Experience with Alemtuzumab, Fludarabine, and Melphalan Reduced-Intensity Conditioning Hematopoietic Cell Transplantation in Patients with Nonmalignant Diseases Reveals Good Outcomes and That the Risk of Mixed Chimerism Depends on Underlying Disease, Stem

Alemtuzumab, fludarabine, and melphalan reduced-intensity conditioning (RIC) regimens are increasingly used for the hematopoietic cell transplantation (HCT) of pediatric and young adult patients with nonmalignant diseases. Early experience suggests that these regimens are associated with good survival but a high incidence of mixed chimerism, which we have previously shown to be influenced by the alemtuzumab schedule. We hypothesized that the underlying diagnosis and donor graft source would also affect the development of mixed chimerism and that the majority of patients would survive RIC HCT without graft loss. To examine this, we conducted a retrospective study of 206 patients with metabolic diseases, non-Fanconi anemia marrow failure disorders, and primary immune deficiencies who underwent 210 consecutive RIC HCT procedures at Cincinnati Children's Hospital. Ninety-seven percent of the patients engrafted. Mixed donor and recipient chimerism developed in 46% of patients. Patients with marrow failure had a low risk of mixed chimerism (hazard ratio [HR], .208; 95% confidence interval [CI], .061 to .709; P = .012). The risk of mixed chimerism was high in patients who received a cord blood graft (HR, 3.122; 95% CI, 1.236 to 7.888; P = .016). As expected, patients who received a proximal or higher dose per kilogram of alemtuzumab schedule also experienced higher rates of mixed chimerism (all HR > 2, all P < .05). At the time of last follow-up (median, 654 days; range, 13 to 3337), over 75% of patients had greater than 90% whole blood donor chimerism. A second transplantation was performed in 5% of patients. Three-year survival without retransplantation was 84% (95% CI, 71% to 98%) for patients who underwent transplantation with an HLA-matched sibling donor. Survival without retransplantation was negatively affected by lack of a matched related donor, increasing age, and development of grades III and IV acute graft-versus-host disease. We conclude that alemtuzumab, fludarabine, and melphalan RIC HCT offers good results for many patients and that the risk of developing mixed chimerism is influenced by underlying diagnosis, graft source, and alemtuzumab dosing.

Marsh RA ，Rao MB ，Gefen A ，Bellman D ，Mehta PA ，Khandelwal P ，Chandra S ，Jodele S ，Myers KC ，Grimley M ，Dandoy C ，El-Bietar J ，Kumar AR ，Leemhuis T ，Zhang K ，Bleesing JJ ，Jordan MB ，Filipovich AH ，Davies SM ... -  《-》

Age Impacts Risk of Mixed Chimerism Following Reduced-Intensity Conditioning Hematopoietic Cell Transplantation for Non-Severe Combined Immune Deficiency Inborn Errors of Immunity.

Alemtuzumab, fludarabine, and melphalan containing-reduced intensity conditioning (RIC) is commonly used in patients undergoing allogeneic hematopoietic cell transplantation (HCT) for definitive treatment of high-risk inborn errors of immunity (IEI). Although survival is favorable, there is an increased risk of mixed chimerism leading to secondary graft failure. This study evaluated factors associated with the risk of developing mixed chimerism, particularly the influence of age in patients undergoing allogeneic HCT for non-severe combined immune deficiency (SCID) IEI who received a uniform RIC regimen that included intermediate schedule alemtuzumab, fludarabine, and melphalan. We hypothesized that age would impact the incidence of mixed chimerism. We retrospectively reviewed records of patients who underwent HCT for non-SCID IEI with a uniform RIC regimen that included intermediate schedule alemtuzumab (1 mg/kg divided over days -14 to -10), fludarabine (150 mg/m2 or 5 mg/kg if weight <10 kg divided over days -9 to -4), and melphalan (140 mg/m2 or 4.7 mg/kg if weight <10 kg on day -3) between 2010 and 2020 at our institution. Mixed chimerism was defined as <95% donor chimerism on 2 or more consecutive occasions in whole blood. Ninety-three patients who underwent RIC-HCT for non-SCID IEI using intermediate schedule alemtuzumab, fludarabine, and melphalan were categorized into 3 groups: age <1 year, age 1 to 5 years, and age >5 years. Forty-nine patients (52.7%) developed mixed chimerism, at a median of 34 days post-HCT (range, 10 to 1396 days). Mixed chimerism developed in 88.9% (n = 16/18) of the age <1 year group, in 57.1% (n = 20/35) of the age 1 to 5 years group, and in 35% (n =14/40) of the age >5 years group. Patients age <5 years were significantly more likely to develop mixed chimerism (χ2 (3, N = 93) = 14.8; P = .001). We observed a significantly increased cumulative incidence of developing mixed chimerism associated with age <1 year (P = .0002). Competing risk regression analysis showed a 3-fold higher risk of developing mixed chimerism for age <1 year (subdistribution hazard ratio (HR), 3.05; 95% confidence interval [CI], 1.11 to 8.38; P = .031,) compared to age >5 years and a significantly decreased risk of mixed chimerism in patients who developed acute GVHD prior to any intervention (OR, .24; 95% CI, .09 to .65; P = .005) There were no significant associations between mixed chimerism and graft source, graft type, CD34+ or CD3+ cell dose, HLA match, or underlying disease (hemophagocytic lymphohistiocytosis [HLH] versus non-HLH). Additionally, the need for secondary intervention was evaluated; 27 patients (29.0%) required 1 or more secondary interventions (donor lymphocyte infusion, CD34 boost, or second HCT). Patients age <1 year with mixed chimerism were significantly more likely than patients age >5 years to require secondary intervention for mixed chimerism (P = .004). Our study demonstrates that age <5 years, especially age <1 year, is associated with an increased risk of developing mixed chimerism in patients undergoing RIC-HCT for non-SCID IEI using intermediate-schedule alemtuzumab, fludarabine, and melphalan. Our data suggest tailoring regimen intensity based on age to reduce the incidence of mixed chimerism. Children age <5 years, particularly those age <1 year, require a higher-intensity regimen. Possible strategies include adding thiotepa or using a busulfan-based reduced toxicity regimen.

Fitch T ，Lane A ，McDonnell J ，Bleesing J ，Jordan M ，Kumar A ，Khandelwal P ，Khoury R ，Marsh R ，Chandra S ... -  《-》

An intermediate alemtuzumab schedule reduces the incidence of mixed chimerism following reduced-intensity conditioning hematopoietic cell transplantation for hemophagocytic lymphohistiocytosis.

Reduced-intensity conditioning (RIC) improves the outcomes of hematopoietic cell transplantation (HCT) in patients with hemophagocytic lymphohistiocytosis (HLH). Proximal (ie, close to graft infusion) dosing of alemtuzumab is associated with a high incidence of mixed chimerism, whereas distal (ie, distant from graft infusion) dosing is associated with less mixed chimerism but more acute graft-versus-host disease (GVHD). The alemtuzumab dose per kilogram of body weight also influences these outcomes. We hypothesized that an intermediate alemtuzumab dosing schedule would reduce mixed chimerism and maintain a low incidence of acute GVHD. In this study, 24 consecutive HCTs were performed in patients with HLH or a related disorder using a novel intermediate alemtuzumab schedule of 1 mg/kg starting on day -14. The cumulative incidences (CIs) of mixed chimerism, upfront acute GVHD grades II-IV, and receipt of additional hematopoietic cell products after HCT were compared in patients treated with a distal alemtuzumab schedule (n = 15) and those treated with a proximal alemtuzumab schedule (n = 33). All patients received fludarabine and melphalan. The CI of mixed chimerism was 31% in the intermediate group, 72% in the proximal group (P < .01), and 75% in the distal group patients who received ≥2 mg/kg alemtuzumab (P = .03). The CI of acute GVHD grades II-IV before the development of mixed chimerism was 4% in the intermediate group, 0% in the proximal group, and 13% in the distal group (P = .04, proximal versus distal). The 1-year CI of administration of additional hematopoietic cell products for mixed chimerism (donor lymphocyte infusion ± hematopoietic stem cell boost ± repeat HCT) was 14% in the intermediate group, 53% in the proximal group (P = .01), and 38% in the distal ≥2 mg/kg alemtuzumab group (P = .02). Our findings indicate that intermediate RIC reduces the incidence of mixed chimerism, is associated with a low incidence of upfront acute GVHD, and decreases the need for additional hematopoietic cell products after HCT.

Marsh RA ，Kim MO ，Liu C ，Bellman D ，Hart L ，Grimley M ，Kumar A ，Jodele S ，Myers KC ，Chandra S ，Leemhuis T ，Mehta PA ，Bleesing JJ ，Davies SM ，Jordan MB ，Filipovich AH ... -  《-》

Outcomes of donor lymphocyte infusion for treatment of mixed donor chimerism after a reduced-intensity preparative regimen for pediatric patients with nonmalignant diseases.

Mixed donor chimerism is increasingly common in the pediatric hematopoietic stem cell transplantation (HSCT) setting because of the increased use of reduced-intensity preparative regimens for nonmalignant diseases. Donor lymphocyte infusion (DLI) is potentially useful in the treatment of mixed donor chimerism, but little are data available on the use of DLI in this setting. We conducted a retrospective review of 27 pediatric patients who received DLI for mixed donor chimerism between January 2006 and December 2010 after receiving a preparative regimen of alemtuzumab, fludarabine, and melphalan. Twenty-one patients (78%) were alive at a median of 35 months post-transplant. Seven patients (26%) sustained full donor chimerism after DLI only at a median of 35 months post-HSCT. Nine patients (33%) continued with mixed donor chimerism (median, 38% [range, 18% to 70%]) at a median of 37 months after DLI only. Five patients underwent unconditioned stem cell boosts or second conditioned transplants after no improvement in donor chimerism was seen following DLI. Donor source appeared to contribute to outcomes after DLI; patients with mismatched unrelated donors had earlier first decline in chimerism and timing of first DLI, a higher response rate to DLI, and an increased rate of graft-versus-host disease (GVHD). There was no response to DLI in patients with matched sibling donors. Ten patients, all with improvement in chimerism after DLI, developed acute GVHD after DLI, with 3 having grade III GVHD. Three patients developed chronic GVHD after DLI. These data illustrate the potential efficacy of DLI in the treatment of mixed donor chimerism after a reduced-intensity preparative regimen.

Haines HL ，Bleesing JJ ，Davies SM ，Hornung L ，Jordan MB ，Marsh RA ，Filipovich AH ... -  《-》

A Single-Center Experience Comparing Alemtuzumab, Fludarabine, and Melphalan Reduced-Intensity Conditioning with Myeloablative Busulfan, Cyclophosphamide, and Antithymocyte Globulin for Chronic Granulomatous Disease.

Myeloablative conditioning (MAC) regimens are commonly used in transplantation for chronic granulomatous disease (CGD) but are associated with toxicity. Reduced-intensity conditioning (RIC) regimens have lower toxicity but may fail to achieve stable donor chimerism. We report a comparison between 4 patients who received a RIC regimen consisting of alemtuzumab (1 mg/kg), fludarabine (150 mg/m2), and melphalan (140 mg/m2) and 14 patients who received a MAC regimen consisting of busulfan (area under the curve, 1800 to 2000 µMol/min twice daily × 4 days), cyclophosphamide (50 mg/kg/day × 4), and antithymocyte globulin (15 mg/kg twice daily on days -2 and -1, then daily on days +1 and +2). Seventy-five percent (n = 3) of RIC patients developed mixed chimerism and needed either withdrawal of immune suppression (n = 1) or additional stem cell products (n = 2) to achieve stable donor chimerism. Ninety-two percent (n = 13) of patients in the MAC group maintained >95% donor chimerism. Complications included acute graft-versus-host disease (MAC 64%, RIC 0%), chronic graft-versus-host disease (MAC 28%, RIC 0%), sinusoidal obstructive syndrome (MAC 7%, RIC 0%), bacteremia (MAC 42%, RIC 0%), fungemia (MAC 14%, RIC 0%), viral disease (MAC 7%, RIC 25%), and death (MAC 21%, RIC 0%). A RIC regimen has lower toxicity but frequently requires interventions to maintain donor chimerism compared with a MAC regimen in CGD.

Khandelwal P ，Bleesing JJ ，Davies SM ，Marsh RA ... -  《-》