressed by MAIT cells, modulated the cytokine but not the cytotoxic response triggered by bacteria infected cells. MAIT cells are also activated by and kill epithelial cells expressing endogenous levels of MRI after infection with the invasive bacteria Shigella flexneri. In contrast, MAIT cells were not activated by epithelial cells infected by Salmonella enterica Typhimurium. Finally, MAIT cells are activated in human volunteers receiving an attenuated strain of Shigella dysenteriae-1 tested as a potential vaccine. Thus, in humans, MAIT cells are the most abundant T cell subset able to detect and kill bacteria infected cells.

Human Mucosa-Associated Invariant T cells (MAIT) detect microbe-derived compounds presented by the MHC-like molecule, MR1. These foreign antigens are produced by a wide variety of microbes, including commensal and pathogenic bacteria or yeasts. MAIT cells expend shortly after birth and constitute the major antibacterial T cell subset described and, hence, could play important roles in infectious diseases. Here we show that MAIT cells recognize epithelial cells infected by the intestinal pathogen Shigella flexneri in a process requiring endogenous MR1, while the closely related bacterium Salmonella Tyhpimurium is not. Upon recognition, infected epithelial cells are efficiently lysed by MAIT cells. We also show that the triggering of CD161, a natural killer receptor highly expressed by MAIT cells, can modulate the cytokine but not the cytotoxic function of these cells. Finally, we provide evidence that MAIT cells are activated during the course of an experimental enteric infection in humans. Our study provides important insight on the antibacterial function of MAIT cells and their interaction with pathogenic bacterial species.

Mucosal-associated invariant T cells: unconventional development and function

Mucosal-associated invariant T (MAIT) cells are a population of T cells that display a semi-invariant T cell receptor (TCR) and are restricted by the evolutionarily conserved major histocompatibility complex related molecule, MR1. Here, we review recent knowledge of this T cell population. MAIT cells are abundant in human blood, gut and liver, and display an effector phenotype. They follow an atypical pathway of development and preferentially locate to peripheral tissues. Human and mouse MAIT cells react to bacterially infected cells in an MR1-dependent manner. They migrate to the infection site and can be protective in experimental infection models. MAIT cells secrete interferon-γ, and interleukin-17 under certain conditions. The species conservation, as well as the wide microbial reactivity, infer an important role for this cell population in immunity.

A new Ser472Asn (Cab2(a+)) polymorphism localized within the αIIb "thigh" domain is involved in neonatal thrombocytopenia

BACKGROUND

A new platelet antigen, Cab2(a+), was identified in a case of severe neonatal alloimmune thrombocytopenia (<8 × 10(9)/L) in twins.

STUDY DESIGN AND METHODS

Coding sequences of αIIb and β3 genes from parents were amplified and sequenced. CHO cell lines expressing wild-type or mutated forms of the complex were established to study the role of the mutation in alloimmunization and in αIIbβ3 functions.

RESULTS

The father and twins were heterozygous for a single αIIb c.1508G>A mutation leading to a Ser472Asn substitution. Immunologic assays with transfected CHO cells revealed the Asn472 form of αIIbβ3 responsible for the Cab2(a+) epitope but not an Ala472 form. Using these cells lines we demonstrated that both Ser472Asn and Ser472Ala substitutions produced limited structural alteration as revealed by the reactivity of a panel of anti-αIIbβ3 monoclonal antibodies (MoAbs). Activated Asn472 and Ala472 forms of αIIbβ3 supported 1) binding of soluble fibrinogen and of the ligand mimetic MoAb PAC-1, 2) ligand-induced binding site epitopes exposure (MoAbs AP-5 and D3GP3), and 3) cell aggregation. Adhesion onto adsorbed fibrinogen was conserved and was specifically inhibited by MoAb AP-2 or peptide RGDS. Finally outside-in signaling was not affected.

CONCLUSION

We have characterized a new low-frequency alloantigen (<1%) resulting from the Ser472Asn substitution in αIIb and shown this polymorphism to have a limited effect, if any, on the αIIbβ3 complex functions.