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This white paper was developed to provide leukapheresis guidance for the collection of mononuclear cells from adult and pediatric patients who are destined for immune effector cell (IEC) therapies for commercial and research applications. Currently, there is considerable variability in leukapheresis processes and limited published information regarding best practices relevant to new cellular therapies, especially IECs. Herein the authors address critical leukapheresis questions in five domains to help guide consistent collection processes and ensure high-quality products. The first four domains are onboarding, pre-collection, collection and post-collection, with protocol feasibility, preparation, care and follow-up of the patient/donor at each step, respectively, and technical considerations during collection. The fifth domain of quality assurance focuses on ensuring product potency, purity, safety and auditing.The American Society for Apheresis (ASFA) Clinical Applications Committee (IEC Therapy Subcommittee) was charged by the society's board of directors with working collaboratively with other ASFA committees and organizations, including the Foundation for the Accreditation of Cellular Therapy, Association for the Advancement of Blood and Biotherapies, American Society for Transplantation and Cellular Therapy, National Marrow Donor Program and International Society for CellGene Therapy, to develop guidelines regarding leukapheresis collection of cells destined for the manufacture of IEC therapies. After a review of the literature and discussion with members of the involved committees and various institutions, a draft guidance was created and circulated for comment and revision.Critical aspects of apheresis that could affect the quality and quantity of the leukapheresis product were identified. These areas were then discussed and reviewed. After consensus, the best practice guidelines were proposed and accepted.In the current era of rapid growth of IEC therapies, it is important to address critical leukapheresis steps to provide high-quality products and more consistent practices and to eliminate redundant efforts.

Recipients of solid organ transplantation (SOT) rely on life-long immunosuppression (IS), which is associated with significant side effects. Extracorporeal photochemotherapy (ECP) is a safe, existing cellular therapy used to treat transplant rejection by modulating the recipient’s own blood cells. We sought to induce donor-specific hypo-responsiveness of SOT recipients by infusing ECP-treated donor leukocytes prior to transplant. To this end, we utilized major histocompatibility complex mismatched rodent models of allogeneic cardiac, liver, and kidney transplantation to test this novel strategy. Leukocytes isolated from donor-matched spleens for ECP treatment (ECP-DL) were infused into transplant recipients seven days prior to SOT. Pre-transplant infusion of ECP-DL without additional IS was associated with prolonged graft survival in all models. This innovative approach promoted the production of tolerogenic dendritic cells and regulatory T-cells with subsequent inhibition of T-cell priming and differentiation, along with a significant reduction of donor-specific T-cells in the spleen and grafts of treated animals. This new application of donor-type ECP-treated leukocytes provides insight into the mechanisms behind ECP-induced immunoregulation and holds significant promise in the prevention of graft rejection and reduction in need of global immune suppressive therapy in patients following SOT.

Introduction A phase 1/2 study of betibeglogene autotemcel (beti-cel; LentiGlobin for β-thalassemia) gene therapy in patients with transfusion-dependent β-thalassemia (TDT) demonstrated stable transgene expression with up to 4.5 years follow-up and enabled some patients to achieve transfusion independence. The interim results of two phase 3 studies, HGB-207 (NCT02906202; non-β0/β0 genotypes) and HGB-212 (NCT03207009; β0/β0, β0/β+ IVS-I-110 or β+ IVS-I-110/β+ IVS-I-110 genotypes), are presented here. Methods After G-CSF and plerixafor mobilization, autologous hematopoietic stem cells were collected via apheresis. Using a refined manufacturing process compared to the phase 1/2 study, CD34+ cells were transduced with BB305 lentiviral vector. Patients were infused with transduced cells following pharmacokinetic-adjusted, single-agent busulfan myeloablation. Target busulfan AUC was 3800–4500 (once daily) or 950–1125 (Q6H) μM*min. Statistics are shown as median (min–max). Results As of 13 Dec 2018 and 12 Apr 2019, 31 patients were treated in HGB-207 and HGB-212 with a follow-up of 8.1 (0.5–22.2) and 4.6 (1.5–15.7) months, respectively. Daily average busulfan AUC was 4450 (3709–9087) μM*min. Neutrophil and platelet engraftment were achieved at 25 (13–38) and 44 (20–84) days, respectively. Hospitalization from conditioning to discharge ranged from 30–92 days. In HGB-207, 10/11 patients followed for ≥6 months have stopped transfusions for ≥5.9 months (Figure 1). HbAT87Q levels at Months 6 (n=11), 12 (n=8) and 18 (n=3) were 9.5, 9.2, and 9.5 g/dL, respectively, which contributed to total hemoglobin (Hb) of 11.9, 12.4, and 11.3 g/dL at these time points, respectively. Marrow myeloid:erythroid ratios in 7/8 patients at Month 12 were 0.63–1.90 versus 0.14–0.48 at baseline, indicating improved erythropoiesis. In HGB-212, 3/4 patients followed for ≥6 months stopped transfusions for ≥6 months. Total Hb at last visit ranged from 10.5–13.6 g/dL and HbAT87Q was 9.5–12.6 g/dL at last assessment. Transfusion independence (weighted average Hb ≥9 g/dL without transfusions for ≥12 months) was achieved in 4/5 evaluable patients in HGB-207 and in the only evaluable patient in HGB-212. Post-infusion non-hematologic grade ≥3 adverse events (AEs) in ≥3 patients in either study were stomatitis (n=17), febrile neutropenia (n=11), pyrexia (n=4), epistaxis (n=3), and veno-occlusive liver disease (VOD; n=3). VOD prophylaxis with ursodiol or ursodiol/defibrotide was used in 24/31 patients. One beti-cel-related serious AE of thrombocytopenia was reported; platelet count was 63 × 109/L at last visit (Month 7). All patients remain alive. Summary Following treatment with beti-cel gene therapy, 10/11 and 3/4 patients with ≥6 months follow-up have stopped transfusions in HGB-207 and HGB-212, respectively. The safety profile of treatment with beti-cel is consistent with busulfan myeloablation.

Introduction Myeloablative conditioning (MAC) regimens decrease the risk of relapse in pediatric patients undergoing hematopoietic stem cell transplant (HCT) but cause significant toxicities: transplant-related mortality (TRM) and late effects. Therefore, a MAC regimen that decreases toxicity has the potential to improve overall survival (OS). Busulfan (Bu), fludarabine (Flu), anti-thymocyte globulin (ATG) and 400 cGy of total body irradiation (TBI), a reduced toxicity, MAC regimen was used in pediatric patients. Objectives To evaluate the safety and toxicity of this regimen. Secondary objectives included determining OS at 2 and 5 years, and incidence of relapse and GVHD. Methods We prospectively evaluated 40 patients ≤21 years of age undergoing HCT for high-risk leukemias who received dose-adjusted Bu, Flu, ATG and TBI. Bu pharmacokinetics were measured after a test dose and regimen dose 1 to target AUC of 4000-5000 uMol*min/day. Results Patients were treated between October 2008 and June 2018 (Table 1). OS was 67% and 51% at 2 and 5 years post-HCT, respectively. OS at 2 and 5 years was 70% and 55% for patients with myeloid disease versus 56% and 37% for patients with lymphoid disease, respectively (p=0.18) (Figure 1). Relapse occurred in 11 (28%) at a median of 7 months. TRM was 8% and 13% at 100 days and 1 year post-HCT, respectively. All patients engrafted. >Grade II acute GVHD was seen in 9 (23%); chronic GVHD was seen in 16 (40%). There was no significant impact of age, disease type, donor source or type on HCT outcomes. Long-term toxicities noted were ovarian insufficiency in 8, and short stature, hypothyroidism and learning disabilities in 2 each. Evaluation of Bu AUCs and multivariate analyses are still ongoing. Conclusions Reduced toxicity, MAC regimen was well tolerated with a low incidence of TRM. This regimen shows a trend toward better efficacy in patients with myeloid disease, however larger studies are needed.

Stimulated by the scientific progress in deciphering the principal elements contributing to the clinical efficacy of extracorporeal photochemotherapy (ECP), the American Council on ECP (ACE) was formed, under the auspices of the American Society for Apheresis (ASFA), to develop a field-guiding Consensus Report. ACE is composed of thirty nationally recognized ECP experts, clinically spanning cancer, transplantation, and autoimmunity and scientifically bridging immunology, bioengineering, and hematology. The two-day meeting took place in Manhattan, April 13-14, 2017, and unanimous consensus on nine pivotal points is herein reported. (1) ECP's clinical evolution must now enter a scientifically driven phase. (2) ECP is currently a bidirectional therapy, both immunizing and tolerizing simultaneously, via a single one-size-fits-all inflexible medical device. (3) To preclude inadvertent tolerization in the cancer setting, or immunization in the transplant rejection setting, polarization of ECP to either immunization or tolerization mode to match the clinical need is now possible and necessary. (4) Cutaneous T cell lymphoma (CTCL) is a genetically driven cancer, whose response to ECP is due to enhanced anti-cancer immunity. (5) ECP is a dendritic antigen-presenting cell (DC) based therapy. (6) ECP's efficacy can now be tested in a broad array of cancers. (7) ECP's capacity to tolerize to allotransplants via processing of donor leukocytes merits expedited human investigation. (8) UVA-8-MOP-impacted ECP-induced DC are potent antigen-specific tolerizing agents, while UVA-8-MOP(8-Methoxypsoralen)-spared ECP-induced DC are potent antigen-specific immunizing agents. (9) Six pilot clinical trial areas (CTCL, graft-vs.-host disease, ovarian carcinoma, anti-graft cytotoxic antibodies, pemphigus vulgaris, and haplotype mismatched stem cell transplants) are advised. ACE will be an ongoing advisory group for the field, with the goal of overseeing coordinated clinical and fundamental research efforts.

Aspergillus thyroiditis (AT) has historically been considered a postmortem diagnosis in immunocompromised patients; most have disseminated disease. This report summarizes the clinical challenge of diagnosing AT. It also highlights the value of the early use of thyroid fine-needle aspiration culture and the need for a high index of suspicion to reach the final diagnosis before disease dissemination.

Multimodal treatment in high-risk neuroblastoma has modestly improved survival; limited data exist on the late effects from these regimens. We report the sequelae of treatment incorporating 3 consecutive cycles of high-dose therapy and autologous stem cell transplants (ASCTs) without the use of total body irradiation (TBI). We reviewed the medical records of 61 patients treated on or following the Chicago Pilot 2 protocol between 1991 and 2008. Of the 25 patients who are alive (41%), 19 had near complete data to report. Specific treatment modalities and therapy-related side effects were collected. Fourteen of these 19 patients (74%) received 3 cycles of high-dose therapy with ASCT; follow-up occurred over a median of 13.9 years (range, 5.8 to 18.8 y). The majority of late effects were endocrine-related, including growth failure, hypothyroidism, and hypogonadism. Patients also developed secondary neoplasms and skeletal deformities. The most frequent sequela was hearing loss, seen in 17/19 patients. We found a high prevalence of various late effects in survivors of high-risk neuroblastoma using a non-TBI-based regimen including 3 cycles of high-dose therapy with ASCTs. As current treatment regimens recommend tandem ASCT without TBI, it is imperative that we understand and monitor for the sequelae from these modalities.

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

We report 23 consecutive pediatric patients with MDS who received allogeneic HSCT on IRB approved protocols between 1992 and 2009 at Children's Memorial Hospital (Chicago, IL). Nine patients had de novo MDS, whereas 14 patients had treatment-related MDS. All patients had a documented cytogenetic abnormality, and monosomy 7/7q- was seen in 12 patients (52%). Fourteen of 23 patients received a myeloablative conditioning regimen; RIC regimens were used for the remaining nine. Five patients relapsed post-transplant, including four patients who received RIC transplant and four patients with treatment-related MDS. For the entire group, estimated five-yr RFS and OS were 47% and 50%, respectively. Treatment-related MDS was associated with decreased RFS in comparison with de novo MDS (33% vs. 70%, p = 0.05). Five-year OS rates reached 80% for those with de novo MDS. RIC regimens were associated with decreased three-yr RFS in comparison with myeloablative regimens (22% vs. 68%, p = 0.02). There was no correlation of survival with blast count at diagnosis, IPSS score, cytogenetic abnormality, donor type, or HLA match. Larger series are needed to confirm prognostic factors so that higher-risk patients can be targeted with novel approaches.

We studied the pharmacokinetic (PK) profile of single daily dose i.v. BU in children who underwent reduced-intensity conditioning (RIC) transplantation. A cohort of 19 patientsor =4 years of age (group 1) and 33 patients4 years (group 2) was studied. Patients received a BU test dose for PK studies, followed by two treatment doses adjusted to target an area under the curve (AUC) of 4000 microM min per day. Patients in group 1 attained a lower AUC as compared to group 2 (3568 vs 4035 microM min). In group 1, 67% patients and in group 2, 84% patients achieved AUC within the targeted range. Stable donor chimerism was achieved in 56% patients in group 1 and 79% in group 2. Eight patients required a second transplantation because of graft failure. Because of the concern that a low AUC adversely affected outcomes, a second cohort of 23 patients followed a modified protocol with a targeted AUC of 5000 microM min. A higher AUC was attained (4825 microM min). Stable donor chimerism was achieved in 91% of patients. Our results show that RIC regimens using two single daily doses of i.v. BU are effective in children, but a targeted AUC of 5000 microM min is recommended.

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.

Glanzmann thrombasthenia (GT) is a rare, autosomal recessive coagulopathy characterized by either qualitative or quantitative abnormalities of the membrane glycoprotein αIIbβ3 complex leading to bleeding tendencies, ranging from purpura to life-threatening hemorrhage. Although patients can be managed with supportive measures including platelet transfusions, complications such as alloimmunization are possible. Allogeneic stem cell transplantation (ASCT) can be indicated in severe cases of GT. We report the case of an eight-month-old girl diagnosed with moderate–severe GT, who was successfully treated with a reduced-intensity, human leukocyte antigen (HLA)-identical ASCT.

Niemann-Pick type B (NP) is an autosomal recessive lysosomal storage disorder with variable phenotypes for which few patients have undergone hematopoietic progenitor cell (HPC) transplantation. We present an 18-month old with NP type B who underwent two allogeneic HPC transplants from her HLA-identical sister. Sphingomyelinase in the peripheral leucocytes and skin fibroblasts was absent at diagnosis. Engraftment failed following initial transplant; therefore a second with the same donor was performed. Engraftment since has been durable; all subsequent sphingomyelinase levels have been normal. Our experience indicates that HPC transplantation for patients with NP type B is feasible and beneficial.

Busulfan, an important agent used in conditioning regimens before hematopoietic stem/progenitor cell (HSPC) transplantation, has a “narrow” therapeutic index. Targeted dosing of busulfan based on its pharmacokinetic (PK) profile is often used. We studied the age-dependent PK profile of single daily dose intravenous Bu (IV Bu) in pediatric patients and determined a target range of Bu exposure that is appropriate for children undergoing reduced-intensity conditioning (RIC) HSPC transplantation. The RIC regimen included: fludarabine 30 mg/m2 per day for 6 days (days –10 to –5); single daily treatment doses of IV Bu given over 3 hours each day for 2 days (days –5 and –4), with individualized Bu dosing based on the PK results of a test dose; and rabbit ATG (2 mg/kg/day) or equine ATG (40 mg/kg/day) for 4 days (days –4, –3, –2 and –1). In 2 variations of the regimen, ATG was either eliminated or replaced with extracorporal photopheresis. Allogeneic HSPC were infused on day 0. Cyclosporin A and mycophenolate mofetil were used for graft-versus-host disease prophylaxis. An initial cohort of 52 patients was studied. The median age of the cohort was 7.7 years (range 0.06–17.6), with 19 patients less than 4 years of age (group 1) and 33 patients older than 4 years (group 2). Patients had either malignant or non-malignant diseases (immunodeficiency (n=14), metabolic disease (2), marrow failure (6), histiocytosis (1), ALL (9), AML (5), CML (4), MDS (2), lymphoma (5)), neuroblastoma (4)). Patients received a test dose of IV Bu (0.8 mg/kg) five days before the treatment doses. After the test dose, the median AUC attained was 886 μM·min in group 1 (range 439–1828) and 965 μM·min in group 2 (range 579–1970). Only 59% of the patients in both groups attained a plasma concentration-time “area-under-the-curve” (AUC) within the expected range of 800–1200 μM·min. Based on the test dose PK, patients received individualized treatment doses adjusted to target an AUC of 4000 μM·min per day for 2 days (range 3200–4800 μM·min). The median daily treatment dose of IV Bu given was 3.45 mg/kg in group 1 (range 0.8–7.2) and 3.20 mg/kg in group 2 (range 0.9–5.4), with a distinct and linear inverse-relationship between the weight-normalized treatment dose required and the weight of the patient (treatment dose = 4.0 mg/kg - 0.01*weight in kg, p=0.001). After the adjusted treatment dose, patients who achieved AUC within the targeted range increased to 67% in group 1 and 84% in group 2. Despite the dose adjustment, group 1 attained a lower median treatment dose AUC (3568 μM·min) as compared to group 2 (4035 μM·min) (p=0.001). All patients in this cohort tolerated the conditioning regimen. No patient developed seizures or hepatic veno-occlusive disease. Stable donor chimerism, however, was achieved in only 56% of patients in group 1 and 79% in group 2. Eight patients received a second transplantation because of primary or secondary graft failure. Eight patients died of transplantation-related causes. Because of the concern that a low AUC correlated with an adverse clinical outcome, a second cohort of 23 patients followed a modified protocol in which a treatment dose AUC of 5000 μM·min was targeted (range 4200–5800 μM·min). The median age of the second cohort was 2.1 years (range 0.3–21), with 13 patients less than 4 years and 10 patients older than 4 years. The median daily treatment dose given in this cohort was 4.5 mg/kg (range 2.6–6.5). All patients tolerated the higher Bu treatment dose with minimal regimen-related toxicity. After the treatment dose, patients attained a higher median AUC of 4825 μM·min (range 3719–5900), with over 90% of the patients achieving AUC within the targeted range of 4200–5800 μM·min. The number of patients who achieved stable donor chimerism also increased to 91%. One patient died of a transplantation-related cause. In conclusion, our results showed that RIC regimens utilizing 2 single daily doses of IV Bu were effective and well tolerated in children. An age-dependent variability in the PK profile of IV Bu could have contributed to a higher rate of graft failure in the younger patients after they received the Bu doses targeted to achieve an AUC of 4000 μM·min per day. Since there appears to be a wide safety margin in the upper limit of the Bu therapeutic range in RIC transplantation, a targeted AUC of 5000 μM·min per day for two days is recommended in pediatric patients, especially those less than 4 years of age.

Allogeneic stem cell transplantation is curative for patients with primary immunodeficiency. A unique reduced intensity conditioning regimen has been developed to maximize cure rate and minimize transplant-related toxicity. Between 2000 and 2007, we performed 16 RIT in patients with hyper-IgM syndrome (n=2), severe combined immune deficiency (SCID) (n=10), immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome (IPEX) (n=2), Wiskott-Aldrich syndrome (n=1), and X-linked lymphoproliferative disease (n=1). There were 12 males and 4 females, with a median age at the time of RIT of 8.0 months (range 1.1 months to 8.9 years). Donor sources included peripheral blood stem cells (PBSCs) from matched related donors (n=7) or unrelated donors (n=2), and cord blood units (CBUs) (n=7). The median cell dose was 8.55 × 108 total nucleated cells (TNC)/kg and 6.7 × 106 CD34+cells/kg for the PBSC group, and 1.99 × 108 TNC/kg and 0.71 × 106 CD34+cells/kg for the CBU group. The conditioning regimen consisted of Fludarabine (Flu), days -10 through -5, intravenous Busulfan (Bu), days -5 and -4, and Anti-thymocyte globulin (ATG), days -4 through -1. GVHD prophylaxis included tacrolimus/prednisone (n=1), cyclosporine A (CSA) alone (n=2), and CSA/mycophenolate mofetil (n=13). All patients who received PBSCs from related and unrelated donors engrafted (9/9), whereas only 4/7 (57%) patients who received CBUs engrafted. The 3 patients who experienced primary graft failure had the following diagnoses; IPEX, T−B−NK+ SCID and T−B+NK+ SCID. Their cord blood doses were 0.78, 1.19 and 1.99 × 108 TNC/kg, and 0.11, 0.69, and 0.55 × 106 CD34+cells/kg, respectively. For the 13 patients who engrafted, median time to absolute neutrophil count (ANC) >1000 was 19 days (range 4 to 53) and median time to platelets >50K was 23 days (range 14 to 90). The ANC never dropped

RIC for HSCT has been used to treat a variety of diseases in adults. Acute and chronic graft vs host disease (GVHD) continue to cause morbidity and mortality. ECP is an immunomodulatory cell therapy being investigated as treatment for various immune-mediated disorders, including GVHD. ECP is an established therapy for chronic GVHD, but has not been routinely used as prophylaxis. We hypothesized that combining ECP with RIC prior to HSCT would reduce the incidence of GVHD and 100-day transplant related mortality (TRM) without affecting time to engraftment. Eight children have been enrolled; ranging in age from 10 – 16 years (mean 13.6), with CML (n=2), severe aplastic anemia (SAA) (n=3), ALL in CR2 (n=1), or relapsed Hodgkin’s disease after autologous transplant (n=2). Stem cell sources included peripheral blood from matched related (n=6), mis-matched related (n=1), and matched unrelated (n=1) donors. Conditioning consisted of 2 weekly treatments of ECP (treatment=2 consecutive days) beginning two weeks prior to transplant, followed by fludarabine (days -6 to -2) and targeted dose busulfan to reach a daily AUC of 4000 μmol*min (days -5, -4); GVHD prophylaxis was: mycophenolate mofetil (MMF), cyclosporine, and weekly treatments of ECP starting once leukocyte chimerism reached 50% through day +100. Full engraftment (>95% total donor chimerism) was achieved by day 12 – 81 (median 29 days) in all patients. Two patients required immune modulation for falling chimerism; one responded to removal of immune supression, the other required donor lymphocyte infusion (DLI). Both subsequently developed grade 3 aGVHD. Patients with CML and SAA are fully engrafted and in remission. Four had central line infections, one had adenovirus antigenemia, and all 5 at risk for CMV had reactivation. They underwent pre-emptive treatment without development of disease. ECP was well tolerated. There were no toxic deaths, episodes of veno-occlusive disease or mucositis; none required parenteral nutrition. Patients were admitted to the hospital for 2 days during the preparative regimen (IV busulfan); between day 0 and 100 patients were admitted for a median of 11 days (range 0 – 25). We conclude that in children using ECP as part of RIC and GVHD prevention is feasible, time to engraftment is acceptable, and complications are minimal as evidenced by short inpatient stays. However, immune supression appears to be excessive, given the rates of CMV reactivation and the declining chimerism of two patients while on ECP. ECP appears to be effective in preventing aGVHD, as the only patients who developed aGVHD were those requiring immune modulation. Patient Characteristics Patient # Diagnosis Donor Chimerism > 50% (days) Chimerism > 95% (days) aGVHD cGVHD Disease Status *Interventions due to falling chimerism 1 CML Matched Sib 13 29 None None NED following DLI & Imatinib for rising BCR/ABL, Day +384 2 SAA Matched Sib 8 26 None Extensive NED, Day +328 3 CML Matched Sib 26 63 (following DLI)* Grade 3 Extensive NED, Day +278 4 SAA Mismatched Related 12 81 (following removal of immune supression)* Grade 3 Limited NED, Day +222 5 ALL (CR2) Matched Sib 12 28 None None Relapse, Day +100 6 HD (CR3) MUD 20 33 None None Relapse, Day +100 7 SAA Matched Sib 7 12 None None NED, Day +125 8 HD (CR2) Matched Sib 28 47 None N/A NED, Day +62