Haploidentical Hematopoietic Cell Transplantation Research Articles

SCD Dyslipidemia Normalizes Long-Term Following Nonmyeloablative Hematopoietic Cell Transplantation

Dyslipidemia is common in patients with sickle cell disease (SCD). Individuals with SCD have a unique type of dyslipidemia. This SCD dyslipidemia (hypocholesterolemia subtype) is characterized by low total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), and high-density lipoprotein cholesterol (HDL-c), and normal triglycerides (TG). This SCD dyslipidemia state is theorized to be cardioprotective regarding atherosclerotic risk due to the hypolipidemic condition. Hematopoietic cell transplantation (HCT) is a potentially curative therapy for SCD. Nonmyeloablative HCT has been employed at the National Institutes of Health (NIH) and internationally with good results. Long-term survivors of HCT, specifically for hematologic malignancies, are at increased risk for dyslipidemia (hypercholesterolemia subtype), thus increasing atherosclerotic risk long-term. There are no studies investigating the short or long-term effects of HCT on SCD dyslipidemia. Therefore, we report a novel study to characterize lipid profiles at baseline and after HCT for SCD. This cohort study analyzes data from patients who received their first nonmyeloablative HLA-matched sibling or haploidentical HCT for SCD at the NIH from May 2009 to December 2021. All patients received sirolimus as GVHD prophylaxis. Total cholesterol, HDL-c, LDL-c, and triglycerides were collected pre-HCT, one-year post-HCT, and annually thereafter via a fasting serum-based lipid panel (median follow-up of 4 years). Data were analyzed using linear generalized estimating equation regression models to measure the influence of factors such as year of HCT, sirolimus use, gender, age, and graft failure on TC, LDL-c, HDL-c, and TG levels. A total of 116 patients were included in this analysis. There were 72 male and 44 female patients. The median age was 31 (range 10 to 64) years. 90% of the patients had Hb-SS, 3% Hb-SC, 5% Hb-Sβ 0, and 2% Hb-Sβ +. Overall survival is 87%, and 19% experienced graft failure. The median time on sirolimus post-HCT was one year. Baseline, one-year, and two-year mean (25th, 75th percentile) values, respectively, for the TC, LDL-c, HDL-c, and TG are as follows: TC [130.7 (107.0, 147.0), 183.2 (144.5, 220.0), 175.2 (144.5, 209.0)], LDL-c [72.5 (50.0, 87.0), 109 (73.5, 130), 104.2 (75.5, 128.0)], HDL-c [32.3 (23.8, 39.3), 49.4 (38.0, 55.5), 49.2 (41.5, 58.0)] and TG [127.3 (88.5, 156.5), 125.9 (87.0, 153.5), 112.6 (72.0, 133.5)]. Generally, the first-year post-HCT changes were maintained annually thereafter. (Figure 1). According to linear regression modeling, the change in TC, LDL-c, HDL-c, and TG at one-year post-HCT was +50.3 mg/dL (p<0.0001), +36.4 mg/dL (p <0.0001), +20.4 mg/dL (p<0.0001) and -26.5 mg/dL (p<0.0001), respectively. For failed grafts, the estimated changes after one-year post-HCT in TC, LDL-c, HDL-c, and TG were +6.5 mg/dL (p=0.45), -2.1 mg/dL (p=0.78), +14.8 mg/dL (p<0.0001), and -28.0 (p=0.03), respectively. The use of sirolimus only resulted in a significant change in TG (+32.8 mg/dL (p = 0.004)). Age had statistically significant changes only on TC (+1.08 mg/dL for a one-year change in age, p=0.005) and LDL-c (+0.73 mg/dL for a one-year change in age, p=0.03). There were no significant differences in TC, LDL-c, HDL-c, and TG levels (p>0.05) based on gender and HCT type. To summarize, HCT with sustained grafts led to significant rises in TC, LDL-c, and HDL-c and a decline in TG from baseline to one-year post-HCT, resulting in the normalization of lipid profiles. These changes were maintained annually thereafter. Graft failure most notably resulted in TC and LDL-c level declines back to pre-HCT baseline (Figure 2), while HDL-c and TG levels did not completely revert to baseline values. Sirolimus effects were significant on TG levels alone. These findings suggest that the mechanism underlying SCD dyslipidemia is corrected with the reversal of SCD. Long-term follow-up studies are indicated to assess patients' risk for atherosclerosis and adverse cardiac outcomes.

Opportunistic Infections in Patients Receiving Post-Transplantation Cyclophosphamide: Impact of Haploidentical versus Unrelated Donor Allograft

Post-transplant cyclophosphamide (PTCy) is an effective strategy for graft-versus-host disease (GVHD) prophylaxis and is the standard of care for haploidentical hematopoietic cell transplantation (HCT). It is increasingly used for matched and mismatched unrelated donor (MUD/MMUD) HCT, but infections remain a concern. The objective of this study was to evaluate the characteristics and risk factors for infections in haploidentical and unrelated donor HCT recipients treated with PTCy-based GVHD prophylaxis. This single-center retrospective study examined 354 consecutive adults undergoing HCT with PTCy-based GVHD prophylaxis (161 MUD/MMUD; 193 haploidentical) between 2015 and 2022. Opportunistic infections (OIs) including cytomegalovirus (CMV), adenovirus (AdV), Epstein-Barr virus (EBV), and invasive fungal disease (IFD) were assessed from day 0 through day +365. The one-year cumulative incidence function of OIs and non-relapse mortality were calculated using dates of relapse and repeat HCT as competing risks. Secondary analysis evaluated risk factors for OIs and NRM using univariate and multivariable Cox regression models. Haploidentical HCT recipients had an increased risk of OIs compared to unrelated donor allograft recipients (39% haploidentical vs. 25% MUD/MMUD; HR 1.70; 95% CI 1.16 - 2.49; p=0.006). On multivariable analysis, haploidentical donor (HR 1.50; 95% CI 1.01 - 2.23; p=0.046), prior HCT (HR 1.99; 95% CI 1.29 - 3.09; p=0.002), and diagnosis of acute GVHD (HR 1.47; 95% CI 1.02 - 2.14; p=0.041) were associated with an increased risk of OIs. Non-relapse mortality within the first year was not significantly different between the two groups (HR 1.11; 95% CI 0.64 - 1.93; p=0.70). Overall, haploidentical donor was a significant risk factor for OIs in patients receiving PTCy, although one-year NRM was not different between haploidentical and MUD/MMUD HCT recipients. CMV and adenovirus infections were significantly increased amongst haploidentical HCT recipients, while the incidence of EBV infection and IFD was similar between the groups. Our findings may have implications for infection monitoring and prophylaxis in the setting of PTCy, particularly in haploidentical HCT recipients.

Improvement in Cardiac Morphology Demonstrated by Cardiac Magnetic Resonance Imaging and Echocardiography after Haploidentical Hematopoietic Cell Transplantation in Adults with Sickle Cell Disease

Cardiopulmonary complications account for approximately 40% of deaths in patients with sickle cell disease (SCD). Diffuse myocardial fibrosis, elevated tricuspid regurgitant jet velocity (TRV) and iron overload are all associated with early mortality. While HLA-matched sibling hematopoietic cell transplant (HCT) offers a potential cure, fewer than 20% of patients have a suitable donor. Haploidentical HCT allows for an increased donor pool and has recently demonstrated improved safety and efficacy. Our group has reported improved cardiac morphology via echocardiography at one year after HCT. Herein, we describe the first use of cardiac magnetic resonance imaging (CMR), the gold standard for measuring volume, mass, and ventricular function, to evaluate changes in cardiac morphology post-HCT in adults with SCD. We analyzed baseline and 1-year data from 12 adults with SCD who received nonmyeloablative haploidentical peripheral blood HCT at the NIH. Patients underwent non-contrast CMR at 3T, echocardiography, and laboratory studies. One year after HCT, patients showed marked improvement in cardiac chamber morphology by CMR, including left ventricular (LV) mass and volume (70.2 to 60.1 g/m2, p = 0.02; 114.5 to 90.6 mL/m2, p = 0.001). Furthermore, mean TRV normalized by 1 year, suggesting that HCT may offer a survival benefit. Fewer patients had pathologically prolonged native myocardial T1 times, an indirect marker of myocardial fibrosis at 1 year; these data showed a trend toward significance. In this small sample, CMR was very sensitive in detecting cardiac mass and volume changes after HCT and provided complementary information to echocardiography. Notably, post-HCT improvement in cardiac parameters can be attributed only in part to the resolution of anemia; further studies are required to determine the role of myocardial fibrosis reversal, improved blood flow, and survival impact after HCT for SCD.

Peripheral blood haploidentical hematopoietic cell transplantation for patients aged 70 years and over with acute myeloid leukemia or high-risk myelodysplastic syndrome.

Haploidentical stem cell transplantation (Haplo-SCT) using non-myeloablative conditioning regimen (NMAC) has extended the feasibility of allogeneic transplantation, notably in older patients. However, there is few data specifically focusing on patients aged 70 years and over with AML and MDS. Thus the benefit of transplantation in this population is still debated. Here we report our single center experience of peripheral blood Haplo-SCT with NMAC and post-transplantation cyclophosphamide in AML and MDS patients aged 70 years and over. We analyzed 50 patients (27 AML, 23 MDS) with a median age of 72 years (70-77), 12/50 (24%) with active disease at Haplo-SCT. Cumulative incidence of grade 3-4 acute and moderate or severe chronic GVHD were 6% and 25%, respectively. Non-relapse mortality (NRM) at day +100 was 0%. NRM, relapse, PFS and OS at 3 years were 16%, 18%, 66%, and 69%, respectively. Among patients who were disease free at 2 years post Haplo-SCT, 88% are living without immunosuppressive treatment. Peripheral blood Haplo-SCT is feasible in selected AML/MDS patients over 70 years, without any early NRM. It produces long-term disease control and survival. Thus, age by itself should not be considered as a formal barrier to Haplo-SCT.

High Exposure of Rabbit Anti-Thymocyte Globulin (ATG) Is Strongly Associated with Inferior DFS in Pediatric Patients with Malignancy Undergoing Alpha-Beta T-Cell Depleted Haploidentical HCT

The PTCTC ONC1401 trial reported a 75% 2-year disease-free survival (DFS) for pediatric patients with acute leukemia or MDS undergoing AB-TCR/CD19 depleted (AB-TCD) haploidentical HCT. Patients ≥10 years had significantly worse DFS. Conditioning for AB-TCD HCT typically includes rATG (Thymoglobulin®) 3 mg/kg/day on days -12 to -10. Models of rATG pharmacokinetics (PK) show slower clearance in older children. We hypothesized worse DFS seen in older patients may be due to excessive in vivo T-cell depletion by residual rATG post HCT. Patients undergoing first AB-TCD haploidentical HCT with rATG as the sole serotherapy agent for treatment of malignancy from Dec 2015 to Jan 2023 were included. Patients were treated on PTCTC ONC1401 or institutional prospective trials of AB-TCD. Minimal residual disease (MRD) was determined by the best-available method (multi-parameter flow or next-generation sequencing) for each patient. Predicted pre- and post-HCT AUC of rATG (in AU*day/mL) were retrospectively determined using the software platform InsightRx© (InsightRx, Inc., San Francisco, CA) and a validated PK model for rATG clearance. Quadratic regression was used to identify optimal target windows of rATG exposure for cumulative incidence and Kaplan-Meier estimations. Multivariate analysis (MVA) Cox regression models were built using all covariates with a univariate p-value <0.2. The dataset included 134 patients ( Table 1); median (range) follow-up of survivors was 3.4 years (0.5-7.6). The median age at HCT was 12.3 years (0.4-27.4), and median donor age was 32 years (5-61). The median infused cell doses for CD34 and AB-T-cells were 15.2 (2.5-45.8) x10^6/kg and 7.0 (0.1-27.6) x10^4/kg. The 100-day incidence of rejection was 11.3% (5.8-16.8) with a 3-year EFS of 59% (50.2-67.8). The 3-year incidence of non-relapse mortality (NRM) and relapse were 13.8% (6.9-20.7) and 21.4% (13.8-29). The 100-day incidence of grades 2-4 and 3-4 aGVHD were 24.4% (16.2-32.6) and 8.5% (3.4-13.6), while 3-year incidence of cGVHD was 16.7% (9.1-24.3). The 3-year DFS and OS were 67.6% (59.2-76) and 73.8% (64-83.6). Increased 3-year NRM was seen in patients ≥10 years: 19.9% (10.6-31.4) vs. 5.6% (0.1-13.4) ( p=0.03); in those with sibling vs. parent donors: 27.3% (12.4-42.2) vs. 8.5% (1.6-15.4) (p=0.008); and CMV mismatched donors: 25.5% (9.1-41.3) vs. 10.4% (3.3-17.5) ( p=0.03). There was no difference in relapse between MRD-techniques, so these were combined for subsequent analyses. Lower 3-year relapse was seen in patients who were MRD-negative: 12.6% (5.5-19.7) vs. 45.7% (26.7-64.7) ( p<0.001); and who received targeted small-molecule therapy post-HCT: 0% (0-19.8) vs. 24.1% (15.5-32.7) ( p=0.04). The median predicted pre-HCT AUC of rATG was 63.7 AU*day/mL (16.4-109). A pre-HCT exposure of ≥40 AU*day/mL was associated with decreased rejection: 8.1% (3-13.2) vs. 27.3% (8.8-45.9; p=0.008). A pre-HCT exposure of <80 AU*day/mL was associated with lower 3-year TRM: 8% (1.7-14.3) vs. 33.4% (14.8-52; p<0.001). The 3-year EFS for patients with a pre-HCT AUC of 40-79.9 AU*day/mL was 69.7% (58.7-80.7) vs. 45.4% (31.9-58.9) for those not in goal range ( p=0.004). The median post-HCT AUC of rATG was 9.5 AU*day/mL (1-42.5). There was no different in grade 2-4 (p=0.61) or grade 3-4 (p=0.25) aGVHD or cGVHD (p=0.9) between those with low (<13 AU*day/mL) vs. high (≥13 AU*day/mL) exposure. A low post-HCT AUC was associated with both lower 3-year NRM: 7.2% (0.9-13.5) vs. 28.1% (11.6-44.6) ( p=0.002), and lower 3-year relapse incidence: 15.5% (7-23.7) vs. 34.3% (18.6-50) ( p=0.01). In MRD-negative patients, low vs. high post-HCT rATG AUC was associated with a 3-year DFS of 81.2% (71-91.4) vs. 60.2% (42-78.4) ( p=0.03); in MRD-positive patients, low vs. high post-HCT rATG AUC was associated with a 3-year DFS of 69.3% (47.9-90.7) vs. 17.9% (0.1-39.5) ( p<0.001). MVA showed that high post-HCT rATG exposure, MRD-positivity, and CMV-mismatched donors were associated with worse 3-year DFS ( Table 2). We identified optimal windows for rATG exposure - pre-HCT of 40-79.9 AU*day/mL, post-HCT <13 AU*day/mL - associated with lower rates of rejection, NRM, relapse, and improved DFS. Validation with prospective drug levels and an independent cohort would strengthen these conclusions. Our data indicates that model-based dosing of rATG to target pre- and post-HCT exposure may be superior to weight-based dosing in patients undergoing AB-TCD HCT.

Haploidentical Hematopoietic Cell Transplantation Combined with an Unrelated Cord Blood Unit for Adult Acute Myeloid Leukemia Results in Improved Survival Compared to Haploidentical Hematopoietic Cell Transplantation: Results of a Multicenter, Randomized, Phase III Trial

Introduction Haploidentical hematopoietic cell transplantation (haplo-HCT) is a potent treatment to improve the prognosis of acute myeloid leukemia (AML), but relapse and graft-versus-host disease (GVHD) related to dysregulation of alloreactivity are still the main causes of death posttransplantation. Cord blood graft usually has a promising graft-versus-leukemia effect with a lower cumulative incidence of GVHD. To improve the transplantation strategy, haplo-cord HCT combining haploidentical and unrelated cord blood (UCB) grafts (haplo-cord HCT) has been attempted. Previous studies showed significant improvement in prognosis in B-cell acute lymphoblastic leukemia or refractory acute leukemia patients with haplo-cord HCT compared to haplo-HCT. However, outcomes of haplo-cord HCT for AML patients are not yet clear. This is the first multicentric randomized trial designed specifically for the efficacy and safety of haplo-cord HCT for AML. Methods This is a multicenter, randomized, open-label, phase III study conducted in 5 centers in China (NCT03719534). Patients aged 18-60 years, diagnosed with AML (except for acute promyelocytic leukemia) with measurable residual disease, had an available haploidentical donor and were suitable for allotransplantation were enrolled. Patients were randomized 1:1 to receive UCB and haploidentical grafts infusion after Bu/Cy-based regimen or haploidentical graft infusion only after Bu/Cy-based regimen. The UCB unit, which had at least 3/6 matched HLA loci to the recipient and more than 1×10 4 CD34 + cells/kg of recipient weight, was infused immediately after resuscitation and eight hours before the haploidentical graft infusion. The primary endpoint was 3-year overall survival (OS) and secondary endpoints included progression-free survival (PFS), cumulative incidence of relapse (CIR), and non-relapse mortality (NRM). Results From June 1, 2017, to June 30, 2021, 268 patients were enrolled (Table 1). With a median follow-up of 36.00 months, the 3-year OS was 80.5% (95% CI 73.7-87.9) in the haplo-cord HCT group and 67.8% (95% CI 60.0-76.5) in the haplo-HCT group, respectively (p=0.013, figure 1A). Haplo-cord HCT group showed favorable 3-year PFS and CIR than haplo-HCT group (PFS: 70.3%, 95% CI 62.6-78.8 vs. 57.6%, 95% CI 49.6-67.0, p=0.012; CIR: 12.1%, 95% CI 12.0-12.2 vs. 30.3%, 95% CI 30.1-30.4, p=0.024, figure 1B,C). The 3-year NRM was similar in the two groups (figure 1D). Within two years posttransplantation, the most common grade 3-4 adverse events (AEs) in the haplo-cord HCT and haplo-HCT groups were infections (33.8% and 29.1%), acute GVHD (20.3% and 12.7%) and chronic GVHD (12.0% and 16.4%). AEs leading to death occurred in 8.3% of haplo-cord HCT and 14.9% haplo HCT patients. Post- hoc analysis showed similar median levels of haploidentical chimerism in bone marrow (BM) between the two groups. However, UCB microchimerism was detected in the haplo-cord HCT patients by SNP-NGS in +1m posttransplantation (BM: 0.3%, IQR 0.04-1.6; peripheral blood: 0.06%, IQR 0.03-0.4) and its chimerism percentage decreased with time (figure 1E). Compared to haplo-HCT group, haplo-cord HCT group showed a faster cumulative incidence of neutrophil recovery (p=0.026, figure 1F) and a similar cumulative incidence of platelet recovery. Monitor of immune reconstitution showed a more rapidly increasing rate of T cells in the early period after transplantation in the haplo-cord HCT group (figure 1G). Improved recovery of Th2 (p=0.042), Th17 (p=0.047), Treg (p=0.045), and Tc2 (p=0.045) cells was observed in haplo-HCT group. Conclusions Coinfusion of a UCB unit in haplo-HCT can improve OS in AML patients without excessive AEs, and affect T-cell reconstitution pattern posttransplantation. Haplo-cord HCT could serve as a suitable therapeutic option for this patient population.

Haploidentical Hematopoietic Cell Transplant with Post-Transplant Cyclophosphamide Expedites Donor-Derived Immune Reconstitution in a Pediatric Severe Aplastic Anemia Cohort

Severe aplastic anemia (SAA) is a life-threatening, idiopathic process involving the immune-mediated destruction of hematopoietic stem cells. Treatment involves immunosuppressive therapy (IST) and/or allogeneic hematopoietic cell transplantation (HCT). The latter has recently been optimized with use of a post-transplant cyclophosphamide (PTCy) based graft-versus-host disease (GvHD) platform, permitting successful HCT with only half-HLA-matched haploidentical donors. In pediatrics, this platform results in >90% overall survival with low rates of GvHD and graft failure. However, reports on donor chimerism and immune reconstitution are limited. We hypothesized that a PTCy platform would expedite CD3 donor engraftment and CD4 T cell recovery. In a phase III clinical trial, we treated three cohorts of pediatric (age </=25 years) patients with SAA requiring alloHCT: MUD, MSD, and HAPLO. The MUD cohort included n=15 recipients of 7-8/8 HLA-matched unrelated donor grafts (n=5 7/8, n=10 8/8) with median age 14 years (range 2-17 years), following cyclophosphamide (Cy) 50 mg/kg, fludarabine (Flu) 200 mg/m 2, rabbit anti-thymocyte globulin (rATG) 9 mg/kg total dose rabbit and low dose total body irradiation (TBI) at 200 cGy. The MSD cohort included n=9 recipients of 8/8 HLA-matched sibling donor grafts with median age 15 years (range 12-24 years), following Cy 200 mg/kg and 9 mg/kg rATG. The HAPLO cohort included n=4 recipients of 4/8 HLA-matched related donor grafts with median age 8.5 years (range 2-21 years) following Cy 29 mg/kg, Flu 150 mg/m 2, 9 mg/kg rATG, and low dose TBI at 200 cGy. GvHD prophylaxis consisted of 30 days of mycophenolate mofetil, and 100 days of a calcineurin inhibitor (followed by an 8-10 week taper), with the HAPLO cohort additionally receiving post-transplant Cy (PTCy) 50 mg/kg/day on days +3 and +4. Peripheral blood lymphocyte counts and peripheral blood and bone marrow donor chimerism were evaluated on days +100, +180 and +365. Recipient characteristics were largely equivalent between cohorts, with 43% receiving IST prior to HCT. Clonality was overrepresented in the HAPLO cohort (2 of 4, 1 with monosomy 7 myelodysplastic syndrome and 1 with a large PNH clone), with only 2 of 15 in the MUD and none in the MSD cohorts. Active controlled infections at the time of HCT were additionally overrepresented in the HAPLO cohort, with disseminated pseudomonas in 1. The MUD cohort had 1 with Rhizopus invasive sinusitis (none in the MSD cohort). Achievement of neutrophil engraftment was statistically significantly delayed in the HAPLO cohort at a median of 17 days compared to 12 for MSD and 14 for MUD, p=0.004), however there were no episodes of primary or secondary graft failure. With only a single late death from intracranial hemorrhage in the MUD cohort, OS was equivalent at 2 years (100% in MSD and HAPLO cohorts, 93.3% in MUD). GvHD rates were low with only 1 (MUD) experiencing grade II acute GvHD, and 1 (MUD) experiencing mild chronic GvHD. Immune reconstitution varied by cohort with statistically significantly greater CD3 peripheral blood donor chimerism (p<0.001) as well as CD4 (p=0.04) and CD8 (p=0.03) T cell counts over time for the HAPLO recipients (CD3 chimerism in Fig 1, CD4 count in Fig 2; 2-way ANOVA fixed effects model). Considering a CD4 >200 cell/uL as clinically meaningful, we assessed the proportion of each cohort achieving this milestone at each timepoint. While each cohort had an increase in proportion achieving CD4>200 over time, the HAPLO cohort reached 50% with CD4 >200 at day +100, compared to 11% MUD and 0% MSD (p=0.09). At day +180, the proportion with CD4 >200 were 36% MUD, 25% MSD and 75% HAPLO (1 yr: 90% MUD, 100% MSD and HAPLO). Donor availability remains a challenge to successful transplant for patients with SAA, and haploidentical matches overcome donor limited accessibility. PTCy as GvHD prophylaxis is associated with low incidences of graft failure and severe GvHD. While PTCy might be anticipated to inhibit donor T cells and immune reconstitution, our data, albeit limited by small cohorts, demonstrates superior and more efficient CD3 donor engraftment and CD4 T cell count recovery following HAPLO HCT with PTCy compared to non-PTCy based MUD and MSD cohorts.

Effectiveness of In Vivo T-Cell Depleted Regimen Containing Porcine Antilymphocyte Globulin and Rabbit Antithymocyte Globulin in Preventing Acute Gvhd after Haploid Hematopoietic Stem Cell Transplantation

Objective To compare the clinical efficacy of porcine antilymphocyte globulin (p-ALG) and rabbit antithymocyte globulin (r-ATG) in the treatment of hematologic malignancies using haploid hematopoietic stem cell transplantation (haplo- HSCT), this study was conducted. Methods This was a single center retrospective analysis of 178 subjects who received haplo-HSCT with p-ALG or r-ATG from January 2020 to December 2022. The patients were divided into three groups according to the doses of p-ALG or r-ATG used in the conditioning regimens. The study evaluated and compared the occurrence of early fever, graft versus host disease (GVHD), infection, and survival among the three groups of patients. Results A total of 178 patients were enrolled in the study with a median age of 30 (14-61) years, including 95 men and 83 women. The median follow-up time post-transplantation was 20.1 (1.7-36.9) months. The study included 57 patients in the p-ALG 75mg/kg group, 49 patients in the p-ALG 90mg/kg group, and 72 patients in the r-ATG 7.5mg/kg group, respectively. The incidences of neutrophil and platelet engraftment, respectively, were 100%,93.5%, and 91.3% (p=0.133); 100%, 93.6%, 90.3% (p=0.033) in P-ALG 75mg/kg, P-ALG 90mg/kg and r-ATG 7.5mg/kg. The median time to neutrophil engraftment was 11 days for the P-ALG 75mg/kg group, 12 days for the P-ALG 90mg/kg group, and 12 days for the r-ATG 7.5mg/kg group (p=0.133). The median time to platelet engraftment was 12 days for the P-ALG 75mg/kg group, 14 days for the P-ALG 90mg/kg group, and 13 days for the r-ATG 7.5mg/kg group (p=0.033). In the p-ALG 75mg/kg, p-ALG 90mg/kg, and r-ATG 7.5mg/kg groups, 16 patients (28.1%), 24 patients (49.0%) and 35 patients (48.6%) developed fever within 14 days after transplantation, respectively. Cytokine release syndrome was found to be the most common cause of fever. The incidence of grades Ⅱ-Ⅳ acute GVHD (aGVHD) and grades Ⅲ-Ⅳ aGVHD, respectively, were 15.8%, 12.2%, and 12.5% (p=0.853); 5.3%, 2.0%, and 5.6% (p=0.523) in P-ALG 75mg/kg, P-ALG 90mg/kg and r-ATG 7.5mg/kg. The cumulative incidence of chronic GVHD at 1 year was 14.0%, 10.2%, and 15.3% (p=0.731) in the three groups. 43.9%, 71.4%, and 61.1% of patients in the p-ALG 75mg/kg, p-ALG 90mg/kg and r-ATG 7.5mg/kg groups, respectively, experienced at least one infection within 1 year after haplo-HSCT (p=0.0.13). Notably, the CMV infection rate in the p-ALG 75mg/kg group was significantly lower than in the p-ALG 90mg/kg and r-ATG 7.5mg/kg groups. The 2-year overall survival (OS) rates of p-ALG 75mg/kg, p-ALG 90mg/kg and r-ATG 7.5mg/kg groups were 78.2%, 70.6%, and 72.3% (p=0.491). The cumulative incidence of 2-year relapse were 33.0%, 29.8%, and 30.0% (p=0.834). ConclusionsCompared with r-ATG group, the p-ALG 75mg/kg group showed a lower incidence of infection. However, there were no significant differences between the two groups in terms of the incidence of grades Ⅱ-Ⅳ aGVHD, 2-year overall survival (OS), and 2-year cumulative incidence of relapse. p-ALG (75mg/kg) has a comparable effect on the prevention of GVHD after haplo-HSCT with a lower incidence of infection. Keywords: Porcine antilymphocyte globulin; Rabbit antithymocyte Globulin; Haploidentical hematopoietic cell transplantation; Graft versus host disease; Infection

Itacitinib for Prevention of Graft-Versus-Host Disease and Cytokine Release Syndrome with T-Cell Replete Peripheral Blood Haploidentical Transplantation

Introduction: Haploidentical peripheral blood allogeneic hematopoietic cell transplantation (PB haplo-HCT) can be complicated by graft-versus-host disease (GVHD) and cytokine release syndrome (CRS). Acute GVHD rates are higher with PB grafts compared with bone marrow, affecting 35-45% of patients and outcomes are poor in steroid refractory cases. Severe CRS occurs in 10-15% of patients receiving PB haplo-HCT and is associated with high non-relapse mortality and one-year overall survival between 25-30%. As interferon-γ and IL-6 are important mediators in both acute GVHD and CRS, we hypothesized that JAK1 inhibition with itacitinib could prevent these toxicities without impairing engraftment. Here we report outcomes from our study of itacitinib with haplo-HCT (NCT03755414). Methods: Patients with AML, MDS, ALL, or NHL in remission undergoing PB haplo-HCT were treated with itacitinib 200 mg/day on days -3 through +100 (first 20 patients) or 180 (second 22 patients), followed by a taper. Myeloablative and reduced intensity conditioning were allowed. GVHD prophylaxis was tacrolimus, mycophenolate mofetil, and post-transplant cyclophosphamide. Primary outcomes were incidence of primary graft failure and incidence of grade III-IV acute GVHD. Secondary outcomes included incidence and severity of CRS, relapse, GRFS, and overall survival. Results: Forty-two patients were enrolled and underwent transplantation on study between November 2019 and December 2022, median days of follow up was 453 days (range 142-1259). The patient population had a median age of 60 years (20 - 73 years) with the majority of patients having AML (AML 60%, ALL 21%), MDS 10%, MF 5%, NHL 4%). All patients with AML, MDS, or ALL were in a complete morphologic remission, although 45% had disease by either cytogenetics, next generation sequencing, or measurable residual disease assay (flow cytometry for AML/MDS, NGS for ALL). There were no cases of grade III-IV acute GVHD. The cumulative incidence of grade II acute GVHD on day 100 was 17.3% (95% CI, 7% - 31%), day 180 was 20.5% and day 365 was 20.5%. There were no cases of severe CRS with 90% of patients having grade 1 CRS and 10% having no CRS. No anti-IL6R or steroid therapy was used. There were no cases of primary graft failure. The cumulative incidence of relapse at 1 year was 10% (95% CI, 3% to 22%) and at 2 years was 14% (95% CI, 5% to 29%). In patients who survived without relapse to day 100, the 1-year cumulative incidence of moderate or severe chronic GVHD was 5% (95% CI 1% - 17%). The refined GRFS at day +180 was 85% (95% CI 69% - 93%) and at day +365 was 79% (95% CI 62% - 89%). Overall survival at 180 days 87% (95% CI 72% - 94%) and at 1 year was 80% (95% CI 63% - 90%). Analysis of peripheral blood mononuclear cells at day +28, +60, and +100, revealed that patients on itacitinib, compared with control haplo-HCT patients, had lower numbers of CD4 and CD8 central memory T cells, lower numbers of CD4 and CD8 naïve T cells, and higher numbers of classical monocytes, nonclassical monocytes, and both myeloid and plasmacytoid dendritic cells. In itacitinib treated patients, T-cell subsets expressed lower LAG3 and PD-1 and higher TIGIT, while monocytes expressed higher HLA-DR, CD80, and CD86. Conclusions: Itacitinib with PB haplo-HCT was safe with low rates of acute and chronic GVHD, without increased risk of relapse or transplant related mortality. Severe CRS was not seen in this trial, and no anti-IL6 or steroid therapy was used. The addition of Jak inhibition to standard PtCy based GVHD prophylaxis was associated with encouraging rates of GRFS and OS on this pilot and expansion study. Patients on itacitinib have unique immune reconstitution characteristics both in terms of PBMC counts and signaling markers within subsets.

Phase I Trial of Allogeneic Donor Gamma Delta T Cell Infusion Post-Hematopoietic Cell Transplantation, an Interim Safety Report

Background Patients with 2017 European LeukemiaNet (ELN) adverse risk acute myeloid leukemia (AML) are at 40% risk of relapse leading to poor survival after allogeneic hematopoietic cell transplantation (allo-HCT) (Hansen TCT 2021, Jimenez BMT 2021). Ex vivo donor-derived gamma delta T cells (GDT) expanded with artificial antigen presented calls (aAPC) are a novel therapy with potent MHC-independent antineoplastic cytotoxicity. An ongoing phase 1/1b study is evaluating the safety and potential efficacy of ex vivo expanded donor GDT after reduced-intensity conditioning (RIC) allo-HCT in patients with ELN adverse risk AML ( NCT05015426). We report on manufacturing, safety, and correlative biology of expanded donor GDT after allo-HCT in the first 5 treated patients (Table 1). Methods The primary endpoint is the maximum-tolerated dose (MTD) of allogeneic donor GDT as a single infusion at day 60 after RIC allo-HCT. Next generation sequencing was used for measurable residual disease (MRD) assessment pre-HCT and post-GDT infusion. Donor GDT collected from the same donor of the allo-HCT were enriched from non-mobilized leukapheresis product by stimulation with zoledronic acid and IL-2 for 7 days followed by alpha beta T cell depletion using the Miltenyi CliniMACS. Enriched GDT (>90% TCRVδ2) were then co-cultured with irradiated aAPCs in Wilson Wolf G-Rex 100MCS over 10 days (Boucher J. Immunother 2023). This single center, investigator-initiated phase 1 trial is testing 3 distinct dose cohorts of infused GDT (5 x 10 6 cells/kg, 2.5 x 10 7 cells/kg, and 1 x 10 8 cells/kg) with acceptable range of 25% margin. A Bayesian optimal interval design is used to guide dose escalation/de-escalation decisions. Results First 3 patients enrolled in dose level 1 (DL1) cohort received GDT dose of 6.25 x 10 6 cells/kg, while last 2 patients enrolled in DL2 cohort received 3.13 x 10 7 cells/kg dose. Dose-limiting toxicities (DLT) were evaluated for 42 days following GDT infusion and no DLT were observed. None of the treated patients experienced cytokine release syndrome (CRS), Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS) or graft-versus-host disease (GVHD) during DLT period. Among patients treated on DL1, patient #01 had ASXL1 AML with MRD pos (VAF 43.9%) prior to RIC haploidentical (Haplo) HCT. He is in ongoing complete remission (CR) 9 months post-HCT and has had no GVHD. Patient #02 had MRD pos (VAF 61.7%) AML with TP53 mutation/complex karyotype prior to RIC matched sibling donor allo-HCT. He is in CR and has mild chronic GVHD at 7 months post-HCT. Patient #03 with pre-HCT MRD negRUNX1 AML is in ongoing CR 7 months post-RIC Haplo HCT with no GVHD. At day 28 and day 120 post-GDT, all 3 patients were MRD neg in bone marrow and had 100% bone marrow and peripheral blood leukocyte and granulocyte chimerism. In DL2 cohort, patient #04 with RUNX1 AML and patient #05 with t(9;22) AML both were MRD neg prior to RIC Haplo HCT and remain in CR with no GVHD at 5 and 4 months post-HCT, respectively. At day 28 post-GDT, both patients were MRD neg and had 100% chimerism. Patient #05 had a fall during DLT period in a setting of orthostatic hypotension requiring hospitalization for 24 hours for hydration. This was the only grade 3 adverse event observed in this trial. Serum cytokines analyzed included IL2, IL6, IL15, IFNγ, TNFα, Angiopoietin 1&2, and GM-CSF (Figure 1). We compared results prior and up to 90 days post-GDT infusion and found no significant differences, which can explain no CRS or ICANS events yet observed on this trial. Immunophenotype (TCRVδ2, TCRVδ1, PD1, CTLA4, TIGIT and CD28) of GDT was analyzed in samples of donor apheresis, pre- and post-enrichment, infused GDT product and at days 28 and 90 post-infusion. GDT (TCRVδ2) persisted at day 28 and day 90 post-infusion and expressed low levels of cell surface inhibitory receptors. Conclusion This preliminary interim report demonstrates favorable safety and tolerability of donor GDT therapy with no CRS, ICANS or GVHD in first 5 patients treated in this trial. All these patients with adverse risk AML are in ongoing MRD neg CR following RIC allo-HCT, including 2 pre-HCT MRD pos cases with TP53 AML and AXSL1 AML. Early results of this trial are promising, which provides validation for continued testing of adoptive transfer of ex vivo expanded donor GDT. Updated results of this trial will be presented at the annual conference.

Delayed Initiation of Calcineurin Inhibitor Is Critical for Tolerance Induction By Posttransplant Cyclophosphamide

[Introduction] We have previously shown that T-cell exhaustion of donor alloreactive T cells plays a critical role in tolerance induction after mouse allogeneic hematopoietic cell transplantation (allo-HCT) (Asakura S: JCI 2010). Emerging evidence indicates that T-cell exhaustion is a multistep process, including precursors of exhausted T cells (pTex) with stem cell-like properties, pTex-derived transitory exhausted T cells (transitory-Tex) with potent effector-like functions, and terminally exhausted T cells (terminal-Tex) with the expression of multiple inhibitory receptors and severely impaired functions. We have demonstrated, for the first time, that calcineurin inhibitors (CNIs) inhibit tolerance induction by suppressing the terminal exhaustion of donor T cells while inducing transitory-Tex after allo-HCT in mice (Senjo H: Blood 2023). In contrast, post-transplantation cyclophosphamide (PTCy) efficiently induces tolerance with low incidence of chronic GVHD. In the current study, we evaluated the mechanisms by which PTCy could induce tolerance even with the use of CNIs. [Methods] In mouse haploidentical HCT model,B6D2F1 recipients (H-2 b/d) were lethally irradiated and transplanted with 2 × 10 6 T cells together with T-cell-depleted bone marrow cells from C57BL/6 (H-2 b) donors on day 0. CSP (25 mg/kg) was administered from either day 0 (early-CSP) or day 5 (late-CSP), and PTCy (50 mg/kg) was i.p. injected on day 3 after HCT. In clinical study, peripheral blood mononuclear cells were prospectively collected from patients who underwent PTCy-based haplo-PBSCT at our institutions after approval of institutional review. [Results] We have shown that Ly6C is a specific marker for transitory-Tex in mice (Senjo H: Blood 2023). In mice, early-CSP followed by PTCy (CSP→PTCy) significantly expanded Ly6C +PD-1 +TOX low CD8 + T cells and Ly6C +PD-1 +GZMB + CD4 + T cells on day 14, while late-CSP following PTCy (PTCy→CSP) induced T-cell differentiation towards Ly6C -PD-1 +TOX high terminally exhausted T cells. When CSP→PTCy recipients were injected with anti-PD-L1 monoclonal antibodies, transitory-Tex demonstrated vigorous proliferation, while terminal-Tex did not respond to PD-1 blockade. These findings indicate that CSP administration after PTCy promotes tolerance induction, whereas CSP administered before PTCy inhibits tolerance induction. Next, we explored the specific markers for human transitory-Tex using scRNA-seq of T cells from the patients who underwent PTCy haplo-PBSCT, in which tacrolimus (TAC) was started either from day -1 (early-TAC) or day 5 (late-TAC). UMAP analysis showed that early-TAC expanded cluster 5 (C5) out of six CD8 + clusters (C1-C6) and C8 out of three CD4 + clusters (C7-C9) (Fig.1). C5 highly expressed exhaustion markers such as Tox and Pdcd1, together with effector molecules such as Prf1, Gzmb and Cx3cr1, while C8 was characterized with high expression of Gzmb, indicating that C5 and C8 are the human counterparts of transitory-Tex. Analysis of differentially expressed genes showed that Fcgr3a (CD16A) was selectively expressed in C5, while Gzmb and Cd74 were selectively expressed in C8. These two populations showed robust proliferative responses to TCR stimulation in vitro. ScTCR-seq demonstrated that C5 and C8 clusters showed less TCR diversity compared to other clusters, suggesting that C5 and C8 were enriched with alloreactive donor T cells that clonally expanded post-transplant. FCM confirmed that both CX3CR1 +CD16 + CD8 + T cells and GZMB +CD74 +CD4 + T cells were significantly increased in the early-TAC group compared to the late-TAC group on day 28 (Fig. 2). In the early-TAC group, 2/9 patients developed moderate and severe chronic GVHD, and only 1/9 patient was off-immunosuppressants (Fig 2). In sharp contrasts, in the late-TAC group, no patient developed chronic GVHD, and 7/9 patients were off-immunosuppressants. Importantly, two patients who developed chronic GVHD had a particularly high proportions of CX3CR1 +CD16 +CD8 + and GZMB +CD74 +CD4 + transitory-Tex on day 28 after HCT (Fig.2). [Conclusion] Our study demonstrated that early initiation of CNIs before PTCy induced transitory-Tex and inhibited tolerance induction after PTCy haplo-PBSCT. Administration of CNIs after PTCy is critical for tolerance reduction without chronic GVHD.

Post-transplantation cyclophosphamide is associated with increased bacterial infections.

Post-transplant cyclophosphamide (PTCy) is increasingly used to reduce graft-versus-host disease after hematopoietic cell transplantation (HCT); however, it might be associated with more infections. All patients who were ≥2 years old, receiving haploidentical or matched sibling donor (Sib) HCT for acute leukemias or myelodysplastic syndrome, and either calcineurin inhibitor (CNI)- or PTCy-based GVHD prophylaxis [Haploidentical HCT with PTCy (HaploCy), 757; Sibling with PTCy (SibCy), 403; Sibling with CNI-based (SibCNI), 1605] were included. Most bacterial infections occurred within the first 100 days; 953 patients (34.5%) had at least 1 infection and 352 patients (13%) had ≥2 infections. Patients receiving PTCy had a greater incidence of bacterial infections by day 180 [HaploCy 46%; SibCy 48%; SibCNI 35%; p < 0.001]. Compared with the SibCNI without infection cohort, 1.99-fold, 3.33-fold, 2.78-fold, and 2.53-fold increased TRM was seen for the HaploCy cohort without infection and HaploCy, SibCy, and SibCNI cohorts with infection, respectively. Bacterial infections increased mortality [HaploCy (HR1.84, 99% CI: 1.45-2.33, p < 0.0001), SibCy cohort (HR,1.68, 99% CI: 1.30-2.19, p < 0.0001), and SibCNI cohort (HR,1.76, 99% CI: 1.43-2.16, p < 0.0001). PTCy was associated with increased bacterial infections regardless of donor, and bacterial infections were associated with increased mortality irrespective of GVHD prophylaxis. Patients receiving PTCy should be monitored carefully for bacterial infections following PTCy.

Anti-Hla Donor-Specific Antibodies Are Associated to Infection and Not to the Engraftment Rate in Outpatient Haploidentical Hematopoietic Cell Transplantation.

Recipients of a related haploidentical stem cell transplant (haplo-SCT) can have preformed antibodies to HLA donor’s antigens. The aim of the study was to evaluate the engraftment rate and major clinical associations of anti-HLA donor-specific antibodies (DSA) at two mean fluorescence intensity (MFI) thresholds in recipients of an outpatient haplo-SCT. Seventy haplo-HCT recipients were analyzed. A virtual crossmatch was performed using the donor HLA typing and the recipient’s anti-HLA DSA test results. Data for anti-HLA-A, -B, -C, and -DR were analyzed. Recipients with DSA ≥ 500 MFI were considered positive, and those with < 500 were considered negative; the same was adopted for MFI ≥ 1000. Post-transplant infection was higher in recipients with DSA ≥ 500 MFI (84.6%, p = 0.041). First-year mortality was higher in DSA-positive patients ≥ 500 MFI, p = 0.004, and DSA ≥ 1000 MFI, p = 0.022, than in DSA-negative recipients. Graft failure in the first 100 days was not associated with DSA ≥ 500 or ≥ 1000 MFI. There was no difference in acute (a-GVHD) or chronic (c-GVHD) graft versus host disease between DSA-positive and negative patients. There was no association of anti-HLA DSA at MFI ≥ 500 and ≥ 1000 with graft failure, however, increased infection and 1st-year mortality were documented in related haplo-HCT at the MFI cutoffs studied.

Effect of donor age in patients with acute myeloid leukemia undergoing haploidentical hematopoietic cell transplantation vary by conditioning intensity and recipient age.

We investigated the impact of donor age (younger [≤35 years] vs. older [>35 years]) after accounting for other non-HLA and HLA factors on outcomes of patients with acute myeloid leukemia undergoing HLA-haploidentical hematopoietic cell transplantation (n = 790). The effect differed by conditioning-partly related to the differences in the recipient age in myeloablative (MAC; median 46 years) versus reduced-intensity/non-myeloablative conditioning (RIC/NMA; median 61 years) groups. With MAC (n = 320), donor age had no impact on acute graft-versus-host disease (GVHD), but older donors were associated with a significantly higher risk of chronic GVHD (hazard ratio [HR]: 1.6, 95% confidence interval [CI]: 1.10-2.30, p = .02) independent of recipient age and other factors. Donor age had no impact on either relapse or non-relapse mortality (NRM). The impact of donor/recipient age on overall survival changed over time. Older donors were associated with significantly higher late overall mortality (>6 months) in younger recipients (≤ 50 years; HR: 2.2, 95% CI: 1.03-4.6, p = .04) but not older recipients. With RIC/NMA (n = 470), neither recipient's nor donor's age influenced the risk of GVHD. Donor age had no significant impact on the risk of relapse, but older donors were associated with a significantly higher risk of NRM (HR: 1.6, 95% CI: 1.02-2.6, p = .04) independent of recipient age. Older donor age was associated with significantly higher late overall mortality (>9 months) in older recipients (>50 years; HR: 1.66, 95% CI: 1.0-2.67; p = .049) but not in younger recipients. Donor selection based on donor age may require a tailored approach for a particular recipient.

Incidence and Impact of Fungal Infections in Post-Transplantation Cyclophosphamide-Based Graft-versus-Host Disease Prophylaxis and Haploidentical Hematopoietic Cell Transplantation: A Center for International Blood and Marrow Transplant Research Analysis

Patients who underwent their first HCT between 2012 and 2017 for acute myeloid leukemia, acute lymphoblastic leukemia, and myelodysplastic syndrome and received a related haploidentical transplant with PTCy (HaploCy; n=757) or a Sib transplant with PTCy (SibCy; n=403) or CNI (SibCNI; n=1605) were analyzed. The incidence of FI by day 180 post-HCT was calculated as cumulative incidence with death as the competing risk. The associations of FI with overall survival, transplant-related mortality, chronic GVHD, and relapse at 2 years post-HCT were examined in Cox proportional hazards regression models. Factors significantly associated with the outcome variable at a 1% level were kept in the final model. By day 180 post-HCT, 56 (7%) HaploCy, 24 (6%), SibCy, and 59 (4%) SibCNI recipients developed ≥1 FI (P < .001). The cumulative incidence of yeast FI was 5.2% (99% confidence interval [CI], 3.3% to 7.3%) for HaploCy, 2.2% (99% CI, .7% to 4.5%) for SibCy, and 1.9% (99% CI, 1.1% to 2.9%) for SibCNI (P=.001), and that of mold FI was 2.9% (99% CI, 1.5% to 4.7%), 3.7% (99% CI, 91.7% to 6.6%), and 1.7% (99% CI, 1.0% to 2.6%), respectively (P=.040). FI was associated with an increased risk of death, with an adjusted hazard ratio (HR) of 4.06 (99% CI, 2.2 to 7.6) for HaploCy, 4.7 (99% CI, 2.0 to 11.0) for SibCy, and 3.4 (99% CI, 1.8 to 6.4) for SibCNI compared with SibCNI without FI (P < .0001 for all). Similar associations were noted for transplantation-related mortality. FI did not impact rates of relapse or chronic GVHD. Rates of FI by day 180 ranged between 1.9% and 5.2% for yeast FI and from 1.7% to 3.7% for mold FI across the 3 cohorts. The use of PTCy was associated with higher rates of yeast FI only in HaploHCT and with mold FI in both HaploHCT and SibHCT. The presence of FI by day 180 was associated with increased risk for overall mortality and transplant-related mortality at 2 years regardless of donor type or PTCy use. Although rates of FI were low with PTCy, FI is associated with an increased risk of death, underscoring the need for improved management strategies.

Prophylactic donor lymphocyte infusion after haploidentical hematopoietic cell transplantation and post-transplant cyclophosphamide for treatment of high-risk myeloid neoplasms in children: A retrospective study.

Post-transplant cyclophosphamide (PTCy) has been recommended for prevention of graft-versus-host disease (GvHD) following haploidentical hematopoietic cell transplantation (haplo-HCT) for treatment of malignant blood diseases, but disease relapse remains a problem. Although donor lymphocyte infusion (DLI) is reported to be effective for treating post-transplantation relapse, the efficacy and safety of prophylactic-DLI (pro-DLI) post haplo-HCT, and PTCy in pediatric patients with hematological malignancies is unknown. We retrospectively analyzed the outcomes of 54 pediatric patients with high-risk myeloid neoplasms who received a PTCy regimen for GvHD prophylaxis and pro-DLI after haploidentical peripheral blood stem cell transplantation. The high-risk myeloid neoplasms in this cohort included acute myeloid leukemia (n=46) and myelodysplastic syndromes (n=8). Median follow-up was for 19.7 (range: 3.4-46.6) months. The cumulative incidences of grade II-IV and III-IV acute GvHD were 37.0% (95% CI: 22.7%-48.7%) and 16.7% (95% CI: 6.1%-26.0%), respectively. There were no graft-failure events, and the 2-year rate of moderate/severe chronic GvHD was 8.1% (95% CI: 0%-16.7%). The 2-year non-relapse mortality, relapse, disease-free survival, GvHD-free relapse-free survival, and overall survival rates were 5.1% (95% CI: 0%-11.7%), 16.6% (95% CI: 5.3%-26.6%), 78.9% (95% CI: 68.0%-91.6%), 62.2% (95% CI: 49.4%-78.3%), and 87.3% (95% CI: 78.3%-97.4%), respectively. Prophylactic donor lymphocyte infusion in the setting of haploidentical hematopoietic cell transplantation with post-transplant cyclophosphamide appears to be effective and safe in pediatric patients with high-risk myeloid neoplasms.

Reduced post-transplant cyclophosphamide dose with antithymocyte globulin in peripheral blood stem cell haploidentical transplantation.

Post-transplant cyclophosphamide (PT-Cy) is effective for graft-versus-host disease (GVHD) prophylaxis, but it may cause dose-dependent toxicities, particularly in frail patients. Therefore, we compared the outcomes with a reduced PT-Cy total dose (70 mg/kg) to those with the standard PT-Cy dose (100 mg/kg) in haploidentical hematopoietic cell transplantation (HCT) patients aged ≥65 years and those with cardiac comorbidities. All consecutive patients with a hematological malignancy receiving peripheral blood stem cells (PBSCs) after a thiotepa-based conditioning with low-dose antithymocyte globulin were included. Thirty-three patients received PT-Cy at 70 mg/kg and 25 at 100 mg/kg. PT-Cy dose reduction did not increase the risk of GVHD and was associated with faster neutrophil and platelet recovery, and lower cumulative incidences of bacteremia (38% versus 72%, p = 0.004) and cardiac complications (12% versus 44%, p = 0.028). At 2 years, GVHD-free, relapse-free survival (GRFS) was higher with the reduced dose compared to the standard dose (60% versus 33%, p = 0.04). In conclusion, reducing PT-Cy total dose to 70 mg/kg is a safe and valid approach for elderly patients and those with cardiac comorbidities underdoing haploidentical HCT with PBSCs and low-dose antithymocyte globulin. The reduced PT-Cy dose was associated with improved hematological count recovery, lower incidence of toxicities, and higher GRFS.

Characterization of engraftment dynamics in myelofibrosis after allogeneic hematopoietic cell transplantation including novel conditioning schemes.

Myelofibrosis (MF) is a rare hematopoietic stem cell disorder progressing to bone marrow (BM) failure or blast phase. Allogeneic hematopoietic cell transplantation (HCT) represents a potentially curative therapy for a limited subset of patients with advanced MF, who are eligible, but engraftment in MF vs. AML is delayed which promotes complications. As determinants of engraftment in MF are incompletely characterized, we studied engraftment dynamics at our center. A longitudinal cohort of 71 allogeneic HCT performed 2000-2019 with >50% after 2015 was evaluated. Median time to neutrophil engraftment ≥0.5x109/l was +20 days post-transplant and associated with BM fibrosis, splenomegaly and infused CD34+ cell number. Engraftment dynamics were similar in primary vs. secondary MF and were independent of MF driver mutations in JAK2, CALR and MPL. Neutrophil engraftment occurred later upon haploidentical HCT with thiotepa-busulfan-fludarabine conditioning, post-transplant cyclophosphamide and G-CSF (TBF-PTCy/G-CSF) administered to 9.9% and 15.6% of patients in 2000-2019 and after 2015, respectively. Engraftment of platelets was similarly delayed, while reconstitution of reticulocytes was not affected. Since MF is a rare hematologic malignancy, this data from a large number of HCT for MF is essential to substantiate that later neutrophil and platelet engraftment in MF relates both to host and treatment-related factors. Observations from this longitudinal cohort support that novel conditioning schemes administered also to rare entities such as MF, require detailed evaluation in larger, multi-center cohorts to assess also indicators of long-term graft function and overall outcome in patients with this infrequent hematopoietic neoplasm undergoing allogeneic transplantation.

Transplantation after CD45-ADC corrects Rag1 immunodeficiency in congenic and haploidentical settings

Mutations in the recombinase-activating genes 1 and 2 (RAG1, RAG2) cause a spectrum of phenotypes, ranging from severe combined immune deficiency to combined immune deficiency with immune dysregulation (CID-ID). Hematopoietic cell transplantation is a curative option. Use of conditioning facilitates robust and durable stem cell engraftment and immune reconstitution but may cause toxicity. Transplantation from haploidentical donors is associated with poor outcome in patients with CID-ID. We sought to evaluate multilineage engraftment and immune reconstitution after conditioning with CD45-antibody drug conjugate (CD45-ADC) as a single agent in hypomorphic mice with Rag1 mutation treated with congenic and haploidentical hematopoietic cell transplantation. Rag1-F971L mice, a model of CID-ID, were conditioned with various doses of CD45-ADC, total body irradiation, or isotype-ADC, and then given transplants of total bone marrow cells from congenic or haploidentical donors. Flow cytometry was used to assess chimerism and immune reconstitution. Histology was used to document reconstitution of thymic architecture. Conditioning with CD45-ADC as a single agent allowed robust engraftment and immune reconstitution, with restoration of thymus, bone marrow, and peripheral compartments. The optimal doses of CD45-ADC were 1.5 mg/kg and 5 mg/kg for congenic and haploidentical transplantation, respectively. No graft-versus-host disease was observed. Conditioning with CD45-ADC alone allows full donor chimerism and immune reconstitution in Rag1 hypomorphic mice even following haploidentical transplantation, opening the way for the implementation of similar approaches in humans.

Haploidentical donor hematopoietic cell transplantation for myelodysplastic/myeloproliferative overlap neoplasms: results from a North American collaboration.

Haploidentical donors offer a potentially readily available donor, especially for non-White patients, for hematopoietic cell transplantation (HCT). In this North American collaboration, we retrospectively analyzed outcomes of first HCT using haploidentical donor and post-transplantation cyclophosphamide (PTCy) in myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) overlap neoplasms (MDS/MPN). We included 120 consecutive patients who underwent HCT using a haploidentical donor for MDS/MPN across 15 centers. Median age was 62.5 years and 38% were of non-White/Caucasian ethnicity. The median follow-up was 2.4 years. Graft failure was reported in seven of 120 (6%) patients. At 3 years, nonrelapse mortality (NRM) was 25% (95% confidence interval [CI]: 17-34), relapse 27% (95% CI: 18-36), grade 3-4 acute graftversus- host disease 12% (95% CI: 6-18), chronic graft-versus-host disease requiring systemic immunosuppression 14% (95% CI: 7-20), progression-free survival (PFS) 48% (95% CI: 39-59), and overall survival (OS) 56% (95% CI: 47-67). On multivariable analysis, NRM was statistically significantly associated with advancing age at HCT (per decade increment, subdistribution hazard ratio [sdHR] =3.28; 95% CI: 1.30-8.25); relapse with the presence of mutation in EZH2/RUNX1/SETBP1 (sdHR=2.61; 95% CI: 1.06-6.44); PFS with advancing age at HCT (per decade increment, HR=1.98, 95% CI: 1.13-3.45); and OS with advancing age at HCT (per decade increment, HR=2.01; 95% CI: 1.11-3.63) and splenomegaly at HCT/prior splenectomy (HR=2.20; 95% CI: 1.04-4.65). Haploidentical donors are a viable option for HCT in MDS/MPN, especially for those disproportionately represented in the unrelated donor registry. Hence, donor mismatch should not preclude HCT for patients with MDS/MPN, an otherwise incurable malignancy. In addition to patient age, disease-related factors including splenomegaly and high-risk mutations dominate outcomes following HCT.