Efficacy of low dose antithymocyte globulin on overall survival, relapse rate, and infectious complications following allogeneic peripheral blood stem cell transplantation for leukemia in children

A Comparative Analysis of Low Dose Grafalon® Versus Thymoglobuline® as Serotherapy in Hematopoietic Stem Cell Transplant in Pediatric and Young Adult Population

Anti-thymocyte globulin (ATG) forms an essential component of conditioning in hematopoietic stem cell transplantation (HSCT). Due to the shift of donor preference to alternate donors, reliance on rabbit-ATG (rATG) has increased. Two different forms of rATG (Thymoglobuline® and Grafalon®) are available for clinical use but data to support the use of one over the other is sparse. We retrospectively analyzed data of 144 patients who underwent allogenic-HSCT for benign hematological conditions at our center, from August 2019 to August 2023. Of these, 87 received Grafalon® and 57 received Thymoglobuline®. The majority (77.7%) underwent HSCT for hemoglobinopathies and all received pre-transplant immunosuppression. Engraftment kinetics was similar in 2 cohorts. Six patients had primary graft failure (PGF). There was no difference in the incidence of PGF stratified by serotherapy. Overall survival(OS) for the cohort was 74.9%. Kaplan-Meier estimate of OSand EFSwas significantly better in Grafalon® group than Thymoglobuline® (84.4 ± 0.04% vs 64.1% ±0.065%) (p-value= 0.04%) and (84.4 ± 0.04% and 61.2%±0.065% (p-value = 0.01)). Extensive chronic GVHD was (14%) higher in Thymoglobuline® group and (2.3%) in Grafalon®. Immune reconstitution at day + 100 was not statistically different between the two groups. On univariate analysis, Thymoglobuline® serotherapy (OR (95% CI) =4.665 (1.2-18.04))was associated with increased risk of acute grade III-IV GvHD. In our study, Grafalon® tended to have better OS, decreased incidence of acute grade III-IV GvHD, and extensive cGVHD. There was no difference in engraftment kinetics, PGF, and immune reconstitution between 2 cohorts of serotherapy.

Anti-thymocyte globulin combined with post-transplantation cyclophosphamide reduce graft-versus-host disease in hematopoietic stem cell transplantation for pediatric leukemia

This retrospective analysis evaluated the use of anti-thymocyte globulin (ATG) with or without post-transplantation cyclophosphamide (PTCy) for graft-versus-host disease (GvHD) prophylaxis in children with acute leukemia undergoing hematopoietic stem cell transplantation (HSCT). The study included 57 children, with 35 in the ATG-PTCy group and 22 in the ATG group. While overall incidence of acute and chronic GvHD did not differ significantly between groups, the ATG-PTCy group had lower rates of grade II-IV acute GvHD (p = 0.013) and moderate-to-severe chronic GvHD (p = 0.001) compared to the ATG group. Importantly, ATG-PTCy significantly improved GvHD/relapse-free survival (GRFS) compared to ATG (65.71% vs. 36.63%; p = 0.003). There were no differences in engraftment, infection rates, immune reconstitution, overall survival, leukemia-free survival, relapse rate, or non-relapse mortality between the two groups. Combining ATG with PTCy may reduce moderate-to-severe GvHD and improve GRFS in children undergoing HSCT for acute leukemia.

Improving Outcomes with Haploidentical Stem Cell Transplantation [HaploSCT] in Children Using Post-transplant Cyclophosphamide: a Single Center Experience

Haplo-identical stem cell transplant using post-transplant cyclophosphamide is increasingly being used in children without a matched sibling donor. Between 2010 and June 2021, 127 children underwent 138 transplants with a median age of 7.1 years for malignant and non-malignant disorders. Conditioning regimens included both myeloablative and reduced intensity regimens with peripheral blood stem cells as the main graft source. Engraftment occurred in 113 [81.9%] at a median of 16 days [range: 10-32] with primary graft failure in 10.2%. Cumulative incidence of grade II-IV acute graft versus host disease (GVHD) was 49.5% and chronic GVHD in 40.7%. Majority [92.7%] had at least one infection with 31% incidence of bacterial infection, 76% incidence of viral and 16% incidence of fungal infection. The 2-year overall survival (OS) is 54.9 ± 4.6% with a lower survival among young children aged 0-5 years [28.2 ± 6.4%] compared to 5-10 years [71.3 ± 6.8%] and 11-15 years [55.7 ± 8.8%] [p = 0.032]. 2-year OS has gradually improved from 25.0 ± 2.1% for 2010-2013 to 47.5 ± 6.2% for 2014-2017 and 67.1 ± 6.6% for 2018-2021 [p = 0.049]. On multivariate analysis, bacterial infection [p = 0.017], invasive fungal disease [p = 0.002] and graft failure [p = 0.029] negatively impacted overall survival. Haplo-identical SCT with post-transplant cyclophosphamide is a reasonable option for children who do not have a matched sibling donor. Strategies to reduce graft failure, infection related mortality and GVHD needs to be explored.

Individualized dose of anti-thymocyte globulin based on weight and pre-transplantation lymphocyte counts in pediatric patients: a single center experience

Anti-thymocyte globulin (ATG) has become a standard in preventing GVHD in related and unrelated donor transplantation, but there is no consensus on the best administration schedule. The PARACHUTE trial reported excellent CD4 immune reconstitution (CD4 IR) using a dosing schedule based on the patient's weight and pre-conditioning absolute lymphocyte count (ALC). In 2015 we introduced the PARACHUTE dosing schedule for pediatric patients at our center. One hundred one patients were transplanted for malignant and non-malignant diseases. In this non-concurrent cohort CD4 IR+, defined by a single CD4 count >50/µL on day 90, was seen in 81% of patients. The incidence of grade II-IV and III to IV aGvHD was 26.6% and 15.3% and 5% for cGvHD with no severe cases. We found no difference in aGvHD between donor type and stem cell sources. Five-year EFS and OS were 77.5% and 83.5%. Grade III-IV GFRS was 75.2%. CD4 IR+ patients had better EFS (93.1% vs. 77.7%, p = 0.04) and lower non-relapse mortality (2.7% vs. 22.2%, p = 0.002). The PARACHUTE ATG dosing schedule individualized by weight and ALC results in good early immune reconstitution, low incidence of cGvHD, and favorable survival for patients with different disease groups, donor types, and stem cell sources.

Impact of anti-thymocyte globulin on survival outcomes in female-to-male allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic cell transplantation between female donors and male recipients (female-to-male allo-HCT) is a well-established risk factor for inferior survival outcomes due to a higher incidence of graft-versus-host disease (GVHD). However, a clinical significance of anti-thymocyte globulin (ATG) in the female-to-male allo-HCT has not been elucidated. In this study, we retrospectively evaluated male patients who underwent allo-HCT between 2012 and 2019 in Japan. In the female-to-male allo-HCT cohort (n = 828), the use of ATG was not associated with a decreased risk of GVHD (HR of acute GVHD 0.691 [95% CI: 0.461-1.04], P = 0.074; HR of chronic GVHD 1.06 [95% CI: 0.738-1.52], P = 0.76), but was associated with favorable overall survival (OS) and a decreased risk of non-relapse mortality (NRM) (HR of OS 0.603 [95% CI: 0.400-0.909], P = 0.016; HR of NRM 0.506 [95% CI: 0.300-0.856], P = 0.011). The use of ATG in female-to-male allo-HCT resulted in survival outcomes that were almost equivalent to those in the male-to-male allo-HCT group. Therefore, GVHD prophylaxis with ATG might overcome the inferiority of survival outcomes in female-to-male allo-HCT.

Prognostic impact of total body irradiation dose in pediatric acute lymphoblastic leukemia patients treated with allogeneic hematopoietic stem cell transplantation in second complete remission

Background

Allogeneic HSCT may improve survival in pediatric ALL patients who relapse. In this study, we analyzed the outcome and prognostic factors of 62 ALL patients (35 male, 56.5%) who received allogeneic HSCT in second complete remission (CR) at our institution between April 1st 2009 and December 31st 2019.

Methods

The median time from diagnosis to relapse was 35.1 months (range, 6.0‒113.6 mo). Fifty-three patients (85.5%) experienced bone marrow relapse only. The number of patients who received transplant according to each donor type was as follows: HLA matched family donor 17 (27.4%), matched unrelated donor (UD) 22 (35.5%), mismatched donor 23 (37.1%). All patients received HSCT with a myeloablative conditioning, 58 patients (93.5%) with the incorporation of TBI [31 patients 12 Gray (Gy), 24 patients 13.2 Gy, 3 patients 8 Gy].

Results

The 5-year event-free survival (EFS), and overall survival of the study group was 41.3±6.3% (26/62), and 42.3±6.6% (27/62), respectively. The cumulative incidence of relapse and transplant-related mortality was 57.1±6.4% and 1.6±1.6%, respectively. Infant ALL, shorter time from diagnosis to relapse, and TBI dose of 12 Gy, rather than 13.2 Gy, resulted in significantly worse EFS. In multivariate analysis, infant ALL and TBI dose of 12 Gy during conditioning predicted significantly lower EFS.

Conclusion

In our study group, treatment with a higher dose of TBI during conditioning resulted in better EFS for ALL patients who underwent HSCT in second CR. Further study is needed to determine potential long-term complications associated with a higher TBI dose.

Features of cytomegalovirus infection and evaluation of cytomegalovirus-specific T cells therapy in children’s patients following allogeneic hematopoietic stem cell transplantation: A retrospective single-center study

Cytomegalovirus (CMV) infection remains a critical cause of mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT), despite improvement by pre-emptive antivirus treatment. CMV-specific cytotoxic T lymphocytes (CMV-CTL) are universally used and proven well-tolerance after allo-HSCT in adult clinical trials. However, it is not comprehensively evaluated in children’s patients. Herein, we conducted a retrospective study to determine the risk factors of CMV infection and evaluation of CMV-CTL in children patients who underwent allo-HSCT. As result, a significantly poor 5-year overall survival was found in the CMV infection group (87.3 vs. 94.6%, p=0.01). Haploidentical HSCT (haplo-HSCT) was identified as an independent risk factor for CMV infection through both univariate and multivariate analyses (p<0.001, p=0.027, respectively). Furthermore, the cumulative incidence of CMV infection was statistically higher in the haplo-HSCT group compared to the HLA-matched donor group (44.2% vs. 21.6%, p<0.001). Finally, the overall response rate of CMV-CTL was 89.7% (26/29 patients) in CMV infection after allo-HSCT. We concluded that CMV infection following allo-HSCT correlated with increased mortality in children’s patients, and haplo-HSCT was an independent risk factor for CMV infection. Adoptive CMV-CTL cell therapy was safe and effective in pediatric patients with CMV infection.

The Potential Association of Delayed T Lymphocyte Reconstitution Within Six Months Post-Transplantation With the Risk of Cytomegalovirus Retinitis in Severe Aplastic Anemia Recipients

Background

Delayed immune reconstitution after allogeneic hematopoietic stem cell transplantation (HSCT) is significantly associated with cytomegalovirus (CMV) infection. The aim of this study was to observe the recovery trend of peripheral lymphocyte subsets and immunoglobulins in HSCT recipients who developed CMV retinitis (CMVR).

Methods

We identified 37 CMVR cases and 303 non-CMVR controls in this case-control study from a database of 404 consecutive severe aplastic anemia patients who received allogeneic HSCT at a single center between 2015 and 2020. We analyzed the transplant outcomes and immune reconstitution principles with a focus on lymphocyte CD series and immunoglobulin series within the first year post-HSCT.

Results

Thirty-seven patients (55 eyes) were diagnosed with CMVR, with a mean onset time of 155 days post-HSCT. Among the 37 patients, one never had CMV detected in his blood but had a high CMV load in his intraocular fluid at the time of CMVR diagnosis. In the controls, 195 had CMV viremia and 108 did not. Compared with controls, CMVR cases had a longer duration of CMV viremia and a higher peak number of CMV load. T lymphocyte subsets including CD3, CD4 and CD8 were significantly lower in CMVR cases within six months after HSCT (all p < 0.05). Immunoglobulins also showed a slower recovery trend in CMVR cases. The recovery of B lymphocytes and natural killer cells exhibited no significant differences between the two groups.

Conclusions

It is not enough to develop fundus screening strategies by merely relying on the CMV serostatus of recipients. Dynamic and continuous monitoring of T lymphocyte subsets, especially within six months post-HSCT, as well as serum immunoglobulin levels, can provide assistance with screening program of CMVR in HSCT recipients with severe aplastic anemia.

A Case of Disseminated Herpes Zoster Presenting as Vesicles Limited to Skin Lesions with Lymphoma Cutis Involvement

After primary infection, varicella zoster virus (VZV) causes prolonged latent infections that may reactivate, depending on the immunologic status of the host. We present a case of VZV reactivation in a 10-year-old male patient that underwent unrelated peripheral blood stem cell transplantation (uPBSCT) for T-lymphoblastic lymphoma with lymphoma cutis lesions. This patient had a history of herpes zoster involving the right L2-5 dermatome and trigeminal V1 dermatome prior to uPBSCT. Three months post-uPBSCT, the patient’s underlying disease relapsed, and the patient presented with lymphoma cutis lesions. A few days after a skin biopsy was performed to pathologically confirm skin relapse, vesicles appeared only involving the skin areas with lymphoma cutis. This case illustrates how decreased areas of epidermal immune mechanisms may cause atypical presentations of varicella infection.

Adverse Effects of Immunosuppression: Infections

Immunosuppressive therapies are currently indicated for a wide range of diseases. As new agents emerge and indications evolve the landscape grows increasingly complex. Therapies can target pathologic immune system over-activation in rheumatologic or autoimmune disease, or conditioning and graft versus host disease (GVHD) prophylactic regimens may eliminate or inhibit host immune function to improve graft survival and risk of complication in solid organ transplantation (SOT) or hematopoietic stem cell transplantation (HSCT). With immunosuppressive therapy, infections occur. Complex disease states, host factors, and concomitant therapies contribute to a "net state" of immunosuppression that must be considered and may confound perceived increased infection risks in patients receiving treatment.

Clinical characteristics and viral load patterns in children with cytomegalovirus gastrointestinal disease after allogeneic hematopoietic stem cell transplantation

Cytomegalovirus (CMV) reactivation in allogeneic hematopoietic stem cell transplantation (allo-HSCT) causes significant morbidity and mortality. This study aimed to investigate the clinical characteristics of children diagnosed with CMV GI disease after allo-HSCT. This was a retrospective cohort study of patients <19 years old that underwent allo-HSCT during an 11-year period. Of the 756 patients, 55.5% (n = 420) experienced post-transplant CMV DNAemia, 2.9% (n = 22) were diagnosed with proven CMV GI diseases, and the highest incidence was found in familial mismatched donors (5.6%, P = 0.029). CMV GI disease was diagnosed <100 days of transplant in 68.2% (n = 15/22), and 13.6% (n = 3/22) did not have concurrent CMV DNAemia. Patients were divided into five groups based on the patterns of CMV viremia initiation and duration post-HSCT. At 3 months post-transplant, lower CD4+ (P = 0.006) and CD8+ (P = 0.011) T-cell counts were observed in patients with waxing and waning CMV viral load titers >100 days post-transplant (groups 1-3) compared to those with CMV DNAemia only prior to 100 days post-transplant and those without concurrent CMV DNAemia (groups 4-5). A higher 1-year all-cause mortality was observed in groups 1-3 compared to groups 4-5 (42.8% vs. 0%; P = 0.051). Active surveillance and aggressive management of CMV reactivation is crucial, especially in children with delayed CD4+ and CD8+ T-cell reconstitution after allo-HSCT.

Serotherapy as Graft-Versus-Host Disease Prophylaxis in Haematopoietic Stem Cell Transplantation for Acute Lymphoblastic Leukaemia

Serotherapy comprising agents such as anti-thymocyte globulin, anti-T-lymphocyte globulin, and the anti-CD52 monoclonal antibody alemtuzumab is used widely to reduce the incidence of graft-versus-host disease (GvHD) after paediatric haematopoietic stem cell transplantation (HSCT). The outcome of transplants using matched unrelated donors now approaches that of matched sibling donors. This is likely due to better disease control in recipients, the use of donors more closely human-leukocyte antigen (HLA)-matched to recipients, and more effective graft-versus-host disease (GvHD) prophylaxis. The price paid for reduced GvHD is slower immune reconstitution of T cells and thus more infections. This has led to studies looking to optimise the amount of serotherapy used. The balance between prevention of GvHD on one side and prevention of infections and relapse on the other side is quite delicate. Serotherapy is given with chemotherapy-/radiotherapy-based conditioning prior to HSCT. Due to their long half-lives, agents used for serotherapy may be detectable in patients well after graft infusion. This exposes the graft-infused T cells to a lympholytic effect, impacting T-cell recovery. As such, excessive serotherapy dosing may lead to no GvHD but a higher incidence of infections and relapse of leukaemia, while under-dosing may result in a higher chance of serious GvHD as immunity recovers more quickly. Individualised dosing is being developed through studies including retrospective analyses of serotherapy exposure, population pharmacokinetic modelling, therapeutic drug monitoring in certain centres, and the development of dosing models reliant on factors including the patient's peripheral blood lymphocyte count. Early results of "optimal" dosing strategies for serotherapy and conditioning chemotherapy show promise of improved overall survival.