Cellular immune reconstitution after haploidentical transplantation in children

Reduction of Minimal Residual Disease in Pediatric B-lineage Acute Lymphoblastic Leukemia by an Fc-optimized CD19 Antibody

Prognosis of primary refractory and relapsed pediatric B-lineage acute lymphoblastic leukemia (ALL) is very poor. Relapse rates significantly correlate with persistent minimal residual disease (MRD). In MRD, favorable effector-target ratios prevail and thus this situation might be optimally suited for immunotherapy with antibodies recruiting immunological effector cells. We here report on the generation, preclinical characterization and first clinical application in B-lineage ALL of an Fc-optimized CD19 antibody. This third-generation antibody (4G7SDIE) mediated enhanced antibody-dependent cellular cytotoxicity (ADCC) against leukemic blasts with effector cells from healthy volunteers and B-lineage ALL patients. The antibody was produced in a university-owned production unit and was applied on a compassionate use basis to 14 pediatric patients with refractory and relapsed B-lineage ALL at the stage of MRD. In 10/14 patients, MRD was reduced by ≥ 1 log or below the patient-individual detection limit, and 5/14 patients have achieved ongoing complete molecular remission with a median leukemia-free survival of 428 days. Two additional patients died in complete molecular remission due to complications not related to antibody therapy. Besides profound in vivo B-cell depletion, side effects were negligible. A clinical phase 1/2 study to further assess the therapeutic activity of 4G7SDIE is in preparation.

Haploidentical Transplantation in Children with Acute Leukemia: The Unresolved Issues

Allogeneic hematopoietic stem cell transplantation (HSCT) remains a curative option for children with high risk and advanced acute leukemia. Yet availability of matched family donor limits its use and although matched unrelated donor or mismatched umbilical cord blood (UCB) are viable options, they fail to meet the global need. Haploidentical family donor is almost universally available and is emerging as the alternate donor of choice in adult patients. However, the same is not true in the case of children. The studies of haploidentical HSCT in children are largely limited to T cell depleted grafts with not so encouraging results in advanced leukemia. At the same time, emerging data from UCBT are challenging the existing paradigm of less stringent HLA match requirements as perceived in the past. The use of posttransplantation cyclophosphamide (PTCY) has yielded encouraging results in adults, but data in children is sorely lacking. Our experience of using PTCY based haploidentical HSCT in children shows inadequacy of this approach in younger children compared to excellent outcome in older children. In this context, we discuss the current status of haploidentical HSCT in children with acute leukemia in a global perspective and dwell on its future prospects.

Favorable NK cell activity after haploidentical hematopoietic stem cell transplantation in stage IV relapsed Ewing's sarcoma patients

Natural killer (NK) cell activity has been shown to have potential activity against Ewing's sarcoma (EWS) especially in tumors with low HLA I expression and high NKG2D expression. Two patients with metastatic relapsed and primary metastatic stage IV EWS who had received two courses of high dose chemotherapy with autologous stem cell rescue were transplanted from a haploidentical parental stem cell donor. Patients are alive in ongoing CR for 10.2 and 3.4 years now. Post transplant local second and first relapses were treated successfully in both patients. In vivo IL-2 stimulation not only increased the number and activity of effector cells in one patient but was also associated with severe GvHD. In vitro studies demonstrated high NK cell activity against K562 and relevant activity against EWS cell line A673 post transplant. NK activity was enhanced by cytokine prestimulation as well as by EWS targeting anti-GD2 Ab. Haploidentical hematopoietic stem cell transplantation (HSCT) might contribute to long-term survival by NK cell-mediated effect exerted by donor-derived NK cells. Local tumor recurrence was manageable in both high-risk patients indicating systemic immune control preventing subsequent metastasizing. The efficacy of haploidentical HSCT, cytokine application and tumor targeting antibodies for the use of Ab-dependent cellular cytotoxicity needs evaluation in clinical trials.

Rapid generation of NY-ESO-1-specific CD4+ THELPER1 cells for adoptive T-cell therapy

Tumor-associated antigens such as NY-ESO-1 are expressed in a variety of solid tumors but absent in mature healthy tissues with the exception of germline cells. The immune system anti-cancer attack is mediated by cell lysis or induction of growth arrest through paralysis of tumor cells, the latter of which can be achieved by tumor-specific CD4⁺, IFNγ-producing T_Helper type 1 (T_H1) cells. Translation of these immune-mediated mechanisms into clinical application has been limited by availability of immune effectors, as well as the need for complex in vitro protocols and regulatory hurdles. Here, we report a procedure to generate cancer-testis antigen NY-ESO-1-targeting CD4⁺ T_H1 cells in vitro for cancer immunotherapy in the clinic. After in vitro sensitization by stimulating T cells with protein-spanning, overlapping peptide pools of NY-ESO-1 in combination with IL-7 and low dose IL-2, antigen-specific T cells were isolated using IFNγ capture technique and subsequently expanded with IL-2, IL-7 and IL-15. Large numbers of NY-ESO-1-specific CD4⁺ T cells with a T_H1 cytokine profile and lower numbers of cytokine-secreting CD8⁺ T cells could be generated from healthy donors with a high specificity and expansion potential. Manufactured CD4⁺ T cells showed strong specific T_H1-responses with IFNγ⁺, TNFα⁺, IL-2⁺ and induced cell cycle arrest and apoptosis in tumor cells. The protocol is GMP-grade and approved by the regulatory authorities. The tumor-antigen specific CD4⁺ T_H1 lymphocytes can be adoptively transferred as a T-cell therapy to boost anticancer immunity and this novel cancer treatment approach is applicable to both T cells from healthy allogeneic donors as well as to autologous T cells derived from cancer patients.

[Hematopoietic stem cell transplantation in 2012: who? Where? How?]

Allogeneic bone marrow transplantation has dramatically changed over the years since its beginnings. The diseases treated with transplantation (malignant hemopathies, severe benign hemopathies such as congenital or acquired congenital medullary aplasia, hemoglobinopathies, as well as severe immune system deficiencies and certain overload diseases), stem cell sources (bone marrow, peripheral stem cells, placental blood), donor types (intrafamilial, nonrelated, totally or partially compatible), conditioning regimen (immunosuppressors, graft manipulation), and supportive care increasingly vary. Allogeneic stem cell transplantation and more widely cellular therapies now need to be discussed. In this paper, we propose an overview of these therapies in 2012 for pediatric patients.

Improved early outcomes using a T cell replete graft compared with T cell depleted haploidentical hematopoietic stem cell transplantation

Haploidentical stem cell transplantation (SCT) has been generally performed using a T cell depleted (TCD) graft; however, a high rate of nonrelapse mortality (NRM) has been reported, particularly in adult patients. We hypothesized that using a T cell replete (TCR) graft followed by effective posttransplantation immunosuppressive therapy would reduce NRM and improve outcomes. We analyzed 65 consecutive adult patients with hematologic malignancies who received TCR (N = 32) or TCD (N = 33) haploidentical transplants. All patients received a preparative regimen consisting of melphalan, fludarabine, and thiotepa. The TCR group received posttransplantation treatment with cyclophosphamide (Cy), tacrolimus (Tac), and mycophenolate mofetil (MMF). Patients with TCD received antithymocyte globulin followed by infusion of CD34+ selected cells with no posttransplantation immunosuppression. The majority of patients in each group had active disease at the time of transplantation. Outcomes are reported for the TCR and TCD recipients, respectively. Engraftment was achieved in 94% versus 81% (P = NS). NRM at 1 year was 16% versus 42% (P = .02). Actuarial overall survival (OS) and progression-free survival (PFS) rates at 1 year posttransplantation were 64% versus 30% (P = .02) and 50% versus 21% (P = .02). The cumulative incidence of grade II-IV acute graft-versus-host disease (aGVHD) was 20% versus 11% (P = .20), and chronic GVHD (cGVHD) 7% versus 18% (P = .03). Improved reconstitution of T cell subsets and a lower rate of infection were observed in the TCR group. These results indicate that a TCR graft followed by effective control of GVHD posttransplantation may lower NRM and improve survival after haploidentical SCT.

Clinical options after failure of allogeneic hematopoietic stem cell transplantation in patients with hematologic malignancies

Disease recurrence is the single most common cause of death after allogeneic or autologous hematopoietic stem cell transplantation (HSCT). Disease status and chemosensitivity at the time of transplantation, as well as the development of graft-versus-host disease (GVHD), are factors known to influence the risk of relapse post-HSCT. Both acute and chronic GVHD have been associated with decreased relapse rates; however, owing to toxicity, overall survival is not consistently improved in these patients. Furthermore, there is a transient period of immunodeficiency after HSCT, which may permit residual malignant cells to proliferate early in the post-transplant course, before the donor immune system can establish a graft-versus-tumor response. Patients who fail an initial HSCT have an extremely poor outcome; therefore, maneuvers to prevent, identify and treat recurrent disease as early as possible in these situations are necessary. Strategies to distinguish graft-versus-tumor from GVHD, to enhance both general and disease-specific immune reconstitution after transplantation, and to increase donor-mediated anti-host immune reactions are being investigated in clinical trials. Single agent nontoxic post-HSCT chemotherapy, cellular therapies and second allogeneic HSCT using reduced intensity regimens are among the modalities under investigation.

The burden of cure: long-term side effects following hematopoietic stem cell transplantation (HSCT) in children

Children who survive hematopoietic stem cell transplantation (HSCT) are at risk for an inordinate number of long-term side effects. Late effects can be secondary to the underlying diagnosis for which the transplant is performed, prior treatment of the disease, the transplant preparative regimen, treatment of the complications of transplant, and immunologic interactions between the graft and the host. This article describes the risks and manifestations of the most commonly reported late effects in survivors of pediatric HSCT.

Stem cell source and outcome after hematopoietic stem cell transplantation (HSCT) in children and adolescents with acute leukemia

Allogeneic hematopoietic stem cell transplantation from siblings, unrelated donors or HLA mismatched family members has become an important procedure to offer a chance of cure to children and adolescents with acute leukemia at high risk of relapse and those with certain genetic diseases. Bone marrow (BM) was the only stem cell source for many years. During the past 15 years, peripheral blood stem cells from granulocyte colony-stimulating factor (G-CSF) mobilized healthy donors, or umbilical cord blood from related or unrelated donors, have become available. Each stem cell source has different risks/benefits for patients and donors, the choice depending not only on availability, but also on HLA compatibility and urgency of the HSCT. This review will analyze the advantages and limitations of each of these options, and the main criteria which can be applied when choosing the appropriate stem cell source for pediatric transplant recipients with acute leukemia.