Harnessing T cell exhaustion and trogocytosis to isolate patient-derived tumor-specific TCR

To study and then harness the tumor-specific T cell dynamics after allogeneic hematopoietic stem cell transplant, we typed the frequency, phenotype, and function of lymphocytes directed against tumor-associated antigens (TAAs) in 39 consecutive transplanted patients, for 1 year after transplant. We showed that TAA-specific T cells circulated in 90% of patients but display a limited effector function associated to an exhaustion phenotype, particularly in the subgroup of patients deemed to relapse, where exhausted stem cell memory T cells accumulated. Accordingly, cancer-specific cytolytic functions were relevant only when the TAA-specific T cell receptors (TCRs) were transferred into healthy, genome-edited T cells. We then exploited trogocytosis and ligandome-on-chip technology to unveil the specificities of tumor-specific TCRs retrieved from the exhausted T cell pool. Overall, we showed that harnessing circulating TAA-specific and exhausted T cells allow to isolate TCRs against TAAs and previously not described acute myeloid leukemia antigens, potentially relevant for T cell-based cancer immunotherapy.

Revealing and harnessing CD39 for the treatment of colorectal cancer and liver metastases by engineered T cells

OBJECTIVE

Colorectal tumours are often densely infiltrated by immune cells that have a role in surveillance and modulation of tumour progression but are burdened by immunosuppressive signals, which might vary from primary to metastatic stages. Here, we deployed a multidimensional approach to unravel the T-cell functional landscape in primary colorectal cancers (CRC) and liver metastases, and genome editing tools to develop CRC-specific engineered T cells.

DESIGN

We paired high-dimensional flow cytometry, RNA sequencing and immunohistochemistry to describe the functional phenotype of T cells from healthy and neoplastic tissue of patients with primary and metastatic CRC and we applied lentiviral vectors (LV) and CRISPR/Cas9 genome editing technologies to develop CRC-specific cellular products.

RESULTS

We found that T cells are mainly localised at the front edge and that tumor-infiltrating T cells co-express multiple inhibitory receptors, which largely differ from primary to metastatic sites. Our data highlighted CD39 as the major driver of exhaustion in both primary and metastatic colorectal tumours. We thus simultaneously redirected T-cell specificity employing a novel T-cell receptor targeting HER-2 and disrupted the endogenous TCR genes (TCR editing (TCRED)) and the CD39 encoding gene (ENTPD1), thus generating TCREDENTPD1KOHER-2-redirected lymphocytes. We showed that the absence of CD39 confers to HER-2-specific T cells a functional advantage in eliminating HER-2+ patient-derived organoids in vitro and in vivo.

CONCLUSION

HER-2-specific CD39 disrupted engineered T cells are promising advanced medicinal products for primary and metastatic CRC.

Case report: Ponatinib as a bridge to CAR-T cells and subsequent maintenance in a patient with relapsed/refractory Philadelphia-like acute lymphoblastic leukemia

Philadelphia (Ph)-like acute lymphoblastic leukemia (ALL) constitutes a heterogeneous subset of ALL with a uniformly unfavorable prognosis. The identification of mutations amenable to treatment with tyrosine kinase-inhibitors (TKIs) represents a promising field of investigation. We report the case of a young patient affected by relapsed/refractory Ph-like ALL treated with chimeric antigen receptor T (CAR-T) cells after successful bridging with compassionate-use ponatinib and low-dose prednisone. We restarted low-dose ponatinib maintenance three months later. Twenty months later, measurable residual disease negativity and B-cell aplasia persist. To the best of our knowledge, this is the first case reporting the use of ponatinib in Ph-like ALL as a bridge to and maintenance after CAR-T cell therapy.

CD4 CAR-T cells targeting CD19 play a key role in exacerbating cytokine release syndrome, while maintaining long-term responses

BACKGROUND

To date, T cells redirected with CD19-specific chimeric antigen receptors (CAR) have gained impressive success in B-cell malignancies. However, treatment failures are common and the occurrence of severe toxicities, such as cytokine release syndrome (CRS), still limits the full exploitation of this approach. Therefore, the development of cell products with improved therapeutic indexes is highly demanded.

METHODS

In this project, we investigated how CD4 and CD8 populations cooperate during CD19 CAR-T cell responses and what is their specific role in CRS development. To this aim, we took advantage of immunodeficient mice reconstituted with a human immune system (HuSGM3) and engrafted with the B-cell acute lymphoblastic leukemia cell line NALM-6, a model that allows to thoroughly study efficacy and toxicity profiles of CD19 CAR-T cell products.

RESULTS

CD4 CAR-T cells showed superior proliferation and activation potential, which translated into stronger stimulation of myeloid cells, the main triggers of adverse events. Accordingly, toxicity assessment in HuSGM3 mice identified CD4 CAR-T cells as key contributors to CRS development, revealing a safer profile when they harbor CARs embedded with 4-1BB, rather than CD28. By comparing differentially co-stimulated CD4:CD8 1:1 CAR-T cell formulations, we observed that CD4 cells shape the overall expansion kinetics of the infused product and are crucial for maintaining long-term responses. Interestingly, the combination of CD4.BBz with CD8.28z CAR-T cells resulted in the lowest toxicity, without impacting antitumor efficacy.

CONCLUSIONS

Taken together, these data point out that the rational design of improved adoptive T-cell therapies should consider the biological features of CD4 CAR-T cells, which emerged as crucial for maintaining long-term responses but also endowed by a higher toxic potential.

Full chimaeric CAR.CIK from patients engrafted after allogeneic haematopoietic cell transplant: Feasibility, anti-leukaemic potential and alloreactivity across major human leukocyte antigen barriers

Cytokine-induced killer lymphocytes (CIK) are a promising alternative to conventional donor lymphocyte infusion (DLI), following allogeneic haematopoietic cell transplantation (HCT), due to their intrinsic anti-tumour activity and reduced risk of graft-versus-host disease (GVHD). We explored the feasibility, anti-leukaemic activity and alloreactive risk of CIK generated from full-donor chimaeric (fc) patients and genetically redirected by a chimeric antigen receptor (CAR) (fcCAR.CIK) against the leukaemic target CD44v6. fcCAR.CIK were successfully ex-vivo expanded from leukaemic patients in complete remission after HCT confirming their intense preclinical anti-leukaemic activity without enhancing the alloreactivity across human leukocyte antigen (HLA) barriers. Our study provides translational bases to support clinical studies with fcCAR.CIK, a sort of biological bridge between the autologous and allogeneic sources, as alternative DLI following HCT.

Expression of inducible factors reprograms CAR-T cells for enhanced function and safety

Despite the success of CAR-T cell cancer immunotherapy, challenges in efficacy and safety remain. Investigators have begun to enhance CAR-T cells with the expression of accessory molecules to address these challenges. Current systems rely on constitutive transgene expression or multiple viral vectors, resulting in unregulated response and product heterogeneity. Here, we develop a genetic platform that combines autonomous antigen-induced production of an accessory molecule with constitutive CAR expression in a single lentiviral vector called Uni-Vect. The broad therapeutic application of Uni-Vect is demonstrated in vivo by activation-dependent expression of (1) an immunostimulatory cytokine that improves efficacy, (2) an antibody that ameliorates cytokine-release syndrome, and (3) transcription factors that modulate T cell biology. Uni-Vect is also implemented as a platform to characterize immune receptors. Overall, we demonstrate that Uni-Vect provides a foundation for a more clinically actionable next-generation cellular immunotherapy.

Efficacy of CAR-T immunotherapy in MET overexpressing tumors not eligible for anti-MET targeted therapy

Background

Aberrant activation of the MET receptor in cancer is sustained by genetic alterations or, more frequently, by transcriptional upregulations. A fraction of MET-amplified or mutated tumors are sensible to MET targeting agents, but their responsiveness is typically short-lasting, as secondary resistance eventually occurs. Since in the absence of genetic alterations MET is usually not a tumor driver, MET overexpressing tumors are not/poorly responsive to MET targeted therapies. Consequently, the vast majority of tumors exhibiting MET activation still represent an unmet medical need.

Methods

Here we propose an immunotherapy strategy based on T lymphocytes expressing a Chimeric Antigen Receptor (CAR) targeting MET overexpressing tumors of different histotypes. We engineered two different MET-CAR constructs and tested MET-CAR-T cell cytotoxic activity against different MET overexpressing models, including tumor cell lines, primary cancer cells, organoids, and xenografts in immune-deficient mice.

Results

We proved that MET-CAR-T exerted a specific cytotoxic activity against MET expressing cells. Cell killing was proportional to the level of MET expressed on the cell surface. While CAR-T cytotoxicity was minimal versus cells carrying MET at physiological levels, essentially sparing normal cells, the activity versus MET overexpressing tumors was robust, significantly controlling tumor cell growth in vitro and in vivo. Notably, MET-CAR-T cells were also able to brake acquired resistance to MET targeting agents in MET amplified cancer cells carrying secondary mutations in downstream signal transducers.

Conclusions

We set and validated at the pre-clinical level a MET-CAR immunotherapy strategy potentially beneficial for cancers not eligible for MET targeted therapy with inhibitory molecules, including those exhibiting primary or secondary resistance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02479-y.

CAR T-cell manufacturing from naive/stem memory T-lymphocytes enhances antitumor responses while curtailing cytokine release syndrome

Chimeric antigen receptor (CAR) T cell expansion and persistence represent key factors to achieve complete responses and prevent relapses. These features are typical of early memory T cells, which can be highly enriched through optimized manufacturing protocols. Here, we investigated the efficacy and safety profiles of CAR T cell products generated from preselected naive/stem memory T cells (T_N/SCM), as compared with unselected T cells (T_BULK). Notwithstanding their reduced effector signature in vitro, limiting CAR T_N/SCM doses showed superior antitumor activity and the unique ability to counteract leukemia rechallenge in hematopoietic stem/precursor cell–humanized mice, featuring increased expansion rates and persistence together with an ameliorated exhaustion and memory phenotype. Most relevantly, CAR T_N/SCM proved to be intrinsically less prone to inducing severe cytokine release syndrome, independently of the costimulatory endodomain employed. This safer profile was associated with milder T cell activation, which translated into reduced monocyte activation and cytokine release. These data suggest that CAR T_N/SCM are endowed with a wider therapeutic index compared with CAR T_BULK.

Time 2EVOLVE: predicting efficacy of engineered T-cells - how far is the bench from the bedside?

Immunotherapy with gene engineered CAR and TCR transgenic T-cells is a transformative treatment in cancer medicine. There is a rich pipeline with target antigens and sophisticated technologies that will enable establishing this novel treatment not only in rare hematological malignancies, but also in common solid tumors. The T2EVOLVE consortium is a public private partnership directed at accelerating the preclinical development of and increasing access to engineered T-cell immunotherapies for cancer patients. A key ambition in T2EVOLVE is to assess the currently available preclinical models for evaluating safety and efficacy of engineered T cell therapy and developing new models and test parameters with higher predictive value for clinical safety and efficacy in order to improve and accelerate the selection of lead T-cell products for clinical translation. Here, we review existing and emerging preclinical models that permit assessing CAR and TCR signaling and antigen binding, the access and function of engineered T-cells to primary and metastatic tumor ligands, as well as the impact of endogenous factors such as the host immune system and microbiome. Collectively, this review article presents a perspective on an accelerated translational development path that is based on innovative standardized preclinical test systems for CAR and TCR transgenic T-cell products.

Time to evolve: predicting engineered T cell-associated toxicity with next-generation models

Despite promising clinical results in a small subset of malignancies, therapies based on engineered chimeric antigen receptor and T-cell receptor T cells are associated with serious adverse events, including cytokine release syndrome and neurotoxicity. These toxicities are sometimes so severe that they significantly hinder the implementation of this therapeutic strategy. For a long time, existing preclinical models failed to predict severe toxicities seen in human clinical trials after engineered T-cell infusion. However, in recent years, there has been a concerted effort to develop models, including humanized mouse models, which can better recapitulate toxicities observed in patients. The Accelerating Development and Improving Access to CAR and TCR-engineered T cell therapy (T2EVOLVE) consortium is a public–private partnership directed at accelerating the preclinical development and increasing access to engineered T-cell therapy for patients with cancer. A key ambition in T2EVOLVE is to design new models and tools with higher predictive value for clinical safety and efficacy, in order to improve and accelerate the selection of lead T-cell products for clinical translation. Herein, we review existing preclinical models that are used to test the safety of engineered T cells. We will also highlight limitations of these models and propose potential measures to improve them.

Disrupting N-glycan expression on tumor cells boosts chimeric antigen receptor T cell efficacy against solid malignancies

Immunotherapy with chimeric antigen receptor (CAR)-engineered T cells showed exceptional successes in patients with refractory B cell malignancies. However, first-in-human studies in solid tumors revealed unique hurdles contributing to poor demonstration of efficacy. Understanding the determinants of tumor recognition by CAR T cells should translate into the design of strategies that can overcome resistance. Here, we show that multiple carcinomas express extracellular N-glycans, whose abundance negatively correlates with CAR T cell killing. By knocking out mannoside acetyl-glucosaminyltransferase 5 (MGAT5) in pancreatic adenocarcinoma (PAC), we showed that N-glycans protect tumors from CAR T cell killing by interfering with proper immunological synapse formation and reducing transcriptional activation, cytokine production, and cytotoxicity. To overcome this barrier, we exploited the high metabolic demand of tumors to safely inhibit N-glycans synthesis with the glucose/mannose analog 2-deoxy-d-glucose (2DG). Treatment with 2DG disrupts the N-glycan cover on tumor cells and results in enhanced CAR T cell activity in different xenograft mouse models of PAC. Moreover, 2DG treatment interferes with the PD-1-PD-L1 axis and results in a reduced exhaustion profile of tumor-infiltrating CAR T cells in vivo. The combined 2DG and CAR T cell therapy was successful against multiple carcinomas besides PAC, including those arising from the lung, ovary, and bladder, and with different clinically relevant CAR specificities, such as CD44v6 and CEA. Overall, our results indicate that tumor N-glycosylation regulates the quality and magnitude of CAR T cell responses, paving the way for the rational design of improved therapies against solid malignancies.

102 The deep phenotype characterization of ‘Off-the-Shelf’ CD19-chimeric antigen receptor (CAR) T cells allows to identify their subset complexity and to optimize their manufacturing

Background

Umbilical cord blood (UCB) represents a promising source of T cells for the generation of ‘off-the-shelf’ T cells engineered to express a chimeric antigen receptor (CAR). This study is aimed at understanding the composition of T cell subsets within UCB-CAR-T cells.

Methods

T cells, either from UCB or peripheral mononuclear cells (PBMCs) of healthy donors, were activated in vitro with CD3/CD28 mAbs either conjugated to magnetic beads (Dynabeads) or to a colloidal polymeric nanomatrix (TransAct; Miltenyi Biotec). T cells were then transduced with lentiviral vectors encoding for CD19-CD28z or CD19-4-1BBz CARs. The deep phenotype analyses of the CD19-CAR-T cells (N=32) was performed through a multidimensional flow cytometry to assess the expression/co-expression of T cell-associated markers (N=29). The NGFR was utilized as probe for the expression of CD19-CAR. To select the pertinent markers characterising the different groups, we applied a machine learning technique called L0-regularized logistic regression,1 2 and implemented in the R packageL0Learn. 5-fold cross-validation (CV) was used to select the optimal values of the tuning parameters. CD19-CAR-T cells have been also characterized for the transcriptomic profile by parallel quantitative PCR using the high throughput BioMark HD platform and for cytokines, perforin and granzyme B release upon the co-culture with CD19 expressing or not target cells.

Results

T lymphocytes UCB showed efficient expression of the CARs (40–70% of positive cells). Different T cell subsets could discriminate the composition of T cells activated with either Beads or TranAct. CD4+NGFR+CD45RA+ or CD8+NGFR+CD45RA+ T cells associated with different combinations of CCR7, CD62L, LAG3, CD57, CD56 could discriminate between cells activated with Beads vs. TranAct (figures 2–3). CD8+NGFR+CD45RO+CD279−CD152+ T cells were also differentially expressed in TranAct vs. Beads. The PCA analyses also highlighted differences in terms of CD19-CAR-T cell subsets (such as CD8+NGFR+CD45RO+CD62L+, CD8+NGFR+CD45RO+CCR7+, CD8+NGFR+CD45RO+CD272+TIM−3+, CD8+NGFR+CD45RO+CD272+TIM−3+, CD8+NGFR+CD45RA+CD272+TIM−3− and CD4+NGFR+CD45RA+CD272−TIM−3+) in PBMCs vs. UCBs (figure 1). In addition, bystander T cells with different phenotype not expressing the CARs were also detected within the populations of T cells with different origins. Similarly, different T subsets were found in relationship with the sources of T cells. These CD19-CAR-T cells were also characterized for the anti-tumor activity and transcriptomic profiling.

Abstract 102 Figure 1

PCA of CAR-T cells from UCB vs. PBMCs

Abstract 102 Figure 2

PCA of CAR-T cells from UCB to compare TransAct vs. beads

Abstract 102 Figure 3

PCA of CD19-CAR-T cells to compare TransAct vs. Beads irrespective of the source of the T cells

Conclusions

The combination of deep phenotype characterization with novel statistical tools allowed to identify the complexity of subsets in the engineered T cells in relationship with the starting material and the methods for the activation of the lymphocytes. These findings have important implications for the optimization of the manufacturing of CD19-CAR-T cells.

References

Antoine Dedieu, Hussein Hazimeh, and Rahul Mazumder. Learningsparse classifiers: Continuous and mixed integer optimization perspectives. Journal of Machine Learning Research 2021.

Hussein Hazimeh and Rahul Mazumder. Fast best subset selection: Coordinatedescent and local combinatorial optimization algorithms. Operations Research 2020;68(5):1517–1537.

Ethics Approval

Sidra Medicine’s Ethics Board approval, #1812044429

Myeloid cell-based delivery of IFN-γ reprograms the leukemia microenvironment and induces anti-tumoral immune responses

The immunosuppressive microenvironment surrounding tumor cells represents a key cause of treatment failure. Therefore, immunotherapies aimed at reprogramming the immune system have largely spread in the past years. We employed gene transfer into hematopoietic stem and progenitor cells to selectively express anti-tumoral cytokines in tumor-infiltrating monocytes/macrophages. We show that interferon-γ (IFN-γ) reduced tumor progression in mouse models of B-cell acute lymphoblastic leukemia (B-ALL) and colorectal carcinoma (MC38). Its activity depended on the immune system's capacity to respond to IFN-γ and drove the counter-selection of leukemia cells expressing surrogate antigens. Gene-based IFN-γ delivery induced antigen presentation in the myeloid compartment and on leukemia cells, leading to a wave of T cell recruitment and activation, with enhanced clonal expansion of cytotoxic CD8+ T lymphocytes. The activity of IFN-γ was further enhanced by either co-delivery of tumor necrosis factor-α (TNF-α) or by drugs blocking immunosuppressive escape pathways, with the potential to obtain durable responses.

Human T cells engineered with a leukemia lipid-specific TCR enables donor-unrestricted recognition of CD1c-expressing leukemia

Acute leukemia relapsing after chemotherapy plus allogeneic hematopoietic stem cell transplantation can be treated with donor-derived T cells, but this is hampered by the need for donor/recipient MHC-matching and often results in graft-versus-host disease, prompting the search for new donor-unrestricted strategies targeting malignant cells. Leukemia blasts express CD1c antigen-presenting molecules, which are identical in all individuals and expressed only by mature leukocytes, and are recognized by T cell clones specific for the CD1c-restricted leukemia-associated methyl-lysophosphatidic acid (mLPA) lipid antigen. Here, we show that human T cells engineered to express an mLPA-specific TCR, target diverse CD1c-expressing leukemia blasts in vitro and significantly delay the progression of three models of leukemia xenograft in NSG mice, an effect that is boosted by mLPA-cellular immunization. These results highlight a strategy to redirect T cells against leukemia via transfer of a lipid-specific TCR that could be used across MHC barriers with reduced risk of graft-versus-host disease.

Leukaemia therapy may benefit from the use of antigens that are less restricted to individual donors. Here the authors engineered T cells with a TCR specific for a CD1c restricted lipid leukaemia antigen and show that they can protect against disease progression in mouse leukaemia xenograft models.

Characterization and Functional Analysis of CD44v6.CAR T Cells Endowed with a New Low-Affinity Nerve Growth Factor Receptor-Based Spacer

Effectiveness of adoptively transferred chimeric antigen receptor (CAR) T cells strongly depends on the quality of CAR-mediated interaction of the effector cells with the target antigen on tumor cells. A major role in this interaction is played by the affinity of the single-chain variable fragment (scFv) for the antigen, and by the CAR design. In particular, the spacer domain may impact on the CAR T cell function by affecting the length and flexibility of the resulting CAR. This study addresses the need to improve the manufacturing process and the antitumor activity of CD44v6-specific CAR T cells by defining the optimal structure of a spacer region derived from the extracellular domain of the human low-affinity nerve growth factor receptor (LNGFR). We tailored the LNGFR spacer to modulate CAR length to efficiently recognize distal or proximal epitopes and to allow selection of transduced CAR T cells by the use of clinical-grade validated manufacturing systems. The different LNGFR spacers investigated in this study are responsible for the generation of CAR T cells with a different memory phenotype, which is mainly related to the level of CAR expression and the extent of the associated tonic signaling. In particular, the CD44v6-NWN2.CAR T cells are enriched in central memory cells and show improved in vitro functions in terms of killing capability, and in vivo antitumor activity against hematological and solid tumors. Clinical Trial Registration numbers: clinicaltrial.gov NCT04097301; ClinicalTrials.gov, NCT00423124.

Two subsets of stem-like CD8+ memory T cell progenitors with distinct fate commitments in humans

T cell memory relies on the generation of antigen-specific progenitors with stem-like properties. However, the identity of these progenitors has remained unclear, precluding a full understanding of the differentiation trajectories that underpin the heterogeneity of antigen-experienced T cells. We used a systematic approach guided by single-cell RNA-sequencing data to map the organizational structure of the human CD8+ memory T cell pool under physiological conditions. We identified two previously unrecognized subsets of clonally, epigenetically, functionally, phenotypically and transcriptionally distinct stem-like CD8+ memory T cells. Progenitors lacking the inhibitory receptors programmed death-1 (PD-1) and T cell immunoreceptor with Ig and ITIM domains (TIGIT) were committed to a functional lineage, whereas progenitors expressing PD-1 and TIGIT were committed to a dysfunctional, exhausted-like lineage. Collectively, these data reveal the existence of parallel differentiation programs in the human CD8+ memory T cell pool, with potentially broad implications for the development of immunotherapies and vaccines.

Next-Generation Manufacturing Protocols Enriching TSCM CAR T Cells Can Overcome Disease-Specific T Cell Defects in Cancer Patients

Chimeric antigen receptor (CAR) T cell expansion and persistence emerged as key efficacy determinants in cancer patients. These features are typical of early-memory T cells, which can be enriched with specific manufacturing procedures, providing signal one and signal two in the proper steric conformation and in the presence of homeostatic cytokines. In this project, we exploited our expertise with paramagnetic beads and IL-7/IL-15 to develop an optimized protocol for CAR T cell production based on reagents, including a polymeric nanomatrix, which are compatible with automated manufacturing via the CliniMACS Prodigy. We found that both procedures generate similar CAR T cell products, highly enriched of stem cell memory T cells (T_SCM) and equally effective in counteracting tumor growth in xenograft mouse models. Most importantly, the optimized protocol was able to expand CAR T_SCM from B-cell acute lymphoblastic leukemia (B-ALL) patients, which in origin were highly enriched of late-memory and exhausted T cells. Notably, CAR T cells derived from B-ALL patients proved to be as efficient as healthy donor-derived CAR T cells in mediating profound and prolonged anti-tumor responses in xenograft mouse models. On the contrary, the protocol failed to expand fully functional CAR T_SCM from patients with pancreatic ductal adenocarcinoma, suggesting that patient-specific factors may profoundly affect intrinsic T cell quality. Finally, by retrospective analysis of in vivo data, we observed that the proportion of T_SCM in the final CAR T cell product positively correlated with in vivo expansion, which in turn proved to be crucial for achieving long-term remissions. Collectively, our data indicate that next-generation manufacturing protocols can overcome initial T cell defects, resulting in T_SCM-enriched CAR T cell products qualitatively equivalent to the ones generated from healthy donors. However, this positive effect may be decreased in specific conditions, for which the development of further improved protocols and novel strategies might be highly beneficial.

Extracellular NGFR Spacers Allow Efficient Tracking and Enrichment of Fully Functional CAR-T Cells Co-Expressing a Suicide Gene

Chimeric antigen receptor (CAR)-T cell immunotherapy is at the forefront of innovative cancer therapeutics. However, lack of standardization of cellular products within the same clinical trial and lack of harmonization between different trials have hindered the clear identification of efficacy and safety determinants that should be unveiled in order to advance the field. With the aim of facilitating the isolation and in vivo tracking of CAR-T cells, we here propose the inclusion within the CAR molecule of a novel extracellular spacer based on the low-affinity nerve-growth-factor receptor (NGFR). We screened four different spacer designs using as target antigen the CD44 isoform variant 6 (CD44v6). We successfully generated NGFR-spaced CD44v6 CAR-T cells that could be efficiently enriched with clinical-grade immuno-magnetic beads without negative consequences on subsequent expansion, immuno-phenotype, in vitro antitumor reactivity, and conditional ablation when co-expressing a suicide gene. Most importantly, these cells could be tracked with anti-NGFR monoclonal antibodies in NSG mice, where they expanded, persisted, and exerted potent antitumor effects against both high leukemia and myeloma burdens. Similar results were obtained with NGFR-enriched CAR-T cells specific for CD19 or CEA, suggesting the universality of this strategy. In conclusion, we have demonstrated that the incorporation of the NGFR marker gene within the CAR sequence allows for a single molecule to simultaneously work as a therapeutic and selection/tracking gene. Looking ahead, NGFR spacer enrichment might allow good manufacturing procedures-manufacturing of standardized CAR-T cell products with high therapeutic potential, which could be harmonized in different clinical trials and used in combination with a suicide gene for future application in the allogeneic setting.

Acute Myeloid Leukemia Targeting by Chimeric Antigen Receptor T Cells: Bridging the Gap from Preclinical Modeling to Human Studies

Acute myeloid leukemia (AML) still represents an unmet clinical need for adult and pediatric high-risk patients, thus demanding advanced and personalized therapies. In this regard, different targeted immunotherapeutic approaches are available, ranging from naked monoclonal antibodies (mAb) to conjugated and multifunctional mAbs (i.e., BiTEs and DARTs). Recently, researchers have focused their attention on novel techniques of genetic manipulation specifically to redirect cytotoxic T cells endowed with chimeric antigen receptors (CARs) toward selected tumor associated antigens. So far, CAR T cells targeting the CD19 antigen expressed by B-cell origin hematological cancers have gained impressive clinical results, leading to the possibility of translating the CAR platform to treat other hematological malignancies such as AML. However, one of the main concerns in the field of AML CAR immunotherapy is the identification of an ideal target cell surface antigen, being highly expressed on tumor cells but minimally present on healthy tissues, together with the design of an anti-AML CAR appropriately balancing efficacy and safety profiles. The current review focuses mainly on AML target antigens and the related immunotherapeutic approaches developed so far, deeply dissecting methods of CAR T cell safety improvements, when designing novel CARs approaching human studies.

Abstract 2298: Cytokine-induced killer cells redirected with anti-CD44v6 chimeric antigen receptor against soft tissue sarcomas

Purpose of our study is to explore the anti-sarcoma activity of cytokine-induced killer (CIK) cells engineered with a chimeric antigen receptor (CAR) against the isoform variant 6 of adhesive receptor CD44 (CD44v6). CD44v6 may be an ideal target for immunotherapy as it is a tumor-promoting antigen, associated with the metastatic process and tumor initiating cells. Advanced and metastatic soft tissue sarcomas (STS) are currently incurable and in great need for new therapeutic strategies.

CIK cells are ex vivo expanded T lymphocytes endowed with MHC-independent antitumor activity.

CIK cells are active against STS (Sangiolo et al. Cancer Research 2014) but their function decreases at low effector/target (E/T) ratios with limitations in clinical perspective. We hypothesized that CIK cells may be effective candidates for CAR-based strategies, considering their intense ex vivo expansibility and innate antitumor activity.

Experimental procedures and results. CIK cells were expanded from 9 STS patients and engineered with a lentiviral vector encoding for anti-CD44v6 CAR containing a CD28 signaling domain (Casucci et al, Blood 2013) and the HSV-TK suicide switch. Tumor killing was assessed in vitro against 10 STS (undifferentiated pleomorphic n = 5; Liposarcoma n = 2; Fibrosarcoma n = 1; GIST n = 2), in 2 cases STS targets were autologous.

All 10 STS expressed CD44v6 (Relative Fluorescence Intensity = 4, SE = 1). Mean transduction efficiency was 60% (SE = 6%). Expansion rates and phenotype of CAR-CIK were comparable with unmodified controls (CD3+CD56+ = 50%; CD8 = 66%; NKG2D = 85%).

Anti-CD44v6 CAR-CIK cells efficiently killed STS in vitro. Mean tumor-specific killing, at low E/T ratios, was significantly higher compared with unmodified CIK cells: 98% vs 84% (E/T = 10:1, p>0.05), 89% vs 41% (E/T = 1:1, p = 0.0001), 65% vs 26% (E/T = 1:4 p = 0.0001).

In vitro treatment with Ganciclovir (10 μM) significantly inhibited tumor killing activity of CAR-CIK from 70% to 10% (E/T 1:1, n = 3, p = 0.008).

Blocking experiments (n = 2) with anti-CD44v6 antibody against the same epitope recognized by the CAR (VFF-18) decreased tumor-specific killing from 96% to 43% (E/T = 1:1) and 27% (E/T = 1:2). Adoptive infusion of anti-CD44v6 CAR-CIK cells significantly delayed tumor growth (p = 0.01) and reduced proliferative index (p = 0.001) of established subcutaneous fibrosarcoma xenografts in NOD/SCID mice (n = 3) compared to untreated controls (n = 3) without any sign of toxicity.

Conclusions. Ours is the first report of CAR-engineered CIK cells against solid tumors. This approach significantly potentiates the innate tumor killing ability of CIK cells with a new redirected antitumor specificity. CIK cells may be appealing alternative candidates to conventional T cells for future CAR-based strategies against solid tumors. Our findings support CD44v6 as a valuable target for adoptive cell therapies against currently incurable sarcomas.

Citation Format: Valeria Leuci, Monica Casucci, Giovanni Grignani, Ramona Rotolo, Elisa Vigna, Loretta Gammaitoni, Giulia Mesiano, Lorenzo D’Ambrosio, Massimo Aglietta, Attilio Bondanza, Dario Sangiolo. Cytokine-induced killer cells redirected with anti-CD44v6 chimeric antigen receptor against soft tissue sarcomas. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2298.

Exploiting Secreted Luciferases to Monitor Tumor Progression In Vivo

Secreted luciferases provide a simple, accurate, and cost-effective tool to monitor tumor response after treatment in small animal models. This protocol describes all the steps required to generate human tumor cell lines expressing this reporter gene and to monitor in vivo tumor progression after injection in immunocompromised mice by means of serial peripheral blood sampling and analysis.

Clinical pharmacology of CAR-T cells: Linking cellular pharmacodynamics to pharmacokinetics and antitumor effects

Adoptive cell transfer of T cells genetically modified with tumor-reactive chimeric antigen receptors (CARs) is a rapidly emerging field in oncology, which in preliminary clinical trials has already shown striking antitumor efficacy. Despite these premises, there are still a number of open issues related to CAR-T cells, spanning from their exact mechanism of action (pharmacodynamics), to the factors associated with their in vivo persistence (pharmacokinetics), and, finally, to the relative contribution of each of the two in determining the antitumor effects and accompanying toxicities. In light of the unprecedented curative potential of CAR-T cells and of their predicted wide availability in the next few years, in this review we will summarize the current knowledge on the clinical pharmacology aspects of what is anticipated to be a brand new class of biopharmaceuticals to join the therapeutic armamentarium of cancer doctors.

Overcoming the toxicity hurdles of genetically targeted T cells

The recent successes of clinical trials with T cells genetically modified with either clonal T cell receptors or chimeric antigen receptors have also highlighted their potential toxicities. The aim of this focused review was to describe the adverse events observed in these clinical trials and to link them to the complex biology of genetically targeted T cells. Finally, strategies to overcome these toxicities will be proposed and discussed, including the use of suicide genes and other innovative gene therapy strategies.

Adoptive immunotherapy with genetically modified lymphocytes in allogeneic stem cell transplantation

Hematopoietic stem cell transplantation from a healthy donor (allo-HSCT) represents the most potent form of cellular adoptive immunotherapy to treat malignancies. In allo-HSCT, donor T cells are double edge-swords: highly potent against residual tumor cells, but potentially highly toxic, and responsible for graft versus host disease (GVHD), a major clinical complication of transplantation. Gene transfer technologies coupled with current knowledge on cancer immunology have generated a wide range of approaches aimed at fostering the immunological response to cancer cells, while avoiding or controlling GVHD. In this review, we discuss cell and gene therapy approaches currently tested in preclinical models and in clinical trials.

Is vitamin D supplementation necessary in healthy full-term breastfed infants? A follow-up study of bone mineralization in healthy full-term infants with and without supplemental vitamin D

AIM

The aim of the study is to establish whether healthy full-term breastfed infants require supplemental vitamin D for proper bone mineralization.

METHODS

Bone mineralization was studied by performing ultrasound scans of 73 healthy full-term subjects at the age of 3 months. The infants were divided into three groups. Group A: breastfed without supplemental vitamin D (BF); group B: breastfed with supplement of 400 IU/day of vitamin D (BFD); group C: fed with formula (with and without supplemental vitamin D 400 IU/day) (FF). The values of mcSOS (m/sec) and mcBTT (µsec) were assessed in all subjects.

RESULTS

A statistically significant difference has been found between group A vs group B both in mcSOS (P=0.03) and in mcBTT (P=0.01) values and also between group A vs group C both in mcSOS (P=0.012) and in mcBTT (P=0.003) values. Significant differences between group B vs group C were not found. In 75% of subjects of group A mcSOS and mcBTT values were ≤ the 10th percentile, while in group B they were between the 10th and 50th percentile. In FF infants given supplemental vitamin D mcSOS and mcBTT values were between the 25th and 75th percentile.

CONCLUSION

Human breast milk is an appropriate source of nutrition for the growth of healthy full-term newborns, but is poor in vitamin D as demonstrated by the impaired bone mineralization in the breastfed infants without supplemental vitamin D. The results presented demonstrate that exclusively breastfed infants require at least 400 IU/day of supplemental vitamin D.

Suicide gene therapy to increase the safety of chimeric antigen receptor-redirected T lymphocytes

Chimeric antigen receptors (CARs) are generated by fusing the antigen-binding motif of a monoclonal antibody (mAb) with the signal transduction machinery of the T-cell receptor (TCR). The genetic modification of T lymphocytes with chimeric receptors specific for tumor-associated antigens (TAAs) allows for the redirection towards tumor cells. Clinical experience with CAR-redirected T cells suggests that antitumor efficacy associates with some degree of toxicity, especially when TAA expression is shared with healthy tissues. This situation closely resembles the case of allogeneic hematopoietic stem cell transplantation (HSCT), wherein allorecognition causes both the graft-versus-leukemia (GVL) effect and graft-versus-host disease (GVHD). Suicide gene therapy, i.e. the genetic induction of a conditional suicide phenotype into donor T cells, enables dissociating the GVL effect from GVHD. Applying suicide gene modification to CAR-redirected T cells may therefore greatly increase their safety profile and facilitate their clinical development.

Aminoterminal B-type natriuretic peptide (NT-proBNP) in the therapy of patent ductus arteriosus

BACKGROUND

NT-proBNP is a reliable index in case of cardiac diseases.

OBJECTIVE

To evaluate the diagnostic usefulness of NT-proBNP as index of the closure of patent ductus arteriosus (PDA) in ELBW.

METHODS

Considered 73 ELBW (mGA 26+3 weeks; mBW 789 g) with echocardiographical diagnosis of PDA. The closure of the duct was spontaneous in 22%, pharmacological in 49.3% and by surgical ligation in 28.7%. Plasma NT-proBNP levels were measured on day 3 in 35 preterm infants; in 20 of them concentrations of the peptide were assayed on day 3 and on closure of the duct.

RESULTS

On day 3 the median of NT-proBNP levels was 13718 pg/ml (range 1918-70000). Peptide concentrations did not differ between pharmacological treatment and surgical ligation (respectively 13718 and 12342 pg/ml; p = 0.33). Concentrations of NT-proBNP were significantly lower on the closure of the duct (p < 0.0001) compared to concentrations on day 3 (median 12666 at day 3 versus 2443.5 pg/ml at closure), with a decrease of 80.71%.

CONCLUSIONS

ELBW showed high variability of NT-proBNP concentrations both on day 3 and on closure of PDA. Although NT-proBNP high levels were indicative of the presence of hsPDA, due to the extreme heterogeneity of the values it was not possible to determine an absolute cut-off concentration of NT-proBNP below which closure of the duct occurred, while a decrease of NT-proBNP > or =80% was a reliable index of PDA closure.

A numerical tool for reproducing driver behaviour: experiments and predictive simulations

This paper presents the simulation tool called SDDRIVE (Simple Simulation of Driver performance), which is the numerical computerised implementation of the theoretical architecture describing Driver-Vehicle-Environment (DVE) interactions, contained in Cacciabue and Carsten [Cacciabue, P.C., Carsten, O. A simple model of driver behaviour to sustain design and safety assessment of automated systems in automotive environments, 2010]. Following a brief description of the basic algorithms that simulate the performance of drivers, the paper presents and discusses a set of experiments carried out in a Virtual Reality full scale simulator for validating the simulation. Then the predictive potentiality of the tool is shown by discussing two case studies of DVE interactions, performed in the presence of different driver attitudes in similar traffic conditions.

Loss of mismatched HLA in leukemia after stem-cell transplantation

BACKGROUND

Transplantation of hematopoietic stem cells from partially matched family donors is a promising therapy for patients who have a hematologic cancer and are at high risk for relapse. The donor T-cell infusions associated with such transplantation can promote post-transplantation immune reconstitution and control residual disease.

METHODS

We identified 43 patients who underwent haploidentical transplantation and infusion of donor T cells for acute myeloid leukemia or myelodysplastic syndrome and conducted post-transplantation studies that included morphologic examination of bone marrow, assessment of hematopoietic chimerism with the use of short-tandem-repeat amplification, and HLA typing. The genomic rearrangements in mutant variants of leukemia were studied with the use of genomic HLA typing, microsatellite mapping, and single-nucleotide-polymorphism arrays. The post-transplantation immune responses against the original cells and the mutated leukemic cells were analyzed with the use of mixed lymphocyte cultures.

RESULTS

In 5 of 17 patients with leukemia relapse after haploidentical transplantation and infusion of donor T cells, we identified mutant variants of the original leukemic cells. In the mutant leukemic cells, the HLA haplotype that differed from the donor's haplotype had been lost because of acquired uniparental disomy of chromosome 6p. T cells from the donor and the patient after transplantation did not recognize the mutant leukemic cells, whereas the original leukemic cells taken at the time of diagnosis were efficiently recognized and killed.

CONCLUSIONS

After transplantation of haploidentical hematopoietic stem cells and infusion of donor T cells, leukemic cells can escape from the donor's antileukemic T cells through the loss of the mismatched HLA haplotype. This event leads to relapse.

Role of natural killer cell alloreactivity in HLA-mismatched hematopoietic stem cell transplantation

Because of the expression of inhibitory receptors (KIR) for major histocompatibility complex (MHC) class I allotypes, a person's natural killer (NK) cells will not recognize and will, therefore, kill cells from individuals lacking his/her KIR epitopes. This study investigated the role of NK cell alloreactivity in human HLA haplotype-mismatched hematopoietic stem cell transplantation and, specifically, the role of the three major NK specificities, ie, those for HLA-C group 1, HLA-C group 2, and HLA-Bw4 alleles. In 20 of 60 donor-recipient pairs, KIR epitope incompatibility and functional analyses of donor NK cell clones predicted donor NK cells could cause graft-versus-host (GVH)/graft-versus-leukemia (GVL) reactions. NK cell clones of donor origin were obtained from transplanted recipients and tested for lysis of recipient's cryopreserved pretransplant lymphocytes. Despite the absence of GVH disease, we detected high frequencies of NK clones which killed recipient's target cells. Lysis followed the rules of NK cell alloreactivity, being blocked only by the MHC class I KIR epitope which was missing in the recipient. The alloreactive NK clones also killed the allogeneic leukemia. Transplants from these KIR epitope incompatible donors had higher engraftment rates. Therefore, a GVL effector and engraftment facilitating mechanism, which is independent of T-cell-mediated GVH reactions, may be operational in HLA mismatched hematopoietic cell transplants.

CD44 signaling through p56lck involves lateral association with CD4 in human CD4+ T cells

CD44 is a family of mucin-like membrane proteins generated by alternative splicing of several exons, and participate in T cell adhesion and activation. CD44-mediated signaling involves activation of p56(lck) and leads to ZAP-70 phosphorylation. The aim of the present study was to identify the signaling pathways that follow CD44-triggered ZAP-70 phosphorylation and the molecular mechanisms underlying the CD44 interaction with p56(lck). We found that CD44 cross-linking by mAb in CD4(+) peripheral blood T cells promotes formation of a trimeric complex of Grb2, phospholipase (PLC)-gamma1 and a 36-38 kDa phosphoprotein, and the activation of PLC-gamma1. The amount of inositol triphosphate and the time kinetics of its generation were comparable to those following CD3 cross-linking. Co-capping, co-immunoprecipitation and fluorescence resonance energy transfer experiments showed that CD44 associates with CD4 and CD3 on the cell surface. This association suggests functional interplay between the CD4-TCR complex and CD44. In line with this possibility, we found that CD4 triggering by gp120, a natural ligand of CD4, potentiates CD44-mediated adhesion to hyaluronic acid. Moreover, Ca2+ mobilization induced by CD44 cross-linking by mAb was higher in a subclone of the HUT78 cell line expressing CD4 than in a non-expressing subclone.