William T. Tse

Reduced intensity haemopoietic stem-cell transplantation for treatment of non-malignant diseases in children

BACKGROUND Transplantation of allogeneic haemopoietic stem cells can cure several non-malignant disorders in children. Transplantation with reduced intensity preparation might achieve the same goals but with less toxicity. We undertook a pilot study to determine engraftment rates, kinetics of engraftment, toxicity, and acute graft-versus-host disease (GVHD) associated with a uniform reduced intensity haemopoietic stem-cell transplant (HSCT) regimen for children with non-malignant diseases. METHODS We studied 13 paediatric patients with non-malignant disorders who underwent reduced intensity HSCT at Childrens Memorial Hospital from January, 2000, to February, 2004. Stem-cell sources included unrelated donor, matched-sibling peripheral blood stem cells, and unrelated cord blood. A uniform preparative regimen was used, consisting of fludarabine, busulfan, and anti-thymocyte globulin. Major endpoints were engraftment, transplant-related mortality at day 100, short-term toxicities, and incidence of acute GVHD. RESULTS 72% of evaluable patients achieved full donor engraftment. There was rapid reconstitution of platelets (median 13.5 days) and neutrophils (median 18 days). Short-term toxicities were minimal, as seen by a median length of hospital stay of 7 days (between days 0-100). Incidence of grade II-IV acute GVHD was 8%. Two patients died before day 100 from underlying disease and viral infection, respectively (day 100 transplant-related mortality of 15%). The 1-year overall survival was 84% (95% CI 64-100). Most patients with immunodeficiencies and metabolic disorders had excellent donor engraftment and disease resolution or stabilisation, but most of those with haemoglobinopathies rejected their graft. INTERPRETATION This reduced intensity regimen followed by HSCT provides a good alternative to myeloablative HSCT for children with non-malignant disorders, except for haemoglobinopathies, in which engraftment is poor. Even patients with unrelated donor haemopoietic stem-cell transplants had adequate engraftment with acceptable toxicities.

Bistable switches control memory and plasticity in cellular differentiation

Development of stem and progenitor cells into specialized tissues in multicellular organisms involves a series of cell fate decisions. Cellular differentiation in higher organisms is generally considered irreversible, and the idea of developmental plasticity in postnatal tissues is controversial. Here, we show that inhibition of mitogen-activated protein kinase (MAPK) in a human bone marrow stromal cell-derived myogenic subclone suppresses their myogenic ability and converts them into satellite cell-like precursors that respond to osteogenic stimulation. Clonal analysis of the induced osteogenic response reveals ultrasensitivity and an “all-or-none” behavior, hallmarks of a bistable switch mechanism with stochastic noise. The response demonstrates cellular memory, which is contingent on the accumulation of an intracellular factor and can be erased by factor dilution through cell divisions or inhibition of protein synthesis. The effect of MAPK inhibition also exhibits memory and appears to be controlled by another bistable switch further upstream that determines cell fate. Once the memory associated with osteogenic differentiation is erased, the cells regain their myogenic ability. These results support a model of cell fate decision in which a network of bistable switches controls inducible production of lineage-specific differentiation factors. A competitive balance between these factors determines cell fate. Our work underscores the dynamic nature of cellular differentiation and explains mechanistically the dual properties of stability and plasticity associated with the process.

High WT1 gene expression before haematopoietic stem cell transplant in children with acute myeloid leukaemia predicts poor event-free survival.

WT1 gene expression has been proposed as a useful marker of minimal residual disease in leukaemia. Its utility in paediatric haematopoietic stem cell transplantation (HSCT) has not been studied. We studied the prognostic value of WT1 expression in peripheral blood prior to HSCT in 36 children with acute myeloid leukaemia (AML). Samples were obtained 2 weeks pre‐transplant to determine the level of WT1 expression. WT1 expression was normalized using K562 cells as a control and a relative value of 0·5 was chosen as the cut‐off point between high and low WT1 expression. The median level of pre‐transplant WT1 expression in the 36 patients was 0·09 (range 0·0001–11·0), with 11patients having WT1 ≥ 0·5 and 25, WT1 < 0·5. After HSCT, 76% of patients with high pre‐transplant WT1 expression relapsed, in contrast to 0% of the patients with low WT1 expression. Those with high WT1 expression had significantly lower 5‐year event‐free survival (EFS) (18%, 95% CI 0–40%) as compared to those with low WT1 expression (68%, 95% CI 50–86%, P = 0·007). Multivariate analysis showed that pre‐transplant WT1 level is the only significant prognostic factor for the difference in EFS. Our finding suggests that elevated WT1 gene expression before HSCT in paediatric AML predicts relapse and poor long‐term EFS. A larger prospective study is warranted to compare the value of high WT1 expression and other markers of minimal residue disease in predicting clinical outcomes after HSCT.

Reduced intensity transplants (RIT) in pediatrics: a review.

Abstract:  We describe the experience with reduced intensity transplants (RIT) in pediatric patients and review the basis for this approach using adult examples and series of patients. We report the experience with RIT in two pediatric studies.

IV pentamidine for Pneumocystis jiroveci pneumonia prophylaxis in pediatric allogeneic stem cell transplant patients

IV pentamidine for Pneumocystis jiroveci pneumonia prophylaxis in pediatric allogeneic stem cell transplant patients

Single Daily Busulfan Dosing for Infants with Nonmalignant Diseases Undergoing Reduced-Intensity Conditioning for Allogeneic Hematopoietic Progenitor Cell Transplantation

Busulfan (Bu) is widely used in conditioning regimens for infants undergoing allogeneic hematopoietic progenitor cell transplantation (HPCT), but the best approach to administer Bu in this population is still unknown. Here, we report a single-center experience of the use of a test dose to guide dose adjustment of intravenous (i.v.) Bu therapy in infants. Between 2004 and 2013, 33 infants younger than 1 year with nonmalignant conditions received allogeneic peripheral blood or cord blood HPCT after a reduced-intensity conditioning (RIC) regimen consisting of fludarabine, antithymocyte globulin, and 2 single daily doses of i.v. Bu. Pharmacokinetic results of a test dose of i.v. Bu (.8 mg/kg) were used to determine the dose of 2 single daily i.v. Bu regimen doses, adjusted to target an area under the curve (AUC) of 4000 μMol*minute per day in a first cohort (n = 12) and 5000 μMol*minute in a second cohort (n = 21). The mean Bu clearance in our infant patients was found to be 3.67 ± 1.03 mL/minute/kg, and the test dose clearance was highly predictive of the regimen dose clearance. The mean AUC achieved after the first single daily regimen dose was 3951 ± 1239 in the AUC 4000 cohort and 4884 ± 766 for the AUC 5000 cohort. No patient in either cohort developed hepatic sinusoidal obstructive syndrome or seizures attributable to Bu. Primary graft failure occurred in 4 patients and secondary graft failure occurred in 3, predominantly in the AUC 4000 cohort (6 of 7). Among the engrafted patients (n = 28), 16 achieved full donor chimerism and 9 patients attained stable mixed chimerism. Overall survival of patients at 6 years after transplantation was 59.5% for the AUC 4000 cohort and 85.4% for the AUC 5000 cohort, with primary graft failure in the first cohort being a major contributor to morbidity. Logistic regression analysis showed that the risk of graft failure increased significantly if cord blood hematopoietic progenitor cells were used or if total Bu exposure was below 4000 μMol*minute per day for 2 days. The difference in clinical outcomes between the 2 cohorts supports the conclusion that targeting a higher Bu AUC of 5000 μMol*minute per day for 2 days improves donor engraftment in infants with nonmalignant conditions undergoing RIC HPCT without increasing toxicity. Measuring i.v. Bu pharmokinetics using a test dose allows timely adjustment of single daily regimen doses and optimization of total Bu exposure, resulting in an effective and safe regimen for these infants.

The Impact of High-resolution HLA-A, HLA-B, HLA-C, and HLA-DRB1 on Transplant-related Outcomes in Single-unit Umbilical Cord Blood Transplantation in Pediatric Patients.

Current practice for selecting donor units for umbilical cord blood transplant (UCBT) involves matching at HLA-A and HLA-B by low-resolution typing and the HLA-DRB1 allele by high-resolution (HR) typing. We retrospectively studied the impact of HR allele matching at HLA-A, HLA-B, HLA-C, and HLA-DRB1 on transplant-related outcomes in 60 single-unit UCBTs in pediatric patients with malignant and nonmalignant conditions. Five-year overall survival of our cohort was 71% (95% confidence interval, 58-81); 27% experienced primary graft failure. Applying HR typing, donor-recipient mismatch variability increased ranging from 1/8 to 8/8, however, no impact on primary graft failure, graft-versus-host disease or posttransplant infection was observed. UCBTs with ≥6/8 HR matches did have a better overall survival (P=0.04) and decreased transplant-related mortality (P=0.02) compared with <6/8 HR matches. Using standard HLA typing, we showed an increased incidence of acute graft-versus-host disease (grade II to IV) and decreased transplant-related mortality in comparing the matched (6/6) versus ⩽5/6 group (P=0.05 and 0.05, respectively). These data support the use of current guidelines for umbilical cord blood selection and encourage utilization of HR typing to select umbilical cord blood units matched at ≥6/8 especially when appropriate ≥5/6 units are available.

Fecal calprotectin and serum albumin as markers of gastrointestinal graft versus host disease

BACKGROUND Acute graft versus host disease (aGVHD) affects approximately 30-60% of patients after allogeneic hematopoietic stem cell transplantation (HCT) and our ability to predict who develops this complication and their response to treatment is limited. Fecal calprotectin has recently gained popularity as an effective marker of GI inflammation in patients with Inflammatory Bowel Disease (IBD). METHODS Fecal calprotectin and albumin were evaluated as prognostic and predictive markers of aGVHD in 60 adult and pediatric HCT patients. Stool samples were sent for calprotectin quantification prior to starting conditioning, at day 14 post-HCT, at day 28 post-HCT, and at onset of aGVHD ± 2 days. RESULTS Fecal calprotectin did not differentiate patients with GI-GVHD and non-GI GVHD and did not vary based on severity. However, in patients with steroid-refractory GI aGVHD, significantly higher fecal calprotectin levels were noted. At onset of lower-GI symptoms, steroid refractory patients (n = 3) had a mean fecal calprotectin level of 449 ug/g (range 116-1111 ug/g) and a mean albumin of 1.93 g/dL (range 1.6-2.3 g/dL) compared with a mean fecal calprotectin of 24 ug/g (range 16-31 ug/g) and a mean albumin of 3.3 g/dL (range 2.3-3.9 g/dL) in steroid responsive patients (n = 9) (fecal calprotectin p = 0.032, albumin p = 0.027). CONCLUSION Patients with steroid-refractory GI aGVHD had higher fecal calprotectin levels and lower albumin levels than patients with steroid-responsive disease. We recommend further studies to evaluate non-invasive tests with fecal calprotectin in combination with albumin in predicting steroid refractory disease at onset of symptoms to potentially identify patients that may benefit from upfront escalation in GVHD treatment.

Early mixed T-cell chimerism is predictive of pediatric AML or MDS relapse after hematopoietic stem cell transplant

Patients with acute myeloid leukemia (AML) who relapse after hematopoietic stem cell transplantation (HCT) have dismal outcomes. Our ability to predict those at risk for relapse is limited. We examined chimerism trends post‐HCT in 63 children who underwent HCT for AML or myelodysplastic syndrome (MDS). Mixed T‐cell chimerism at engraftment and absence of chronic graft versus host disease (cGVHD) were associated with relapse (P = 0.04 and P = 0.02, respectively). Mixed T‐cell chimerism at engraftment was predictive in patients without cGVHD (P = 0.03). Patients with engraftment mixed T‐cell chimerism may warrant closer disease monitoring and consideration for early intervention.

Long-term follow-up of children with chronic myeloid leukemia after hematopoietic stem cell transplantation and tyrosine kinase inhibitor therapy

Larisa Brogile, Nobuko Hijiya, Irene B. Helenowski, Kimberley Dilley, Jen Schneiderman, William Tse, Reggie Duerst, Morris Kletzel, Elaine Morgan and Sonali Chaudhury Department of Pediatrics, Division of Hematology, Oncology and Stem Cell Transplant, Ann & Robert H. Lurie Children’s Hospital of Chicago, Northwestern University Feinberg School of Medicine, Chicago, IL, USA; Department of Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA