Racial/ ethnic disparities in availability of volunteer unrelated donors for allogeneic transplantation

Despite the global unrelated donor (URD) registry size, the degree to which URD availability is a transplant barrier is not established. We evaluated the availability of 3,843 URDs requested for 455 diverse adult patients (predominantly with acute leukemia). URDs for non-Europeans were more likely to be domestic and had markedly lower Donor Readiness Scores. Of URDs requested for confirmatory HLA-typing (CT) alone (i.e. without simultaneous workup), 1,894/3,529 (54%) were available. Availability of domestic URDs was 45%. Donor Readiness Score was highly predictive of CT availability. Compared with Europeans (n=335), more non-European patients (n=120) had >10 URDs requested and <5 available. Of workup requests (after CT or CT-workup), <70% (604/889, 68%) were available. More non-Europeans had <2 URDs available. URD availability for CT was markedly worse for non-Europeans, with availabilities for African, non-Black Hispanic, and Asian patients of 150/458 (33%), 120/258 (47%) and 119/270 (44%), respectively, with further decrements in URD workup availability. Our data suggest the functional size of the URD pool is much smaller than appreciated, mandating major operational changes for transplant Centers and donor registries. Likelihood of donor availability should have a high priority in donor selection. Considering patient ancestry and URD Donor Readiness Scores, Centers should pursue, and registries permit, simultaneous pursuit of many URDs, and abandon futile searches. Patients should be informed about their likelihood of donor availability and alternative options. Finally, while registries should address high URD attrition and speed procurement, use of all HLA-disparate graft types is needed to facilitate timely transplantation for all.

Reduced-Intensity Compared to Nonmyeloablative Conditioning in Patients with Non-Hodgkin Lymphoma Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

Reduced-intensity conditioning (RIC) and nonmyeloablative (NMA) conditioning are preferred for patients with non-Hodgkin lymphoma (NHL) undergoing allogeneic hematopoietic stem cell transplantation (allo-HCT). Although prior studies have suggested that higher-intensity regimens in RIC-NMA conditioning are associated with inferior outcomes in patients with NHL, the optimal conditioning regimen remains unknown. We performed a retrospective single-center analysis to determine outcomes of adult patients with B cell and T cell NHL who underwent allo-HCT and received either RIC or NMA conditioning between March 2008 and December 2019. RIC regimens included fludarabine-cyclophosphamide-thiotepa-4 Gy-total body irradiation (Flu-Cy-TT-4Gy-TBI), fludarabine-melphalan (Flu-Mel), fludarabine-cyclophosphamide-4 Gy-total body irradiation (Flu-Cy-4Gy-TBI), and fludarabine-busulfan-4 (Flu-Bu-4). The NMA regimen comprised fludarabine-cyclophosphamide-2 Gy-total body irradiation (Flu-Cy-2Gy-TBI). The primary outcome was overall survival (OS); secondary outcomes included progression-free survival (PFS), nonrelapse mortality (NRM), and the incidence of acute and chronic graft-versus-host-disease (GVHD). Of 279 transplants recipients (median age, 58 years), 110 received RIC (55% Flu-Mel, 38% Flu-Cy-TT-4Gy-TBI, 6% Flu-Bu-4, 1% Flu-Cy-4Gy-TBI) and 169 received NMA conditioning with Flu-Cy-2Gy-TBI. With a median of 64 months of follow-up post-allo-HCT, there was no significant difference in OS between the NMA and RIC groups (median, not reached [NR] versus 103 months; P = .1), and this was maintained on multivariable analysis. Similarly, after adjustment for all independently significant covariates (age, Karnofsky Performance Status [KPS], Hematopoietic Cell Transplantation Comorbidity Index [HCT-CI], and disease histology), the regression analysis showed no significant difference in PFS with RIC compared to NMA conditioning (hazard ratio [HR] 1.38; 95% confidence interval [CI], .92 to 2.09; P = .24). On univariable analysis, there was no significant difference in NRM between the RIC and NMA arms (100-day estimate, 10.0% versus 1.8%; P = .5). After adjustment for age, ethnicity, KPS, HCT-CI, GVHD prophylaxis, and donor source, RIC conditioning was associated with a significantly higher incidence of NRM compared to NMA conditioning (HR, 2.61; 95% CI, 1.04 to 6.52; P = .039). On multivariable analysis, compared with the NMA arm, the RIC arm had higher rates of grade II-IV (HR, 2.25; 95% CI, 1.31 to 3.86; P = .002) and grade III-IV acute GVHD (HR, 5.62; 95% CI, 2.03 to 15.6; P < .001). The findings of this study suggest that NMA conditioning with Flu-Cy-TBI-2Gy may be considered over more intensive RIC regimens for patients with NHL undergoing allo-HCT.

Prospective analysis to determine barriers to allogeneic hematopoietic cell transplantation in patients with acute leukemia

Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative treatment for patients with acute leukemia. Despite this, studies have shown that only a minority of patients ultimately proceed to allo-HCT. The primary objective of this prospective, observational study was to identify the rate of allo-HCT in patients for whom it was recommended, and reasons why patients deemed appropriate and eligible for HCT did not subsequently undergo transplant. Between April 2016 and April 2021, adult patients with newly diagnosed or relapsed/refractory acute leukemia were enrolled at the time of induction/reinduction therapy. Initial transplantation workup and allo-HCT recommendations were made during the early phase of induction/reinduction. Of the 307 enrolled patients, allo-HCT was recommended to 85% (n = 259), of whom 66% (n = 170) underwent transplant. Donor sources comprised 54% human leukocyte antigen (HLA)-matched unrelated donors, 20% HLA-matched sibling donors and HLA-mismatched graft sources with 15% umbilical cord blood units, 8% HLA-mismatched unrelated donors, and 4% HLA-haploidentical donors. The most common reason for transplant disqualification in the 89 patients in whom it was initially recommended was persistent/relapsed disease (70%), followed by early patient death (10%). In this prospective study, we report a high allo-HCT rate, which may be due to early transplant referral and workup. The main allo-HCT barrier was disease control, followed by early patient death. With the increasing availability of HLA-mismatched graft sources, the lack of donor availability was not a transplant barrier. Further development of novel transplant strategies for patients not achieving remission and improvements in induction regimens could result in increased allo-HCT utilization.

The Simplified Comorbidity Index predicts non-relapse mortality in reduced-intensity conditioning allogeneic haematopoietic cell transplantation

Comorbidity assessment before allogeneic haematopoietic cell transplantation (allo-HCT) is essential for estimating non-relapse mortality (NRM) risk. We previously developed the Simplified Comorbidity Index (SCI), which captures a small number of 'high-yield' comorbidities and older age. The SCI was predictive of NRM in myeloablative CD34-selected allo-HCT. Here, we evaluated the SCI in a single-centre cohort of 327 patients receiving reduced-intensity conditioning followed by unmanipulated allografts from HLA-matched donors. Among the SCI factors, age above 60, mild renal impairment, moderate pulmonary disease and cardiac disease were most frequent. SCI scores ranged from 0 to 8, with 39%, 20%, 20% and 21% having scores of 0-1, 2, 3 and ≥4 respectively. Corresponding cumulative incidences of 3-year NRM were 11%, 16%, 22% and 27%; p = 0.03. In multivariable models, higher SCI scores were associated with incremental risks of all-cause mortality and NRM. The SCI had an area under the receiver operating characteristic curve of 65.9%, 64.1% and 62.9% for predicting 1-, 2- and 3-year NRM versus 58.4%, 60.4% and 59.3% with the haematopoietic cell transplantation comorbidity index. These results demonstrate for the first time that the SCI is predictive of NRM in patients receiving allo-HCT from HLA-matched donors after reduced-intensity conditioning.

Association between busulfan exposure and survival in patients undergoing a CD34+ selected stem cell transplantation

Busulfan is an alkylating drug routinely used in conditioning regimens for allogeneic hematopoietic cell transplantation (allo-HCT). A myeloablative conditioning regimen, including busulfan, is commonly used in patients undergoing T-cell depletion (TCD) and allo-HCT, but data on optimal busulfan pharmacokinetic (PK) exposure in this setting are limited. Between 2012 and 2019, busulfan PK was performed to target an area under the curve exposure between 55 and 66 mg × h/L over 3 days using a noncompartmental analysis model. We retrospectively re-estimated busulfan exposure following the published population PK (popPK) model (2021) and correlated it with outcomes. To define optimal exposure, univariable models were performed with P splines, wherein hazard ratio (HR) plots were drawn, and thresholds were found graphically as the points at which the confidence interval crossed 1. Cox proportional hazard and competing risk models were used for analyses. 176 patients were included, with a median age of 59 years (range, 2-71). Using the popPK model, the median cumulative busulfan exposure was 63.4 mg × h/L (range, 46.3-90.7). The optimal threshold was at the upper limit of the lowest quartile (59.5 mg × h/L). 5-year overall survival (OS) with busulfan exposure ≥59.5 vs <59.5 mg × h/L was 67% (95% CI, 59-76) vs 40% (95% CI, 53-68), respectively (P = .02), and this association remained in a multivariate analyses (HR, 0.5; 95% CI, 0.29; 0.88; P = .02). In patients undergoing TCD allo-HCT, busulfan exposure is significantly associated with OS. The use of a published popPK model to optimize exposure may significantly improve the OS.

Analysis of disparities in time to allogeneic transplantation in adults with acute myelogenous leukemia

Although alternative donors extend transplant access, whether recipient ancestry affects the time to allogeneic transplant is not established. We analyzed the likelihood of clinically significant delays to allograft by patient ancestry in 313 adult patients with acute myelogenous leukemia (AML) who underwent transplantation. Non-European ancestry patients (n = 99) were more likely than Europeans (n = 214) to receive HLA-mismatched donor allografts (45% vs 24%). Overall, the median time from transplant indication to allograft was 127 days (range, 57-1683). In multivariable analysis, non-Europeans had an increased risk of prolonged indication to transplant time >180 days owing to significant delays in indication to consult >90 days and consult to transplant >120 days. Compared with recipients of HLA-matched unrelated donors (URDs), HLA-mismatched adult donor recipients were at an increased risk of delayed indication to transplant, whereas HLA-identical sibling and cord blood recipients were at a lower risk. Subanalysis showed more indication to transplant delays >180 days in non-European (44%) vs European (19%) 8/8 URD recipients. Finally, the pandemic further exacerbated delays for non-Europeans. In summary, although non-European patients with AML are less likely to receive 8/8 URDs as expected, if they do, their transplants are delayed. HLA-identical siblings and cord blood facilitate the fastest transplants regardless of patient ancestry, whereas other adult donor transplants are delayed. Strategies to mitigate referral barriers, hasten donor evaluation, and use all alternative donor sources are critical to ensure timely transplantation for patients with AML.

High-resolution analyses of associations between medications, microbiome, and mortality in cancer patients

Discerning the effect of pharmacological exposures on intestinal bacterial communities in cancer patients is challenging. Here, we deconvoluted the relationship between drug exposures and changes in microbial composition by developing and applying a new computational method, PARADIGM (parameters associated with dynamics of gut microbiota), to a large set of longitudinal fecal microbiome profiles with detailed medication-administration records from patients undergoing allogeneic hematopoietic cell transplantation. We observed that several non-antibiotic drugs, including laxatives, antiemetics, and opioids, are associated with increased Enterococcus relative abundance and decreased alpha diversity. Shotgun metagenomic sequencing further demonstrated subspecies competition, leading to increased dominant-strain genetic convergence during allo-HCT that is significantly associated with antibiotic exposures. We integrated drug-microbiome associations to predict clinical outcomes in two validation cohorts on the basis of drug exposures alone, suggesting that this approach can generate biologically and clinically relevant insights into how pharmacological exposures can perturb or preserve microbiota composition. The application of a computational method called PARADIGM to a large dataset of cancer patients' longitudinal fecal specimens and detailed daily medication records reveals associations between drug exposures and the intestinal microbiota that recapitulate in vitro findings and are also predictive of clinical outcomes.

Molecular predictors of immunophenotypic measurable residual disease clearance in acute myeloid leukemia

Measurable residual disease (MRD) is a powerful prognostic factor in acute myeloid leukemia (AML). However, pre-treatment molecular predictors of immunophenotypic MRD clearance remain unclear. We analyzed a dataset of 211 patients with pre-treatment next-generation sequencing who received induction chemotherapy and had MRD assessed by serial immunophenotypic monitoring after induction, subsequent therapy, and allogeneic stem cell transplant (allo-SCT). Induction chemotherapy led to MRD- remission, MRD+ remission, and persistent disease in 35%, 27%, and 38% of patients, respectively. With subsequent therapy, 34% of patients with MRD+ and 26% of patients with persistent disease converted to MRD-. Mutations in CEBPA, NRAS, KRAS, and NPM1 predicted high rates of MRD- remission, while mutations in TP53, SF3B1, ASXL1, and RUNX1 and karyotypic abnormalities including inv (3), monosomy 5 or 7 predicted low rates of MRD- remission. Patients with fewer individual clones were more likely to achieve MRD- remission. Among 132 patients who underwent allo-SCT, outcomes were favorable whether patients achieved early MRD- after induction or later MRD- after subsequent therapy prior to allo-SCT. As MRD conversion with chemotherapy prior to allo-SCT is rarely achieved in patients with specific baseline mutational patterns and high clone numbers, upfront inclusion of these patients into clinical trials should be considered.

Impact of omitting post-transplant minidose-methotrexate doses in allogeneic hematopoietic cell transplantation

Given prophylactic methotrexate (MTX) is often held in the setting of toxicity we investigated the impact of omitting minidose-MTX dose(s). Outcomes were compared between patients who had 1-3 doses omitted and those who received all four planned doses of minidose-MTX. Of 370 consecutive patients, 50 had MTX dose(s) omitted. When MTX was omitted, initial management was mycophenolate mofetil (MMF; 36/50 patients) with or without corticosteroids (14/50 patients). Rates of grade 3-4 acute GVHD were similar between groups. Omission of minidose-MTX resulted in an increased risk of chronic GVHD (cGVHD; HR 2.27; p = .024) and decreased overall survival (HR 1.61; p = .024). However, other transplant-related outcomes were comparable. In summary, omission of minidose-MTX doses was not associated with an increased risk of acute GVHD when an alternative was added (e.g. MMF ± corticosteroids). This did not abrogate the increased risk of cGVHD or decreased overall survival.

Disparities in speed to BMT consult and allograft in 279 adults with AML

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Background: Whether patient (pt) ancestry impacts the time to BMT is not established. Methods: We hypothesized that non-European (non-EURO) ancestry AML pts are at increased risk of delayed time to transplant. Thus, we analyzed time to allograft (Allo) by ancestry defining delayed (late) times as: Allo Indication to BMT Consult (Ind. – Consult) > 90 days, Consult – BMT > 120 days & Allo Indication to BMT (Ind. - BMT) > 180 days. We studied pts < 70 yrs transplanted 1/2016-7/2021. Results: In 279 AML pts (median 56 yrs, range 19-69), BMT indication was date of diagnosis if ELN 2017 intermediate/ high risk &/or high risk mutations &/or sAML in 261 (94%) pts, or date of refractory/ relapsed disease in 18 (6%) pts. European (EURO) pts (n = 195, 70%; median 60 yrs) were older than non-EURO pts (n = 84, 30%; median 49 yrs), p <.001. Most HLA-matched sibling (SIB) (27/33, 82%) & 8/8 HLA-matched unrelated donor (mURD, 113/138, 82%) recipients were EURO; more non-EURO pts received HLA-disparate grafts [cord blood (CB)/ haplo/ mmURD]: 48/84 (57%) vs 55/195 (28%), p <.001. Overall, median (range) times for BMT Ind. - Consult, Consult - BMT, & Ind. - BMT were 45 (1-1127), 86 (13-1628), & 135 (23-1683) days. 15% of pts had late BMT Ind. - Consult, 27% late Consult – BMT, & 28% late Ind. - BMT. In multivariate analysis (significant variables in Table), more older pts had late Consult - BMT & Ind. - BMT; more non-EURO pts had late Ind. - Consult, Consult - BMT & Ind. – BMT; & despite mostly being non-EURO (35/67, 52%), fewer CB recipients had late Consult - BMT. In mURD pts, BMT Ind. - BMT time was delayed in non-EURO (median 182 days) vs EURO (median 128 days) pts (p = 0.04); there was no difference in CB pts (BMT Ind. - BMT EURO pt median 118 vs non-EURO pt median 108 days, p = 0.42). During the pandemic, as compared with EURO pts BMT delays were further exacerbated in non-EURO pts (Ind. - Consult median 13 & Ind. - BMT median 33 days). Conclusions: Few older non-EURO pts are allografted. Matched SIB & 8/8 mURD transplants predominantly serve EURO pts; the majority of non-EURO pts receive HLA-disparate grafts. Older age & non-EURO ancestry are associated with delayed BMT. CB transplants (CBT) are the fastest regardless of ancestry. Finally, the pandemic further exacerbated delays for non-EURO pts. Strategies to mitigate referral barriers (esp. for older non-EURO pts), prompt adult donor evaluations, efficient URD searches, & utilization of all alternative donors are critical to ensure timely BMT for all. Given the rapid availability, CBT should have high priority in high-risk or urgent pts & speedy graft procurement can compensate for late referral. [Table: see text]

Hematopoietic Cell Transplantation is Feasible in Patients with Prior COVID-19 Infection

There are limited data on outcomes of patients with prior Coronavirus disease 2019 (COVID-19) who proceeded to autologous or allogeneic hematopoietic cell transplantation (HCT). Whether these patients are more susceptible to poor outcomes and recurrence of COVID-19 is unknown. We report a retrospective analysis of outcomes of 15 consecutive patients with hematologic malignancies who experienced COVID-19 and subsequently underwent autologous (n = 8) or allogeneic (n = 7) HCT between June 17, 2020, and February 17, 2021. The cohort included patients with asymptomatic past infections or symptomatic COVID-19 disease. Data were obtained from chart review. Descriptive statistics were used to summarize patient characteristics. Among eight patients who underwent autologous HCT, four had a diagnosis of multiple myeloma and four had a diagnosis of non-Hodgkin's lymphoma. Four of these eight patients did not test positive for anti-SARS-CoV-2 IgG antibody at any point during the course of treatment. The other four patients had detectable anti-SARS-CoV-2 IgG antibodies before undergoing autologous HCT, but only two of these patients remained anti-SARS-CoV-2 IgG antibody-positive at their last follow-up. One patient died from progression of disease. Seven patients with prior COVID-19 underwent allogeneic HCT for acute lymphoblastic leukemia (n = 3), acute myelogenous leukemia (n = 1), chronic myelogenous leukemia in lymphoid blast crisis (n = 1), myelodysplastic syndrome (n = 1), or myelofibrosis (n = 1). Three of the seven patients tested positive for anti-SARS-CoV-2 IgG antibodies following the initial COVID-19 diagnosis; however, only one of these patients retained anti-SARS-CoV-2 IgG antibody following allogeneic HCT. One patient died of infection (fungal and Pneumocystis jirovecii pneumonia) occurring in the context of ongoing treatment for graft-versus-host disease. None of the 15 patients had recurrent COVID-19 infection. Based on our experience, autologous and allogeneic HCT can be safely performed in selected patients with previous COVID-19 infection.

595. Letermovir (LTV) for Secondary Cytomegalovirus (CMV) Prevention in High Risk Hematopoietic Cell Transplant (HCT) Recipients: Interim Results of a Single Center, Open Label Study

Background

Letermovir (LTV) is effective for prevention (ppx) of primary clinically significant CMV infection (csCMVi) in the first 100 days after hematopoietic cell transplant (HCT). Data on LTV for secondary ppx is limited. We report on the efficacy and safety of LTV administered for 14 weeks as secondary CMV ppx.

Methods

Patients (pts) enrolled in an open label study of LTV (ClinicalTrials.gov identifier: NCT04017962) from August 2019 through February 2021 were analyzed. Key eligibility criteria were: CMV high risk (receipt of mismatched and/or T-cell depleted HCT and/or graft versus host disease (GVHD) requiring systemic immunosuppressants) AND prior csCMVi with either undetectable CMV (≤ 136 IU/mL) or ≥ 2 consecutive values &lt; 300 IU/mL at enrollment. Pts with breakthrough csCMVi on LTV or history of LTV resistance were excluded. LTV was administered for 14 weeks or csCMVi whichever occurred first. The study duration was 24 weeks. CMV was monitored per standards of care. The primary endpoint was csCMVi by week 14. Secondary endpoints were csCMVi by week 24, LTV resistance, CMV end-organ disease (EOD) and adverse events (AE) at least possibly related to LTV.

Results

Of 20 pts analyzed, the median age was 58 years (interquartile range [IQR] 46-63); 17 (85%) pts were CMV seropositive, 7 (35%) received mismatched HCT (haploidentical 3, cord blood 3; mismatched unrelated 1), 9 (45%) received CD34 selected allograft and 9 (45%) had GVHD at enrollment. Fourteen (70%) pts had received prior LTV. The median time from HCT to enrollment was 156 (IQR 37-244) and 55 (IQR 40-69) days for pts with and without prior LTV, respectively (P=0.16). CMV at enrollment was &lt; 136IU/mL for 8 (40%) pts. By week 14, 4 (20%) pts developed csCMVi at median 48 days (range 40-66). Resistance testing performed in 3 of the 4 pts, identified LTV resistance mutations in 2 pts. There were no AEs related to LTV, and none developed EOD. Two pts developed csCMVi in the follow up phase. Three pts died during follow up (due to relapse, treatment related toxicity and GVHD), and four pts are in follow up.

Conclusion

LTV secondary prophylaxis was safe and prevented recurrent csCMVi in 80% of high risk patients, including patients with prior LTV exposure. Our data supports the utility of LTV for secondary CMV prevention following HCT.

Disclosures

Boglarka Gyurkocza, MD, Actinium Pharma, Inc. (Grant/Research Support, Research Grant or Support) Genovefa Papanicolaou, MD, ADMA biologics and Siemens Healthineers (Consultant, Other Financial or Material Support)AlloVir (Consultant, Other Financial or Material Support)Amplyx (Scientific Research Study Investigator, Other Financial or Material Support)Astellas (Consultant, Grant/Research Support, Scientific Research Study Investigator, Research Grant or Support, Other Financial or Material Support)Behring (Consultant, Other Financial or Material Support)Chimerix (Consultant, Grant/Research Support, Scientific Research Study Investigator, Research Grant or Support, Other Financial or Material Support)Cidara (Consultant, Other Financial or Material Support)Merck & Co (Consultant, Grant/Research Support, Scientific Research Study Investigator, Research Grant or Support, Other Financial or Material Support)Partners Therapeutics (Consultant, Other Financial or Material Support)Shionogi (Consultant, Other Financial or Material Support)Shire/Takeda (Consultant, Grant/Research Support, Scientific Research Study Investigator, Research Grant or Support, Other Financial or Material Support) Genovefa Papanicolaou, MD, allovir (Individual(s) Involved: Self): Consultant; amplyx (Individual(s) Involved: Self): Consultant; behring (Individual(s) Involved: Self): Consultant; Merck&Co (Individual(s) Involved: Self): Consultant, Investigator and received funding and consulting fees from Merck, Chimerix, Shire and Astellas, Research Grant or Support; octapharma (Individual(s) Involved: Self): Consultant; Partners Therapeutics (Individual(s) Involved: Self): Consultant; takeda (Individual(s) Involved: Self): Consultant, Scientific Research Study Investigator

Fractionated Infusion of Hematopoietic Progenitor Cells Does Not Improve Neutrophil Recovery or Survival in Allograft Recipients

Allogeneic hematopoietic cell transplantation (HCT) offers a potentially curative therapy in patients with hematologic malignancies; however, nonrelapse mortality (NRM) remains a concern. Strategies to improve neutrophil recovery and immune reconstitution are needed to decrease NRM. Murine models of allogeneic HCT suggest that fractionated hematopoietic progenitor cell (HPC) infusion may improve engraftment through improved access of HPCs to a viable hematopoietic niche. The primary objective of the present study was to determine the impact of fractionated infusion versus unfractionated (bulk) infusion of HPCs on the time to achieve neutrophil engraftment. Secondary objectives included the effect of fractionated versus bulk infusion of HPCs on platelet engraftment, immune reconstitution, the incidence of acute graft-versus-host disease (GVHD) grade II-IV, NRM, and overall survival (OS). In this randomized phase 2 study, patients with hematologic malignancies undergoing allogeneic HCT were randomized to receive HPC infusion as a bulk (bulk arm) or in fractions (fractionated arm): 4 × 106 CD34+ cells/kg recipient weight infused on day 0, with the remaining HPCs CD34+ cell-selected then infused in equally distributed aliquots on days 2, 4, and 6 post-HCT. Randomization was stratified by type of transplant, unmodified (i.e. T cell-replete graft) versus CD34+ cell-selected (T cell-depleted graft). Patients whose donor failed to collect at least 7 × 106 CD34+ cells/kg of recipient weight received bulk HPC infusions regardless of randomization, for safety. These patients continued the HCT process on study but were replaced until each arm reached the prespecified accrual target. Per protocol, these patients were not included in this modified intention-to-treat analysis. A total of 116 patients were enrolled. Donors of 42 patients failed to mobilize the minimum CD34+ cell dose (7 × 106 cells/kg recipient weight) and were excluded from the analysis. The 74 evaluable patients included 38 randomized to the bulk arm and 36 randomized to the fractionated arm. All patients engrafted. The median time to an absolute neutrophil count of ≥0.5 × 109/L was 11 days on both arms. The day +180 median CD4+ cell count was 179 cells/µL in the bulk arm and 111 cells/µL in the fractionated arm (P = .779). The cumulative incidence of grade II-IV acute GVHD on post-transplant day +100 was 32% in the bulk arm and 17% in the fractionated arm (P = .131). Two patients in the bulk arm, but none in the fractionated arm, experienced grade III-IV GVHD. The 4-year OS was 60% in the bulk arm and 62% in the fractionated arm (P = .414), whereas the 4-year cumulative incidences of NRM and relapse were similar in the 2 arms. Fractionated infusion of HPCs in allogeneic HCT recipients did not impact neutrophil or CD4+ cell recovery, NRM, relapse, or OS when compared with bulk HPC infusion. We also observed that with current mobilization techniques, it was unlikely that more than 60% of healthy donors would be able to collect >7 × 106 CD34+ cells/kg recipient weight for adult recipients. © 2021 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

Venetoclax-based combinations in AML and high-risk MDS prior to and following allogeneic hematopoietic cell transplant

The role of allogeneic hematopoietic cell transplant (allo-HCT) as consolidation after initial venetoclax therapy and the efficacy of venetoclax salvage therapy for relapse after allo-HCT in patients with acute myeloid leukemia (AML) are unclear. We conducted a retrospective study of patients with AML or myelodysplastic syndrome (MDS) who received venetoclax either before or after allo-HCT at Memorial Sloan Kettering Cancer Center and Yale University from 11 August 2016 to 16 November 2020. Among 39 heavily pretreated patients who received venetoclax before allo-HCT, median OS from allo-HCT was not reached after a median follow up of 12.5 months resulting in a 12-month OS estimate of 79.0%. In 37 patients who had received venetoclax-based combinations as salvage therapy after allo-HCT, the overall response rate was 32% with a median OS of 4.7 months (12-month OS estimate: 43.4%). Four patients underwent a second allo-HCT following venetoclax-based salvage therapy suggesting it as a potential salvage treatment option.

Relapse after Allogeneic Stem Cell Transplantation of Acute Myelogenous Leukemia and Myelodysplastic Syndrome and the Importance of Second Cellular Therapy

Patients with acute myelogenous leukemia (AML) or myelodysplastic syndrome (MDS) who relapse after allogeneic hematopoietic cell transplantation (allo-HCT) generally have poor overall survival (OS). Interventions that result in improved OS after relapse are not well established. The efficacy of second cellular therapy and specific indications are matters of debate. This study was conducted to evaluate factors associated with postrelapse survival and the efficacy of a second course of cellular therapy. We retrospectively analyzed consecutive patients with AML and MDS who underwent a first allo-HCT between 2010 and 2017 at our center but subsequently relapsed. One hundred and four patients with AML and 44 patients with MDS were included (total n = 148). Bone marrow (BM) and peripheral blood stem cell grafts were either unmodified or T cell-depleted (TCD) by CD34⁺ selection ex vivo. Forty-five patients (30.4%) received a second cellular therapy after relapse, either a second allo-HCT (n = 28; 18.9%) or donor leukocyte infusion (DLI) (n = 17; 11.5%). The median age at transplantation was 60 years (range, 24 to 78 years). The median time to relapse (TTR) after transplantation was 6.5 months (range, 1 to 60.9 months), and the ensuing median OS was 6 months (95% confidence interval [CI], 4.8 to 8.9 months). In univariable analysis, longer TTR, relapse type (measurable residual disease versus morphologic), relapse occurring in the most recent years, and receipt of cellular therapy after relapse were associated with better outcomes, whereas adverse cytogenetics and/or abnormality of TP53, as well as NPM1 mutation in patients with AML, were associated with adverse outcomes. Relapse type, year of relapse, and a variable resulting from the combination of TTR and receipt of second cellular therapy remained significantly associated with postrelapse survival in multivariable analysis. In a separate multivariable model, adjusted only for TTR, relapse type, and receipt of second cellular therapy, an adverse effect of NPM1 mutation on survival was confirmed. We could not show an effect of post-transplantation maintenance on survival after relapse. In both univariable and multivariable analysis, we found a positive association for second cellular therapy with survival after relapse in patients who relapsed early (<6 months) after allo-HCT and a similar trend in patients who relapsed late (>12 months) after transplantation. Two-year OS after a second cellular therapy was 44.9% (95% CI, 28.5% to 61.4%), and it was significantly better in patients with <5% BM blasts before cell infusion. We could not show different effects on survival after second cellular therapy for DLI versus second allo-HCT in univariable analysis. Survival after relapse is improving over time, but this remains a challenging event, especially for patients who relapse early after transplantation. We found that a second cellular therapy could offer a benefit even in these cases. Nonetheless, more research is needed to clarify the most appropriate treatment choices after relapse. These are probably driven by underlying genetic and immunologic conditions, which should be the focus of future studies.

Combining the Disease Risk Index and Hematopoietic Cell Transplant Co-Morbidity Index provides a comprehensive prognostic model for CD34+-selected allogeneic transplantation

T cell depletion by CD34⁺ cell selection of hematopoietic stem cell allografts ex vivo reduces the incidence and severity of GvHD, without increased risk of relapse in patients with acute leukemia in remission or MDS. The optimal candidate for CD34⁺-selected HCT remains unknown, however.

OBJECTIVE

To determine outcomes based on both disease- and patient-specific factors, we evaluated a prognostic model combining the Disease Risk Index (DRI) and Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI), an approach recently shown to predicted overall survival in a broad population of allograft recipients (1).

METHODS

This was a retrospective analysis of 506 adult recipients of first allogeneic HCT with CD34+ selected PBSCs from 7/8- or 8/8-matched donors for AML (n = 290), ALL (n = 72), or MDS (n = 144). The Kaplan-Meier method estimated OS and RFS. The cumulative incidence method for competing risks estimated relapse and non-relapse mortality (NRM). We evaluated the univariate association between variables of interest and OS and RFS using the log-rank test. Cox regression models assessed the adjusted effect of covariates on OS/RFS.

RESULTS

Stratification of patients based on a composite of DRI (low/intermediate vs. high/very high) and HCT-CI (0-2 vs. ≥ 3) revealed differences in OS and RFS between the 4 groups. Compared with reference groups of patients with low/intermediate DRI and low or high HCT-CI, those with high DRI had a greater risk of death (HR 2.30; 95% CI 1.39, 3.81) and relapse or death (HR 2.50; 95% CI 1.55, 4.05) than patients with any HCT-CI but low/intermediate DRI (HR death 1.80; 95% CI 1.34, 2.43; HR relapse/death 1.68; 95% CI 1.26, 2.24).

CONCLUSIONS AND CLINICAL IMPLICATIONS

A model combining DRI and HCT-CI predicted survival after CD34⁺ cell-selected HCT. Application of this combined model to other cohorts, both in retrospective analyses and prospective trials, will enhance clinical decision making and patient selection for different transplant approaches.

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available on request from the corresponding author, C Cho. In order to protect the privacy of research participants, the data are not publicly available.

High progression-free survival after intermediate intensity double unit cord blood transplantation in adults

Cord blood transplantation (CBT) after high intensity or nonmyeloablative conditioning has limitations. We investigated cyclosporine-A/mycophenolate mofetil-based intermediate intensity (cyclophosphamide 50 mg/kg, fludarabine 150 mg/m2, thiotepa 10 mg/kg, total body irradiation 400 cGy) unmanipulated double-unit CBT (dCBT) with prioritization of unit quality and CD34+ cell dose in graft selection. Ninety adults (median age, 47 years [range, 21-63]; median hematopoietic cell transplantation comorbidity index, 2 [range, 0-8]; 61 [68%] acute leukemia) received double-unit grafts (median CD34+ cell dose, 1.3 × 105/kg per unit [range, 0.2-8.3]; median donor-recipient human leukocyte antigen (HLA) match, 5/8 [range 3-7/8]). The cumulative incidences of sustained CB engraftment, day 180 grade III-IV acute, and 3-year chronic graft-versus-host disease were 99%, 24%, and 7%, respectively. Three-year transplant-related mortality (TRM) and relapse incidences were 15% and 9%, respectively. Three-year overall survival (OS) is 82%, and progression-free survival (PFS) is 76%. Younger age and higher engrafting unit CD34+ cell dose both improved TRM and OS, although neither impacted PFS. Engrafting unit-recipient HLA match was not associated with any outcome with a 3-year PFS of 79% in 39 patients engrafting with 3-4/8 HLA-matched units. In 52 remission acute leukemia patients, there was no association between minimal residual disease (MRD) and 3-year PFS: MRD negative of 88% vs MRD positive of 77% (P = .375). Intermediate intensity dCBT is associated with high PFS. Use of highly HLA mismatched and unmanipulated grafts permits wide application of this therapy, and the low relapse rates support robust graft-versus-leukemia effects even in patients with MRD.

Off-the-shelf EBV-specific T cell immunotherapy for rituximab-refractory EBV-associated lymphoma following transplantation

BACKGROUNDAdoptive transfer of donor-derived EBV-specific cytotoxic T-lymphocytes (EBV-CTLs) can eradicate EBV-associated lymphomas (EBV-PTLD) after transplantation of hematopoietic cell (HCT) or solid organ (SOT) but is unavailable for most patients.METHODSWe developed a third-party, allogeneic, off-the-shelf bank of 330 GMP-grade EBV-CTL lines from specifically consented healthy HCT donors. We treated 46 recipients of HCT (n = 33) or SOT (n = 13) with established EBV-PTLD, who had failed rituximab therapy, with third-party EBV-CTLs. Treatment cycles consisted of 3 weekly infusions of EBV-CTLs and 3 weeks of observation.RESULTSEBV-CTLs did not induce significant toxicities. One patient developed grade I skin graft-versus-host disease. Complete remission (CR) or sustained partial remission (PR) was achieved in 68% of HCT recipients and 54% of SOT recipients. For patients who achieved CR/PR or stable disease after cycle 1, one year overall survival was 88.9% and 81.8%, respectively. In addition, 3 of 5 recipients with POD after a first cycle who received EBV-CTLs from a different donor achieved CR or durable PR (60%) and survived longer than 1 year. Maximal responses were achieved after a median of 2 cycles.CONCLUSIONThird-party EBV-CTLs of defined HLA restriction provide safe, immediately accessible treatment for EBV-PTLD. Secondary treatment with EBV-CTLs restricted by a different HLA allele (switch therapy) can also induce remissions if initial EBV-CTLs are ineffective. These results suggest a promising potential therapy for patients with rituximab-refractory EBV-associated lymphoma after transplantation.TRIAL REGISTRATIONPhase II protocols (NCT01498484 and NCT00002663) were approved by the Institutional Review Board at Memorial Sloan Kettering Cancer Center, the FDA, and the National Marrow Donor Program.FUNDINGThis work was supported by NIH grants CA23766 and R21CA162002, the Aubrey Fund, the Claire Tow Foundation, the Major Family Foundation, the Max Cure Foundation, the Richard "Rick" J. Eisemann Pediatric Research Fund, the Banbury Foundation, the Edith Robertson Foundation, and the Larry Smead Foundation. Atara Biotherapeutics licensed the bank of third-party EBV-CTLs from Memorial Sloan Kettering Cancer Center in June 2015.

Characteristics and Impact of Post-Transplant Interdisciplinary Palliative Care Consultation in Older Allogeneic Hematopoietic Cell Transplant Recipients

Context and Objectives: The myriad of benefits of early palliative care (PC) integration in oncology are well established, and emerging evidence suggests that PC improves symptom burden, mood, and quality of life for hematopoietic cell transplant (HCT) recipients. Specific impact of PC consultation on outcomes of older allogeneic HCT (allo-HCT) recipients, a historically high-risk population vulnerable to transplant-related complications and mortality, has not been explored. Design and Methods: In this single institution, retrospective analysis of 527 first allo-HCT recipients aged ≥60 years, we characterized 75 patients who had received post-HCT PC consultation and its association with geriatric vulnerabilities identified by pre-HCT geriatric assessment. We also examined end-of-life care outcomes among patients who died within one-year of allo-hematopoietic cell transplantation. Results: In multivariate analysis, higher disease risk, female gender, and, importantly, pre-HCT functional limitation (hazard ratio 2.35, 95% confidence interval, 1.35-4.09, p = 0.003) were associated with post-HCT PC utilization. Within one-year of hematopoietic cell transplantation, 127 patients died; among those, recipients of early PC consultation had significantly higher rates of hospice enrollment (25% vs. 9%, p = 0.019) and lower rates of hospital death (71% vs. 90%, p = 0.013), intensive care unit admission (44% vs. 75%, p = 0.001), and high-intensity medical care in last 30 days of life (46% vs. 77%, p = 0.001). Conclusions: Our results highlight important pre-HCT risk factors associated with increased PC needs posthematopoietic cell transplantation and benefits of PC involvement for older allo-HCT recipients at the end of life. Prospective studies should examine the optimal timing of PC consultation and its multidimensional benefits for older allo-HCT patients.

Microbiota as Predictor of Mortality in Allogeneic Hematopoietic-Cell Transplantation

BACKGROUND

Relationships between microbiota composition and clinical outcomes after allogeneic hematopoietic-cell transplantation have been described in single-center studies. Geographic variations in the composition of human microbial communities and differences in clinical practices across institutions raise the question of whether these associations are generalizable.

METHODS

The microbiota composition of fecal samples obtained from patients who were undergoing allogeneic hematopoietic-cell transplantation at four centers was profiled by means of 16S ribosomal RNA gene sequencing. In an observational study, we examined associations between microbiota diversity and mortality using Cox proportional-hazards analysis. For stratification of the cohorts into higher- and lower-diversity groups, the median diversity value that was observed at the study center in New York was used. In the analysis of independent cohorts, the New York center was cohort 1, and three centers in Germany, Japan, and North Carolina composed cohort 2. Cohort 1 and subgroups within it were analyzed for additional outcomes, including transplantation-related death.

RESULTS

We profiled 8767 fecal samples obtained from 1362 patients undergoing allogeneic hematopoietic-cell transplantation at the four centers. We observed patterns of microbiota disruption characterized by loss of diversity and domination by single taxa. Higher diversity of intestinal microbiota was associated with a lower risk of death in independent cohorts (cohort 1: 104 deaths among 354 patients in the higher-diversity group vs. 136 deaths among 350 patients in the lower-diversity group; adjusted hazard ratio, 0.71; 95% confidence interval [CI], 0.55 to 0.92; cohort 2: 18 deaths among 87 patients in the higher-diversity group vs. 35 deaths among 92 patients in the lower-diversity group; adjusted hazard ratio, 0.49; 95% CI, 0.27 to 0.90). Subgroup analyses identified an association between lower intestinal diversity and higher risks of transplantation-related death and death attributable to graft-versus-host disease. Baseline samples obtained before transplantation already showed evidence of microbiome disruption, and lower diversity before transplantation was associated with poor survival.

CONCLUSIONS

Patterns of microbiota disruption during allogeneic hematopoietic-cell transplantation were similar across transplantation centers and geographic locations; patterns were characterized by loss of diversity and domination by single taxa. Higher diversity of intestinal microbiota at the time of neutrophil engraftment was associated with lower mortality. (Funded by the National Cancer Institute and others.).

A Single-Center, Open-Label Trial of Isavuconazole Prophylaxis against Invasive Fungal Infection in Patients Undergoing Allogeneic Hematopoietic Cell Transplantation

Isavuconazole is a broad-spectrum triazole approved for treatment of invasive fungal infections (IFIs). In this open-label, single-arm study, we evaluated isavuconazole for antifungal prophylaxis after allogeneic hematopoietic cell transplantation (HCT). Adult patients admitted for first HCT received micafungin 150 mg i.v. daily from admission through day +7 (D+7) post-transplantation (±2 days) followed by isavuconazole prophylaxis (i.v./p.o. 372 mg every 8 hours for 6 doses and then 372 mg daily) through maximum D+98 post-HCT. Patients were followed through D+182. The primary endpoint was prophylaxis failure, defined as discontinuation of prophylaxis for proven/probable IFI; systemic antifungal therapy for >14 days for suspected IFI; toxicity leading to discontinuation; or an adverse event. Between June 2017 and October 2018, 99 patients were enrolled in the study, of whom 95 were included in our analysis. The median patient age was 57 years (interquartile range [IQR], 50 to 66 years). Sixty-four (67%) patients received peripheral blood, 17(18%) received bone marrow, and 14 (15%) received a cord blood allograft for acute leukemia (55%), lymphoma (17%), myelodysplastic syndrome (16%), or another hematologic disease (14%). One-third (n = 31; 33%) of patients underwent CD34⁺-selected HCT. Isavuconazole prophylaxis was given for a median of 90 days (IQR, 87 to 91 days). Ten patients (10.7%) met the primary endpoint. Candidemia occurred in 3 patients (3.1%), 1 of whom had grade III skin acute graft-versus-host disease (GVHD). Toxicity leading to discontinuation occurred in 7 patients (7.4%). The most common toxicity was liver function abnormalities in 5 patients, including grade 1 transaminitis in 2 patients and grade 3 hyperbilirubinemia in 3 patients. Four patients (4.2%) had early discontinuation of isavuconazole for reasons not meeting the primary study endpoint. Six patients died during the study period, including 3 during prophylaxis and 3 during follow-up. No deaths were attributed to isavuconazole. The majority (85%) of allogeneic HCT recipients completed isavuconazole prophylaxis according to protocol. The rate of breakthrough candidemia was 3.1%, and there were no invasive mold infections. Our data support the utility of isavuconazole for antifungal prophylaxis after HCT.

Phase I/II multisite trial of optimally dosed clofarabine and low-dose TBI for hematopoietic cell transplantation in acute myeloid leukemia

Clofarabine is an immunosuppressive purine nucleoside analog that may have better anti-leukemic activity than fludarabine. We performed a prospective phase I/II multisite trial of clofarabine with 2 Gy total body irradiation as non-myeloablative conditioning for allogeneic hematopoietic cell transplantation in adults with acute myeloid leukemia who were unfit for more intense regimens. Our main objective was to improve the 6-month relapse rate following non-myeloablative conditioning, while maintaining historic rates of non-relapse mortality (NRM) and engraftment. Forty-four patients, 53 to 74 (median: 69) years, were treated with clofarabine at 150 to 250 mg/m² , of whom 36 were treated at the maximum protocol-specified dose. One patient developed multifactorial acute kidney injury and another developed multiorgan failure, but no other grade 3 to 5 non-hematologic toxicities were observed. All patients fully engrafted. The 6-month relapse rate was 16% (95% CI, 5%-27%) among all patients and 14% (95% CI, 3%-26%) among high-risk patients treated at the maximum dose, meeting the pre-specified primary efficacy endpoint. Overall survival was 55% (95% CI, 40%-70%) and leukemia-free survival was 52% (95% CI, 37%-67%) at 2 years. Compared to a historical high-risk cohort treated with the combination of fludarabine at 90 mg/m² and 2 Gy TBI, protocol patients treated with the clofarabine-TBI regimen had lower rates of overall mortality (HR of 0.50, 95% CI, 0.28-0.91), disease progression or death (HR 0.48, 95% CI, 0.27-0.85), and morphologic relapse (HR 0.30, 95% CI, 0.13-0.69), and comparable NRM (HR 0.85, 95% CI 0.36-2.00). The combination of clofarabine with TBI warrants further investigation in patients with high-risk AML.

Reconstitution of the gut microbiota of antibiotic-treated patients by autologous fecal microbiota transplant

Antibiotic treatment can deplete the commensal bacteria of a patient's gut microbiota and, paradoxically, increase their risk of subsequent infections. In allogeneic hematopoietic stem cell transplantation (allo-HSCT), antibiotic administration is essential for optimal clinical outcomes but significantly disrupts intestinal microbiota diversity, leading to loss of many beneficial microbes. Although gut microbiota diversity loss during allo-HSCT is associated with increased mortality, approaches to reestablish depleted commensal bacteria have yet to be developed. We have initiated a randomized, controlled clinical trial of autologous fecal microbiota transplantation (auto-FMT) versus no intervention and have analyzed the intestinal microbiota profiles of 25 allo-HSCT patients (14 who received auto-FMT treatment and 11 control patients who did not). Changes in gut microbiota diversity and composition revealed that the auto-FMT intervention boosted microbial diversity and reestablished the intestinal microbiota composition that the patient had before antibiotic treatment and allo-HSCT. These results demonstrate the potential for fecal sample banking and posttreatment remediation of a patient's gut microbiota after microbiota-depleting antibiotic treatment during allo-HSCT.

Impact of geriatric vulnerability on outcomes of older patients in allogeneic hematopoietic cell transplantation

7017

Background: Older patients are at increased risk for complications and death following allogeneic hematopoietic cell transplantation (allo-HCT). Traditional transplant-specific prognostic indices such as hematopoietic cell transplant comorbidity index (HCT-CI) may not capture all underlying geriatric vulnerabilities, and in-depth evaluation by a geriatrician prior to transplant may not always be available. We hypothesize that routine pre-transplant assessments by interdisciplinary clinical providers may help uncover additional geriatric deficits. Methods: Using an institutional database of 457 adults age 60 years and older (range 60-78.7) who underwent first allo-HCT for hematological malignancies from 2010 to 2017, we retrospectively examined the prevalence and the prognostic impact of pre-transplant geriatric deficits identified by interdisciplinary clinical providers including geriatric domains of functional activity, cognition, medication, nutrition, mobility, and routine laboratory tests. Results: With a median follow-up of 37 months for survivors, the 3-year probability of overall survival (OS) was 50% (95% CI 45-55). The 2-year cumulative incidence of non-relapse mortality (NRM) was 25% (95% CI 22-28). Among pre-transplant geriatric variables, we found that impairment in instrumental activities of daily living (IADL) was associated with increased NRM and inferior PFS and OS. In multivariate analyses, mismatched donor, age-adjusted HCT-CI > 4 (aaHCTCI), and IADL impairment were associated with NRM, while high/very high disease risk index (DRI), IADL impairment, and positive CMV status were associated with OS. The combination of IADL impairment with either aaHCTCI or DRI readily stratifies NRM and OS, respectively. Conclusions: Our findings establish a simple assessment tool to risk stratify older patients prior to allo-HCT using IADL and aaHCTCI and DRI. These results may provide an entry point for prospective, interventional trials to reduce NRM and toxicities for older allo-HCT patients.

Rapid reduction of peripheral blasts in older patients with refractory acute myeloid leukemia (AML) using reinduction with single agent anti-CD45 targeted iodine (131I) apamistamab [Iomab-B] radioimmunotherapy in the phase III SIERRA trial

7048

Background: The SIERRA trial is a prospective, randomized, phase 3, open-label, ongoing multicenter trial for patients aged ≥55 years with active, relapsed/refractory (R/R) AML evaluating allogeneic hematopoietic cell transplantation (HCT) versus conventional care (CC). Recent preliminary data demonstrated robust donor engraftment in all patients treated with Iomab-B (Blood 2018 132:1017) despite active disease. We hypothesize that successful engraftment was due to rapid disease reduction with Iomab-B. Methods: Patients are randomized to receive Iomab-B and HCT or to a CC therapy including approved targeted agents followed by HCT if in remission. Majority of patients (79%) in the CC arm did not achieve CR and the study allowed crossover to receive Iomab-B. Results: Data were evaluated for the first 25% of patients (N=38). Twenty-nine patients received Iomab-B, either directly (N=19) or via crossover (N=10). Median baseline marrow blasts were 30% (4-74) for Iomab-B and 24% (6-70%) for CC, which increased to 45% (10-70%) at crossover. Peripheral blast data was available in 16 patients (Iomab 7, Crossover 9). By day 3 post-Iomab, blasts were reduced by 98% with 100% reduction by day 8 (assuming 0% blasts due to lack of differential at WBC 0.1; Table). All patients engrafted with ANC at a median of 13 days (9-22 days). Conclusions: Targeted re-induction radioimmunotherapy with single agent Iomab-B rapidly decreases peripheral blasts in chemotherapy refractory AML. This significant reduction of leukemia burden followed by successful engraftment after HCT is encouraging in this underserved population. Clinical trial information: NCT02665065. [Table: see text]

Development and characterization of a canine-specific anti-CD94 (KLRD-1) monoclonal antibody

Natural killer (NK) cells are non-T, non-B lymphocytes are part of the innate immune system and function without prior activation. The human NK cell surface determinant, CD94, plays a critical role in regulation of NK cell activity as a heterodimer with NKG2 subclasses. Canine NK cells are not as well defined as the human and murine equivalents, due in part to the paucity of reagents specific to cell surface markers. Canines possess NK/NKT cells that have similar morphological characteristics to those found in humans, yet little is known about their functional characteristics nor of cell surface expression of CD94. Here, we describe the development and function of a monoclonal antibody (mAb) to canine (ca) CD94. Freshly isolated canine CD94⁺ cells were CD3^+/-, CD8^+/-, CD4-, CD21-, CD5^low, NKp46⁺, and were cytotoxic against a canine target cell line. Anti-caCD94 mAb proved useful in enriching NK/NKT cells from PBMC for expansion on CTAC feeder cells in the presence of IL-2 and IL-15. The cultured cells were highly cytolytic with co-expression of NKp46 and reduced expression of CD3. Transmission electron microscopy revealed expanded CD94⁺ lymphocytes were morphologically large granular lymphocytes with large electron dense granules. Anti-caCD94 (mAb) can serve to enrich NK/NKT cells from dog peripheral blood for ex vivo expansion for HCT and is a potentially valuable reagent for studying NK/NKT regulation in the dog.

Second allogeneic hematopoietic cell transplantation for relapse after first allografts

We analyzed outcomes of 126 patients with hematologic malignancies, who relapsed after first allogeneic hematopoietic cell transplantation (HCT) and received subsequent allografts. In 17 cases, the original donors were utilized, while in 109 cases different donors were identified. The 2-year overall survival (OS), relapse, and non-relapse mortality (NRM) rates were 33%, 42%, and 33%, respectively. Patients with early relapse after first allogeneic HCT (within 100 days vs. 100 days to 12 months vs. >12 months) had higher relapse rates (50% vs. 47% vs. 34%, respectively; p = .01) and worse OS (15% vs. 25% vs. 45%, respectively, p = .005) at 2 years after second allogeneic HCT. In conclusion, second allogeneic HCT should be considered in patients who relapse after first allografts, especially in those who relapse after more than a year. Utilizing a different donor for the second allotransplant including umbilical cord blood or HLA-haploidentical, related donors did not adversely impact outcomes.

Immune Cytopenias after Ex Vivo CD34+-Selected Allogeneic Hematopoietic Cell Transplantation

Immune-mediated cytopenias (ICs), such as immune thrombocytopenia and immune hemolytic anemia, are among the adverse events after allogeneic hematopoietic cell transplantation (allo-HCT). Previous reports suggest that in vivo T cell depletion may increase the incidence of IC after allo-HCT. We evaluated whether a strategy that reduces functional donor T cells via ex vivo CD34⁺-selection associates with the development of IC in a cohort of 408 patients who underwent allo-HCT for hematologic malignancy. The cumulative incidence of IC at 6, 12, and 36 months after the 30-day landmark post-HCT was 3.4%, 4.9%, and 5.8%, respectively. Among 23 patients who developed IC, 7 died of relapse-related mortality and 4 of nonrelapse mortality. A median 2 types of treatment (range, 1 to 5) was required to resolve IC, and there was considerable heterogeneity in the therapies used. In univariable analyses, a hematologic malignancy Disease Risk Index (DRI) score of 3 was significantly associated with an increased risk of IC compared with a DRI of 1 or 2 (hazard ratio [HR], 4.12; P = .003), and IC (HR, 2.4; P = .03) was associated with increased risk of relapse. In a multivariable analysis that included DRI, IC remained significantly associated with increased risk of relapse (HR, 2.4; P = .03). Our findings show that IC events occur with relatively similar frequency in patients after ex vivo CD34⁺-selected allo-HCT compared with unmodified allo-HCT, suggesting that reduced donor T cell immunity is not causative of IC. Moreover, we noted a possible link between its development and/or treatment and increased risk of relapse.