αβ+ /CD19+ -depleted haploidentical stem cell transplantation for children with acute leukemia: Is there a protective effect of increased γδ+ T-cell content in the graft?

Haploidentical Stem Cell Transplantation With TCR-αβ + /CD19 + Depletion in High-risk Pediatric Leukemias: Experience From a Referral Center in Peru

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) using TCR αβ+/CD19+ depletion provides an alternative treatment for patients with high-risk (HR) leukemias without a matched donor, especially in developing nations with limited donor registries. We present the outcomes of 36 patients <16 years with HR leukemia who underwent haplo-HSCT with TCR αβ + /CD19 + depletion between 2018 and 2022 at a referral center in Peru. Survival probabilities and cumulative incidence functions were calculated using the Kaplan-Meier method. Patients were followed for a median of 17.38 months (range: 2.34 to 60.36 mo). The 5-year overall survival (OS), 5-year event-free survival (EFS), and non-relapse mortality rates were 72.1%, 72.2%, and 16.7%, respectively. The incidence of relapse for the entire group was 11.1%. Acute graft versus host disease (GvHD) was observed in 36.1% of the patients, with only 2.8% experiencing grade III-IV acute GvHD. No patients developed chronic GvHD. Among all patients, CMV reactivations were observed in 27.78%, HHV-6 reactivations in 33.33%, and ADV or BK virus reactivations in 16.67%. Our study suggests that haplo-HSCT with TCR αβ+/CD19+ depletion is a safe and effective treatment for HR pediatric leukemias. Adopting this approach in major transplant centers throughout the country could improve outcomes for this group of patients.

Comprehensive up-to-date analysis on TCRαβ/CD19-depleted hematopoietic stem cell transplantation in pediatric hematological malignancies

This meta-analysis assesses the efficacy of TCRαβ+/CD19+ depleted hematopoietic stem cell transplantation (HSCT) in pediatric patients with hematological malignancies, bridging the gap in the heterogeneous results of published studies. We analyzed post-HSCT complications and survival outcomes in 1068 children across 14 studies, using both aggregated and patient-level data from acute myeloid leukemia/myelodysplastic syndromes (AML/MDS) and acute lymphoblastic leukemia (ALL) studies, employing the IPDfromKM technique for time-to-event data reconstruction. The analysis reveals a 95 % engraftment success rate (95 % CI: 93-97) and 6-year overall survival and disease-free survival (DFS) rates of 67.2 % and 66.3 %, respectively, with no significant differences in DFS between haploidentical and unrelated donors (hazard ratio = 0.9, 95 % CI: 0.53-1.55). Acute graft-versus-host disease (GvHD) grades III-IV and chronic GvHD incidences were 8 % (95 % CI: 6-11) and 17 % (95 % CI: 10-27). The relapse rate was 27 % (95 % CI: 21-33), with relapse-related mortality at 21 % (95 % CI: 15-28) and HSCT-related mortality at 12 % (95 % CI: 7-19). Relapse was significantly lower in patients (mostly ALL) receiving total body irradiation (risk ratio = 0.53, P = 0.04). These findings underscore TCRαβ/CD19-depleted HSCT as a valuable option for patients without HLA-matched donors, highlighting the need for larger, multicenter studies.

European flow cytometry quality assurance guidelines for the diagnosis of primary immune deficiencies and assessment of immune reconstitution following B cell depletion therapies and transplantation

Over the last 15 years activity of diagnostic flow cytometry services have evolved from monitoring of CD4 T cell subsets in HIV-1 infection to screening for primary and secondary immune deficiencies syndromes and assessment of immune constitution following B cell depleting therapy and transplantation. Changes in laboratory activity in high income countries have been driven by initiation of anti-retroviral therapy (ART) in HIV-1 regardless of CD4 T cell counts, increasing recognition of primary immune deficiency syndromes and the wider application of B cell depleting therapy and transplantation in clinical practice. Laboratories should use their experience in standardization and quality assurance of CD4 T cell counting in HIV-1 infection to provide immune monitoring services to patients with primary and secondary immune deficiencies. Assessment of immune reconstitution post B cell depleting agents and transplantation can also draw on the expertise acquired by flow cytometry laboratories for detection of CD34 stem cell and assessment of MRD in hematological malignancies. This guideline provides recommendations for clinical laboratories on providing flow cytometry services in screening for immune deficiencies and its emerging role immune reconstitution after B cell targeting therapies and transplantation.

Haploidentical HSCT in the Treatment of Pediatric Hematological Disorders

Allogeneic hematopoietic stem cell transplantation has become a treatment option for otherwise non-curative conditions, both malignant and benign, affecting children and adults. Nevertheless, the latest research has been focusing extensively on transplantation from related and unrelated haploidentical donors, suitable for patients requiring emergent hematopoietic stem cell transplantation (HSCT) in the absence of an HLA-matched donor. Haploidentical HSCT (haplo-HSCT) can be an effective treatment for non-malignant pediatric disorders, such as primary immunodeficiencies or hemoglobinopathies, by enabling a much quicker selection of the appropriate donor for virtually all patients, low incidence of graft-versus-host disease (GVHD), and transplant-related mortality (TRM). Moreover, the outcomes of haplo-HSCT among children with hematological malignancies have improved radically. The most demanding tasks for clinicians are minimizing T-cell-mediated alloreactivity as well as early GVHD prevention. As a result, several T-cell depletion approaches, such as ex vivo T-cell depletion (TCD), and T-cell replete approaches, such as a combination of anti-thymocyte globulin (ATG), post-transplantation cyclophosphamide (PTCy), cyclosporine/tacrolimus, mycophenolate mofetil, or methotrexate, have been taken up. As more research is needed to establish the most beneficial form of therapy, haplo-HSCT is currently considered an alternative donor strategy for pediatric and adult patients with complications like viral and bacterial infections, invasive fungal disease, and GVHD.

Pediatric acute myeloid leukemia - novel approaches

PURPOSE OF REVIEW

Despite higher remission and survival rates than observed in adults, children with acute myeloid leukemia (AML) still suffer unacceptably high rates of treatment failure and late toxicities. Ongoing work aims to improve these long-term outcomes through improvements in the utilization of current therapies, the incorporation of novel chemotherapy agents, and improved use of current or novel cellular and immunotherapeutic approaches. In this review, we highlight recent advances and contextualize them within this evolving landscape.

RECENT FINDINGS

Novel agents such as the B-cell lymphoma 2 inhibitor venetoclax and the menin inhibitors have shown promising results with implications for large portions of the pediatric AML population. Older agents are being used in novel combinations (e.g. gemtuzumab ozogamicin) or are expanding into pediatrics after longer use in adults (e.g. Fms-like tyrosine kinase 3 inhibitors). Finally, immunotherapeutic approaches offer new options for patients with high-risk or relapsed disease.

SUMMARY

Recent findings have altered the landscape of pediatric AML therapy with exciting immediate and long-term implications. Ongoing studies may soon define this as standard as well. After many years in which few new therapies have become available for children with AML, recent and upcoming advances may soon dramatically alter the therapeutic landscape.

TCRαβ/CD19 cell-depleted HLA-haploidentical transplantation to treat pediatric acute leukemia: updated final analysis

ABSTRACT

TCRαβ/CD19 cell depletion is a promising graft manipulation technique frequently used in the context of human leukocyte antigen (HLA)-haploidentical hematopoietic stem cell transplantation (HSCT). We previously reported the results of a phase I-II clinical trial (NCT01810120) to assess the safety and the efficacy of this type of exvivo T-cell depletion in 80 children with acute leukemia, showing promising survival outcomes. We now report an updated analysis on a cohort of 213 children with a longer follow-up (median, 47.6 months for surviving patients). With a 5-year cumulative incidence of nonrelapse mortality of 5.2% (95% confidence interval [CI], 2.8%-8.8%) and a cumulative incidence of relapse of 22.7% (95% CI, 16.9%-29.2%), projected 10-year overall and disease-free survival (DFS) were 75.4% (95% CI, 68.6%-80.9%) and 71.6% (95% CI, 64.4%-77.6%), respectively. Cumulative incidence of both grade II-IV acute and chronic graft-versus-host disease were low (14.7% and 8.1%, respectively). In a multivariable analysis for DFS including type of disease, use of total body irradiation in the conditioning regimen (hazard ratio [HR], 0.5; 95% CI, 0.26-0.98; P = .04), disease status at HSCT (complete remission [CR] ≥3 vs CR 1/2; HR, 2.23; 95% CI, 1.20-4.16; P = .01), and high levels of pre-HSCT minimal residual disease (HR, 2.09; 95% CI, 1.01-4.33; P = .04) were independently associated with outcome. In summary, besides confirming the good outcome results already reported (which are almost superimposable on those of transplant from HLA-matched donors), this clinical update allows the identification of patients at higher risk of treatment failure for whom personalized approaches, aimed at reducing the risk of relapse, are warranted.