Pharmacokinetic and Pharmacodynamic Characteristics of Tripegfilgrastim, a Pegylated G-CSF, in Pediatric Patients with Solid Tumors.

A long-acting granulocyte colony-stimulating factor, tripegfilgrastim, was approved in Korea for the prevention of chemotherapy-induced neutropenia in adult patients. In this study, we evaluated the pharmacokinetics, pharmacodynamics, and safety of tripegfilgrastim in pediatric patients. A phase I, open-label, single ascending-dose study was performed in pediatric patients with solid tumors or lymphoma (ClinicalTrials.gov, NCT02963389). The patients were stratified according to age groups (aged 6 to 12 or 12 to 19 years) and received a single subcutaneous dose of tripegfilgrastim 60 µg/kg or 100 µg/kg. Tripegfilgrastim was administered 24 hours after the end of the chemotherapy, and serial blood sampling and safety monitoring were conducted. Twenty-seven patients with solid tumors were enrolled in this study. Tripegfilgrastim was detectable in plasma for an extended period (terminal half-life > 40 hours), and plasma concentrations increased slightly less than dose proportionally. The mean duration of grade 4 neutropenia was reduced as the average tripegfilgrastim concentration during the initial neutrophil recovery process increased. No substantial differences in the pharmacokinetic and pharmacodynamic responses were observed between the two age groups. When stratified by body weight, weighing more than 45 kg has a higher risk of a prolonged neutropenia period when receiving the lower dose (60 µg/kg) of tripegfilgrastim. Tripegfilgrastim was generally safe and well-tolerated in the pediatric patients. These results justify further clinical investigations of tripegfilgrastim at 100 µg/kg dose in pediatric patients.

Somatic uniparental disomy mitigates the most damaging EFL1 allele combination in Shwachman-Diamond syndrome.

Shwachman-Diamond syndrome (SDS; OMIM #260400) is caused by variants in SBDS (Shwachman-Bodian-Diamond syndrome gene), which encodes a protein that plays an important role in ribosome assembly. Recent reports suggest that recessive variants in EFL1 are also responsible for SDS. However, the precise genetic mechanism that leads to EFL1-induced SDS remains incompletely understood. Here we present 3 unrelated Korean SDS patients who carry biallelic pathogenic variants in EFL1 with biased allele frequencies, resulting from a bone marrow-specific somatic uniparental disomy in chromosome 15. The recombination events generated cells that were homozygous for the relatively milder variant, allowing for the evasion of catastrophic physiologic consequences. However, the milder EFL1 variant was still solely able to impair 80S ribosome assembly and induce SDS features in cell line and animal models. The loss of EFL1 resulted in a pronounced inhibition of terminal oligopyrimidine element-containing ribosomal protein transcript 80S assembly. Therefore, we propose a more accurate pathogenesis mechanism of EFL1 dysfunction that eventually leads to aberrant translational control and ribosomopathy.

Effectiveness and Safety of Clofarabine Monotherapy or Combination Treatment in Relapsed/Refractory Childhood Acute Lymphoblastic Leukemia: A Pragmatic, Non-interventional Study in Korea.

PURPOSE: Effectiveness and safety of clofarabine (one of the treatment mainstays in pediatric patients with relapsed/refractory acute lymphoblastic leukemia [ALL]) was assessed in Korean pediatric patients with ALL to facilitate conditional coverage with evidence development. MATERIALS AND METHODS: In this multicenter, prospective, observational study, patients receiving clofarabine as mono/combination therapy were followed up every 4-6 weeks for 6 months or until hematopoietic stem cell transplantation (HSCT). Response rates, survival outcomes, and adverse events were assessed. RESULTS: Sixty patients (2-26 years old; 65% B-cell ALL, received prior ≥ 2 regimen, 68.3% refractory to previous regimen) were enrolled and treated with at least one dose of clofarabine; of whom 26 (43.3%) completed 6 months of follow-up after the last dose of clofarabine. Fifty-eight patients (96.7%) received clofarabine combination therapy. Overall remission rate (complete remission [CR] or CR without platelet recovery [CRp]) was 45.0% (27/60; 95% confidence interval [CI], 32.4 to 57.6) and the overall response rate (CR, CRp, or partial remission [PR]) was 46.7% (28/60; 95% CI, 34.0 to 59.3), with 11 (18.3%), 16 (26.7%), and one (1.7%) patients achieving CR, CRp, and PR, respectively. The median time to remission was 5.1 weeks (95% CI, 4.7 to 6.1). Median duration of remission was 16.6 weeks (range, 2.0 to 167.6 weeks). Sixteen patients (26.7%) proceeded to HSCT. There were 24 deaths; 14 due to treatment-emergent adverse events. CONCLUSION: Remission with clofarabine was observed in approximately half of the study patients who had overall expected safety profile; however, there was no favorable long-term survival outcome in this study.

Pharmacokinetics of high-dose carboplatin in children undergoing high-dose chemotherapy and autologous stem cell transplantation with BSA-based dosing.

Body surface area (BSA)-based carboplatin dosing is used in various centers due to practical issues of renal function-based dosing with area under the curve (AUC) measurement. Pharmacokinetic (PK) analysis of high-dose carboplatin was performed in pediatric solid tumor patients undergoing high-dose chemotherapy (HDCT) and autologous stem cell transplantation (ASCT) with BSA-based dosing to calculate the AUCs achieved with this dosing method and to find the correlation between the PK and the renal functions and the adverse events. Carboplatin was administered as once daily intravenous doses at 300, 400, or 500 mg/m2/day over 1 h for 3 or 4 days. On the first and the last day of carboplatin administration, PK samplings were done at 0, 1, 2, and 5 h and only at 0 h on any other days. Mean AUC on the first and the last day were 4.85 ± 0.95 min × mg/mL and 5.27 ± 1.04 min × mg/mL, respectively (n = 23). Overall, negative correlations between the renal functions and the AUCs were mild to moderate, but they were stronger in nephrectomized patients. 51Cr-EDTA clearance decreased with statistical significance with each additional dose of carboplatin (P = 0.020). Optimal high-dose carboplatin dosing method and optimal target AUCs for the different tumors need further analysis.

Tandem high-dose chemotherapy with topotecan-thiotepa-carboplatin and melphalan-etoposide-carboplatin regimens for pediatric high-risk brain tumors.

BACKGROUND: High-dose chemotherapy (HDC) and autologous stem-cell transplantation (auto-SCT) are used to improve the survival of children with high-risk brain tumors who have a poor outcome with the standard treatment. This study aims to evaluate the outcome of HDC/auto-SCT with topotecan-thiotepa-carboplatin and melphalan-etoposide-carboplatin (TTC/MEC) regimens in pediatric brain tumors. METHODS: We retrospectively analyzed the data of 33 children (median age 6 years) who underwent HDC/auto-SCT (18 tandem and 15 single) with uniform conditioning regimens. RESULTS: Eleven patients aged < 3 years at diagnosis were eligible for HDC/auto-SCT to avoid or defer radiotherapy. In addition, nine patients with high-risk medulloblastoma (presence of metastasis and/or postoperative residual tumor ≥ 1.5 cm2), eight with other high-risk brain tumor (six CNS primitive neuroectodermal tumor, one CNS atypical teratoid/rhabdoid tumor, and one pineoblastoma), and five with relapsed brain tumors were enrolled. There were three toxic deaths, and two of which were due to pulmonary complications. The main reason for not performing tandem auto-SCT was due to toxicities and patient refusal. The event-free survival (EFS) and overall survival (OS) rates of all patients were 59.4% and 80.0% at a median follow-up with 49.1 months from the first HDC/auto-SCT, respectively. The EFS/OS rates of patients aged < 3 years at diagnosis, high-risk medulloblastoma, other high-risk brain tumor, and relapsed tumors were 50.0/81.8%, 87.5/85.7%, 66.7/88.9%, and 20.0/60.0%, respectively. CONCLUSIONS: Although tandem HDC/auto-SCT with TTC/MEC regimens showed promising survival rates, treatment modifications are warranted to reduce toxicities. The survival rates with relapsed brain tumors were unsatisfactory despite HDC/auto-SCT, and further study is needed.

Acute Kidney Injury in Pediatric Cancer Patients.

OBJECTIVE: To analyze the incidence of acute kidney injury (AKI) in the first year after cancer diagnosis in children and to evaluate the short-term and long-term effects on renal function and proteinuria. STUDY DESIGN: Retrospective review of medical records was done on children who were diagnosed and treated for cancer at Seoul National University Hospital between 2004 and 2013. AKI was defined according to the Kidney Disease: Improving Global Outcomes criteria. Impaired renal function of estimated glomerular filtration rate less than 90 mL/minute/1.73 m2 and development of proteinuria of cancer survivors were also assessed. RESULTS: This study included 1868 patients who were diagnosed with cancer at a median age of 7.9 years. During the course of treatment, 983 patients (52.6%) developed 1864 episodes of AKI, and the cumulative incidence at 2 weeks, 3 months, and 1 year after diagnosis was 28.9%, 39.6%, and 53.6%, respectively. The 1-year cumulative incidence was the highest in patients with acute myeloid leukemias (88.4%). In all, 6.1% of patients had more than 4 episodes of AKI and 11.8% of patients had stage 3 AKI. Among the 1096 childhood cancer survivors, 22.6% were found to have impaired renal function. A greater number of AKI episodes (≥4 times) and nephrectomy were independent risk factors of impaired renal function. Also, 8.2% of the survivors developed proteinuria among 742 childhood cancer survivors. CONCLUSIONS: A large percentage of children with cancer experience AKI during the course of treatment, and AKI is associated with impaired long-term renal function.

Successful Treatment of Pediatric Epstein-Barr Virus-positive Aggressive Natural Killer-Cell Leukemia.

Epstein-Barr virus (EBV)-positive aggressive natural killer-cell leukemia (ANKL) is a rare malignancy of mature natural killer cells, with a very poor survival rate. Patients have a rapidly declining clinical course and a poor prognosis, with a median survival of only a few months. Herein, we describe a 16-year-old boy who was diagnosed with EBV-positive ANKL and successfully treated using combination chemotherapy and a subsequent allogeneic hematopoietic stem cell transplantation (alloHSCT). The patient is disease free 4 years and 9 months after alloHSCT. Thus, combination chemotherapy followed by alloHSCT seems to be a promising therapeutic option for EBV-positive ANKL.

Quantification of Thiopurine Nucleotides in Erythrocytes and Clinical Application to Pediatric Acute Lymphoblastic Leukemia.

BACKGROUND: Concentrations of 6-thioguanine (6TG) nucleotides and 6-methylmercaptopurine (6MMP) nucleotides in RBCs were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). This assay was validated for clinical use and was applied to blood samples from patients taking mercaptopurine (6MP). METHODS: RBCs were hemolyzed and deproteinized using perchloric acid, followed by heating for the hydrolysis of nucleotides, and the resultant base was measured using LC-MS/MS. Precision, recovery, linearity, matrix effect, and limit of quantification was validated for clinical application. Our results were compared with another institution's established LC-MS/MS assay. We measured the concentrations of 6TG and 6MMP in RBCs of pediatric patients with acute lymphoblastic leukemia (ALL), and the clinical impact of those metabolites was investigated. RESULTS: The imprecision coefficient of variations of 6TG and 6MMP were 5.7%-8.1%, and the bias was within 5%. Lower limits of quantification were set at 54 ng/mL for 6TG and 1036 ng/mL for 6MMP. Correlation coefficients for 6TG and 6MMP were 0.997 and 1.0 in a comparison study. For clinical proof-of-concept, 74 blood samples were collected from 37 pediatric ALL patients receiving maintenance therapy. Concentration of 6TG ranged from 16.1 to 880 pmol/8 × 10 RBCs and that of 6MMP from 55 to 20,937 pmol/8 × 10 RBCs. The 6MP metabolites were not correlated with WBC or absolute neutrophil count. On the other hand, the higher 6MMP level was associated with elevated alanine aminotransferase and aspartate aminotransferase. CONCLUSIONS: In this study, an assay for the quantification of 6TG and 6MMP in RBCs was established and applied to pediatric ALL patients. Interindividual variability in 6MP metabolite concentrations was considerable and associated with elevation of liver enzymes, which may be useful in the clinical monitoring of 6MP maintenance therapy in pediatric ALL patients.

Hydroxycoumarin OT-55 kills CML cells alone or in synergy with imatinib or Synribo: Involvement of ER stress and DAMP release.

We synthetized and investigated the anti-leukemic potential of the novel cytostatic bis(4-hydroxycoumarin) derivative OT-55 which complied with the Lipinski's rule of 5 and induced differential toxicity in various chronic myeloid leukemia (CML) cell models. OT-55 triggered ER stress leading to canonical, caspase-dependent apoptosis and release of danger associated molecular patterns. Consequently, OT-55 promoted phagocytosis of OT-55-treated CML cells by both murine and human monocyte-derived macrophages. Moreover, OT-55 inhibited tumor necrosis factor α-induced activation of nuclear factor-кB and produced synergistic effects when used in combination with imatinib to inhibit colony formation in vitro and Bcr-Abl+ patient blast xenograft growth in zebrafish. Furthermore, OT-55 synergized with omacetaxine in imatinib-resistant KBM-5 R cells to inhibit the expression of Mcl-1, triggering apoptosis. In imatinib-resistant K562 R cells, OT-55 triggered necrosis and blocked tumor formation in zebrafish in combination with omacetaxine.

Favorable Outcome of Post-Transplantation Cyclophosphamide Haploidentical Peripheral Blood Stem Cell Transplantation with Targeted Busulfan-Based Myeloablative Conditioning Using Intensive Pharmacokinetic Monitoring in Pediatric Patients.

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) with post-transplantation cyclophosphamide (PTCy) was performed previously in adults using a nonmyeloablative conditioning regimen and bone marrow as a graft source. In an effort to reduce relapse rates, myeloablative conditioning regimens with higher intensities are now used. We used an intensive daily pharmacokinetic monitoring method for busulfan dosing in children for effective myeloablation and to reduce toxicity. Here, we report the retrospective results of 34 patients (median age 11.1 years) who underwent haplo-HSCT with PTCy using a targeted busulfan-based myeloablative conditioning regimen and peripheral blood as a stem cell source. The donor-type neutrophil engraftment rate was 97.1%, and the cumulative incidence rates of grade II to IV and grade III to IV acute and extensive chronic graft-versus-host disease were 38.2%, 5.9%, and 9.1%, respectively. The overall survival and event-free survival rates, and treatment-related mortality were 85.0%, 79.4%, and 2.9%, respectively. Based on the subgroup analysis of patients with malignancies (n = 23), the relapse incidence rate was 21.7%. Haplo-HSCT using PTCy with targeted busulfan-based myeloablative conditioning and peripheral blood as a stem cell source was a safe and promising therapeutic option for children.

Gallbladder wall oedema and ascites are independent predictors of progression to hepatic veno-occlusive disease for children with hematopoietic stem cell transplantation.

OBJECTIVES: To evaluate the predictive value of ultrasonography in children with clinically suspicious hepatic veno-occlusive disease (VOD) after hematopoietic stem cell transplantation (HSCT). METHODS: Among 216 children who underwent HSCT, 70 also underwent colour Doppler ultrasonography. Of these, 59 had only one sign/symptom, which did not fulfil the diagnostic criteria (clinical suspicion of VOD) at that time. VOD was confirmed in 20 patients (VOD group), while 39 had other conditions (non-VOD group). The following findings were reviewed and compared between groups: left portal vein (peak velocity, direction), left hepatic artery (peak-systolic/end-diastolic velocities, resistive index), middle hepatic vein (peak velocity, phasicity), hepatomegaly, splenomegaly, gallbladder wall thickness, and ascites. RESULTS: The VOD group showed significantly higher reversed flow in portal vein (P = 0.011), peak systolic velocity of left hepatic artery (P = 0.028), monophasicity of middle hepatic vein (P = 0.015), hepatomegaly (P = 0.001), gallbladder wall thickness (P < 0.001), and ascites (P < 0.001). Multivariate regression revealed that gallbladder wall thickness and ascites (odds ratio = 35.370, 56.393) were associated with VOD. CONCLUSIONS: The presence of reversed flow in portal vein, increased peak systolic velocity of hepatic artery, monophasicity of hepatic vein, hepatomegaly, gallbladder wall thickness, and ascites were significantly associated with progression to VOD in children with clinically suspicious VOD after HSCT. KEY POINTS: • Ultrasonography with Doppler can help predict progression to VOD. • Gallbladder wall oedema and ascites are the independent predictors of progression to VOD.

Foundation of pediatric cancer treatment in Lao People's Democratic Republic at the Lao-Korea National Children's Hospital.

AIM: The Lao-Korea National Children's Hospital initiated and developed a pediatric cancer treatment program for the first time in September 2012, through education by the Lee Jong-Wook project, establishment of infrastructure by the Korea International Cooperation Agency, and cooperation of medical staff. MATERIAL AND METHODS: we describe the experience of initiating and building this program by retrospectively reviewing the data from pediatric patients with cancer diagnosed at the Lao-Korea National Children's Hospital between September 2012 and December 2016. RESULTS: A total of 78 patients diagnosed with acute lymphoblastic leukemia (ALL) (n = 44), acute myeloid leukemia (AML) (n = 12), chronic myeloid leukemia (n = 7), lymphoma (n = 6), retinoblastoma (n = 5), Wilms tumor (n = 3), and germ cell tumor (n = 1) were included. Of the 44 patients with ALL, 40 received induction chemotherapy, and 4 refused chemotherapy. Of these 40 patients, 29 (73.6%) achieved complete remission (CR) and 9 (22.5%) died during chemotherapy. Of the 29 patients with CR, 4 completed the chemotherapy, 19 were still on chemotherapy, 4 relapsed, and 2 were deceased. Treatment was unsuccessful for all 12 patients with AML. CONCLUSION: We successfully initiated the pediatric cancer care program but faced challenges associated with high mortality because of insufficient resources. We should continue our efforts to find more abandoned patients, detect cancer earlier, and reduce the overall associated mortality.

High-dose chemotherapy and autologous peripheral blood stem cell transplantation with BCVAC regimen followed by maintenance chemotherapy for children with very high risk acute lymphoblastic leukemia.

Allogeneic hematopoietic stem cell transplantation (HSCT) is the recommended treatment for children with very high risk acute lymphoblastic leukemia (ALL), but it requires adequate institutional infrastructure, experience, and expertise, especially for alternative donor HSCT. We review our experience with high-dose chemotherapy (HDCT) and autologous peripheral blood stem cell transplantation (APBSCT), followed by post-APBSCT maintenance chemotherapy for children with very high risk ALL. Between August 1997 and November 2012, our institute was not successful with HLA-haploidentical HSCT. Thus, if patients lacked HLA-matched allogeneic donors or cord blood donors, we treated them with HDCT and APBSCT with carmustine, etoposide, cytarabine, and cyclophosphamide, followed by post-APBSCT maintenance chemotherapy with vincristine, oral prednisolone, methotrexate, and 6-mercaptopurine.Ten patients underwent HDCT and APBSCT due to relapse, biphenotype leukemia, Philadelphia translocation, MLL rearrangement, hypodiploidy, and initial white blood cell count above 20.0 × 109/L. At a median 7.4 years from HDCT to APBSCT, overall survival (OS) was 70.0% ± 14.5% and event-free survival (EFS) was 70.0% ± 14.5%. Adverse events were tolerable, without treatment-related mortality.This historical analysis may be a useful reference when allogeneic HSCT including alternative donor HSCT cannot be performed for children with very high risk ALL.

Therapy-related Acute Myeloid Leukemia After the Treatment of Primary Solid Cancer in Children: A Single-center Experience.

Therapy-related acute myeloid leukemia (t-AML) has a dismal prognosis and is one of the most frequent second malignant neoplasms which could be encountered by pediatric oncologists. Between October 2000 and September 2016, 16 patients who had primary solid tumors were diagnosed with t-AML at the Seoul National University Children's Hospital. The median patient age at the time of diagnosis of their primary solid tumors was 9.6 years (range, 0.1 to 15.4 y), and that of t-AML was 14.0 years (range, 4.7 to 23.9 y). The median latency period from the end of the primary tumor treatment to the initial diagnosis of t-AML was 29 months (range, 6 to 130 mo). Twelve patients achieved complete remission. Of them, only 7 patients underwent hematopoietic stem cell transplantation (HSCT). The 3-year overall survival (OS) rates and event-free survival rates were 33.7±12.2% and 26.9±11.5% respectively. The patients who underwent HSCT showed favorable 5-year OS rates (57.1±18.7%), whereas the 5-year OS rates of those who did not undergo HSCT was 0%. This study demonstrates that an achievement of complete remission and a subsequent HSCT can be the optimal solution for the treatment of t-AML, and this strategy showed acceptable outcomes.

The dialkyl resorcinol stemphol disrupts calcium homeostasis to trigger programmed immunogenic necrosis in cancer.

Stemphol (STP) is a novel druggable phytotoxin triggering mixed apoptotic and non-apoptotic necrotic-like cell death in human acute myeloid leukemia (AML). Use of several chemical inhibitors highlighted that STP-induced non-canonical programmed cell death was Ca2+-dependent but independent of caspases, poly (ADP-ribose) polymerase-1, cathepsin, or calpains. Similar to thapsigargin, STP led to increased cytosolic Ca2+ levels and computational docking confirmed binding of STP within the thapsigargin binding pocket of the sarco/endoplasmic reticulum (ER) Ca2+-ATPase (SERCA). Moreover, the inositol 1,4,5-trisphosphate receptor is implicated in STP-modulated cytosolic Ca2+ accumulation leading to ER stress and mitochondrial swelling associated with collapsed cristae as observed by electron microscopy. Confocal fluorescent microscopy allowed identifying mitochondrial Ca2+ overload as initiator of STP-induced cell death insensitive to necrostatin-1 or cycloheximide. Finally, we observed that STP-induced necrosis is dependent of mitochondrial permeability transition pore (mPTP) opening. Importantly, the translational immunogenic potential of STP was validated by HMGB1 release of STP-treated AML patient cells. STP reduced colony and in vivo tumor forming potential and impaired the development of AML patient-derived xenografts in zebrafish.

Pediatric patients undergoing hematopoietic stem cell transplantation can greatly benefit from a novel once-daily intravenous busulfan dosing nomogram.

Busulfan, a bifunctional alkylating agent, has been used as a conditioning regimen prior to allogeneic hematopoietic stem cell transplantation (HSCT). The aim of this study was to derive a novel once-daily intravenous (IV) busulfan dosing nomogram for pediatric patients undergoing HSCT using a population pharmacokinetic (PK) model. A population PK analysis was performed using 2183 busulfan concentrations in 137 pediatric patients (age: 0.6-22.2 years), who received IV busulfan once-daily for 4 days before undergoing HSCT. Based on the final population PK model, an optimal once-daily IV busulfan dosing nomogram was derived. The percentage of simulated patients achieving the daily target area under the concentration-time curve (AUC) by the new nomogram was compared with that by other busulfan dosing regimens including the FDA regimen, the EMA regimen, and the empirical once-daily regimen without therapeutic drug monitoring (TDM). A one-compartment open linear PK model incorporating patient's body surface area, age, dosing day, and aspartate aminotransferase as a significant covariate adequately described the concentration-time profiles of busulfan. An optimal dosing nomogram based on the PK model performed significantly better than the other dosing regimens, resulting in >60% of patients achieving the target AUC while the percentage of patients exceeding the toxic AUC level was kept <25% during the entire treatment period. A novel once-daily busulfan dosing nomogram for pediatric patients undergoing HSCT is useful for clinicians, particularly in a setting where TDM service is not readily available or to optimize the dose on day 1.

A Significant Influence of Metronidazole on Busulfan Pharmacokinetics: A Case Report of Therapeutic Drug Monitoring.

Busulfan is a cytotoxic agent used in preconditioning for hematopoietic stem cell transplantation. Therapeutic drug monitoring of busulfan is necessary owing to its narrow therapeutic range. Patients undergoing preconditioning are susceptible to infection and might require coadministration of antibiotics. We present a case study of a 3-year-old girl with precursor T-cell acute lymphoblastic leukemia who received intravenous busulfan before hematopoietic stem cell transplantation. Metronidazole was coadministered before the third dose of busulfan because of Clostridium difficile infection. The daily pharmacokinetic analysis revealed that the clearance reduced to 57% of that before the coadministration. Although the underlying mechanism is unclear, a significant pharmacokinetic interaction was observed between busulfan and metronidazole, underscoring the importance of therapeutic drug monitoring.

Effect of donor STAT4 polymorphism rs7574865 on clinical outcomes of pediatric acute leukemia patients after hematopoietic stem cell transplant.

STAT4 polymorphism, rs7574865 is linked to various autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. Its T minor allele is associated with higher STAT4 mRNA and protein expression, indicating a stronger skewed immune response than the norm. Although widely studied in autoimmune disease patients and the general population, its effect on immunocompromised subjects is still unknown. Especially in situations, i.e. post-hematopoietic stem cell transplantation (post-HSCT), where control of the immune response is crucial. Hence, this study investigates if the presence of the T minor allele in donors would affect immunological response and clinical outcomes post-HSCT. Samples from 161 pediatric patients who underwent allogeneic HSCT for acute leukemia and showed complete chimerism by donor cells were obtained. Six clinical outcomes were investigated; hepatic veno-occlusive disease, acute graft-vs-host disease, chronic graft-vs-host disease, cytomegalovirus (CMV) infection, relapse and overall survival. The TT genotype was found to be significant in the occurrence of CMV infection (P=0.049), showing higher incidence of CMV infection compared to the others. Multivariate analysis confirmed that association of the TT genotype is independent from other variables in CMV infection occurrence (P=0.010). This is the first study on STAT4 polymorphism rs7574865 in allogeneic HSCT as well as immunocompromised patients. As the TT genotype is associated with autoimmune diseases, our results seem at a paradox with current evidence hinting at a different role of STAT4 in normal circumstances versus immunocompromised patients. Further investigation is needed to elicit the reason behind this and discover novel applications for better post-transplant outcomes.