Insufficient immune reconstitution (IR) is a major determinant of morbidity and mortality after allogeneic hematopoietic cell transplantation (allo-HCT). Strategies for graft-versus-host disease (GVHD)-prophylaxis, such as anti-thymocyte globulin (ATG) and post-transplant cyclophosphamide (PTCy), modulate immune recovery, but their effects on IR in matched unrelated donor (MUD) allo-HCT remain incompletely defined. In this retrospective bi-centric study, we analyzed patients with myeloid malignancies undergoing MUD allo-HCT who received ATG or PTCy per center policy. Longitudinal IR and clinical outcomes were assessed. IR was defined as sustained recovery of CD3+CD4+ cells >200/μl and CD19+ cells >50/μl. The impact of GVHD-prophylaxis (ATG vs PTCy) on IR dynamics was explored. A total of 252 patients were included. By day +365, 16.7% achieved IR, which was independently associated with superior OS (HR 0.39, 95% CI 0.17–0.90; p=0.026) and lower TRM (HR 0.08, 95% CI 0.01–0.63; p=0.017). In multivariable competing-risk analyses, younger donor age (sHR 0.97, 95% CI 0.94–1.00; p=0.037) and PTCy (sHR 0.49, 95% CI 0.27–0.84; p=0.01) were associated with higher probability of IR by month +18. The association between PTCy and IR was attenuated after adjusting for therapy-requiring acute or chronic GVHD, which independently delayed IR (HR 0.31, 95% CI 0.20–0.48; p<0.001). ATG and PTCy showed distinct IR trajectories: ATG associated with earlier NK expansion, PTCy led to enhanced adaptive T- and B-cell recovery from day +100. IR strongly predicted survival, independently of GVHD-prophylaxis. Prospective studies are warranted to better define determinants of IR after MUD allo-HCT in the PTCy era.

Introduction:Letermovir (LET) is an effective prophylaxis for human cytomegalovirus (HCMV) reactivations in HCMV-seropositive patients after allogeneic stem cell transplantation (allo-SCT). HCMV promotes polyfunctional T-cell responses, leading to HCMV-specific immune reconstitution (IR), thus contributing to polyclonal IR. Methods:We retrospectively analyzed HCMV-seropositive patients undergoing allo-SCT with ATG-based GvHD prophylaxis to assess the impact of LET on timing and quality of polyclonal IR. Two cohorts were identified: a pre-emptive treatment (PET) historical cohort transplanted without LET prophylaxis and a LET cohort receiving LET until at least day +100. All patients underwent weekly HCMV-DNA monitoring during the first 100 days post-allo-SCT. Immune monitoring was performed by flow cytometry, quantifying CD3+CD4+, CD3+CD8+ T-cells, CD19+ B-cells, and CD56+CD16+ NK-cells monthly during the first year after transplantation. Results:A total of 276 HCMV-seropositive patients were analyzed, 99 (36%) in the LET cohort and 177 (64%) in the PET cohort. LET significantly reduced the incidence of clinically significant HCMV infections during the first 100 days [28.3% in the LET cohort vs. 68.4% in the PET cohort (p<0.001)]. The cumulative incidence of IR 18 months after allo-SCT was comparable in the two groups [24% in the LET cohort vs. 27% in the PET cohort (p=0.393)]. These data were supported by multivariable analysis (HR 1.2, 95% CI 0.74-1.95, p = 0.463). Distinct immune dynamics were observed in the LET cohort, including lower early CD8+ T-cell counts and earlier NK-cell expansion peak. Discussion:Despite these differences, LET does not appear to influence the long-term incidence and composition of IR.

INTRODUCTION:Leukemic stem cells (LSC) are the source of relapse in acute myeloid leukemia (AML). Thus, eliminating LSC is one of the overarching goals of AML research. Radioimmunotherapy is an immunotherapeutic approach which utilizes radioactive isotopes as effector molecules based on the proven ability of ionizing radiation (IR) to kill LSC.It has the potential to eliminate target-antigen negative LSC. AREAS COVERED:LSC biology, radiobiological principles of RIT, an overview of published and unpublished clinical results of RIT in AML. Issues of practical implementation of RIT in clinical trials. EXPERT OPINION:RIT for AML isat a critical juncture. Its ability to target antigen negative LSC gives it an advantage compared with other forms of immunotherapy. In order to compete with other forms of targeted therapy the procedure has to be simplified.

Neurologic complications (NCs), especially those of the central nervous system (CNS), represent a severe complication after allogeneic stem cell transplantation (allo-HSCT) and are associated with relevant morbidity and mortality. We aimed to characterize the potential risk factors for the development of CNS-NC, with a special focus on the role of calcineurin inhibitors (CNIs) as a predisposing factor. For this purpose, we compared cyclosporin A (CsA) versus tacrolimus (TAC) with respect to their influence on the incidence and type of CNS-NC after allo-HSCT. We retrospectively analyzed the incidence, risk factors, and impact on outcomes of CNS-NC diagnosed during the post-transplantation follow-up in patients with different high-risk hematologic malignancies who underwent allo-HSCT at our institution over a 20-year period. All patients included in the analysis received CNI (CsA or TAC) as graft-versus-host disease (GVHD) prophylaxis. We evaluated a total of 739 consecutive patients who underwent transplantation between December 1999 and April 2019. During a median follow-up of 6.8 years, we observed a CNS-NC incidence of 17%. The development of CNS-NC was associated with decreased overall survival (OS) and increased transplantation-related mortality (TRM). The most frequent CNS-NCs were infections (30%) and neurologic adverse events related to the administration of CNI, TAC, or CsA as GVHD prophylaxis (42%). In the multivariable analysis, age, total body irradiation (TBI), and severe acute GVHD and chronic GVHD were significant risk factors in the development of CNS-NCs. TAC compared with CsA emerged as an independent predisposing factor for CNS-NCs. The TAC-associated risk of CNS-NCs was related mostly to the occurrence of transplantation-associated thrombotic microangiopathy (TA-TMA) with neurologic manifestations (neuro-TA-TMA), although the general TA-TMA incidence was comparable in the 2 CNI subgroups. CNS-NCs are associated with poor prognosis after allo-HSCT, with TAC emerging as a potential yet insufficiently characterized predisposing factor.

The treatment of relapsed/refractory acute myeloid leukemia (AML) is associated with a dismal prognosis. The allogeneic hematopoietic cell transplantation (allo-HCT) is frequently performed as salvage therapy. Reduced intensity conditioning protocols have been developed with the aim of reducing the leukemia burden without increasing their toxicity. We compared the reduced intensity conditioning FM140 (fludarabine, 150 mg/m2; melphalan 140 mg/m2) with FBM110 (fludarabine 150 mg/m2; BCNU, also known as carmustine, 300-400 mg/m2; and melphalan 110 mg/m2). From the European Bone Marrow Transplantation (EBMT) Acute Leukemia Working Party registry, we identified 293 adult patients (FM140, n = 118 and FBM110, n = 175) with AML with relapsed/refractory disease prior to allo-HCT. There were some differences such as age (FM140 = 59.5 years vs. FBM110 = 65.1 years, p < 0.001) and graft-versus-host disease (GvHD) prophylaxis based on in vivo T-cell depletion (TCD, FM140 = 39% vs. FBM110 = 75%, p < 0.001). No differences were observed between FM140- and FBM110-treated patients regarding overall survival (OS) (2-year OS: 39.3% vs. 45.7%, p = 0.58), progression-free survival (PFS) (2-year PFS: 36.1% vs. 37.3%, p = 0.69), non-relapse mortality (NRM) (2-year NRM: 15.3% vs. 25.7%, p = 0.10) and relapse incidence (RI) (2-year RI: 48.6% vs. 37.0%, p = 0.7). In conclusion, despite differences in age and GvHD prophylaxis, AML patients with active disease undergoing allo-HCT after FBM110 conditioning showed similar outcomes compared to FM140.

Introduction. Letermovir (LTV) showed to reduce the incidence of Cytomegalovirus (CMV) reactivations in CMV-seropositive patients after allogeneic stem cell transplantation (allo-SCT). CMV reactivations are known to stimulate polyfunctional T-cell responses, which foster the development of CMV-specific immune reconstitution (IR) and contribute to the advent of the polyclonal IR after allo-SCT. Since IR plays an important role in influencing outcome of transplanted patients, we aimed at investigating the impact of LTV in the advent and timing of polyclonal IR after allo-SCT. Methods. We conducted a retrospective analysis of CMV-seropositive patients consecutively undergoing allo-SCT at our center. We defined two cohorts according to the administration of LTV: (1) the no-LTV-cohort, encompassing patients who did not receive LTV, but pre-emptive treatment (PET) in case of CMV-reactivation (historical cohort, transplanted between 2013-2018); (2) the LTV-cohort, including patients who received LTV until at least day +100 after allo-SCT (transplanted between 2019-2023). CMV-DNA monitoring was performed weekly using real-time PCR from blood samples for the first 100 days after allo-SCT. Immune monitoring was performed using a flow cytometry-based assay to identify and determine the percentages and absolute counts of T (CD3+), B (CD19+), and natural killer (NK) cells (CD16+CD56+) as well as the CD4 and CD8 subpopulations of T cells in peripheral blood. Immune monitoring was performed monthly during the first year after allo-SCT and afterwards every 3 months until IR, which was defined as the detection in 2 consecutive measurements of CD3+CD4+-T-cells > 200 cells/µl and CD19+-B-cells > 50cells/µl. Statistical analysis included univariate methods using the Mann-Whitney test for continuous variables and the chi-square and Fischer exact test for nominal ones. For multivariable analysis, Cox- and competing risks regressions were used. Results. The study included 363 CMV-seropositive transplanted patients, with 128 (35%) in the LTV cohort and 235 patients (65%) in the historical no-LTV cohort. Patient characteristics, including age at time of allo-SCT, type of disease, disease status at allo-SCT, EBMT risk score, conditioning regimen and graft versus host (GVHD) prophylaxis, mainly based on ATG, were homogenously balanced between the two groups. The cumulative incidence (CI) of IR at day+ 100 and +180 after allo-SCT showed no significant difference between the two cohorts . Multivariable analysis indicated that LTV did not affect the occurrence of IR 1 year (y) after allo-SCT. Factors such as older age, high EBMT risk score, active disease at the time of allo-SCT and a CMV-seronegative donor significantly negatively impacted the advent of polyclonal IR. We then analyzed the different cellular population in order to assess the dynamics of the shaping of the immune system in the 2 groups. We found that in the no LTV-group there was a significantly higher expansion of the CD3+CD8+-T-cell fraction during the first 6 months after transplantation as compared to the LTV-cohort: at day +100 we detected 228 CD3+CD8+-T-cells/µl in the no LTV cohort vs. 114/µl in the LTV-cohort (p=0.0016). At day +180 the difference was preserved, with 425 CD3+CD8+-T-cells/µl vs. 204/µl respectively, p=0.001. No difference was observed in the CD3+CD8+-T-cells expansion at 1 y after allo-SCT. We also found a significantly higher peak of expansion of NK-cells at day +100 in the LTV-cohort (243 NK-cells/µl vs. 206 NK-cells/µl in the no LTV, p=0.008), but also in this setting no relevant difference was observed in the long-term follow-up (day+180 and +365). No significant differences were observed between the two cohorts considering the dynamic of expansion of CD3+CD4+-T-cells and CD19+-B-cells during the follow-up post allo-SCT. Conclusions. This is one of the largest retrospective studies evaluating occurrence and dynamic of IR in patients receiving LTV after allo-SCT. We confirmed that LTV could potentially (but transitorily) decrease T-cells (especially in the CD3+CD8+-T-cell fraction), with a peak of expansion of NK-cells in our study occurring at day +100. Despite these differences in the dynamic of polyclonal IR during the early phase after allo-SCT, in the long-term follow-up LTV does not appear to influence the advent, the qualitative composition and the incidence of IR.

BackgroundLow aerobic capacity is associated with an increased mortality risk in allogenic stem-cell transplantation (alloSCT) patients, but currently used risk scores in the pre-transplantation workup are still underestimating physical activity as a prognostic factor.AimTo examine the physical condition, muscle function, blood inflammation and training adherence of alloSCT patients during inpatient time to identify potential biomarkers associated with development of myopathy and sarcopenia.MethodsPatients undergoing alloSCT were examined at four time points (T0: before alloSCT; Tha: hospital admission; T1: engraftment; T2: inpatient discharge). T0 included cardiopulmonary performance, body composition, grip and knee strength, motor skill tests (One-leg stand/Tinetti/Chair-rising), blood sampling (blood cell profiling and inflammation targets (Kynurenin/high sensitivity C-reactive Protein (hsCRP)/Tumor necrosis factor alpha (TNF-alpha)/Musclin/Galectin-3) and quality of life, state of health, fatigue, muscle weakness and physical activity by questionnaires (IPAQ/BSA/SARC-F/Fatigue). At T1 and T2, blood samples, grip strength and motor skill tests were repeated. Glucocorticoid dose and daily physical activity were documented during inpatient stay.Results26 of 35 included patients (4 females; age 55.58 ± 12.32 years; BMI 24.70 ± 3.27 kg/m2; VO2peak 16.55 ± 4.06 ml/min/kg) could proceed to alloSCT. Grip strength and Tinetti decreased from T0 until T2, no difference in Chair-rising test, One-leg and Tandem stand. All patients engrafted after 24.9 days ± 3.9 days. HsCRP and Kynurenine increased from T0 to T1, decreased at T2. TNF-alpha (T0vsT2/T1vsT2) and Musclin (T0vsT1) decreased. At T2, Galectin-3 was higher compared to T0/T1. Correlation analysis of grip strength and inflammatory markers revealed a positive correlation with TNF-alpha at T2. 50% of patients documented physical activity and questionnaire and reported a 50%-reduction of daily endurance and strength training between T1 to T2.ConclusionAllogeneic stem-cell transplantation is associated with immune system vulnerability due to conditioning, increased inflammation and fatigue, and loss of muscle strength and function. In addition to hsCRP, Kynurenine seems to be a reliable biomarker to monitor acute and regenerative inflammation status of alloSCT patients, while Musclin and Galectin-3 may be added to physiological assessment regarding myopathy and sarcopenia. Grip strength and daily activity level should be documented by professionals to identify risk patients early and support them with optimal (exercise) therapy.

For patients with acute myeloid leukemia, myelodysplastic syndrome, or acute lymphoblastic leukemia, allogeneic hematopoietic cell transplantation (HCT) is a potentially curative treatment. In addition to standard conditioning regimens for HCT, high-dose radioimmunotherapy (RIT) offers the unique opportunity to selectively deliver a high dose of radiation to the bone marrow while limiting side effects. Modification of a CD66b-specific monoclonal antibody (mAb) with a DTPA-based chelating agent should improve the absorbed dose distribution during therapy. The stability and radioimmunoreactive fraction of the radiolabeled mAbs were determined. Before RIT, all patients underwent dosimetry to determine absorbed doses to bone marrow, kidneys, liver, and spleen. Scans were performed twenty-four hours after therapy for quality control. A radiochemical purity of >95% and acceptable radioimmunoreactivity was achieved. Absorbed organ doses for the liver and kidney were consequently improved compared to reported historical data. All patients tolerated RIT well with no treatment-related acute adverse events. Complete remission could be observed in 4/5 of the patients 3 months after RIT. Two patients developed delayed liver failure unrelated to the radioimmunotherapy. The improved conjugation and radiolabeling procedure resulted in excellent stability, radiochemical purity, and CD66-specific radioimmunoreactivity of 90Y-labeled anti-CD66 mAb. RIT followed by conditioning and HCT was well tolerated. Based on these promising initial data, further prospective studies of [90Y]Y-DTPA-Bn-CHX-A″-anti-CD66-mAb-assisted conditioning in HCT are warranted.

No adequate data exist on the impact of multiple myeloma (MM) with extramedullary disease (EMD) after autograft and maintenance therapy.

Supplementary Table from Longitudinal Outcome over Two Decades of Unrelated Allogeneic Stem Cell Transplantation for Relapsed/Refractory Acute Myeloid Leukemia: An ALWP/EBMT Analysis

Introduction Allogeneic hematopoietic stem cell transplantation (alloHCT) is the only potential curative treatment for patients (pts) with high-risk myeloid malignancies. Despite advances in the supportive care over the past decades, alloHCT is still associated with significant toxicity, especially in the elderly population. The choice of an adequate conditioning regimen has become essential in order to prevent treatment-related morbidity and mortality. Since myeloablative conditioning (MAC) is mostly restricted to the younger population due to the high toxicity, reduced-intensity conditioning (RIC) provides an alternative solution. However, especially for pts with high-risk disease, a potential increase in the incidence of relapse must be taken into account. The advent of reduced-toxicity conditioning regimens (RTC), mostly based on treosulfan in combination with fludarabine, offers a balance between a favorable toxicity profile and a strong anti-neoplastic effect. Considering the increasing rates of alloHCT among older pts in the past decades, finding the optimal conditioning regimen is still an unmet need for this collective. The objective of this study is to analyze the outcome of pts aged ≥60 years who underwent alloHCT for myelodysplastic or myeloproliferative disease and received a treosulfan-based conditioning. In order to maximize the anti-leukemic effect of the conditioning in this population we chose the myeloablative dose of treosulfan of 14g/m2 daily. Materials and methods We retrospectively analyzed the outcome of adult pts ≥60 years with myelodysplastic syndrome (MDS), chronic myelomonocytic leukemia (CMML) or myelofibrosis (MF) who underwent their first allo-HCT from a matched or mismatched donor over a period of 10 years at the adult Bone Marrow Transplantation Unit of our institution. The conditioning consisted of a combination of treosulfan 14 g/m2/day on days -6 to -4, fludarabine, 30 mg/m2/day on days -6 to -2, alone or combined with 2 Gy TBI (day 0) for MDS and treosulfan, 14 g/m2/day on days -6 to -4, fludarabine, 30 mg/m2/day on days -6 to -3 for CMML and MF. Endpoints of this analysis were engraftment rate (together with time to engraftment), relapse-free survival (RFS), overall survival (OS), and non-relapse mortality (NRM). Continuous variables were illustrated as median values. NRM, RFS and OS for the whole cohort were analyzed with the Kaplan-Meier method and presented as survival functions. Results Between 01/2012 and 12/2022 91 consecutive elderly pts were eligible for this analysis. Patient and transplant characteristics are listed in Table 1. The median follow-up after allo-HCT was 3.12 years (4 months-10.5 years). Median age was 65 years, 76% (n = 69) of patients had an EBMT (European Society for Blood and Marrow Transplantation) risk score of ≥ 4. In 20 of 91 pts (22%) a 9/10 matched unrelated donor was selected, due to the lack of a more suitable donor. The standard graft versus host disease (GVHD) prophylaxis was a combination of calcineurin inhibitors (CNI) +/- mycophenolate mofetil and Anti-T-lymphocyte globulin (ATG) (n= 85, 94%). Neutrophil engraftment was achieved in 98% (n= 89) of pts. The median time to engraftment was 13 days (12, 15). Fourteen of 91 pts (15%) developed severe (grade III-IV) acute GVHD, and 44% (n= 40) had chronic GVHD of any grade. Considering early toxicity, 2 patients of 91 (2%) died before day +30 after alloHCT due to transplant-related toxicity, overall 6 of 91 (7%) in the first 100 days after alloHCT. The 2-year OS was 55% (95% CI, 44.7-.66.2) (Figure 1) and RFS was 48.5% (95% CI, 38.9-60.5). The 2-year NRM was 37% (95% CI, 33.5-39.5). No significant differences have been observed in the outcome of the different disease entities. Main causes of death were infections (n= 15, 32%), GVHD (n=13, 27.7%) and disease relapse (n= 13, 27.7%). Conclusions Our retrospective analysis suggests that a treosulfan-based RTC with myeloablative potential in an elderly and frail population of pts with high-risk myeloid diseases is feasible, with an excellent engraftment rate and a limited early toxicity, and promotes disease control. We report a 2-year NRM of 37%, which was partially due to severe GvHD in a cohort of pts with a relatively high-proportion of mismatched donors (20%). The role of post-transplant cyclophosphamide as backbone of the GvHD prophylaxis of RTC regimes should be further evaluated, in prospective trials.

Older age and a high burden of comorbidities often drive the selection of low-intensity conditioning regimens in allogeneic hematopoietic stem cell transplantation recipients. However, the impact of comorbidities in the low-intensity conditioning setting is unclear. We sought to determine the contribution of individual comorbidities and their cumulative burden on the risk of nonrelapse mortality (NRM) among patients receiving low-intensity regimens. In a retrospective analysis of adults (>= 18 years) who underwent transplantation for acute myeloid leukemia in the first complete remission between 2008 and 2018, we studied recipients of low-intensity regimens as defined by the transplantation conditioning intensity (TCI) scale. Multivariable Cox models were constructed to study associations of comorbidities with NRM. Comorbidities identified as putative risk factors in the low-TCI setting were included in combined multivariable regression models assessed for overall survival, NRM, and relapse. A total of 1663 patients with a median age of 61 years received low-TCI regimens. Cardiac comorbidity (including arrhythmia/valvular disease) and psychiatric disease were associated with increased NRM risk (hazard ratio [HR], 1.54; 95% confidence interval [CI], 1.13-2.09 and HR, 1.69; 95% CI, 1.02-2.82, respectively). Moderate pulmonary dysfunction, though prevalent, was not associated with increased NRM. In a combined model, cardiac, psychiatric, renal, and inflammatory bowel diseases were independently associated with adverse transplantation outcomes. These findings may inform patient and regimen selection and reinforce the need for further investigation of cardioprotective transplantation approaches.

Introduction. Persistent thrombocytopenia (PT) due to delayed primary platelet recovery or secondary graft failure with prolonged thrombocytopenia is a relevant and relatively common complication after allogeneic stem cell transplantation (alloSCT). It can result in transfusion dependence and hemorrhagic events, leading to increase of morbidity and mortality. Concomitant causes of PT after alloSCT are several and can include viral infections, graft-versus-host disease (GvHD), drug toxicity, thrombotic microangiopathy (TMA) and immune thrombocytopenia (ITP). Together with the treatment of the primary cause and the support with platelet transfusion, the use of thrombopoietin receptor agonists (TPO-RAs), which proved to be effective in several scenarios (e.g. ITP or aplastic anemia), is gaining a fundamental role also in the post alloSCT setting. To date, the use of TPO-RAs after transplant has been investigated in small studies or case reports. In this study, we evaluated the use of romiplostim in a larger patient cohort to determine its safety, efficacy and potential predictors of response. Materials and methods. We conducted a retrospective study on consecutive patients undergoing alloSCT and receiving romiplostim for the treatment of PT at the bone marrow transplantation unit of the University Hospital of Ulm. PT was defined as a platelet count < 20 Giga/l for 7 consecutive days after engraftment, the need for continuous transfusion during the post-transplant follow-up or a not rapidly reversible decrease of >50% of the platelet count not due to relapse of underlying hematological disease. Response to treatment was defined as a platelet count >50 Giga/l for at least 7 consecutive days without transfusion. Patients with residual bone marrow involvement of primary hematological disease were excluded. Univariate analysis was conducted using Fisher's exact test or Mann-Whitney-U-test. Results. Between 01/2019 and 12/2021 we identified a total of 119 out of 255 transplanted patients (46,7%) with PT receiving, as a part of the treatment, romiplostim during the post-transplant follow-up. Patient characteristics are listed in Table 1. The median platelet count at baseline was 32 Giga/l (r = 0 - 88). We started with romiplostim 250μg on a weekly basis, in 46,2% of cases the dose was escalated to 500 µg during treatment. Seventy-three percent showed a clinical response to treatment with a median time to response of 40 days (r = 7 - 565). We observed adverse events like thrombosis, pain syndrome, dizziness in only 8,4% of patients. The median duration of treatment was 168 days (r = 18 - 761). In patients with response, the median platelet count was 91 Giga/l (r = 53 - 212). In univariate analysis, we evaluated potential risk factors associated with poor response to romiplostim. While the presence of a viral reactivation (like CMV, EBV, BKV, HSV1) requiring systemic treatment was associated with a significant lower response rate (47.6% versus 79.6%, respectively for patients with or without reactivation, p= 0.005), the presence of active GvHD (also in case of steroid-refractory (SR) forms), of TMA and the number of CD34-positive stem cells of the graft did not play a role in determining the efficacy of romiplostim. We also evaluated the influence of graft cryopreservation, which was performed increasingly during the SARS-CoV-2 pandemic, on the rate of efficacy of romiplostim in PT treatment. We could not identify a significant difference as compared to the non-cryopreserved grafts. Conclusion. Our results indicate that romiplostim is overall well tolerated and represents a reasonable and effective treatment for PT after alloSCT. We observed that viral infections requiring systemic antiviral treatment could represent a predictor of worse response, which could potentially be explained by the myelotoxicity induced not only by the virus itself but also as a consequence of antiviral substances. Of note, especially considering that SR GvHD or TMA did not seem to impair the efficacy of romiplostim, the stimulation of TPO receptor could play a role in reducing the rate of morbidity and mortality associated with such severe complications of the post transplant follow-up. Also, cryopreservation did not impact on the rate of success of TPO-RAs based treatment strategy. These preliminary results need to be further validated in larger and prospective cohorts. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Allogeneic hematopoietic stem cell transplantation (HCT) is standard treatment for adult high-risk (HR) acute lymphoblastic leukemia (ALL) and contributed to the overall improved outcome. We report a consecutive cohort of prospectively defined HR patients treated on German Multicenter Acute Lymphoblastic Leukemia trials 06/99-07/03 with similar induction/consolidation therapy and HCT in first remission. A total of 542 patients (15-55 years) with BCR-ABL-negative ALL were analyzed. Sixty-seven percent received HCT from matched unrelated donors (MUD) and 32% from matched sibling donors (MSD). The incidence of non-relapse mortality (NRM) was 20% at 5 years. NRM occurred after median 6.6 months; the leading cause (46%) was infection. NRM after MUD decreased from 39% in trial 06/99 to 16% in trial 07/03 (P < .00001). Patient age was the strongest predictor of NRM. The 5-year relapse incidence was 23% using MSD and 25% using MUD. Minimal residual disease (MRD) was the strongest predictor of relapse (45% for molecular failure versus 6% for molecular CR; P < .0001). The median follow-up was 67 months, and the 5-year survival rate was 58%. Age, subtype/high risk feature, MRD status, trial and acute GvHD were significant prognostic factors. We provide a large reference analysis with long follow-up confirming a similar outcome of MSD and MUD HCT and improved NRM for MUD HCT over years. MRD has a strong impact on relapse risk, whereas age was the strongest predictor of NRM. New adapted conditioning strategies should be considered for older patients combined with the goal to reduce the MRD level before stem cell transplantation.

IntroductionVaccination against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is approved and recommended for immunocompromised patients such as patients after allogeneic stem cell transplantation (allo-SCT). Since infections represent a relevant cause of transplant related mortality we analyzed the advent of immunization to SARS-CoV-2 vaccination in a bicentric population of allogeneic transplanted patients.MethodsWe retrospectively analyzed data of allo-SCT recipients in two German transplantation centers for safety and serologic response after two and three SARS-CoV-2 vaccinations. Patients received mRNA vaccines or vector-based vaccines. All patients were monitored for antibodies against SARS-CoV2-spike protein (anti-S-IgG) with an IgG ELISA assay or an EIA Assay after two and three doses of vaccination.ResultsA total of 243 allo-SCT patients underwent SARS-CoV-2 vaccination. The median age was 59 years (range 22-81). While 85% of patients received two doses of mRNA vaccines, 10% had vector-based vaccines and 5% received a mixed vaccination. The two vaccine doses were well tolerated with only 3% patients developing a reactivation of graft versus host disease (GvHD). Overall, 72% of patients showed a humoral response after two vaccinations. In the multivariate analysis age at time of allo-SCT (p=0.0065), ongoing immunosuppressive therapy (p= 0.029) and lack of immune reconstitution (CD4-T-cell counts <200/μl, p< 0.001) were associated with no response. Sex, intensity of conditioning and the use of ATG showed no influence on seroconversion. Finally, 44 out of 69 patients that did not respond after the second dose received a booster and 57% (25/44) showed a seroconversion.DiscussionWe showed in our bicentric allo-SCT patient cohort, that a humoral response could be achieve after the regular approved schedule, especially for those patients who underwent immune reconstitution and were free from immunosuppressive drugs. In over 50% of the initial non-responders after 2-dose vaccination, a seroconversion can be achieved by boostering with a third dose.