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.

Targeted therapies in retinoblastoma: GD2-directed immunotherapy following autologous stem cell transplantation and evaluation of alternative target B7-H3.

BACKGROUND: GD2-directed immunotherapy is highly effective in the treatment of high-risk neuroblastoma (NB), and might be an interesting target also in other high-risk tumors. METHODS: The German-Austrian Retinoblastoma Registry, Essen, was searched for patients, who were treated with anti-GD2 monoclonal antibody (mAb) dinutuximab beta (Db) in order to evaluate toxicity, response and outcome in these patients. Additionally, we evaluated anti-GD2 antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) in retinoblastoma cell lines in vitro. Furthermore, in vitro cytotoxicity assays directed against B7-H3 (CD276), a new identified potential target in RB, were performed. RESULTS: We identified four patients with relapsed stage IV retinoblastoma, who were treated with Db following autologous stem cell transplantation (ASCT). Two out of two evaluable patients with detectable tumors responded to immunotherapy. One of these and another patient who received immunotherapy without residual disease relapsed 10 and 12 months after start of Db. The other patients remained in remission until last follow-up 26 and 45 months, respectively. In vitro, significant lysis of RB cell lines by ADCC and CDC with samples from patients and healthy donors and anti-GD2 and anti-CD276-mAbs were demonstrated. CONCLUSION: Anti-GD2-directed immunotherapy represents an additional therapeutic option in high-risk metastasized RB. Moreover, CD276 is another target of interest.

Haploidentical hematopoietic stem cell transplantation as individual treatment option in pediatric patients with very high-risk sarcomas.

Background: Prognosis of children with primary disseminated or metastatic relapsed sarcomas remains dismal despite intensification of conventional therapies including high-dose chemotherapy. Since haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is effective in the treatment of hematological malignancies by mediating a graft versus leukemia effect, we evaluated this approach in pediatric sarcomas as well. Methods: Patients with bone Ewing sarcoma or soft tissue sarcoma who received haplo-HSCT as part of clinical trials using CD3+ or TCRα/ß+ and CD19+ depletion respectively were evaluated regarding feasibility of treatment and survival. Results: We identified 15 patients with primary disseminated disease and 14 with metastatic relapse who were transplanted from a haploidentical donor to improve prognosis. Three-year event-free survival (EFS) was 18,1% and predominantly determined by disease relapse. Survival depended on response to pre-transplant therapy (3y-EFS of patients in complete or very good partial response: 36,4%). However, no patient with metastatic relapse could be rescued. Conclusion: Haplo-HSCT for consolidation after conventional therapy seems to be of interest for some, but not for the majority of patients with high-risk pediatric sarcomas. Evaluation of its future use as basis for subsequent humoral or cellular immunotherapies is necessary.

Recurrent SARS-CoV-2 Infection and Impaired Immunologic Response in a Pediatric Oncologic Patient While Treated With Radiochemotherapy.

Immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in pediatric patients with malignant disease may be affected by tumor therapy. Here, we report the case of a child with rhabdomyosarcoma and recurrent SARS-CoV-2 infection. Immunologic responses, analyzed by T-cell activity and anti-viral IgG levels, were impaired and not durable as a result of intensive radiochemotherapy.

Introducing isotonic fluids into pediatric oncology.

Objective: Hypotonic fluids are commonly used in pediatric oncology despite evidence that these fluids can lead to hospital-acquired hyponatremia. This practice is most likely due to lack of data evaluating risks and benefits of isotonic fluids in pediatric oncology. To address this issue, our study investigates the effects of exchanging hypotonic fluids with isotonic fluids in a large pediatric oncology unit. Study Design: Prevalence of laboratory disorders before and after the change to balanced, isotonic fluids for all patients are compared in this retrospective analysis. Disturbances in electrolyte levels, fluid-, acid-base balance and kidney function were examined. Results: The rate of hyponatremia was reduced using isotonic fluids. There were no hypernatremic events. Volume overload might increase the use of furosemide when using isotonic fluids. Potassium and bivalent cation levels increased. The risk of acidosis is greatly reduced, whereas alkalosis was more frequent due to furosemide use. The rate of acute kidney injury did not increase. Conclusion: Using isotonic fluids for hyper-hydration in pediatric oncology lead to a modest reduction of hospital-acquired hyponatremia without causing hypernatremia, but the effects on fluid balance need further investigation. The additional intake of bivalent cations and buffering anions in balanced fluids has measurable effects.

Matched versus Haploidentical Hematopoietic Stem Cell Transplantation as Treatment Options for Primary Immunodeficiencies in Children.

Primary immunodeficiencies (PIDs) are inherited disorders of the immune system with allogeneic hematopoietic stem cell transplantation (HSCT) as the only curative treatment in some of them. In case an HLA-matched donor is not available, HSCT from a haploidentical family donor may be considered. We compared the outcomes of HSCT from HLA-matched unrelated or related donors (MUDs or MRDs) and mismatched related haploidentical donors (MMRDs) in patients with a variety of PIDs in 2 centers. A total of 44 pediatric patients were evaluated. We reviewed the outcomes of 25 children who underwent transplantation with HLA-matched grafts (MRD, n = 13; MUD, n = 12) and 19 patients receiving haploidentical stem cells. Bone marrow (BM) was transplanted in 85% (MRD) and 75% (MUD) of the matched cohort and peripheral blood stem cells (PBSCs) in 15% (MRD), 25% (MUD), and 100% (MMRD). All but 9 patients (MRD, n = 6; MMRD, n = 3) with severe combined immunodeficiency (SCID) received a chemotherapy-based conditioning regimen. Immune reconstitution of T, B, and natural killer cells was comparable for all groups with an advantage of recipients of MRD grafts in early CD4 reconstitution. However, deaths due to viral infections occurred more often in the haploidentical cohort. The disease-free survival was 91.7% (MRD), 66.7% (MUD), and 62.7% (MMRD), respectively. Grade II to IV acute graft-versus-host disease (GVHD) occurred in 15% (MRD), 8% (MUD), and 21% (MMRD) of the patients. Only 1 patient had severe grade IV GVHD in the MRD group, whereas no grade >II GVHD was observed in the MUD or MMRD cohort. These data indicate that in the absence of a suitable HLA-identical family donor, haploidentical HSCT may be a viable option for patients with life-threatening disease and urgent need of HSCT.

Defibrotide for the Treatment of Pediatric Inflammatory Multisystem Syndrome Temporally Associated With Severe Acute Respiratory Syndrome Coronavirus 2 Infection in 2 Pediatric Patients.

The pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus 2 infection is a severe complication of coronavirus disease 2019. Since impaired coagulation and thrombosis/endotheliitis are suspected pathomechanisms, we treated 2 patients with defibrotide, a profibrinolytic, antithrombotic, antiinflammatory oligonucleotide. Symptoms resolved during treatment. Moreover, coagulation parameters indicating hypofibrinolysis and complement activation normalized. The pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus 2 infection is a severe complication of coronavirus disease 2019. Since impaired coagulation and thrombosis/endotheliitis are suspected pathomechanisms, 2 patients received defibrotide, a profibrinolytic, antithrombotic, antiinflammatory oligonucleotide. Symptoms resolved and hypofibrinolysis/complement activation normalized during treatment.

ADCC can improve graft vs leukemia effect after T- and B-cell depleted haploidentical stem cell transplantation in pediatric B-lineage ALL.

Posttransplant relapsed B-cell precursor ALL can be cured by 2nd hematopoietic stem cell transplantation (HSCT) in 20% of patients. The major cause of death after second HSCT is leukemic relapse. One reliable predictor for survival after 2nd-HSCT are posttransplant MRD levels. Patients with detectable or increase of MRD are likely to relapse. Patients in complete molecular remission show the best leukemia-free survival and lowest cumulative incidence (CI) of relapse. As patients who undergo second or subsequent HSCT are high-risk patients, we evaluated the prophylactic use of the chimeric Fc-optimized CD19-4G7SDIE-mAb. Posttransplant relapsed CD19+ BCP-ALL patients, who underwent a second or subsequent haplo-HSCT from a T- and B-cell depleted graft received posttransplant prophylactic CD19-4G7SDIE-mAb treatment on compassionate use in complete molecular remission, to increase the antileukemic activity of the new reconstituting immune system by recruiting Fc-expressing effector cells. NK cells recovered early and robust. The 3 year overall survival in 15 evaluable patients was 56%, the 3 year event-free survival was 55% and the CI of relapse 38%. Compared to a historical control group, the CI of relapse was markedly lower and consecutively the EFS higher. Posttransplant-targeted therapy may overcome the need for unspecific GvL effect of undesired GvHD, that can cause severe morbidity and mortality. Due to a low adverse event profile the CD19-4G7SDIE-mAb may be suitable for broad administration to consolidate posttransplant MRD negativity.