Bone marrow disease in rhabdomyosarcoma visualized by 2-[18F]fluorodeoxyglucose positron emission tomography/computed tomography

Bone marrow metastases-noted in 6% of patients with rhabdomyosarcoma-have been linked to very poor outcomes. Bilateral bone marrow sampling from iliac crests has been the gold standard for bone marrow examination in rhabdomyosarcoma, but sampling errors due to patchy bone marrow involvement may limit its sensitivity. Here, we report the case of a 6-year-old boy with embryonal rhabdomyosarcoma of the skull base and multiple 2-[18F]fluoro-2-deoxy-D-glucose (2-[18F]FDG)-avid bone marrow metastases visualized by positron emission tomography and computed tomography (2-[18F]FDG PET/CT). His bone marrow aspirates were tumor-free. This case illustrates the diagnostic value of 2-[18F]FDG PET/CT in the detection of bone marrow metastases in rhabdomyosarcoma patients, which may re-shape the definition of bone marrow disease and, ultimately, alter disease staging and risk stratification.

Approaches for bridging therapy prior to chimeric antigen receptor T cells for relapsed/refractory acute lymphoblastic B-lineage leukaemia in children and young adults

The ongoing development of immunotherapies, including chimeric antigen receptor (CAR) T cells, has revolutionized cancer treatment. In paediatric relapsed/refractory B-lineage acute leukaemia antiCD19-CARs induced impressive initial response rates, with event-free survival plateauing at 30-50% in long-term follow-up data. During the interval between diagnosis of relapse or refractoriness and CAR T cell infusion, patients require a bridging therapy. To date, this therapy has consisted of highly variable approaches based on local experience. Here, in an European collaborative effort of paediatric and adult haematologists, we summarise current knowledge with the aim of establishing a guidance for bridging therapy. This includes treatment strategies for different patient subgroups, the advantages and disadvantages of low- and highintensity regimens, and the potential impact of bridging therapy on outcome after CAR T cell infusion. This guidance is a step towards a cross-institutional harmonization of bridging therapy, including personalized approaches. This will allow better comparability of clinical data and increase the level of evidence for the treatment of children and young adults with relapsed/refractory B-lineage ALL until CAR T cell infusion.

Influence of ATLG Serum Levels on CD3/CD19-depleted Hematopoietic Grafts and on Immune Recovery in Pediatric Haplo-HSCT

Anti-T lymphocyte globulin (ATLG) significantly reduces the risk of engraftment failure in allogeneic hematopoietic stem cell transplantation (HSCT), but hampers post-transplant immune reconstitution. We hypothesized that in patients receiving haploidentical CD3/CD19-depleted grafts these double-edged effects could be better balanced by attaining high ATLG serum concentrations before transplant, but as low as possible on the day of transplant. Therefore, we moved the start of ATLG application to day -12 and determined serum concentrations of T cell specific ATLG in pediatric patients treated with three established dosing regimens (15, 30, or 60 mg/kg). Corresponding mean T cell specific ATLG serum concentrations at day 0 were 1.14, 2.99, or 12.10 µg/ml, respectively. Higher ATLG doses correlated with higher peak levels at days -8 and -7 and reduced graft rejection, while lower ATLG doses correlated with significantly faster post-transplant recovery of T and NK cells. The rate of graft-versus-host disease (GvHD) remained low independent from ATLG doses. Moreover, in vitro assays showed that ATLG concentrations of 2.0 µg/ml and lower only slightly reduced the activity of NK cells and, therefore, the function of such effector cells might be preserved in the grafts. Pharmacokinetic analysis, compatible with linear first order kinetics, revealed similar half-life values independent of ATLG doses. Hence, the day on which a desired ATLG serum level is reached can be calculated prior to HSCT. Our retrospective study demonstrates the relevance of dosing and time of administration of ATLG on engraftment and immune recovery in ex vivo CD3/CD19-depleted haploidentical HSCT.

Combination of nivolumab with standard induction chemotherapy in children and adults with EBV-positive nasopharyngeal carcinoma : Protocol of a prospective multicenter phase 2 trial

BACKGROUND

Treatment of Epstein-Barr virus(EBV)-positive nasopharyngeal carcinoma (NPC) with cisplatin/5-fluorouracil (5-FU) induction chemotherapy, followed by radiochemotherapy and subsequent interferon‑β, has yielded high survival rates in children, adolescents, and young adults. A previous study has shown that reduction of radiation dose from 59.4 to 54.0 Gy appears to be safe in patients with complete response (CR) to induction chemotherapy. As immune checkpoint-inhibitors have shown activity in NPC, we hypothesize that the addition of nivolumab to standard induction chemotherapy would increase the rate of complete tumor responses, thus allowing for a reduced radiation dose in a greater proportion of patients.

METHODS

This is a prospective multicenter phase 2 clinical trial including pediatric and adult patients with their first diagnosis of EBV-positive NPC, scheduled to receive nivolumab in addition to standard induction chemotherapy. In cases of non-response to induction therapy (stable or progressive disease), and in patients with initial distant metastasis, treatment with nivolumab will be continued during radiochemotherapy. Primary endpoint is tumor response on magnetic resonance imaging (MRI) and positron emission tomography (PET) after three cycles of induction chemotherapy. Secondary endpoints are event-free (EFS) and overall survival (OS), safety, and correlation of tumor response with programmed cell death ligand 1 (PD-L1) expression.

DISCUSSION

As cure rates in localized EBV-positive NPC today are high with standard multimodal treatment, the focus increasingly shifts toward prevention of late effects, the burden of which is exceptionally high, mainly due to intense radiotherapy. Furthermore, survival in patients with metastatic disease and resistant to conventional chemotherapy remains poor. Primary objective of this study is to investigate whether the addition of nivolumab to standard induction chemotherapy in children and adults with EBV-positive NPC is able to increase the rate of complete responses, thus enabling a reduction in radiation dose in more patients, but also offer patients with high risk of treatment failure the chance to benefit from the addition of nivolumab.

TRIAL REGISTRATION

EudraCT (European Union Drug Regulating Authorities Clinical Trials Database) No. 2021-006477-32.

Th1 cytokines in pediatric acute lymphoblastic leukemia

Immune milieus play an important role in various types of cancer. The present study focuses on the effect of Th1 cytokines on pediatric acute lymphoblastic leukemia (ALL). The reaction of ALL cell lines and patient-derived xenografts (PDX) to the most important Th1 cytokines TNF-α (tumor necrosis factor alpha) and IFN-γ (interferon gamma) is analyzed and correlated with the respective cytokine receptors and the intracellular signaling molecules. ALL cell lines and ALL PDX display a great heterogeneity in cell death after incubation with TNF-α and IFN-γ. Several samples show a dose-dependent and additive induction of cell death by both cytokines; others do not react at all or even display an increased viability. Apoptosis is the main type of cell death induced by Th1 cytokines in ALL cells. Over all leukemia cells analyzed, IFN-γ receptor (IFNGR) shows a higher expression than both TNF-receptors, resulting in higher phosphorylation of STAT1 (signal transducer and activator of transcription) compared to phosphorylation of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B-cells) in the TNF pathway. The activation of STAT1 correlates with the amount of cell death after stimulation with Th1 cytokines. TNF-α and IFN-γ lead to heterogeneous reactions in ALL cell lines and ALL PDX but are able to induce cell death by apoptosis in the majority of ALL blasts. The correlation of a high expression of IFNGR and following activation of STAT1 with cell death indicates an important role for IFN-γ signaling in this setting.

Excellent outcome of stem cell transplantation for sickle cell disease

Many sickle cell disease (SCD) patients lack matched family donors (MFD) or matched unrelated donors (MUD), implying haploidentical donors (MMFD) as a logical donor choice. We used a reduced toxicity protocol for all donor types. We included 31 patients (2-22 years) with MFD (n = 15), MMFD (10), or MUD (6) HSCT and conditioning with alemtuzumab/ATG, thiotepa, fludarabine and treosulfan, and post-transplant cyclophosphamide for MMFD. After the initial six patients, treosulfan was replaced by targeted busulfan (AUC 65-75 ng*h/ml). After a median follow-up of 26 months (6-123), all patients are alive and off immunosuppression. Two MMFD patients experienced secondary graft failure with recurrence of SCD, both after treosulfan conditioning. Neither acute GVHD ≥ °III nor moderate/severe chronic GVHD was observed. The disease-free, severe GVHD-free survival was 100%, 100%, and 80% in the MFD, MUD, and MMFD groups, respectively (p = 0.106). There was a higher rate of virus reactivation in MMFD (100%) and MUD (83%) compared to MFD (40%; p = 0.005), but not of viral disease (20% vs 33% vs 13%; p = 0.576). Six patients had treosulfan-based conditioning, two of whom experienced graft failure (33%), compared to 0/25 (0%) after busulfan-based conditioning (p = 0.032). Donor chimerism was ≥ 80% in 28/31 patients (90%) at last follow-up. Reduced toxicity myeloablative conditioning resulted in excellent overall survival, negligible GVHD, and low toxicity among all donor groups in pediatric and young adult patients with SCD.

Modular pooled discovery of synthetic knockin sequences to program durable cell therapies

Chronic stimulation can cause T cell dysfunction and limit the efficacy of cellular immunotherapies. Improved methods are required to compare large numbers of synthetic knockin (KI) sequences to reprogram cell functions. Here, we developed modular pooled KI screening (ModPoKI), an adaptable platform for modular construction of DNA KI libraries using barcoded multicistronic adaptors. We built two ModPoKI libraries of 100 transcription factors (TFs) and 129 natural and synthetic surface receptors (SRs). Over 30 ModPoKI screens across human TCR- and CAR-T cells in diverse conditions identified a transcription factor AP4 (TFAP4) construct that enhanced fitness of chronically stimulated CAR-T cells and anti-cancer function in vitro and in vivo. ModPoKI's modularity allowed us to generate an ∼10,000-member library of TF combinations. Non-viral KI of a combined BATF-TFAP4 polycistronic construct enhanced fitness. Overexpressed BATF and TFAP4 co-occupy and regulate key gene targets to reprogram T cell function. ModPoKI facilitates the discovery of complex gene constructs to program cellular functions.

Rational design of PD-1-CD28 immunostimulatory fusion proteins for CAR T cell therapy

BACKGROUND

In many situations, the therapeutic efficacy of CAR T cells is limited due to immune suppression and poor persistence. Immunostimulatory fusion protein (IFP) constructs have been advanced as a tool to convert suppressive signals into stimulation and thus promote the persistence of T cells, but no universal IFP design has been established so far. We now took advantage of a PD-1-CD28 IFP as a clinically relevant structure to define key determinants of IFP activity.

METHODS

We compared different PD-1-CD28 IFP variants in a human leukemia model to assess the impact of distinctive design choices on CAR T cell performance in vitro and a xenograft mouse model.

RESULTS

We observed that IFP constructs that putatively exceed the extracellular length of PD-1 induce T-cell response without CAR target recognition, rendering them unsuitable for tumour-specific therapy. IFP variants with physiological PD-1 length ameliorated CAR T cell effector function and proliferation in response to PD-L1+ tumour cells in vitro and prolonged survival in vivo. Transmembrane or extracellular CD28 domains were found to be replaceable by corresponding PD-1 domains for in vivo efficacy.

CONCLUSION

PD-1-CD28 IFP constructs must mimic the physiological interaction of PD-1 with PD-L1 to retain selectivity and mediate CAR-conditional therapeutic activity.

Anti-GD2 Antibody Dinutuximab Beta and Low-Dose Interleukin 2 After Haploidentical Stem-Cell Transplantation in Patients With Relapsed Neuroblastoma: A Multicenter, Phase I/II Trial

PURPOSE

Patients with relapsed high-risk neuroblastoma (rHR-NB) have a poor prognosis. We hypothesized that graft-versus-neuroblastoma effects could be elicited by transplantation of haploidentical stem cells (haplo-SCT) exploiting cytotoxic functions of natural killer cells and their activation by the anti-GD2 antibody dinutuximab beta (DB). This phase I/II trial assessed safety, feasibility, and outcomes of immunotherapy with DB plus subcutaneous interleukin-2 (scIL2) after haplo-SCT in patients with rHR-NB.

METHODS

Patients age 1-21 years underwent T-/B-cell-depleted haplo-SCT followed by DB and scIL2. The primary end point 'success of treatment' encompassed patients receiving six cycles, being alive 180 days after end of trial treatment without progressive disease, unacceptable toxicity, acute graft-versus-host-disease (GvHD) ≥grade 3, or extensive chronic GvHD.

RESULTS

Seventy patients were screened, and 68 were eligible for immunotherapy. Median number of DB cycles was 6 (range, 1-9). Median number of scIL2 cycles was 3 (1-6). The primary end point was met by 37 patients (54.4%). Median observation time was 7.8 years. Five-year event-free survival (EFS) and overall survival from start of trial treatment were 43% (95% CI, 31 to 55) and 53% (95% CI, 41 to 65), respectively. Five-year EFS among patients in complete remission (CR; 52%; 95% CI, 31 to 69) or partial remission (44%; 95% CI, 27 to 60) before immunotherapy were significantly better compared with patients with nonresponse/mixed response/progressive disease (13%; 95% CI, 1 to 42; P = .026). Overall response rate in 43 patients with evidence of disease after haplo-SCT was 51% (22 patients), with 15 achieving CR (35%). Two patients developed GvHD grade 2 and 3 each. No unexpected adverse events occurred.

CONCLUSION

DB therapy after haplo-SCT in patients with rHR-NB is feasible, with low risk of inducing GvHD, and results in long-term remissions likely attributable to increased antineuroblastoma activity by donor-derived effector cells.

Automated production of specific T cells for treatment of refractory viral infections after allogeneic stem cell transplantation

Therapy resistant viral reactivations significantly contribute to mortality after hematopoietic stem cell transplantation. Adoptive cellular therapy with virus-specific T cells has shown efficacy in various single center trials. However, scalability of this therapy is hampered by laborious production methods. In this study we describe the in-house production of virus-specific T cells (VST) in a closed system (CliniMACS Prodigy® system by Miltenyi Biotec). In addition, we report the efficacy in 26 patients with viral disease post HSCT in a retrospective analysis (ADV n=7, CMV n=8, EBV n=4, multi-viral n=7). Production of VST was successful in 100% of cases. Safety profile of VST therapy was favorable (n=2 adverse event grade 3, n=1 grade 4; all three were reversible). A response was seen in 20 of 26 patients (77%). Responding patients had a significantly better OS than patients without response (p.

In vivo PDX CRISPR/Cas9 screens reveal mutual therapeutic targets to overcome heterogeneous acquired chemo-resistance

Resistance towards cancer treatment represents a major clinical obstacle, preventing cure of cancer patients. To gain mechanistic insights, we developed a model for acquired resistance to chemotherapy by treating mice carrying patient derived xenografts (PDX) of acute lymphoblastic leukemia with widely-used cytotoxic drugs for 18 consecutive weeks. In two distinct PDX samples, tumors initially responded to treatment, until stable disease and eventually tumor re-growth evolved under therapy, at highly similar kinetics between replicate mice. Notably, replicate tumors developed different mutations in TP53 and individual sets of chromosomal alterations, suggesting independent parallel clonal evolution rather than selection, driven by a combination of stochastic and deterministic processes. Transcriptome and proteome showed shared dysregulations between replicate tumors providing putative targets to overcome resistance. In vivo CRISPR/Cas9 dropout screens in PDX revealed broad dependency on BCL2, BRIP1 and COPS2. Accordingly, venetoclax re-sensitized derivative tumors towards chemotherapy, despite genomic heterogeneity, demonstrating direct translatability of the approach. Hence, despite the presence of multiple resistance-associated genomic alterations, effective rescue treatment for polychemotherapy-resistant tumors can be identified using functional testing in preclinical models.

Amsacrine combined with etoposide and methylprednisolone is a feasible and safe component in first-line intensified treatment of pediatric patients with high-risk acute lymphoblastic leukemia in CoALL08-09 trial

BACKGROUND

The prognosis of children with acute lymphoblastic leukemia (ALL) has improved considerably over the past five decades. However, to achieve cure in patients with refractory or relapsed disease, novel treatment options are necessary.

METHODS

In the multicenter trial Cooperative Study Group for Childhood Acute Lymphoblastic Leukemia (CoALL)08-09, one additional treatment element consisting of the rarely used chemotherapeutic agent amsacrine combined with etoposide and methylprednisolone (AEP) (amsacrine 2 × 100 mg/m² , etoposide 2 × 500 mg/m² , and methylprednisolone 4 × 1000 mg/m² ) was incorporated into the first-line treatment of pediatric patients with poor treatment responses at the end of induction (EOI), measured by minimal residual disease (MRD). These patients were stratified into a high-risk intensified arm (HR-I), including an AEP element at the end of consolidation. Patients with induction failure (IF), that is, with lack of cytomorphological remission EOI, were eligible for hematopoietic stem cell transplantation (HSCT) after remission had been reached. These patients received AEP as a part of their MRD-guided bridging-to-transplant treatments.

RESULTS

A significant improvement in probability of overall survival (pOS) was noted for the CoALL08-09 HR-I patients compared to MRD-matched patients from the preceding CoALL07-03 trial in the absence of severe or persistent treatment-related toxicities. Relapse rate and probability of event-free survival (pEFS) did not differ significantly between trials. In patients with IF, stable or improved MRD responses after AEP were observed without severe or persistent treatment-related toxicities.

CONCLUSION

In conclusion, AEP is well tolerated as a component of the HR treatment and is useful in bridging-to-transplant settings.

RASA2 ablation in T cells boosts antigen sensitivity and long-term function

The efficacy of adoptive T cell therapies for cancer treatment can be limited by suppressive signals from both extrinsic factors and intrinsic inhibitory checkpoints1,2. Targeted gene editing has the potential to overcome these limitations and enhance T cell therapeutic function3-10. Here we performed multiple genome-wide CRISPR knock-out screens under different immunosuppressive conditions to identify genes that can be targeted to prevent T cell dysfunction. These screens converged on RASA2, a RAS GTPase-activating protein (RasGAP) that we identify as a signalling checkpoint in human T cells, which is downregulated upon acute T cell receptor stimulation and can increase gradually with chronic antigen exposure. RASA2 ablation enhanced MAPK signalling and chimeric antigen receptor (CAR) T cell cytolytic activity in response to target antigen. Repeated tumour antigen stimulations in vitro revealed that RASA2-deficient T cells show increased activation, cytokine production and metabolic activity compared with control cells, and show a marked advantage in persistent cancer cell killing. RASA2-knockout CAR T cells had a competitive fitness advantage over control cells in the bone marrow in a mouse model of leukaemia. Ablation of RASA2 in multiple preclinical models of T cell receptor and CAR T cell therapies prolonged survival in mice xenografted with either liquid or solid tumours. Together, our findings highlight RASA2 as a promising target to enhance both persistence and effector function in T cell therapies for cancer treatment.

Immunological recovery following HLA-matched CD3+ TCR αß+/CD19+ depleted hematopoietic stem cell transplantation in children

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative option for children with both malignant and nonmalignant diseases. T-cell depletion techniques may result in reduced transplant-related mortality compared with unmanipulated grafts due to a lower incidence of GvHD.

METHODS

Immune recovery and outcome were analyzed in a cohort of 23 patients with malignant and nonmalignant diseases who received CD3+TCRαβ+ T- and B-cell-depleted allografts from matched donors after reduced-intensity or myeloablative conditioning. The median number of CD34+, CD3+TCRαβ+, and CD19+B-cells infused was 12.7 × 10⁶ /kg, 16.8 × 10³ /kg, and 96 × 10³ /kg bodyweight.

RESULTS

With a median follow-up of 36 (range 1-73) months, overall survival and disease-free survival at 3 years were 65.2% and 60.8%. Eight patients died, six due to the underlying disease and two of extended visceral cGvHD. Immune reconstitution, disease-free, and overall survivals were similar compared with a historical cohort of 23 patients transplanted with matched unmanipulated bone marrow. A significant lower rate of higher grade (III-IV) aGvHD was observed in the manipulated HSCT group (8.7% vs. 26%; p = 0.001), whereas the incidence of cGvHD was equal.

CONCLUSIONS

Our data suggest that this graft manipulation strategy could be a safe and effective alternative to conventional HSCT techniques in matched donors.

Design and Evaluation of TIM-3-CD28 Checkpoint Fusion Proteins to Improve Anti-CD19 CAR T-Cell Function

Therapeutic targeting of inhibitory checkpoint molecules in combination with chimeric antigen receptor (CAR) T cells is currently investigated in a variety of clinical studies for treatment of hematologic and solid malignancies. However, the impact of co-inhibitory axes and their therapeutic implication remains understudied for the majority of acute leukemias due to their low immunogenicity/mutational load. The inhibitory exhaustion molecule TIM-3 is an important marker for the interaction of T cells with leukemic cells. Moreover, inhibitory signals from malignant cells could be transformed into stimulatory signals by synthetic fusion molecules with extracellular inhibitory receptors fused to an intracellular stimulatory domain. Here, we designed a variety of different TIM-3-CD28 fusion proteins to turn inhibitory signals derived by TIM-3 engagement into T-cell activation through CD28. In the absence of anti-CD19 CAR, two TIM-3-CD28 fusion receptors with large parts of CD28 showed strongest responses in terms of cytokine secretion and proliferation upon stimulation with anti-CD3 antibodies compared to controls. We then combined these two novel TIM-3-CD28 fusion proteins with first- and second-generation anti-CD19 CAR T cells and found that the fusion receptor can increase proliferation, activation, and cytotoxic capacity of conventional anti-CD19 CAR T cells. These additionally armed CAR T cells showed excellent effector function. In terms of safety considerations, the fusion receptors showed exclusively increased cytokine release, when the CAR target CD19 was present. We conclude that combining checkpoint fusion proteins with anti-CD19 CARs has the potential to increase T-cell proliferation capacity with the intention to overcome inhibitory signals during the response against malignant cells.

Multimodal Treatment of Nasopharyngeal Carcinoma in Children, Adolescents and Young Adults-Extended Follow-Up of the NPC-2003-GPOH Study Cohort and Patients of the Interim Cohort

Simple Summary

Multimodal treatment of nasopharyngeal carcinoma (NPC) in children and young adults with induction chemotherapy, followed by radiochemotherapy and interferon-β (IFN-β) maintenance, has been successfully applied in studies NPC-91 and NPC-2003 of the German Society of Pediatric Oncology and Hematology (GPOH). We, here, present updated survival rates of the NPC-2003 study cohort after longer follow-up and include 21 additional patients recruited after closure of the study and treated as per the NPC-2003 study protocol (interim cohort) in our survival analysis. Survival rates remain high after extended follow-up and in the larger cohort with EFS and OS of 94% and 97%, respectively, reinforcing the high antitumor efficacy of this multimodal treatment concept. Seven patients with CR after induction therapy received a reduced radiation dose of 54 Gy, and none of them relapsed. Thus, the reduction of radiation dose seems feasible and has the potential to reduce treatment-related late effects in this vulnerable population.

Abstract

Nasopharyngeal carcinoma (NPC) in children and young adults has been treated within two consecutive prospective trials in Germany, the NPC-91 and the NPC-2003 study of the German Society of Pediatric Oncology and Hematology (GPOH). In these studies, multimodal treatment with induction chemotherapy, followed by radio (chemo)therapy and interferon-beta maintenance, yielded promising survival rates even after adapting total radiation doses to tumor response. The outcome of 45 patients in the NPC-2003 study was reassessed after a median follow-up of 85 months. In addition, we analyzed 21 further patients after closure of the NPC-2003 study, recruited between 2011 and 2017, and treated as per the NPC-2003 study protocol. The EFS and OS of 66 patients with locoregionally advanced NPC were 93.6% and 96.7%, respectively, after a median follow-up of 73 months. Seven patients with CR after induction therapy received a reduced radiation dose of 54 Gy; none relapsed. In young patients with advanced locoregional NPC, excellent long-term survival rates can be achieved by multimodal treatment, including interferon-beta. Radiation doses may be reduced in patients with complete remission after induction chemotherapy and may limit radiogenic late effects.

Analysis of self-reported activities of daily living, motor performance and physical activity among children and adolescents with cancer: Baseline data from a randomised controlled trial assessed shortly after diagnosis of leukaemia or non-Hodgkin lymphoma

OBJECTIVE

Cancer diagnosis, treatment side effects and physical inactivity can lead to reduced muscle strength. Patients undergoing acute treatment experience many burdens that can restrict their mobility and autonomy, leading to limited independence and loss of resources to cope with everyday tasks. In this work, we analyse the status quo and potential influencing factors for the accomplishment of activities of daily living (ADLs) shortly after cancer diagnosis.

METHODS

We recruited participants ages 4-18 years diagnosed with acute leukaemia or non-Hodgkin lymphoma. For the baseline analysis, we assessed (1) physical function limitations using the Activities Scale for Kids©, (2) exercise-related ADLs simulated with the Functional ADL Screen, (3) motor performance using the Motor Performance in Paediatric Oncology test and (4) physical activity (PA) level measured using an accelerometer.

RESULTS

We conducted the baseline assessment 19.2 ± 12.6 days post-diagnosis in 41 patients. All participants reported functional limitations in ADLs and PA. Motor performance was reduced for all abilities. Cumulative steroid dose was negatively correlated with hand grip strength (r = -0.50, p = 0.009).

CONCLUSION

Shortly after diagnosis of paediatric cancer, patients experience various physical impairments that can be counteracted with regular, instructed exercise interventions.

Genome‐wide off‐target analyses of CRISPR/Cas9‐mediated T‐cell receptor engineering in primary human T cells

Objectives

Exploiting the forces of human T cells for treatment has led to the current paradigm of emerging immunotherapy strategies. Genetic engineering of the T‐cell receptor (TCR) redirects specificity, ablates alloreactivity and brings significant progress and off‐the‐shelf options to emerging adoptive T‐cell transfer (ACT) approaches. Targeted CRISPR/Cas9‐mediated double‐strand breaks in the DNA enable knockout or knock‐in engineering.

Methods

Here, we perform CRISPR/Cas9‐mediated TCR knockout using a therapeutically relevant ribonucleoprotein (RNP) delivery method to assess the safety of genetically engineered T‐cell products. Whole‐genome sequencing was performed to analyse whether CRISPR/Cas9‐mediated DNA double‐strand break at the TCR locus is associated with off‐target events in human primary T cells.

Results

TCRα chain and TCRβ chain knockout leads to high on‐target InDel frequency and functional knockout. None of the predicted off‐target sites could be confirmed experimentally, whereas whole‐genome sequencing and manual Integrative Genomics Viewer (IGV) review revealed 9 potential low‐frequency off‐target events genome‐wide. Subsequent amplification and targeted deep sequencing in 7 of 7 evaluable loci did not confirm these low‐frequency InDels. Therefore, off‐target events are unlikely to be caused by the CRISPR/Cas9 engineering.

Conclusion

The combinatorial approach of whole‐genome sequencing and targeted deep sequencing confirmed highly specific genetic engineering using CRISPR/Cas9‐mediated TCR knockout without potentially harmful exonic off‐target effects.

Protective T cell receptor identification for orthotopic reprogramming of immunity in refractory virus infections

Viral infections cause life-threatening disease in immunocompromised patients and especially following transplantation. T cell receptor (TCR) engineering redirects specificity and can bring significant progress to emerging adoptive T cell transfer (ACT) approaches. T cell epitopes are well described, although knowledge is limited on which TCRs mediate protective immunity. In this study, refractory adenovirus (AdV) infection after hematopoietic stem cell transplantation (HSCT) was treated with ACT of highly purified Hexon5-specific T cells using peptide major histocompatibility complex (pMHC)-Streptamers against the immunodominant human leukocyte antigen (HLA)-A∗0101-restricted peptide LTDLGQNLLY. AdV was successfully controlled through this oligoclonal ACT. Novel protective TCRs were isolated ex vivo and preclinically engineered into the TCR locus of allogeneic third-party primary T cells by CRISPR-Cas9-mediated orthotopic TCR replacement. Both TCR knockout and targeted integration of the new TCR in one single engineering step led to physiological expression of the transgenic TCR. Reprogrammed TCR-edited T cells showed strong virus-specific functionality such as cytokine release, effector marker upregulation, and proliferation capacity, as well as cytotoxicity against LTDLGQNLLY-presenting and AdV-infected targets. In conclusion, ex vivo isolated TCRs with clinical proven protection through ACT could be redirected into T cells from naive third-party donors. This approach ensures that transgenic TCRs are protective with potential off-the-shelf use and widened applicability of ACT to various refractory emerging viral infections.

Effects of strength exercise interventions on activities of daily living, motor performance, and physical activity in children and adolescents with leukemia or non-Hodgkin lymphoma: Results from the randomized controlled ActiveADL Study

OBJECTIVES

Pediatric patients with cancer experience impairments in muscle strength and physical activity (PA) that may reduce autonomy during hospitalization. To determine the effects of strength exercise interventions on the accomplishment of activities of daily living (ADLs), motor performance, and PA in children with leukemia or non-Hodgkin lymphoma, we randomly allocated patients (4-18 years) immediately after diagnosis into two exercise groups.

METHODS

The intervention group (IG; n = 21) received a specific strength training combined with a standard care exercise program, whereas the control group (CG; n = 20) was provided standard care exercise program without any targeted muscle strengthening. After the baseline visit, participants were followed-up three times until intensive treatment cessation. We assessed physical function limitations using the Activities Scale for Kids© (ASK) and Functional ADL Screen. Secondary outcomes were PA levels using accelerometer and motor performance as measured by MOON-test (motor performance in pediatric oncology-test).

RESULTS

In both groups, ADL accomplishment had significantly increased (p < 0.05). However, no significant between-group differences for ASK outcome were noted. Motor performance was reduced in all motor abilities.

CONCLUSIONS

Both exercise interventions were effective to maintain ADLs and motor performance during intensive treatment. In comparison, regular strength exercise interventions in the course of therapy tended to be more beneficial with regards to muscular explosive and endurance strength.

Targeted T cell receptor gene editing provides predictable T cell product function for immunotherapy

Adoptive transfer of T cells expressing a transgenic T cell receptor (TCR) has the potential to revolutionize immunotherapy of infectious diseases and cancer. However, the generation of defined TCR-transgenic T cell medicinal products with predictable in vivo function still poses a major challenge and limits broader and more successful application of this "living drug." Here, by studying 51 different TCRs, we show that conventional genetic engineering by viral transduction leads to variable TCR expression and functionality as a result of variable transgene copy numbers and untargeted transgene integration. In contrast, CRISPR/Cas9-mediated TCR replacement enables defined, targeted TCR transgene insertion into the TCR gene locus. Thereby, T cell products display more homogeneous TCR expression similar to physiological T cells. Importantly, increased T cell product homogeneity after targeted TCR gene editing correlates with predictable in vivo T cell responses, which represents a crucial aspect for clinical application in adoptive T cell immunotherapy.

Clofarabine increases the eradication of minimal residual disease of primary Bprecursor acute lymphoblastic leukemia compared to high-dose cytarabine without improvement of outcome

Novel treatment strategies are needed to improve cure for all children with acute lymphoblastic leukemia. To this end, we investigated the therapeutic potential of clofarabine in primary acute lymphoblastic leukemia in trial CoALL 08-09. The primary study objective was the minimal residual disease (MRD)-based comparative assessment of cytotoxic efficacies of clofarabine 5x40 mg/m2 versus high-dose cytarabine (HIDAC) 4x3g/m2, both in combination with PEG-ASP 2500 IU/m2 as randomized intervention in early consolidation. The secondary objective was an outcome analysis focused on treatment-arm dependence and MRD after randomized intervention. In B-cell precursor (BCP)-ALL, eradication of MRD was more profound after clofarabine compared to cytarabine, with 93 vs 79 of 143 randomized patients per arm reaching MRD-negativity (Chi-square test P=.03, left-sided P(Fisher's exact test)=.04). MRD status of BCP-ALL after randomized intervention maintained its prognostic relevance, with a significant impact on event-free survival (EFS) and relapse rate. However, no difference in outcome regarding EFS and overall survival (OS) between randomized courses was observed (5- year EFS: clofarabine 85.7, SE=4.1 vs HIDAC 84.8, SE=4.7 (P=.96); OS: 95.7, SE=1.9 vs 92.2, SE=3.2 (P=.59)), independent of covariates or overall risk strata. Severe toxicities between randomized and subsequent treatment elements were also without significant difference. In conclusion, clofarabine/PEG-ASP is effective and safe, but greater cytotoxic efficacy of clofarabine compared to HIDAC did not translate into improved outcomes indicating a lack of surrogacy of post-intervention MRD at the trial level as opposed to the patient level, which hampers a broader implementation of this regimen in the frontline treatment of ALL.

Transient Hyperammonemic Encephalopathy in a Child with Relapsed Acute Lymphoblastic Leukemia and Severe Tumor Lysis Syndrome

Idiopathic hyperammonemia (IHA) is a severe condition, which has been reported in intensive chemotherapy and bone marrow transplantation. This case elucidates the diagnostic dilemma in children undergoing initiation of chemotherapy and developing severe disorders of qualitative and quantitative consciousness in the presence of hyperammonemia (HA) and lactic acidosis. The role of mitoxantrone as a causative agent for IHA in children is elusive. Children undergoing chemotherapy are often in a poor general condition, and the clinical presentation of HA is heterogeneous. This case should be a reminder for clinicians to check for HA in children with tumor lysis syndrome and acute neurological deterioration.

Combined tumor-directed recruitment and protection from immune suppression enable CAR T cell efficacy in solid tumors

CAR T cell therapy remains ineffective in solid tumors, due largely to poor infiltration and T cell suppression at the tumor site. T regulatory (Treg) cells suppress the immune response via inhibitory factors such as transforming growth factor-β (TGF-β). Treg cells expressing the C-C chemokine receptor 8 (CCR8) have been associated with poor prognosis in solid tumors. We postulated that CCR8 could be exploited to redirect effector T cells to the tumor site while a dominant-negative TGF-β receptor 2 (DNR) can simultaneously shield them from TGF-β. We identified that CCL1 from activated T cells potentiates a feedback loop for CCR8+ T cell recruitment to the tumor site. This sustained and improved infiltration of engineered T cells synergized with TGF-β shielding for improved therapeutic efficacy. Our results demonstrate that addition of CCR8 and DNR into CAR T cells can render them effective in solid tumors.

Blinatumomab in pediatric patients with relapsed/refractory B-cell precursor acute lymphoblastic leukemia

OBJECTIVE

Pediatric patients with relapsed or refractory acute lymphoblastic leukemia have a poor prognosis. We here assess the response rates, adverse events, and long-term follow-up of pediatric patients with relapsed/refractory acute lymphoblastic leukemia receiving blinatumomab.

METHODS

Retrospective analysis of a single-center experience with blinatumomab in 38 patients over a period of 10 years.

RESULTS

The median age at onset of therapy was 10 years (1-21 years). Seventy-one percent of patients had undergone at least one hematopoietic stem cell transplantation (HSCT) prior to treatment with blinatumomab. We observed a response to blinatumomab in 13/38 patients (34%). The predominant side effect was febrile reactions, nearly half of the patients developed a cytokine release syndrome. Eight events of neurotoxicity were registered over the 78 cycles (15%). To date, nine patients (24%) are alive and in complete molecular remission. All survivors underwent haploidentical HSCT after treatment with blinatumomab.

CONCLUSIONS

Despite heavy pretreatment of most of our patients, severe adverse events were rare and response rates encouraging. Blinatumomab is a valuable bridging salvage therapy for relapsed or refractory patients to a second or even third HSCT.

Antiemetic Prophylaxis with Fosaprepitant and 5-HT3-Receptor Antagonists in Pediatric Patients Undergoing Autologous Hematopoietic Stem Cell Transplantation

Background

High-dose myeloablative conditioning prior to autologous hematopoietic stem cell transplantation (autoHSCT) in pediatric patients is usually highly emetogenic. The antiemetic neurokinin-1 receptor antagonist fosaprepitant was safe and effective in children receiving highly emetogenic chemotherapy. Data on fosaprepitant during autoHSCT in children are currently not available.

Methods

A total of 35 consecutive pediatric patients, who received an antiemetic prophylaxis with fosaprepitant (4 mg/kg; single dose, max. 1 x 150 mg/kg BW) and ondansetron (24-hours continuous infusion; 8–32 mg/24h) or granisetron (2 x 40 µg/kg∙d⁻¹) during highly emetogenic conditioning chemotherapy before autoHSCT were retrospectively analyzed, and their results were compared with a control group comprising 35 consecutive pediatric patients, who received granisetron or ondansetron only. The antiemetic efficacy and the safety of the two prophylaxis regimens were compared with respect to three time periods after the first chemotherapy administration (0–24h, >24–120h, >120–240h).

Results

Clinical adverse events and clinically relevant increases/decreases of laboratory markers were similarly low and did not significantly differ between the two study groups (p>0.05). The registered number of vomiting events was significantly higher in the control group in the time periods of 0–24h (64 vs 22 events; p<0.01), >24–120h (135 vs 78 events; p<0.0001), >120–240h (268 vs 105 events; p<0.0001), and the whole observation period 0–240h (467 vs 205 events; p<0.0001). The percentage of patients experiencing vomiting was higher in the control group during the time period of >24–120h (100% vs 74.3%) but not the other analyzed time periods (p>0.05).

Conclusion

The fosaprepitant-based antiemetic prophylaxis was safe, well tolerated and significantly reduced vomiting in children undergoing highly emetogenic chemotherapy prior to autoHSCT. Prospective randomized trials are necessary to confirm these results.

Leukemia escape in immune desert: intraocular relapse of pediatric pro-B-ALL during systemic control by CD19-CAR T cells

Background

Relapsed/refractory B-precursor acute lymphoblastic leukemia (BCP-ALL) remains a major therapeutic challenge in pediatric hematology. Chimeric antigen receptor (CAR) T cells targeting CD19 have shown remarkable initial response rates in BCP-ALL patients, while long-term leukemia control rate is only about 50%. So far, main mechanisms of BCP-ALL relapse after CD19-CAR T-cell therapy have been either insufficient CAR T-cell persistence in vivo or loss of surface CD19.

Case Report

Here, we report an exceptional presentation of BCP-ALL relapse in the eye during the systemic control through CAR T-cell therapy. We report a case of fatal intraocular relapse in a pediatric patient with pro-B-ALL after initial response to CD19-CAR T-cell therapy. One month after CD19-CAR T-cell therapy, remission was documented by bone marrow aspirate analysis with absence of CD19⁺ cells and CD19-CAR T cells could be detected in both peripheral blood and bone marrow. At the same time, however, the patient presented with progressive visual disturbance and CD19⁺ cells were found within the anterior chamber of the eye. Despite local and systemic therapy, ocular relapse led to BCP-ALL dissemination and systemic relapse within weeks. The eye represents a rare site for local manifestation of BCP-ALL, but isolated intraocular relapse is a clinically unreckoned presentation of BCP-ALL in the era of CD19-CAR T cells.

Conclusion

During systemic control of BCP-ALL through CD19-CAR T cells, relapse can emerge in the eye as an immune-privileged organ. Ocular symptoms after CD19-CAR T-cell therapy should guide the clinician to elucidate the etiology in a timely fashion in order to adjust leukemia treatment strategy. Both, local immune escape as well as insufficient CAR T-cell persistence may have contributed to relapse in the reported patient. Mechanisms of relapse in an immune desert under CAR T-cell therapy require future clinical and experimental attention. In particular, ocular symptoms after CAR T-cell therapy should be considered a potentially early sign of leukemia relapse.

CRISPR-Cas9-Mediated Glucocorticoid Resistance in Virus-Specific T Cells for Adoptive T Cell Therapy Posttransplantation

Immunosuppression posttransplantation exposes patients to an increased risk for refractory viral infections as an important cause of morbidity and mortality. Protective T cell immunity can be restored by adoptive T cell transfer, but ongoing immunosuppression limits efficacy of T cell responses. In order to deliver protection against viral pathogens and allow at the same time necessary steroid therapy, we generated glucocorticoid-resistant T cells by CRISPR-Cas9-mediated knockout of the glucocorticoid receptor in primary human virus-specific T cell products. Characterization of the T cell product revealed high efficiency of glucocorticoid receptor knockout and high purity of virus-specific T cells. This tandem T cell engineering preserved protective T cell functionality, such as cytotoxicity, CD107a degranulation, proliferative capacity, and cytokine release patterns. Virus-specific T cells with glucocorticoid receptor knockout were resistant to the suppressive effect of dexamethasone treatment on lymphocyte proliferation and cytokine secretion (tumor necrosis factor alpha [TNF-α], interleukin-4 [IL-4], IL-6, and sFas). Additionally, glucocorticoid receptor knockout cells remained sensitive to cyclosporine A treatment, thereby providing a rescue approach for patients in case of safety issues. This novel approach provides a therapeutic option for the treatment of patients with viral infections after transplantation who are receiving glucocorticoid therapy.

Leukemia-induced dysfunctional TIM-3+CD4+ bone marrow T cells increase risk of relapse in pediatric B-precursor ALL patients

Interaction of malignancies with tissue-specific immune cells has gained interest for prognosis and intervention of emerging immunotherapies. We analyzed bone marrow T cells (bmT) as tumor-infiltrating lymphocytes in pediatric precursor-B cell acute lymphoblastic leukemia (ALL). Based on data from 100 patients, we show that ALL is associated with late-stage CD4⁺ phenotype and loss of early CD8⁺ T cells. The inhibitory exhaustion marker TIM-3 on CD4⁺ bmT increased relapse risk (RFS = 94.6/70.3%) confirmed by multivariate analysis. The hazard ratio of TIM-3 expression nearly reached the hazard ratio of MRD (7.1 vs. 8.0) indicating that patients with a high frequency of TIM-3⁺CD4⁺ bone marrow T cells at initial diagnosis have a 7.1-fold increased risk to develop ALL relapse. Comparison of wild type primary T cells to CRISPR/Cas9-mediated TIM-3 knockout and TIM-3 overexpression confirmed the negative effect of TIM-3 on T cell responses against ALL. TIM-3⁺CD4⁺ bmT are increased in ALL overexpressing CD200, that leads to dysfunctional antileukemic T cell responses. In conclusion, TIM-3-mediated interaction between bmT and leukemia cells is shown as a strong risk factor for relapse in pediatric B-lineage ALL. CD200/TIM-3-signaling, rather than PD-1/PD-L1, is uncovered as a mechanism of T cell dysfunction in ALL with major implication for future immunotherapies.

Low mutational load in pediatric medulloblastoma still translates into neoantigens as targets for specific T-cell immunotherapy

BACKGROUND

Medulloblastoma is the most common malignant brain tumor in childhood and adolescence. Although some patients present with distinct genetic alterations, such as mutated TP53 or MYC amplification, pediatric medulloblastoma is a tumor entity with minimal mutational load and low immunogenicity.

METHODS

We identified tumor-specific mutations using next-generation sequencing of medulloblastoma DNA and RNA derived from primary tumor samples from pediatric patients. Tumor-specific mutations were confirmed using deep sequencing and in silico analyses predicted high binding affinity of the neoantigen-derived peptides to the patients' human leukocyte antigen molecules. Tumor-specific peptides were synthesized and used to induce a de novo T-cell response characterized by interferon gamma and tumor necrosis factor alpha release of CD8⁺ cytotoxic T cells in vitro.

RESULTS

Despite low mutational tumor burden, at least two immunogenic tumor-specific peptides were identified in each patient. T cells showed a balanced CD4/CD8 ratio and mostly effector memory phenotype. Induction of a CD8-specific T-cell response was achieved for the neoepitopes derived from Histidine Ammonia-Lyase (HAL), Neuraminidase 2 (NEU2), Proprotein Convertase Subtilisin (PCSK9), Programmed Cell Death 10 (PDCD10), Supervillin (SVIL) and tRNA Splicing Endonuclease Subunit 54 (TSEN54) variants.

CONCLUSION

Detection of patient-specific, tumor-derived neoantigens confirms that even in tumors with low mutational load a molecular design of targets for specific T-cell immunotherapy is possible. The identified neoantigens may guide future approaches of adoptive T-cell transfer, transgenic T-cell receptor transfer or tumor vaccination.

Health-Related Physical Fitness and Arterial Stiffness in Childhood Cancer Survivors

Introduction: Despite decreasing mortality in pediatric oncology as a result of standardized treatment protocols, the high number of functional and cardiovascular late sequelae due to anticarcinogenic therapy remains unchanged. The aim of this study was to further assess functional limitations in Health-related Physical Fitness (HRPF) and cardiovascular risk by means of markers of arterial stiffness in Childhood Cancer Survivors (CCS).

Materials and Methods: Between March 2016 and August 2017 a total of 92 CCS (Age 12.5 ± 4.2 years, 43 girls) were recruited from their routine follow-up outpatient visit. HRPF was assessed using five Fitnessgram® tasks. Pulse Wave Velocity (PWV) along with peripheral and central blood pressure were assessed using oscillometric measurements performed by Mobil-O-Graph. Z-scores were used to compare the test results either to German reference values or to a recent healthy reference cohort.

Results: In CCS, the HRPF was significantly reduced (z-score: −0.28 ± 1.01, p = 0.011) as compared to healthy peers. The peripheral Systolic Blood Pressure (pSBP) was significantly increased (z-score: 0.31 ± 1.11, p = 0.017) and the peripheral Diastolic Blood Pressure (pDBP) was decreased (z-score: −0.30 ± 1.25, p = 0.040), resulting in an increased pulse pressure. The PWV (p = 0.649) and cSBP (p = 0.408), were neither increased nor showed any association to HRPF.

Discussion: CCS showed functional limitations in HRPF and an increased pulse pressure, which acts as an early onset parameter of arterial stiffness. Both a low HRPF and impaired hemodynamics are independent cardiovascular risk factors and needs to be taken into consideration in tertiary prevention of CCS.

Only strongly enhanced residual FDG uptake in early response PET (Deauville 5 or qPET ≥ 2) is prognostic in pediatric Hodgkin lymphoma: Results of the GPOH-HD2002 trial

PURPOSE

In 2014, we published the qPET method to quantify fluorodeoxyglucose positron emission tomography (FDG-PET) responses. Analysis of the distribution of the quantified signals suggested that a clearly abnormal FDG-PET response corresponds to a visual Deauville score (vDS) of 5 and high qPET values ≥ 2. Evaluation in long-term outcome data is still pending. Therefore, we analyzed progression-free survival (PFS) by early FDG-PET response in a subset of the GPOH-HD2002 trial for pediatric Hodgkin lymphoma (PHL).

PATIENTS/METHODS

Pairwise FDG-PET scans for initial staging and early response assessment after two cycles of chemotherapy were available in 93 PHL patients. vDS and qPET measurement were performed and related to PFS.

RESULTS

Patients with a qPET value ≥ 2.0 or vDS of 5 had 5-year PFS rates of 44%, respectively 50%. Those with qPET values < 2.0 or vDS 1 to 4 had 5-year PFS rates of 90%, respectively 80%. The positive predictive value of FDG-PET response assessment increased from 18% (9%; 33%) using a qPET threshold of 0.95 (vDS ≤ 3) to 30% (13%; 54%) for a qPET threshold of 1.3 (vDS ≤ 4) and to 56% (23%; 85%) when the qPET threshold was ≥ 2.0 (vDS 5). The negative predictive values remained stable at ≥92% (CI: 82%; 98%).

CONCLUSION

Only strongly enhanced residual FDG uptake in early response PET (vDS 5 or qPET ≥ 2, respectively) seems to be markedly prognostic in PHL when treatment according to the GPOH-HD-2002 protocol is given.

Strategies of adoptive T -cell transfer to treat refractory viral infections post allogeneic stem cell transplantation

Background

Allogeneic hematopoietic stem cell transplantation (HSCT) can expose patients to a transient but marked immunosuppression, during which viral infections are an important cause of morbidity and mortality. Adoptive transfer of virus-specific T cells is an attractive approach to restore protective T -cell immunity in patients with refractory viral infections after allogeneic HSCT.

Objectives

This narrative review summarizes clinical evidence and developments of almost 30 years of adoptive T -cell transfer. The review is based on evidence extracted from PubMed searches and the clinical and experimental work of the authors.

Content

Viral infections after HSCT are frequently caused by the endogenous reactivation of persistent pathogens such as cytomegalovirus (CMV), Epstein-Barr virus (EBV), and adenovirus (AdV). Current antiviral medication is not satisfactory and does not treat the underlying pathophysiology which is the lack of specific T -cell immunity. Adoptive transfer of virus-specific T cells could be a potentially curative, pathogen-specific, and non-toxic treatment providing long-term immunity against the virus. The isolation of virus-specific T cells from a healthy donor and infusion into a recipient is known as adoptive T -cell transfer and has been performed in many patients using different treatment protocols. Based on basic research, new isolation protocols aim at a safe and fast availability of cellular products for adoptive T -cell transfer. We summarize preclinical and clinical data on each of the main pathogens and on the technical approaches currently available to target either single antigens or even multiple pathogens.

Conclusion

Cellular therapy is considered as one of the major recent breakthroughs in medicine. Translation of this individualized treatment into first-line clinical routine is still limited. Main hurdles are availability of the technique, limited compatibility of classical phase III designs with cellular therapy, and regulatory restrictions. Multinational efforts are required to clarify the status of cellular treatment in first-line clinical routine with the overall objective to strengthen evidence-based treatment guidelines for the treatment of refractory viral infections post HSCT.

Abstract A043: Anti-CD19 CAR T-cells with a CRISPR/Cas9-mediated T-cell receptor knockout show high functionality in the absence of alloreactivity in vitro

Overall survival of pediatric B-precursor ALL patients reached 90% in recent years. However, the outcome for refractory or relapsed children remains very poor. Anti-CD19 chimeric antigen receptor T-cells (CD19-CAR) showed significant antileukemic activity in relapsed and refractory B-precursor ALL. Especially in children, isolation of a suitable T-cell amount for autologous CAR T-cell manufacturing can be challenging due to low blood volume, low T-cell counts and clinical condition. In this case, the adoptive transfer of CAR T-cells from an unmatched healthy third-party donor provides a promising strategy. In order to prevent life-threatening graft-versus-host disease, a knockout (KO) of the endogenous T-cell receptor (TCR) has to be performed. Here, we generated CD19-CARs with a CRISPR/Cas9 mediated TCR KO, which remain highly functional and show strongly reduced alloreactivity compared to conventional CAR T-cells introduced into third-party T-cells. T-cells were isolated from peripheral blood mononuclear cells (PBMCs) of healthy donors and activated via anti-CD3/anti-CD28 stimulation. Retroviral transduction of a second generation anti-CD19 CAR (containing CD3zeta and 4-1BB stimulatory domains) was performed, followed by CRISPR/Cas9 mediated KO of the T-cell receptor beta chain via electroporation. After eleven days of expansion in the presence of IL-7 and IL-15, cells were purified for TCR KO-CD19-CAR T-cells via magnetic separation. Finally, the cell product was analyzed for cellular characteristics, functionality and alloreactivity by flow cytometry. A mean transduction rate of 37% for CD19-CARs and 40% for TCR KO-CD19-CARs was reached as well as a mean TCR KO rate of 78%. Both CD19-CARs as well as TCR KO-CD19-CARs showed suitable amounts of CD4- (45% vs. 33%) and CD8-T-cells (37% vs. 48%). The phenotype of CD19-CARs and TCR KO-CD19-CARs were comparable with mainly central memory (CM) (38% vs. 40%) and effector memory (EM) (57% vs. 51%) T-cells. The expansion of TCR KO-CD19-CARs was significantly reduced compared to conventional CD19-CARs (54-fold vs. 109-fold). This effect was not mediated by the loss of the TCR, but due to electroporation procedure. While CD19-CARs with or without TCR KO showed almost no background expression of the activation marker CD25 (2% vs 1%), contact with CD19-expressing targeT-cells resulted in a comparable upregulation of CD25 in both groups (95% vs. 94%). Co-culture with a CD19-expressing targeT-cell line led to an increased Interferon-γ secretion compared to unstimulated CARs, which was not significantly altered by the TCR KO (17% CD19-CAR vs. 14% TCR KO-CD19-CAR). CD19-dependent proliferative capacity of CAR T-cells was not influenced by loss of the TCR, as in both cases 97% of the T-cells proliferated after antigen recognition. Both CD19-CARs as well as TCR KO-CD19-CARs showed high, antigen-specific killing of 86% vs. 87% of the CD19-expressing targeT-cells at a 1:1 effector to target ratio. To evaluate the alloreactive potential of those T-cells, T-cells were co-cultured with irradiated PBMCs pooled from six different donors. 20% of TCR-expressing T-cells showed proliferation upon contact with non-HLA-matched PBMCs, whereas T-cells with a TCR KO showed almost no proliferation (&lt;3%), demonstrating significantly reduced alloreactivity of TCR KO T-cells. CD19-CAR T-cells lacking the endogenous TCR show a balanced CD4 to CD8 ratio and high proportion of the favorable CM T-cell phenotype. TCR KO-CD19-CARs remain highly functional and show similar activation, cytotoxicity, proliferative capacity and cytokine secretion as conventional CD19-CARs upon antigen recognition. T-cells with TCR KO do not mediate an alloreactive response to non-HLA-matched PBMCs and therefore are promising candidates for the generation of CAR T-cells derived from nonmatched healthy third-party donors or for use of donor-derived CAR T-cells after haploidentical stem cell transplantation.

Citation Format: Dana Stenger, Tanja Stief, Theresa Käuferle, Semjon Manuel Willier, Felicitas Rataj, Kilian Schober, Ramin Lotfi, Beate Wagner, Dirk H. Busch, Sebastian Kobold, Franziska Blaeschke, Tobias Feuchtinger. Anti-CD19 CAR T-cells with a CRISPR/Cas9-mediated T-cell receptor knockout show high functionality in the absence of alloreactivity in vitro [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A043.

Abstract A224: Bone marrow T-cells are tumor-infiltrating T-cells in pediatric patients with acute leukemia and their phenotype reflects immune evasion of leukemic blasts

Object: Acute leukemia is the most common malignancy in children. Despite recent therapeutic advances patients with relapsed or refractory disease require new treatment options. While synthetic immunotherapies such as chimeric antigen receptor (CAR) T-cells have shown impressive efficacy in B-precursor acute lymphoblastic leukemia (BCP-ALL) patients, the interaction between leukemic blasts and bone marrow T-cells remains largely unknown. Therefore, the role for immune response amplifiers in leukemia patients is currently unclear. Leukemia outgrowth leads to low frequency of physiologic bone marrow populations such as T-cells. Those T-cells are consequently within the site of tumor development and can thus be defined as tumor-infiltrating lymphocytes (TILs). Dysfunction of TILs has been described in a variety of solid and in some hematologic malignancies. To determine the changes driven by leukemia blasts we analyzed T-cells in bone marrow samples from pediatric patients with BCP-ALL, T-precursor ALL (TCP-ALL) and acute myelogenous leukemia (AML) at the time of diagnosis and relapse in comparison to healthy bone marrow donors. Material and Methods: In pilot experiments, any artificial changes in marker expression due to cryopreservation and thawing were excluded (n=5). Then, cryopreserved bone marrow samples from both pediatric patients with acute leukemia (n= 77; BCP-ALL: 18, TCP-ALL: 23, AML: 36) and age-matched healthy bone marrow donors (n=23) were identified in our local biobank. Multicolor flow cytometry was performed to quantify co-inhibitory markers on CD4 and CD8 T-cells in primary (n=49) and relapse leukemia samples (n=28). Results: The frequency of bone marrow T-cells was reduced in patients with acute leukemia in comparison with healthy controls (5.9% vs. 24.4%, mean values, p&lt;0.001). This reduction was more pronounced in BCP-ALL than in AML (0.9% vs. 8.4%, p&lt;0.001). The CD4/CD8 ratio of bone marrow T-cells in leukemia patients was not altered compared with healthy controls (1.27 vs. 1.09, p=0.82). The frequency of regulatory T-cells (Tregs, defined as CD4+ CD25+ CD127low T-cells) was decreased in leukemic bone marrow (7.5% vs. 9.8%, p=0.022). However, while BCP-ALL samples did not show a difference in Treg frequency between initial diagnosis and relapse (8.0 vs. 7.2, p=0.86), there was an increase of Tregs at relapse in AML samples (9.5% vs. 6.2%, p=0.004). Surface markers of T-cell exhaustion such as PD1, TIM-3 and LAG3 were found to be consistently more highly expressed on T-cells of leukemia patients than in healthy controls, both on CD4 and CD8 T-cells. PD1 was more highly expressed in relapse samples than in primary diagnosis samples than in healthy controls: (CD4: 42.3% vs. 28.9% vs. 19.8%, p&lt;0.001; CD8: 45.2% vs. 33.3% vs. 26.5%, p=0.002). This observation was consistent for relapse samples in all three different leukemia subtypes both on CD4 and CD8 T-cells. LAG3 expression on T-cells was increased in leukemia patients vs. healthy controls (CD4: 2.6% vs. 0.7%, p&lt;0.001; CD8: 8.6% vs. 2.2%, p&lt;0.001). The same was observed for TIM3 (CD4: 3.7% vs. 1.3%, p=0.002; CD8: 8.5% vs. 3.3%, p&lt;0.001). However, no difference in LAG3 or TIM-3 expression could be observed between primary disease and relapse. Conclusion: By analyzing bone marrow samples from pediatric leukemia patients and healthy controls, we confirm that bone marrow T-cells of leukemia patients show significant changes compared to healthy individuals. Clinical parameters such as relapse status or leukemia subtype are associated with changes in the T-cell phenotype. Most importantly, PD1 surface expression on T-cells was identified as a marker that correlates with disease status (relapse &gt; primary &gt; healthy). These findings could reflect insufficient immune surveillance of pediatric leukemia by bone marrow T-cells and may provide a rationale for future therapeutic interventions.

Citation Format: Semjon Manuel Willier, Paula Rothaemel, Jonas Wilhelm, Dana Stenger, Theresa Käuferle, Irene Schmid, Michael H. Albert, Vera Binder, Franziska Blaeschke, Tobias Feuchtinger. Bone marrow T-cells are tumor-infiltrating T-cells in pediatric patients with acute leukemia and their phenotype reflects immune evasion of leukemic blasts [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A224.

Systematic identification of cancer-specific MHC-binding peptides with RAVEN

Immunotherapy can revolutionize anti-cancer therapy if specific targets are available. Immunogenic peptides encoded by cancer-specific genes (CSGs) may enable targeted immunotherapy, even of oligo-mutated cancers, which lack neo-antigens generated by protein-coding missense mutations. Here, we describe an algorithm and user-friendly software named RAVEN (Rich Analysis of Variable gene Expressions in Numerous tissues) that automatizes the systematic and fast identification of CSG-encoded peptides highly affine to Major Histocompatibility Complexes (MHC) starting from transcriptome data. We applied RAVEN to a dataset assembled from 2,678 simultaneously normalized gene expression microarrays comprising 50 tumor entities, with a focus on oligo-mutated pediatric cancers, and 71 normal tissue types. RAVEN performed a transcriptome-wide scan in each cancer entity for gender-specific CSGs, and identified several established CSGs, but also many novel candidates potentially suitable for targeting multiple cancer types. The specific expression of the most promising CSGs was validated in cancer cell lines and in a comprehensive tissue-microarray. Subsequently, RAVEN identified likely immunogenic CSG-encoded peptides by predicting their affinity to MHCs and excluded sequence identity to abundantly expressed proteins by interrogating the UniProt protein-database. The predicted affinity of selected peptides was validated in T2-cell peptide-binding assays in which many showed binding-kinetics like a very immunogenic influenza control peptide. Collectively, we provide an exquisitely curated catalogue of cancer-specific and highly MHC-affine peptides across 50 cancer types, and a freely available software (https://github.com/JSGerke/RAVENsoftware) to easily apply our algorithm to any gene expression dataset. We anticipate that our peptide libraries and software constitute a rich resource to advance anti-cancer immunotherapy.

Daunorubicin during delayed intensification decreases the incidence of infectious complications - a randomized comparison in trial CoALL 08-09

Anthracyclines are integral components of antileukemic treatment. Apart from cardiotoxicity, myelosuppression and infectious complications have been described for doxorubicin (DOX) and daunorubicin (DNR) as predominant side effects, but little is known about their differential toxicities. To address the question whether DNR is associated with a lower rate of infectious complications compared with DOX, 307 children with newly diagnosed acute lymphoblastic leukemia, enrolled in trial CoALL 08-09, were randomized to receive either DOX 30 mg/m² (n = 153) or DNR 36 mg/m² (n = 154) in delayed intensification. Hematologic toxicities and stomatitis were less frequent in the DNR group resulting in a significantly lower rate of infections in the DNR arm (27% vs. 59%, p < .0001). Survival was equal in both arms (95% SE 2%) (p = .55), with an insignificant difference in the relapse rate (RR 0.12 (SE = 0.03) in the DOX arm vs. 0.16 (SE = 0.04) in the DNR arm; p = .37; Hazard ratio 1.3; 95% confidence interval 0.7-2.6). In conclusion, DNR given in delayed intensification is associated with a lower incidence of infectious complications without loss of efficacy.

Induction of a central memory and stem cell memory phenotype in functionally active CD4+ and CD8+ CAR T cells produced in an automated good manufacturing practice system for the treatment of CD19+ acute lymphoblastic leukemia

Relapsed/refractory B-precursor acute lymphoblastic leukemia (pre-B ALL) remains a major therapeutic challenge. Chimeric antigen receptor (CAR) T cells are promising treatment options. Central memory T cells (Tcm) and stem cell-like memory T cells (Tscm) are known to promote sustained proliferation and persistence after T-cell therapy, constituting essential preconditions for treatment efficacy. Therefore, we set up a protocol for anti-CD19 CAR T-cell generation aiming at high Tcm/Tscm numbers. 100 ml peripheral blood from pediatric pre-B ALL patients was processed including CD4+/CD8+-separation, T-cell activation with modified anti-CD3/-CD28 reagents and transduction with a 4-1BB-based second generation CAR lentiviral vector. The process was performed on a closed, automated device requiring additional manual/open steps under clean room conditions. The clinical situation of these critically ill and refractory patients with leukemia leads to inconsistent cellular compositions at start of the procedure including high blast counts and low T-cell numbers with exhausted phenotype. Nevertheless, a robust T-cell product was achieved (mean CD4+ = 50%, CD8+ = 39%, transduction = 27%, Tcm = 50%, Tscm = 46%). Strong proliferative potential (up to > 100-fold), specific cytotoxicity and low expression of co-inhibitory molecules were documented. CAR T cells significantly released TH1 cytokines IFN-γ, TNF-α and IL-2 upon target-recognition. In conclusion, partly automated GMP-generation of CAR T cells from critically small blood samples was feasible with a new stimulation protocol that leads to high functionality and expansion potential, balanced CD4/CD8 ratios and a conversion to a Tcm/Tscm phenotype.

Posaconazole plasma concentrations in pediatric patients receiving antifungal prophylaxis during neutropenia

Invasive fungal infections are one of the major complications in pediatric patients during prolonged neutropenia after chemotherapy. Evaluation of the efficacy and safety of the triazole posaconazole in these patients is missing. This multicenter survey analyzed trough concentrations of 33 pediatric patients with a median age of 8 years during 108 neutropenic episodes who received prophylactic posaconazole oral suspension. A total of 172 posaconazole trough levels were determined to median 438 ng/ml (range 111-2011 ng/ml; mean 468 ± 244 ng/ml). Age and gender had no influence on posaconazole plasma levels. Posaconazole was not discontinued due to adverse events in any of the patients. Only hepatic parameters significantly increased beyond the upper normal limit to median values of ALT of 87 U/l (P < .0001), and AST of 67 U/l (P < .0001). One patient with a median posaconazole trough concentration of 306 ng/ml experienced an invasive fungal infection. In conclusion, posaconazole was effective, safe and feasible in 33 pediatric patients with neutropenia ≥5 days after chemotherapy. Median posaconazole plasma concentrations were approximately 1.6-fold lower than the recommended plasma level of 700 ng/ml. Larger patient cohorts are needed to evaluate these findings.

T-cell responses against CD19+ pediatric acute lymphoblastic leukemia mediated by bispecific T-cell engager (BiTE) are regulated contrarily by PD-L1 and CD80/CD86 on leukemic blasts

T-cell immunotherapies are promising options in relapsed/refractory B-precursor acute lymphoblastic leukemia (ALL). We investigated the effect of co-signaling molecules on T-cell attack against leukemia mediated by CD19/CD3-bispecific T-cell engager. Primary CD19+ ALL blasts (n≥10) and physiologic CD19+CD10+ bone marrow precursors were screened for 20 co-signaling molecules. PD-L1, PD-1, LAG-3, CD40, CD86, CD27, CD70 and HVEM revealed different stimulatory and inhibitory profiles of pediatric ALL compared to physiologic cells, with PD-L1 and CD86 as most prominent inhibitory and stimulatory markers. PD-L1 was increased in relapsed ALL patients (n=11) and in ALLs refractory to Blinatumomab (n=5). Exhaustion markers (PD-1, TIM-3) were significantly higher on patients' T cells compared to physiologic controls. T-cell proliferation and effector function was target-cell dependent and correlated to expression of co-signaling molecules. Blockade of inhibitory PD-1-PD-L and CTLA-4-CD80/86 pathways enhanced T-cell function whereas blockade of co-stimulatory CD28-CD80/86 interaction significantly reduced T-cell function. Combination of Blinatumomab and anti-PD-1 antibody was feasible and induced an anti-leukemic in vivo response in a 12-year-old patient with refractory ALL. In conclusion, ALL cells actively regulate T-cell function by expression of co-signaling molecules and modify efficacy of therapeutic T-cell attack against ALL. Inhibitory interactions of leukemia-induced checkpoint molecules can guide future T-cell therapies.