Allogeneic Hematopoietic Stem Cell Transplantation for Mature T/NK-Cell Lymphomas in Children

Mature T/NK-cell lymphomas (MTCLs) are a heterogeneous group of lymphoproliferative disorders, relatively rare in adults and children. Allogeneic hematopoietic stem cell transplantation (HSCT) can be considered in some cases as a consolidation and is the first choice for refractory forms and relapses. We retrospectively analyzed 19 pediatric patients with MTCL who received allogeneic hematopoietic stem cell transplantation from a haploidentical or unrelated donor on the αβ T cell depletion platform. Among the studied patients, cutaneous T-cell lymphoma was diagnosed in 5, hepatosplenic γδT-cell lymphoma in 4, ALK-positive anaplastic large cell lymphoma in 9 patients, and 1 had nasal T/NK cell lymphoma. All patients received myeloablative conditioning based on treosulfan or total body irradiation. Non-relapse mortality was 5%, the cumulative incidence of relapse or progression at 5 years was 27%, 5-year event-free survival was 67%, and 5-year overall survival was 78%. Thus, our data support that allogeneic αβ T-cell-depleted HSCT can provide long-term overall survival of children with high-risk mature T-cell lymphomas.

Impact of Natural Killer Cell-Associated Factors on Acute Leukemia Outcomes after Haploidentical Hematopoietic Stem Cell Transplantation with αβ T Cell Depletion in a Pediatric Cohort

The technique of αβ T cell depletion (αβTCD) is a well-established method of hematopoietic stem cell transplantation (HSCT) for children with acute leukemia owing to the low rates of graft-versus-host disease and nonrelapse mortality (NRM). The graft-versus-leukemia effect is generally ascribed to natural killer (NK) cells conserved within the graft. It is not known whether NK-related factors affect the outcome of αβTCD HSCT, however. The aim of this retrospective study was to explore the impact of NK alloreactivity (based on donor-recipient killer immunoglobulin-like receptor [KIR] mismatch), graft NK cell dose, and blood NK cell recovery on day +30 post-HSCT on the incidences of leukemia relapse and NRM. The pediatric acute leukemia cohort comprised 295 patients who underwent their first HSCT from a haploidentical donor in complete remission. During post hoc analysis, the total cohort was divided into subcohorts by diagnosis (acute lymphoblastic leukemia [ALL]/acute myeloid leukemia [AML]), NK alloreactivity prediction (KIR match/KIR mismatch), graft NK cell dose (less than versus greater than the median value), and blood NK cell recovery on day +30 post-HSCT (less than versus greater than the median value). We also investigated the influence of serotherapy (antithymocyte globulin [ATG] group) versus abatacept + tocilizumab combination [aba+toci] group) on relapse risk in the context of KIR mismatch. The risks of relapse and NRM were calculated by the cumulative risk method, and groups were compared using the Gray test. Multivariate analysis revealed no apparent impact of predicted NK alloreactivity or any other studied NK cell-related factors for the entire cohort. For patients with AML, a significantly higher relapse risk associated with high NK cell graft content on the background of no predicted KIR mismatch (P = .002) was shown. Multivariate analysis confirmed this finding (P = .018); on the other hand, for the KIR-mismatched patients, there was a trend toward a lower risk of relapse associated with high NK cell dose. The use of ATG was associated with a trend toward reduced relapse risk (P = .074) in the AML patients. There was no significant impact of NK-related factors in the ALL patients. Overall, the evaluated NK-related factors did not show a clear and straightforward correlation with the key outcomes of HSCT in our cohort of children with acute leukemia. In practice, the data support prioritization of KIR-mismatched donors for patients with AML. Importantly, a potential interaction of KIR ligand mismatch and NK cell content in the graft was identified. Indirect evidence suggests that additional cellular constituents of the graft could influence the function of NK cells after HSCT and affect their role as graft-versus-leukemia effectors.

Extended characterization of anti-CD19 CAR T cell products manufactured at the point of care using the CliniMACS Prodigy system: comparison of donor sources and process duration

BACKGROUND AIMS

The CliniMACS Prodigy closed system is widely used for the manufacturing of chimeric antigen receptor T cells (CAR-T cells). Our study presents an extensive immunophenotypic and functional characterization and comparison of the properties of anti-CD19 CAR-T cell products obtained during long (11 days) and short (7 days) manufacturing cycles using the CliniMACS Prodigy system, as well as cell products manufactured from different donor sources of T lymphocytes: from patients, from patients who underwent HSCT, and from haploidentical donors. We also present the possibility of assessing the efficiency of transduction by an indirect method.

METHODS

Seventy-six CD19 CAR-T cell products were manufactured using the CliniMACS Prodigy automated system. Immunophenotypic properties, markers of cell activation and exhaustion, antitumor, anti-CD19 specific activity in vitro of the manufactured cell products were evaluated. As an indirect method for assessing the efficiency of transduction, we used the method of functional assessment of cytokine secretion and expression of the CD107a marker after incubation of CAR-T cells with tumor targets.

RESULTS

The CliniMACS Prodigy platform can produce a product of CD19 CAR-T cells with sufficient cell expansion (4.6 × 109 cells-median for long process [LP] and 1.6 × 109-for short process [SP]), transduction efficiency (43.5%-median for LP and 41.0%-for SP), represented mainly by T central memory cell population, with low expression of exhaustion markers, and with high specific antitumor activity in vitro. We did not find significant differences in the properties of the products obtained during the 7- and 11-day manufacturing cycles, which is in favor of reducing the duration of production to 7 days, which may accelerate CAR-T therapy. We have shown that donor sources for CAR-T manufacturing do not significantly affect the composition and functional properties of the cell product.

CONCLUSIONS

This study demonstrates the possibility of using the CliniMACS Prodigy system with a shortened 7-day production cycle to produce sufficient amount of functional CAR-T cells. CAR transduction efficiency can be measured indirectly via functional assays.

Targeted Therapy With Venetoclax and Daratumumab as Part of HSCT Preparative Regimen in Children With Chemorefractory Acute Myeloid Leukemia

The long-term outcome of allogeneic hematopoietic stem cell transplantation (HSCT) in chemorefractory acute myeloid leukemia (AML) remains suboptimal because of a high relapse rate. Enhancement of conditioning regimens by the incorporation of targeted anti-leukemia agents is a potential approach to improve the efficacy of HSCT. In a pilot trial and extended access cohort, we evaluated the safety and potential value of adding combinations of venetoclax and daratumumab to a preparative regimen among children with chemorefractory acute myeloid leukemia grafted with αβ T-cell-depleted peripheral blood stem cells. All 20 patients had active disease status of AML at the time of transplantation. The preparative regimen included myeloablative conditioning based on either total body irradiation or treosulfan. A haploidentical related donor was used as a graft source for all patients. Engraftment was not compromised, and no excess toxicity was noted. Minimal residual disease-negative complete remission was achieved in 17 patients (85%). The cumulative incidence of grade II to IV acute graft-versus-host disease (GVHD) was 17%, and the cumulative incidence of chronic GVHD was 7%. At 2 years, nonrelapse mortality was 10%, relapse incidence was 46%, event-free survival was 44%, and overall survival was 65%. Our data show the possibility of safely adding targeted agents to conditioning regimens; however, no evidence of a significant improvement in long-term transplantation outcomes in this cohort of patients was observed.

Reliable Flow-Cytometric Approach for Minimal Residual Disease Monitoring in Patients with B-Cell Precursor Acute Lymphoblastic Leukemia after CD19-Targeted Therapy

We aimed to develop an antibody panel and data analysis algorithm for multicolor flow cytometry (MFC), which is a reliable method for minimal residual disease (MRD) detection in patients with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) treated with CD19-directed therapy. The development of the approach, which was adapted for the case of possible CD19 loss, was based on the additional B-lineage marker expression data obtained from a study of primary BCP-ALL patients, an analysis of the immunophenotypic changes that occur during blinatumomab or CAR-T therapy, and an analysis of very early CD19-negative normal BCPs. We have developed a single-tube 11-color panel for MFC-MRD detection. CD22- and iCD79a-based primary B-lineage gating (preferably consecutive) was recommended. Based on patterns of antigen expression changes and the relative expansion of normal CD19-negative BCPs, guidelines for MFC data analysis and interpretation were established. The suggested approach was tested in comparison with the molecular techniques: IG/TR gene rearrangement detection by next-generation sequencing (NGS) and RQ-PCR for fusion-gene transcripts (FGTs). Qualitative concordance rates of 82.8% and 89.8% were obtained for NGS-MRD and FGT-MRD results, respectively. We have developed a sensitive and reliable approach that allows MFC-MRD monitoring after CD19-directed treatment, even in the case of possible CD19 loss.

Efficacy and safety of a reduced dose of plerixafor in combination with granulocyte colony-stimulating factor in healthy haploidentical stem cell donors

BACKGROUND AND OBJECTIVES

Implementation of the technique of immunomagnetic selection requires the procurement of a large number of CD34+ cells from haploidentical donors within a single apheresis procedure. The release of stem cells with granulocyte colony-stimulating factor (G-CSF) alone is unsatisfactory in a number of donors, and plerixafor, a CXCR4 chemokine receptor antagonist, could be used as an additional mobilization agent. The aim of our study was to examine whether a lower dose of plerixafor (0.12 mg/kg) can provide sufficient increase in CD34+ cells in the peripheral blood of allogeneic healthy donors in comparison with a historical control group. In addition, we assessed the risk of inability to provide the recipient with a transplant containing the optimal dose of 8-10 × 10⁶ CD34+ cells/kg body weight of the recipient.

MATERIALS AND METHODS

In a prospective, single-arm study, we examined the results of 105 mobilizations in healthy adult haploidentical donors with G-CSF and plerixafor at a dose of 0.12 mg/kg. The historical control group consisted of 106 mobilizations with G-CSF and plerixafor at 0.24 mg/kg.

RESULTS

The median increase in the number of CD34+ cells from day 4 to day 5 of mobilization was 69 cells/μl (range, 28-240) versus 77 cells/μl (24-217) in the groups of 0.12 and 0.24 mg/kg of plerixafor, respectively (p-value 0.255). The apheresis products contained a median of 14.4 × 10⁶ /kg recipient body weight CD34+ cells versus 12.9 × 10⁶ /kg in the groups that received 0.12 and 0.24 mg/kg of plerixafor, respectively (p-value 0.118). The obtained differences were not significant, which means the application of a decreased dose of plerixafor did not affect the results of mobilization.

CONCLUSION

The obtained differences in collection were not significant, and thus the application of a decreased dose of plerixafor did not affect the results of mobilization.

Optimized Conformal Total Body Irradiation Among Recipients of TCRαβ/CD19-Depleted Grafts in Pediatric Patients With Hematologic Malignancies: Single-Center Experience

Total body irradiation (TBI) in combination with chemotherapy is widely used as a conditioning regimen in pediatric and adult hematopoietic stem cell transplantation (HSCT). The combination of TBI with chemotherapy has demonstrated superior survival outcomes in patients with acute lymphoblastic and myeloid leukemia when compared with conditioning regimens based only on chemotherapy. The clinical application of intensity-modulated radiation therapy (IMRT)-based methods (volumetric modulated arc therapy (VMAT) and TomoTherapy) seems to be promising and has been actively used worldwide. The optimized conformal total body irradiation (OC-TBI) method described in this study provides selected dose reduction for organs at risk with respect to the most significant toxicity (lungs, kidneys, lenses). This study included 220 pediatric patients who received OC-TBI with subsequent chemotherapy and allogenic HSCT with TCRαβ/CD19 depletion. A group of 151 patients received OC-TBI using TomoTherapy, and 40 patients received OC-TBI using the Elekta Synergy™ linac with an Agility-MLC (Elekta, Crawley, UK) using volumetric modulated arc therapy (VMAT). Twenty-nine patients received OC-TBI with supplemental simultaneous boost to bone marrow-(SIB to BM) up to 15 Gy: 28 patients (pts)-TomoTherapy; one patient-VMAT. The follow-up duration ranged from 0.3 to 6.4 years (median follow-up, 2.8 years). Overall survival (OS) for all the patients was 63% (95% CI: 56-70), and event-free survival (EFS) was 58% (95% CI: 51-65). The cumulative incidence of transplant-related mortality (TRM) was 10.7% (95% CI: 2.2-16) for all patients. The incidence of early TRM (<100 days) was 5.0% (95% CI: 1.5-8.9), and that of late TRM (>100 days) was 5.7 (95% CI: 1.7-10.2). The main causes of death for all the patients were relapse and infection. The concept of OC-TBI using IMRT VMAT and helical treatment delivery on a TomoTherapy treatment unit provides maximum control of the dose distribution in extended targets with simultaneous dose reduction for organs at risk. This method demonstrated a low incidence of severe side effects after radiation therapy and predictable treatment effectiveness. Our initial experience demonstrates that OC-TBI appears to be a promising technique for the treatment of pediatric patients.

Multiple site place-of-care manufactured anti-CD19 CAR-T cells induce high remission rates in B-cell malignancy patients

Chimeric antigen receptor (CAR) T cells targeting the CD19 antigen are effective in treating adults and children with B-cell malignancies. Place-of-care manufacturing may improve performance and accessibility by obviating the need to cryopreserve and transport cells to centralized facilities. Here we develop an anti-CD19 CAR (CAR19) comprised of the 4-1BB co-stimulatory and TNFRSF19 transmembrane domains, showing anti-tumor efficacy in an in vivo xenograft lymphoma model. CAR19 T cells are manufactured under current good manufacturing practices (cGMP) at two disparate clinical sites, Moscow (Russia) and Cleveland (USA). The CAR19 T-cells is used to treat patients with relapsed/refractory pediatric B-cell Acute Lymphocytic Leukemia (ALL; n = 31) or adult B-cell Lymphoma (NHL; n = 23) in two independently conducted phase I clinical trials with safety as the primary outcome (NCT03467256 and NCT03434769, respectively). Probability of measurable residual disease-negative remission was also a primary outcome in the ALL study. Secondary outcomes include complete remission (CR) rates, overall survival and median duration of response. CR rates are 89% (ALL) and 73% (NHL). After a median follow-up of 17 months, one-year survival rate of ALL complete responders is 79.2% (95%CI 64.5‒97.2%) and median duration of response is 10.2 months. For NHL complete responders one-year survival is 92.9%, and median duration of response has not been reached. Place-of-care manufacturing produces consistent CAR-T cell products at multiple sites that are effective for the treatment of patients with B-cell malignancies.

Strategies to address the challenges associated with product manufacturing can improve chimeric antigen receptor (CAR) cell–based therapeutics. Here the authors report the results of two clinical trials in patients with B-cell malignancies, showing that place-of-care manufacturing has a low production failure rate with CD19-directed CAR-T cell products inducing high remission rates.

Post-Transplantation Immunosuppression After TCRΑβ/CD19 Graft Depletion Does Not Improve HSCT Outcomes in Primary Immunodeficiency

We recently demonstrated that TCRαβ+/CD19+ graft depletion successfully prevents severe acute and chronic graft-versus-host disease (GVHD) in pediatric patients with primary immunodeficiencies (PID) receiving transplants from both matched unrelated and mismatched related donors. However, in all patients, short-term post-hematopoietic stem cell transplantation (HSCT) immunosuppressive therapy (IST) was used. There are limited data on TCRαβ+/CD19+ graft depletion with no post-HSCT IST implementation. In the current study 74 PID patients who underwent first HSCT from matched unrelated (n=51) or mismatched related donors (n=23) with TCRαβ+/CD19+ graft depletion were included. All received as a conditioning regimen a combination of treosulfan with fludarabine and either melphalan or thiotepa. In all, thymoglobulin 5 mg/kg (days -5, -4, -3) and rituximab at day -1 were used. In 48 patients, various approaches to short-term post-transplantation IST were used, and 26 patients received no post-HSCT IST. The rates of engraftment, acute and chronic GVHD, survival, and mortality were similar in those who received and did not receive IST, with a slightly higher incidence of graft rejection in patients not receiving IST: 19% in the non-IST group against 13% in the IST group (P = .41). The incidence of cytomegalovirus reactivation was 50% and 39% (P = .50) and Epstein-Barr virus reactivation 10% and 0 (P = .20) in the IST and non-IST groups, respectively. No grade 4 adverse events were seen in both groups, although in 19 of 40 (47.5%) patients receiving calcineurin inhibitors, the therapy was discontinued before day 45. More robust immune recovery with both T- and B-lymphocytes was observed in the non-IST group. To conclude, TCRαβ+/CD19+ in combination with particular serotherapy effectively prevents severe acute and chronic GVHD in PID. Regarding remaining risks of infectious complications and additional drug-related toxicity, there are no benefits to post-HSCT IST use in these patients.

Efficacy and safety of ruxolitinib in ineffective erythropoiesis suppression as a pretransplantation treatment for pediatric patients with beta-thalassemia major

BACKGROUND

Ineffective erythropoiesis (IE) is the most prominent feature of transfusion-dependent beta-thalassemia (TDT), which leads to extramedullary hemopoiesis. The rejection rate in allogeneic hematopoietic stem cell transplantation (HSCT) is high in heavily transfused patients with TDT accompanied by prominent IE. Therefore, a pretransplantation treatment bridging to HSCT is often used to reduce allosensitization and IE. Ruxolitinib is a JAK-1/JAK-2 inhibitor and has showed its efficacy in suppressing IE and the immune system. A previously published study on RUX in adult patients with TDT has revealed that this treatment significantly reduces spleen size and is well tolerated.

PROCEDURE

Ten patients (5-14 years old) with TDT and an enlarged spleen were enrolled. The dose of ruxolitinib was adjusted for age: for patients <11 years: 40-100 mg/m² total daily dose and for patients >11 years: 20-30 mg/m² total daily dose. HSCT was performed in 8 of 10 patients.

RESULTS

After the first 3 months of ruxolitinib therapy, spleen volume decreased in 9 of 10 cases by 9.1%-67.5% (M = 35.4%) compared with the initial size (P = 0.003). The adverse events of ruxolitinib (infectious complications, moderate thrombocytopenia, and headache) were successfully managed by reducing the dose. The outcomes of HSCT were favorable in seven of eight cases.

CONCLUSION

Ruxolitinib is promising as a short-term pre-HSCT treatment for pediatric patients with TDT and pronounced IE.

Immunophenotypic changes of leukemic blasts in children with relapsed/refractory B-cell precursor acute lymphoblastic leukemia, who have been treated with Blinatumomab

Not available.

Blinatumomab following haematopoietic stem cell transplantation - a novel approach for the treatment of acute lymphoblastic leukaemia in infants

Blinatumomab with subsequent haematopoietic stem cell transplantation was applied in 13 infants with acute lymphoblastic leukaemia (ALL). Eight patients were treated in first remission due to slow clearance of minimal residual disease (MRD); one for MRD-reappearance after long MRD negativity, one for primary refractory disease and three during relapse treatment. In slow MRD responders, complete MRD response was achieved prior to transplantation, with an 18-month event-free survival of 75%. In contrast, only one of five patients with relapsed/refractory ALL is still in complete remission. These data provide a basis for future studies of immunotherapy in very high-risk infant ALL.

Relative expansion of CD19-negative very-early normal B-cell precursors in children with acute lymphoblastic leukaemia after CD19 targeting by blinatumomab and CAR-T cell therapy: implications for flow cytometric detection of minimal residual disease

CD19-directed treatment in B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) frequently leads to the downmodulation of targeted antigens. As multicolour flow cytometry (MFC) application for minimal/measurable residual disease (MRD) assessment in BCP-ALL is based on B-cell compartment study, CD19 loss could hamper MFC-MRD monitoring after blinatumomab or chimeric antigen receptor T-cell (CAR-T) therapy. The use of other antigens (CD22, CD10, CD79a, etc.) as B-lineage gating markers allows the identification of CD19-negative leukaemia, but it could also lead to misidentification of normal very-early CD19-negative BCPs as tumour blasts. In the current study, we summarized the results of the investigation of CD19-negative normal BCPs in 106 children with BCP-ALL who underwent CD19 targeting (blinatumomab, n = 64; CAR-T, n = 25; or both, n = 17). It was found that normal CD19-negative BCPs could be found in bone marrow after CD19-directed treatment more frequently than in healthy donors and children with BCP-ALL during chemotherapy or after stem cell transplantation. Analysis of the antigen expression profile revealed that normal CD19-negative BCPs could be mixed up with residual leukaemic blasts, even in bioinformatic analyses of MFC data. The results of our study should help to investigate MFC-MRD more accurately in patients who have undergone CD19-targeted therapy, even in cases with normal CD19-negative BCP expansion.

Serotherapy-Free Regimen Improves Non-Relapse Mortality and Immune Recovery Among the Recipients of αβ TCell-Depleted Haploidentical Grafts: Retrospective Study in Childhood Leukemia

Depletion of αβ T cells from the graft prevents graft-versus-host disease (GVHD) and improves the outcome of hematopoietic stem cell transplantation (HSCT) from haploidentical donors. Delayed recovery of adaptive immunity remains a problem, which can be approached by adoptive T-cell transfer. In a randomized trial, we have assessed the safety and efficacy of low-dose memory (CD45RA-depleted) donor lymphocytes (mDLI) after HSCT with αβ T-cell depletion. Antithymocyte globulin (ATG) is viewed as an essential component of preparative regimen, critical for both prevention of graft failure and GVHD. Variable pharmacokinetics of ATG may significantly affect lymphocyte subpopulations after HSCT. To uncover the potential of mDLI, we replaced rabbit ATG with tocilizumab and abatacept. Here we compare post hoc the immune recovery and the key clinical outcomes, including nonrelapse mortality (NRM), overall- and event-free survival (OS and EFS), between the cohort enrolled in the prospective randomized trial and a historical cohort, comprised of patients grafted with a conventional ATG-based HSCT with αβ T cell depletion. A cohort of 149 children was enrolled in the prospective trial and 108 patients were selected as historical controls from a prospectively populated database. Patient population was comprised of children with high-risk hematologic malignancies, with more than 90% represented by acute leukemia. Median age at enrollment was 8.8 years. In the prospective cohort 91% of the donors were haploidentical parents, whereas in the historical cohort 72% of the donors were haploidentical. Conditioning was based on either 12Gy total body irradiation or treosulfan. Thiotepa, fludarabine, bortezomib, and rituximab were used as additional agents. Patients in the historical cohort received rabbit ATG at 5 mg/kg total dose, while prospective cohort patients received tocilizumab at 8 mg /kg on day -1 and abatacept at 10 mg/kg on days 0, 7, 14, and 28. Patients in the prospective trial cohort were randomized 1:1 to receive mDLI starting on day 0, whereas 69% of historical cohort patients received mDLI after engraftment, as part of previous trials. Primary engraftment rate was 99% in the prospective cohort and 98% in the historical cohort. The incidence of grade II-IV aGVHD was 13% in the prospective cohort and 16 % in the control group. Chronic GVHD developed among 13% (historical) and 7% (prospective) cohorts (P = .07). The incidence of cytomegalovirus viremia was 51% in the prospective cohort arm and 54% in the historical control arm (p = ns). Overall, in the prospective cohort 2-year NRM was 2%, incidence of relapse was 25%, EFS was 71%, and OS was 80%, whereas in the historical cohort 2-year NRM was 13%, incidence of relapse was 19%, EFS was 67%, and OS was 76%, difference non-significant for relapse and survival. NRM was significantly improved in the ATG-free cohort (P = .002). Recovery of both αβ- and γδ- T cells was significantly improved at days +30 and +60 after HSCT in recipients of ATG-free preparative regimens, as well as recovery of naïve T cells. Among the recipients of αβ T-cell-depleted grafts, replacement of ATG with nonlymphodepleting abatacept and tocilizumab immunomodulation did not compromise engraftment and GVHD control and was associated with significantly lower NRM and better immune recovery early after HSCT.

T-cell tracking, safety, and effect of low-dose donor memory T-cell infusions after αβ T cell-depleted hematopoietic stem cell transplantation

The delayed recovery of adaptive immunity underlies transplant-related mortality (TRM) after αβ T cell-depleted hematopoietic stem cell transplantation (HSCT). We tested the use of low-dose memory donor lymphocyte infusions (mDLIs) after engraftment of αβ T cell-depleted grafts.A cohort of 131 pediatric patients (median age 9 years) were grafted with αβ T cell-depleted products from either haplo (n = 79) or unrelated donors (n = 52). After engraftment, patients received mDLIs prepared by CD45RA depletion. Cell dose was escalated monthly from 25 × 10³ to 100 × 10³/kg (haplo) and from 100 × 10³ to 300 × 10³ /kg (MUD). In a subcohort of 16 patients, T-cell receptor (TCR) repertoire profiling with deep sequencing was used to track T-cell clones and to evaluate the contribution of mDLI to the immune repertoire.In total, 343 mDLIs were administered. The cumulative incidence (CI) of grades II and III de novo acute graft-versus-host disease (aGVHD) was 5% and 2%, respectively, and the CI of chronic graft-versus-host disease was 7%. Half of the patients with undetectable CMV-specific T cells before mDLI recovered CMV-specific T cells. TCR repertoire profiling confirmed that mDLI-derived T cells significantly contribute to the TCR repertoire up to 1 year after HSCT and include persistent, CMV-specific T-cell clones.

BCG-Related Inflammatory Syndromes in Severe Combined Immunodeficiency After TCRαβ+/CD19+ Depleted HSCT

INTRODUCTION

The live-attenuated BCG vaccine is known to cause disseminated Mycobacterium bovis infection in patients with severe combined immunodeficiency (SCID). However, BCG-related post-hematopoietic stem cell transplantation (HSCT) immune reconstitution inflammatory syndromes, similar to those described in patients with HIV infections, are less-known complications of SCID.

PATIENTS AND METHODS

We reported on 22 BCG-vaccinated SCID patients who had received conditioned allogeneic HSCT with TCRαβ+/CD19+ graft depletion. All BCG-vaccinated patients received anti-mycobacterial therapy pre- and post-HSCT. Post-transplant immunosuppression consisted of tacrolimus in 10 patients and of 8 mg/kg tocilizumab (d-1, + 14, + 28) and 10 mg/kg abatacept (d-1, + 5, + 14, + 28) in 11 patients.

RESULTS

Twelve patients, five of whom had BCG infection prior to HSCT, developed BCG-related inflammatory syndromes (BCG-IS). Five developed early BCG-IS with the median time of manifestation 11 days after HSCT, corresponding with a dramatic increase of CD3+TCRγδ+ in at least two patients. Early BCG-IS was noted in only one out of 11 patients who received tocilizumab/abatacept and 4 out of 11 patients who did not. Seven patients developed late BCG-IS which corresponded to T cell immune recovery; at the time of manifestation (median 4.2 months after HSCT), the median number of CD3+ cells was 0.42 × 10⁹/ and CD3+CD4+ cells 0.27 × 10⁹/l. In all patients, late BCG-IS was controlled with IL-1 or IL-6 inhibitors.

CONCLUSION

BCG-vaccinated SCID patients undergoing allogeneic HSCT with TCRαβ+/CD19+ graft depletion are at an increased risk of early and late BCG-IS. Anti-inflammatory therapy with IL-1 and IL-6 blockade is efficient in the prevention of early and treatment of late BCG-IS.

Control of graft-versus-host disease with rabbit anti-thymocyte globulin, rituximab, and bortezomib in TCRαβ/CD19-depleted graft transplantation for leukemia in children: a single-center retrospective analysis of two GVHD-prophylaxis regimens

Both acute GVHD and chronic GVHD remain the leading cause of morbidity and death after allogeneic HSCT. We conducted a retrospective analysis comparing two GVHD-prophylaxis regimens: 35 patients received "Regimen 1" (horse ATG, tacrolimus, and methotrexate) and 46 "Regimen 2" (rabbit ATG, rituximab, and peritransplant bortezomib). All 81 patients with a median age of 9 (0.6-23) years with ALL (n = 31) or AML (n = 50) in complete remission received TCRαβ/CD19-depleted transplants between May 2012 and October 2016, from 40 HLA-matched unrelated and 41 haploidentical donors. After a median follow-up of 3.9 years, the CI of acute GVHD II-IV was 15% (95% CI: 7-30) in the "Regimen 2" group and 34% (95% CI: -54) in the "Regimen 1" group, P = .05. "Regimen 2" was also more effective in the prevention of chronic GVHD; the CI at 1 year after HSCT was 7% (95% CI: 2-19) vs 31% (95% CI: 19-51), P = .005. The CI of relapse at 3 years adjusted for the GVHD-prophylaxis regimen groups 31% (95% CI: 19-51) for the "Regimen 1" vs 21% (95% CI: 11-37) for the "Regimen 2", P = .3. The retrospective observation suggests that the use of the rATG, rituximab, and bortezomib was associated with significantly lower rate of GVHD without the loss of anti-leukemic activity.

αβ T Cell-Depleted Haploidentical Hematopoietic Stem Cell Transplantation without Antithymocyte Globulin in Children with Chemorefractory Acute Myelogenous Leukemia

We evaluated the outcome of αβ T cell-depleted haploidentical hematopoietic stem cell transplantation (HSCT) in a cohort of children with chemorefractory acute myelogenous leukemia (AML). Twenty-two patients with either primary refractory (n = 10) or relapsed refractory (n = 12) AML in active disease status received a transplant from haploidentical donors. The preparative regimen included cytoreduction with fludarabine and cytarabine and subsequent myeloablative conditioning with treosulfan and thiotepa. Antithymocyte globulin was substituted with tocilizumab in all patients and also with abatacept in 10 patients. Grafts were peripheral blood stem cells engineered by αβ T cell and CD19 depletion. Post-transplantation prophylactic therapy included infusion of donor lymphocytes, composed of a CD45RA-depleted fraction with or without a hypomethylating agent. Complete remission was achieved in 21 patients (95%). The cumulative incidence of grade II-IV acute graft-versus-host disease (GVHD) was 18%, and the cumulative incidence of chronic GVHD was 23%. At 2 years, transplantation-related mortality was 9%, relapse rate was 42%, event-free survival was 49%, and overall survival was 53%. Our data suggest that αβ T cell-depleted haploidentical HSCT provides a reasonable chance of long-term survival in a cohort of children with chemorefractory AML and creates a solid basis for further improvement.

Low-dose donor memory T-cell infusion after TCR alpha/beta depleted unrelated and haploidentical transplantation: results of a pilot trial

Recovery of immunity is delayed in recipients of T-depleted grafts. Adoptive transfer of memory T-cells may improve immune response to common pathogens. A cohort of 53 patients with malignant (n = 36) and non-malignant conditions (n = 17) received TCR alpha/beta depleted grafts from haploidentical (n = 25) or MUD (n = 28) donors. Donor lymphocytes were depleted of CD45RA-positive cells. At a median of 48 days after transplantation, patients received DLI at 25 × 10³/kg CD3 cells from haploidentical or 100 × 10³/kg CD3 from MUD donors. Up to 3 doses of donor lymphocytes were administered at monthly intervals, escalating to 100 × 10³/kg in haploidentical transplants and 300 × 10³/kg in MUD transplants. At a median follow-up of 23 months, the cumulative incidence of de novo acute GVHD after DLI is 2% (1 of 43), while the rate of reactivation of preexisting aGVHD was 50% (5 of 10). The transplant-related mortality is 6%. The overall survival rates are 80% and 88% in malignant and non-malignant conditions, respectively. Among patients with absent CMV-specific immune reactivity at baseline (n = 31) expansion of CMV-specific T-cells was demonstrated in 20 (64.5%) within 100 days. Infusions of low dose donor memory T-lymphocytes are safe and constitute a simple measure to prevent infections in the setting of alpha/beta T cell-depleted transplantation.

Prospective Study of a Cohort of Russian Nijmegen Breakage Syndrome Patients Demonstrating Predictive Value of Low Kappa-Deleting Recombination Excision Circle (KREC) Numbers and Beneficial Effect of Hematopoietic Stem Cell Transplantation (HSCT)

BACKGROUND

Nijmegen breakage syndrome (NBS) is a combined primary immunodeficiency with DNA repair defect, microcephaly, and other phenotypical features. It predominantly occurs in Slavic populations that have a high frequency of carriers with the causative NBN gene c.657_661del5 mutation. Due to the rarity of the disease in the rest of the world, studies of NBS patients are few. Here, we report a prospective study of a cohort of Russian NBS patients.

METHODS

35 Russian NBS patients of ages 1-19 years, referred to our Center between years 2012 and 2016, were prospectively studied.

RESULTS

Despite the fact that in 80% of the patients microcephaly was diagnosed at birth or shortly thereafter, the average delay of NBS diagnosis was 6.5 years. Though 80% of the patients had laboratory signs of immunodeficiency, only 51% of the patients experienced significant infections. Autoimmune complications including interstitial lymphocytic lung disease and skin granulomas were noted in 34%, malignancies-in 57% of the patients. T-cell excision circle (TREC)/kappa-deleting recombination excision circle (KREC) levels were low in the majority of patients studied. Lower KREC levels correlated with autoimmune and oncological complications. Fifteen patients underwent hematopoietic stem cell transplantation (HSCT), 10 of them were alive and well, with good graft function. Three patients in the HSCT group and five non-transplanted patients died; tumor progression being the main cause of death. The probability of the overall survival since NBS diagnosis was 0.76 in the HSCT group and 0.3 in the non-transplanted group.

CONCLUSION

Based on our findings of low TRECs in most NBS patients, independent of their age, TREC detection can be potentially useful for detection of NBS patients during neonatal screening. KREC concentration can be used as a prognostic marker of disease severity. HSCT is a viable treatment option in NBS and should be especially considered in patients with low KREC numbers early on, before development of life-threatening complications.

TCR-alpha/beta and CD19 depletion and treosulfan-based conditioning regimen in unrelated and haploidentical transplantation in children with acute myeloid leukemia

We evaluated the depletion of TCR-alpha/beta cells from the graft of children with high-risk AML, who received transplantation from unrelated (n=20) and haploidentical donors (n=13). The preparative regimen included treosulfan, melphalan, fludarabine and anti-thymocyte globulin. Grafts were PBSC engineered by TCR-alpha/beta and CD19 depletion. The graft contained a median of 9 × 10(6)/kg of CD34+ and 20 × 10(3)/kg of αβ-T cells. Post-transplant immune suppression included tacrolimus till day +30 and Mtx in 21 patients, tacrolimus in 5, Mtx in 2 and no prophylaxis in 5 patients. Sixteen patients received native or TCR-alpha/beta-depleted donor lymphocytes at a median of 47 (40-204) days. Median follow-up is 1.76 years. Primary engraftment was achieved in 33 patients (100%). Cumulative incidence of acute GvHD (aGvHD) grade 2-3 was 39 (26-60)%, half of them had skin-only aGvHD. Cumulative incidence of chronic GvHD was 30(18-50)%. Transplant-related mortality is 10(4-26)%. Event-free survival (EFS) is 60(43-76)% and overall survival (OS) is 67(50-84)% at 2 years. In a subgroup of patients, who received transplantation in CR, EFS is 66(48-84)% and OS-72(53-90)% at 2 years. Our data suggest that TCR-alpha/beta and CD19 depletion is a robust method of graft manipulation, which can be used to engineer grafts for children with AML.

Single-Center Experience of Unrelated and Haploidentical Stem Cell Transplantation with TCRαβ and CD19 Depletion in Children with Primary Immunodeficiency Syndromes

The transplantation of stem cells from a matched unrelated donor (MUD) or a haploidentical mismatched related donor (MMRD) is a widely used variant of curative treatment for patients with primary immunodeficiency (PID). Currently, different strategies are used to reduce the risk of post-transplant complications and enhance immune reconstitution. We report the preliminary results of MUD and MMRD transplantation with TCRαβ/CD19 depletion in patients with PID (trial registered at www.clinicaltrials.gov as NCT02327351). Thirty-seven PID patients (median age, 2.6 years; range, .2 to 17) were transplanted from MUDs (n = 27) or haploidentical MMRDs (n = 10) after TCRαβ(+)/CD19(+) graft depletion. The median numbers of CD34(+) and TCRαβ(+) cells in the graft were 11.7 × 10(6)/kg and 10.6 × 10(3)/kg, respectively. Acute graft-versus-host disease (GVHD) was observed in 8 patients (22%), without a statistically significant difference between MUDs and MMRDs; 7 of these patients had grade II acute GVHD and responded to first-line therapy, whereas 1 patient had grade IV acute GVHD with transformation to extensive chronic GVHD. Primary and secondary graft failure (nonengraftment or rejection) was observed in 10 patients (27%), 9 of whom were treated with 1 alkylating agent in the conditioning regimen. All these patients were successfully retransplanted with different rescue protocols. Preliminary data on immune reconstitution were very encouraging. Most patients had significant numbers of T lymphocytes detected on the first assessment (day +30) and more than 500 T cells/μL, on day +120. Based on our preliminary data, no significant difference was seen between MMRD and MUD hematopoietic stem cell transplantation (HSCT). With a median follow-up period of 15 months, the cumulative probabilities of overall patient survival and transplant-related mortality were 96.7% and 3.3%, respectively. Based on the results, the ability to control the main post-transplant complications and the immune reconstitution rates are the main factors leading to successful outcome in patients with PID after TCRαβ(+)-depleted HSCT.

Alkylator-free conditioning regimen for patients with acquired aplastic anemia, transplanted from genetically identical twins

Allogeneic stem cell transplantation remains the best option for young patients with SAA. With genetically identical twin as an ideal donor, the majority of SAA patients require appropriate immunosuppression before and after stem cell transplantation to obtain long-term hematopoietic reconstitution. Alkylating agents, used during conditioning, are associated with short- and long-term toxic effects that lead to poor compliance of treatment and could compromise the quality of future life. Three SAA patients, transplanted from genetically identical twins without using alkylating agents during conditioning, showed rapid and sustained hematological reconstitution without any evidence of conditioning-related toxicity.