CAR-T cell therapy in paediatric acute lymphoblastic leukaemia - past, present and future

Over the last decade, chimeric antigen receptor (CAR)-T cell therapy has emerged as a promising treatment modality for relapsed/refractory B-cell malignancies in both children and adults. As an adoptive immune therapy, CAR-T cells have the potential to overcome disease that is resistant to chemo- and radiotherapy as well as represent a viable option for those who have already reached toxicity ceilings with standard therapies. CD19-directed CAR-T cell products have been licensed for use in paediatric B-cell acute lymphoblastic leukaemia that is refractory, in relapse post-transplant or in second or later relapse. Many challenges remain, rightly resulting in a heavily-mined research field. These include mitigating short-term immune-mediated toxicity, maintaining durability of responses, broadening treatment accessibility and extending its applicability to other malignant settings. In this review, dedicated to marking 60 years since the establishment of the British Society for Haematology, we will focus on the contribution of our community towards the success of CD19-directed CAR-T cell therapy in children. We will put current practice in CAR-T cell therapy into the context of future challenges to be addressed in order for it to fulfil its "game-changing" therapeutic potential

A guide to manufacturing CAR T cell therapies

In recent years, chimeric antigen receptor (CAR) modified T cells have been used as a treatment for haematological malignancies in several phase I and II trials and with Kymriah of Novartis and Yescarta of KITE Pharma, the first CAR T cell therapy products have been approved. Promising clinical outcomes have yet been tempered by the fact that many therapies may be prohibitively expensive to manufacture. The process is not yet defined, far from being standardised and often requires extensive manual handling steps. For academia, big pharma and contract manufacturers it is difficult to obtain an overview over the process strategies and their respective advantages and disadvantages. This review details current production processes being used for CAR T cells with a particular focus on efficacy, reproducibility, manufacturing costs and release testing. By undertaking a systematic analysis of the manufacture of CAR T cells from reported clinical trial data to date, we have been able to quantify recent trends and track the uptake of new process technology. Delivering new processing options will be key to the success of the CAR-T cells ensuring that excessive manufacturing costs do not disrupt the delivery of exciting new therapies to the wide possible patient cohort

Expression of a dominant T-cell receptor can reduce toxicity and enhance tumor protection of allogeneic T-cell therapy

Due to the lack of specificity for tumor antigens, allogeneic T-cell therapy is associated with graft-versus-host disease. Enhancing the anti-tumor specificity while reducing the graft-versus-host disease risk of allogeneic T cells has remained a research focus. In this study, we demonstrate that the introduction of ‘dominant’ T-cell receptors into primary murine T cells can suppress the expression of endogenous T-cell receptors in a large proportion of the gene-modified T cells. Adoptive transfer of allogeneic T cells expressing a ‘dominant’ T-cell receptor significantly reduced the graft-versus-host toxicity in recipient mice. Using two bone marrow transplant models, enhanced anti-tumor activity was observed in the presence of reduced graft-versus-host disease. However, although transfer of T-cell receptor gene-modified allogeneic T cells resulted in the elimination of antigen-positive tumor cells and improved the survival of treated mice, it was associated with accumulation of T cells expressing endogenous T-cell receptors and the development of delayed graft-versus-host disease. The in vivo deletion of the engineered T cells, mediated by endogenous mouse mammary tumor virus MTV8 and MTV9, abolished graft-versus-host disease while retaining significant anti-tumor activity of adoptively transferred T cells. Together, this study shows that the in vitro selection of allogeneic T cells expressing high levels of a ‘dominant’ T-cell receptor can lower acute graft-versus-host disease and enhance anti-tumor activity of adoptive cell therapy, while the in vivo outgrowth of T cells expressing endogenous T-cell receptors remains a risk factor for the delayed onset of graft-versus-host disease

Clinical Utility of Radiologic Disease Reassessment in the Management of Pediatric B-Cell Non-Hodgkin Lymphoma

Although outcomes for children with B-cell non-Hodgkin lymphoma are excellent, between 20% and 40% demonstrate residual radiologic abnormalities at disease assessment during consolidation therapy, the significance of which remains uncertain. The authors report the outcomes for all children treated for B-cell non-Hodgkin lymphoma at our center over an 11-year period. Twenty-four of 64 (38%) children had residual radiologic abnormalities at disease remission assessment. Seven (29%) underwent histologic biopsies that were normal. No children with residual radiologic abnormalities experienced disease relapse or death, suggesting that imaging at this time point creates clinical uncertainty without indicating residual disease or predicting relapse

CD8 T cell tolerance to a tumor-associated self-antigen is reversed by CD4 T cells engineered to express the same T cell receptor

Ag receptors used for cancer immunotherapy are often directed against tumor-associated Ags also expressed in normal tissues. Targeting of such Ags can result in unwanted autoimmune attack of normal tissues or induction of tolerance in therapeutic T cells. We used a murine model to study the phenotype and function of T cells redirected against the murine double minute protein 2 (MDM2), a tumor-associated Ag that shows low expression in many normal tissues. Transfer of MDM2-TCR-engineered T cells into bone marrow chimeric mice revealed that Ag recognition in hematopoietic tissues maintained T cell function, whereas presentation of MDM2 in nonhematopoietic tissues caused reduced effector function. TCR-engineered CD8(+) T cells underwent rapid turnover, downmodulated CD8 expression, and lost cytotoxic function. We found that MDM2-TCR-engineered CD4(+) T cells provided help and restored cytotoxic function of CD8(+) T cells bearing the same TCR. Although the introduction of the CD8 coreceptor enhanced the ability of CD4(+) T cells to recognize MDM2 in vitro, the improved self-antigen recognition abolished their ability to provide helper function in vivo. The data indicate that the same class I-restricted TCR responsible for Ag recognition and tolerance induction in CD8(+) T cells can, in the absence of the CD8 coreceptor, elicit CD4 T cell help and partially reverse tolerance. Thus MHC class I-restricted CD4(+) T cells may enhance the efficacy of therapeutic TCR-engineered CD8(+) T cells and can be readily generated with the same TCR

Clonal expansion of T memory stem cells determines early anti-leukemic responses and long-term CAR T cell persistence in patients

Low-affinity CD19 chimeric antigen receptor (CAR) T cells display enhanced expansion and persistence, enabling fate tracking through integration site analysis. Here we show that integration sites from early (1 month) and late (>3 yr) timepoints cluster separately, suggesting different clonal contribution to early responses and prolonged anti-leukemic surveillance. CAR T central and effector memory cells in patients with long-term persistence remained highly polyclonal, whereas diversity dropped rapidly in patients with limited CAR T persistence. Analysis of shared integrants between the CAR T cell product and post-infusion demonstrated that, despite their low frequency, T memory stem cell clones in the product contributed substantially to the circulating CAR T cell pools, during both early expansion and long-term persistence. Our data may help identify patients at risk of early loss of CAR T cells and highlight the critical role of T memory stem cells both in mediating early anti-leukemic responses and in long-term surveillance by CAR T cells

Molecular remission of infant B-ALL after infusion of universal TALEN gene-edited CAR T cells

Autologous T cells engineered to express chimeric antigen receptor against the B cell antigen CD19 (CAR19) are achieving marked leukemic remissions in early-phase trials but can be difficult to manufacture, especially in infants or heavily treated patients. We generated universal CAR19 (UCART19) T cells by lentiviral transduction of non-human leukocyte antigen-matched donor cells and simultaneous transcription activator-like effector nuclease (TALEN)-mediated gene editing of T cell receptor α chain and CD52 gene loci. Two infants with relapsed refractory CD19(+) B cell acute lymphoblastic leukemia received lymphodepleting chemotherapy and anti-CD52 serotherapy, followed by a single-dose infusion of UCART19 cells. Molecular remissions were achieved within 28 days in both infants, and UCART19 cells persisted until conditioning ahead of successful allogeneic stem cell transplantation. This bridge-to-transplantation strategy demonstrates the therapeutic potential of gene-editing technology

Failure of recombinant factor VIIa in a patient with severe polymicrobial sepsis and postoperative uncontrolled intraabdominal bleeding

<p>Abstract</p> <p>Background</p> <p>This report discusses a case of unsuccessful treatment with recombinant factor VIIa (rFVIIa) in off-label use. The need for international guidelines concerning the off-label use of rFVIIa is outlined as well as the need for methods to control the efficacy of rFVIIa objectively.</p> <p>Case presentation</p> <p>54 year old male with severe polymicrobial sepsis due to a perforated diverticulitis of the sigmoid colon and consecutive overt disseminated intravascular coagulation. He suffered severe intraabdominal bleeding after abdominal surgery despite conventional haemostatic support. Repeated applications of factor VIIa temporarily improved coagulation essays but did not stop clinical bleeding. The patient died in multiorgan failure due to septic and haemorrhagic shock.</p> <p>Conclusion</p> <p>Off-label use of rFVIIa could result in more side effects than could be expected from literature because of a publication bias. However for most off-label applications large prospective, randomised and controlled trials to confirm the positive findings are missing. For the future, not only guidelines concerning the off-label use of rFVIIa are urgently needed but also guidelines for monitoring the efficacy of rFVIIa.</p