High-dose Post-transplant Cyclophosphamide Research Articles

Low dose post-transplant cyclophosphamide and sirolimus induce mixed chimerism with CTLA4-Ig or lymphocyte depletion in an MHC-mismatched murine allotransplantation model

Allogeneic hematopoietic cell transplantation (allo-HCT) offers a curative option for patients with certain non-malignant hematological diseases. High-dose post-transplant cyclophosphamide (PT-Cy) (200 mg/kg) and sirolimus (3 mg/kg), (HiC) synergistically induce stable mixed chimerism. Further, sirolimus and cytotoxic T lymphocyte-associated antigen-4 immunoglobulin (CTLA4-Ig), also known as Abatacept (Aba), promote immune tolerance and allograft survival. Here, in a major histocompatibility complex (MHC)-mismatched allo-HCT murine model, we combined Aba and/or T-cell depleting anti-Thy1.2 (Thy) with a lower dose of PT-Cy (50 mg/kg) and Sirolimus (3 mg/kg), (LoC). While mice in the LoC group showed graft rejection, the addition of Thy to LoC induced similar donor chimerism levels when compared to the HiC group. However, the addition of Aba to LoC led to graft acceptance only in younger mice. When Thy was added to the LoC+Aba setting, graft acceptance was restored in both age groups. Engrafted groups displayed significantly reduced frequencies of recipient-specific interferon-γ-producing T cells as well as an increased frequency in regulatory T cells (Tregs) except in the LoC+Aba group. Splenocytes from engrafted mice showed no proliferation upon restimulation with Balb/c stimulators. Collectively, in combination with Aba or Thy, LoC may be considered to reduce graft rejection in patients who undergo allo-HCT.

Post-Transplant Cyclophosphamide, Abatacept, and Vedolizumab to Prevent Graft-Versus-Host Disease after Hematopoietic Stem Cells Transplantation from Haploidentical Donors in Children with Acute Leukemia: Results of a Prospective Trial

Introduction Graft-versus-host disease (GvHD) remains a crucial complication associated with significant morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). High-dose post-transplantation cyclophosphamide (PTCy) targets alloreactive donor T cells proliferating early after HSCT, promotes regulatory T cells, and prevents severe GVHD. The effectiveness of PTCy-based regimens varies depending on the graft source and intensity of the preparative regimen. Improvement of GVHD control with novel targeted agents, added to the backbone of PTCy, could further increase the safety of HSCT and reduce the morbidity and complications of standard regimens of pharmacological immune suppression. In this pilot trial, we evaluated the safety and efficacy of abatacept and vedolizumab in unmanipulated haploidentical transplantation among children with leukemia. Materials and methods A total of 54 pts with acute leukemia (AML- 18, ALL-36, 26 female, 28 male, the median age at HSCT - 7,4 years (0,4-16,8), underwent unmanipulated allogeneic bone marrow (BM) (n=53) or peripheral blood stem cell (PBSC)(n=1) transplantation between March 2022 and May 2023. All donors were haploidentical relatives, represented Disease status at transplant was CR1 in 25 pts, CR³2 in 29 pts. For all patients, it was the 1-st transplantation. All patients received myeloablative conditioning, either TBI-based (n=30) or 24 treosulfan-based (n=24), with either cyclophosphamide (n=47) or etoposide (n=7) as a second agent. Prophylaxis of graft-versus-host-disease (GVHD) consisted of CsA from day-1 to day 180, 50 mg/kg of Cph on days +3 and +4, abatacept at 10 mg/kg on days +5, +14, +28, +45, +60 and vedolizumab at 10 mg/kg (capped at 300 mg) on days -1, +14, +28. The median dose of CD34+ cells was 4,7 x10 6/kg (range 1,2-17), and the CD3 dose was 42 x10 6/kg. Results Primary engraftment was achieved in 53 (98%) pts; the median time to neutrophil and platelet recovery was 20 and 23 days, respectively. All engrafted pts had verified morphologic remission and achieved complete donor chimerism by day +30. One patient failed to engraft, relapsed, and required rescue with a second HSCT from an alternative donor. The regimen was generally well tolerated. Acute toxicity consisted of grade III-IV mucositis (n=5); grade II-III hemorrhagic cystitis (n=4); grade III-V veno-occlusive disease (n=2) (all cases of VOD developed after pre-HSCT use of inotozumab); bloodstream infections (n=8). Four patients were admitted to the intensive care unit due to septic events or VOD. The median follow-up time for survivors was seven months (range: 1 -15). Transplant-related mortality was 2% (95% CI:0,3-14): one patient with ALL previously treated with inotozumab died in CR due to consequences of severe VOD on day + 60. The cumulative incidence of aGVHD grade II-IV was 36% (95% CI, 25 - 52), and grade 3-4 was 9% (95% CI, 4 - 22). In 13 cases, aGVHD was limited to skin: grade 2 (n=12), grade 4 (n=1), in two cases to the gut: grade 3(n=1), grade 4(n=1), three patients had skin and gut GVHD: grade 2 (n=2), grade 3(n=1) and one had skin and liver GVHD grade 3. The cumulative incidence of gut aGVHD grade II-IV was 9% (95% CI, 4 - 22). Eleven patients with GVHD responded to first-line immunosuppressive treatment, while 8 received additional therapy. The cumulative incidence of relapse was 11% (95%CI:5-26) in the entire cohort. EFS and OS were 89% (95%CI: 79-97) and 98% (95%CI: 94-100). The GVHD- and relapse-free survival was 78% (95%CI:67-88). Conclusion Our data suggest that adding vedolizumab and abatacept to the PTCy-based GVHD prophylaxis backbone is well tolerated and may reduce the incidence of gut GVHD among children with acute leukemia grafted from haploidentical donors. This approach can be further developed to reduce exposure to calcineurin inhibitors and deploy additional anti-leukemia effectors after HSCT.

Cyclophosphamide with cyclosporine A for graft-versus-host disease prophylaxis in adult patients with acute myeloid leukemia undergoing allogeneic hematopoietic stem cell transplantation from human leucocyte antigen-matched donors

BackgroundGraft-versus-host disease (GVHD) is one of the most severe complications in patients with acute myeloid leukemia (AML) who underwent allogenic hematopoietic stem cell transplantation (HSCT). This study addressed the effectiveness and safety outcomes of high dose post-transplant cyclophosphamide (PT-CY) followed by cyclosporine A (CSA) as a GVHD prophylaxis protocol. Patients and MethodsFrom January 2019 to March 2021, AML patients who underwent HSCT, and received high-dose PT-CY followed by CSA were prospectively recruited, assessed, and followed up for one-year post-transplantation (PT). The cumulative incidences of both acute GVHD (aGVHD) at 100 days PT, and chronic GVHD (cGVHD) at one-year PT were assessed. ResultsThis study included 52 patients. The cumulative incidence (95% CIs) of aGVHD was 2.3% (0.3 – 15.4%), while the cumulative incidence of cGVHD was 23.2% (12.2–41.5%). The cumulative incidence of relapse and non-relapse mortality were 15.6%, and 7.9%, respectively. The median duration to reach neutrophil and platelet engraftment was 17 and 13 days, respectively. The overall, progression-free, and GVHD-free/relapse-free survival rates (95% CIs) were 89.6% (76.6 – 95.6%), 77.7% (62.1–87.5%), and 58.2% (41.6 – 71.7%) respectively. The cumulative incidences of the main transplant-related complications were; neutropenic sepsis (48.3%), cytomegalovirus reactivation (21.7%), pneumonia (13.8%), hemorrhagic cystitis (17.8%), septic shock (4.9%), and CSA toxicity (48.9%). ConclusionPT-CY followed by CSA was associated with low cumulative incidences of both aGVHD and cGVHD without increase in either the relapse or transplant-related complications; so, considered as a promising protocol to be widely applied in the settings of HLA-matched donors.

Allogeneic Blood or Marrow Transplantation with High-Dose Post-Transplantation Cyclophosphamide for Acute Lymphoblastic Leukemia in Patients Age ≥55 Years

Patients age ≥55 years with acute lymphoblastic leukemia (ALL) fare poorly with conventional chemotherapy, with a 5-year overall survival (OS) of ∼20%. Tyrosine kinase inhibitors and novel B cell-targeted therapies can improve outcomes, but rates of relapse and death in remission remain high. Allogeneic blood or marrow transplantation (alloBMT) provides an alternative consolidation strategy, and post-transplantation cyclophosphamide (PTCy) facilitates HLA-mismatched transplantations with low rates of nonrelapse mortality (NRM) and graft-versus-host disease (GVHD). The transplantation database at Johns Hopkins was queried for patients age ≥55 years who underwent alloBMT for ALL using PTCy. The database included 77 such patients. Most received reduced-intensity conditioning (RIC) (88.3%), were in first complete remission (CR1) (85.7%), and had B-lineage disease (90.9%). For the entire cohort, 5-year relapse-free survival (RFS) and overall survival (OS) were 46% (95% confidence interval [CI], 34% to 57%) and 49% (95% CI, 37% to 60%), respectively. Grade III-IV acute GVHD occurred in only 3% of patients, and chronic GVHD occurred in 13%. In multivariable analysis, myeloablative conditioning led to worse RFS (hazard ratio [HR], 4.65; P=.001), whereas transplantation in CR1 (HR, .30; P=.004) and transplantation for Philadelphia chromosome-positive (Ph+) ALL versus T-ALL (HR, .29; P=.03) were associated with improved RFS. Of the 54 patients who underwent RIC alloBMT in CR1 for B-ALL, the 5-year RFS and OS were 62% (95% CI, 47% to 74%) and 65% (95% CI, 51% to 77%), respectively, with a 5-year relapse incidence of 16% (95% CI, 7% to 27%) and an NRM of 24% (95% CI, 13% to 36%). RIC alloBMT with PTCy in CR1 represents a promising consolidation strategy for B-ALL patients age ≥55 years.

Effect of CD34+ Cell Dose on the Outcomes of Allogeneic Stem Cell Transplantation with Post-Transplantation Cyclophosphamide

The impact of infused CD34+ cell dose on outcomes after allogeneic hematopoietic stem cell transplantation (alloHSCT) using standard graft-versus-host disease (GVHD) prophylaxis remains controversial. Information on this subject is scarce for alloHSCT using high-dose post-transplantation cyclophosphamide (PTCy). We aimed to assess the effect of CD34+ cell dose in peripheral blood stem cell (PBSC) grafts on the outcome of alloHSCT using PTCy-based GVHD prophylaxis. To do so, we conducted a single-center retrospective analysis of 221 consecutive adult patients who underwent PTCy alloHSCT from HLA-matched sibling donors (MSDs; n=22), HLA-matched unrelated donors (MUDs; n=83), mismatched unrelated donors (MMUDs; n=73), and haploidentical donors (n=43). Based on the binary partitioning method, 5×106/kg was used as the optimal cutoff for CD34+ cell dose. According to our institutional protocol, the maximum CD34+ cell dose was capped at 8×106/kg. The study cohort was divided into 2 groups based on CD34+ cell dose: high dose (>5 to 8×106/kg) and low dose (≤5×106/kg). Patients receiving high-dose CD34+-containing grafts had significantly shorter median times to neutrophil engraftment and platelet engraftment compared to those who received low-dose CD34+ (19 days versus 21 days [P=.002] and 16 days versus 22 days [P=.04], respectively). There were no differences between the high-dose and low-dose groups in the cumulative incidence of day +100 acute GVHD (grade II-IV: 25% versus 23% [P=.7]; grade III-IV: 5% versus 4% [P=.4], respectively) or 2-year chronic GVHD (moderate/severe GVHD: 9% versus 6%; P=.5). There was no impact of CD34+ cell dose on survival outcomes with the use of MSDs, MUDs, or MMUDs. Recipients of haploidentical alloHSCT using low-dose CD34+ cells had significantly worse overall survival (hazard ratio [HR], 6.01; P=.004) and relapse-free survival (HR, 4.57; P=.004). In recipients of PBSC PTCy alloHSCT, infused CD34+ cell doses>5 to 8×106/kg were associated with faster neutrophil and platelet engraftment, independent of donor type. Our study suggests an impact of CD34+ cell dose on survival outcomes only with haploidentical donors, for whom the administration of a CD34+ cell dose≤5×106/kg significantly decreased survival outcomes.

Impact of Early Intrapatient Variability of Tacrolimus Concentrations on the Risk of Graft-Versus-Host Disease after Allogeneic Stem Cell Transplantation Using High-Dose Post-Transplant Cyclophosphamide.

Tacrolimus (Tac) is a pivotal immunosuppressant agent used to prevent graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (alloHSCT). Tac is characterized by a narrow therapeutic window and a high inter-patient and intra-patient pharmacokinetic variability (IPV). Although high IPV of Tac concentrations has been associated with adverse post-transplant outcomes following solid organ transplantation, the effects of Tac IPV on alloHSCT recipients have not been determined. Tac IPV was therefore retrospectively evaluated in 128 alloHSCT recipients receiving high-dose post-transplant cyclophosphamide (PTCy) and the effects of Tac IPV on the occurrence of acute GVHD (aGVHD) were analyzed. Tac IPV was calculated from pre-dose concentrations (C0) measured during the first month after Tac initiation. The cumulative rates of grades II-IV and grades III-IV aGVHD at day +100 were 22.7% and 7%, respectively. Higher Tac IPV was associated with a greater risk of developing GVHD, with patients having IPV > 50th percentile having significantly higher rates of grades II-IV (34.9% vs. 10.8%; hazard ratio [HR] 3.858, p < 0.001) and grades III-IV (12.7% vs. 1.5%; HR 9.69, p = 0.033) aGVHD than patients having IPV ≤ 50th percentile. Similarly, patients with IPV > 75th percentile had higher rates of grades II-IV (41.9% vs. 16.5%; HR 3.30, p < 0.001) and grades III-IV (16.1% vs. 4.1%; HR 4.99, p = 0.012) aGVHD than patients with IPV ≤ 75th percentile. Multivariate analyses showed that high Tac IPV (>50th percentile) was an independent risk factor for grades II-IV (HR 2.99, p = 0.018) and grades III-IV (HR 9.12, p = 0.047) aGVHD. Determination of Tac IPV soon after alloHSCT could be useful in identifying patients at greater risk of aGVHD.

Allogeneic Blood or Marrow Transplantation (AlloBMT) with High-Dose Post-Transplantation Cyclophosphamide (PTCy) for Acute Lymphoblastic Leukemia (ALL) in Patients Aged ≥ 55: Best Results in B ALL in First Remission (CR1) with Reduced-Intensity Conditioning (RIC)

Background: Older patients with ALL fare poorly with conventional chemotherapy. Patients aged 55-65 on E2993 and ≥ 60 treated with Hyper-CVAD have 5-year overall survival (OS) of just 21% and 20%, respectively (Sive. BJH. 2012 and O'Brien. Cancer. 2008). Recently, HyperCVD with inotuzumab +/- blinatumomab in patients ≥ 60 years old with Ph- B ALL demonstrated an improved 5-year OS of 47% with 38% of patients dying in remission (Short. Blood. 2021). AlloBMT provides an alternative consolidation strategy. Registry studies in ALL patients ≥ 60 years old and B ALL patients ≥ 55 years old who underwent alloBMT with RIC in CR1 demonstrated 5 and 3-year OS of 42% and 45%, respectively (Roth-Guepin. Oncotarget. 2017 and Rosko. Am J Hematol. 2017). These studies utilized heterogenous conditioning and graft-versus-host disease (GVHD) prophylaxis regimens. The use of high-dose post-transplantation cyclophosphamide as GVHD prophylaxis facilitates transplants in older adults with low rates of non-relapse mortality, GVHD, and the use of HLA haploidentical donors (Kasamon. JCO. 2015). Methods: The bone marrow transplant database at Johns Hopkins was queried for patients ≥ 55 years old who received a first alloBMT using PTCy from January 2008-January 2021. Characteristics of patients were summarized and compared using Fisher's exact test for categorical variables. Estimators of OS and relapse-free survival (RFS) were reported using the Kaplan-Meier method. Differences in time-to-event outcomes were estimated using Cox proportional hazards model, or Fine and Gray's model for cumulative incidence of relapse (CIR)/nonrelapse mortality (NRM) considering competing risks. Results: A total of 77 patients aged ≥ 55 underwent a first alloBMT with PTCy for ALL. The vast majority were performed in CR1 (85.7%), utilized RIC (88.3%), and were performed for B ALL (90.9%). Demographics and transplant characteristics are presented in Table 1. RIC consisted of fludarabine, cyclophosphamide and total body irradiation followed by PTCy-based GVHD prophylaxis as previously described (Kasamon. BBMT. 2008). Relapse-free survival (RFS) and OS at 5 years for the entire cohort were 46% (95% CI 34-57) and 49% (95% CI 37-60), respectively, with a 5-year CIR of 27% (95% CI 18-38) and NRM of 28% (95% CI 18-39). The cumulative incidences of grade 3-4 acute GVHD at 1 year and chronic GVHD at 3 years were 3% (95% CI, 0% to 9%) and 13% (95% CI 5% to 21%), respectively. In univariate analysis, the use of myeloablative conditioning led to worse RFS (HR 0.25, p=0.0004); while the absence of MRD (HR 2.93, p=0.008), transplant in CR1 (HR 3.81, p=0.0004), and transplant for Ph+ ALL vs. T ALL (HR 3.15, p=0.03) led to improved RFS. Subsequent analysis focusing on the 54 patients receiving RIC alloBMT in CR1 for B ALL demonstrated RFS and OS at 5 years of 61% (95% CI 46-73) and 64% (95% CI 49-76), respectively, (see Figure 1) with a 5-year CIR of 16% (95% CI 7-27) and NRM 24% (95% CI 13-36), although just 7% at 1 year. For B ALL patients transplanted with RIC in CR1, 3-year NRM was higher among patients who received a peripheral blood stem cell transplant (55%, 95% CI 18% to 81%), those treated with rituximab pre-transplant (36%, 95% CI 16% to 57%), and those who received ≥100 mg/m2 of doxorubicin equivalent for ALL (67%, 95% CI 19% to 90%). Outcomes did not differ among the 20% of patients who received pre-transplant blinatumomab compared to those who did not. Among the 23 Ph+ B ALL patients transplanted with RIC in CR1 following treatment with a 2nd or 3rd generation tyrosine kinase inhibitor (TKI), the 5-year CIR was 5% (95% CI, 0% to 22%). Conclusions: RIC AlloBMT with PTCy in CR1 represents a promising consolidation strategy for B ALL patients ≥ 55 years old. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Addition of ATG to Clofarabine-Based Reduced Intensity Conditioning Regimen with PBSC and Ptcy in Adults with Myeloid Malignancies

INTRODUCTION In allogeneic hematopoietic stem cell transplantation (Allo-HSCT), the Clo-Baltimore (CloB) regimen is a variant of the Baltimore reduced-intensity conditioning (RIC) regimen that uses clofarabine in replacement of fludarabine and high-dose post-transplant cyclophosphamide (PTCY). This regimen provides good survivals for patients (pts) with myeloid malignancies (Chevallier et al., Oncotarget 2018). Yet, graft-versus host disease (GVHD) remains a major cause of morbidity and mortality in Allo-HSCT recipients. The administration of anti-thymocyte globulin (ATG) is a standard method to prevent GVHD in matched Allo-HSCT. Here, we retrospectively investigated whether the addition of ATG to CloB conditioning with PTCY was beneficial in terms of GVHD rates. METHODS This retrospective study included all consecutive Allo-HSCT adult recipients with myeloid malignancies transplanted between March 2014 and February 2022 in our hospital after CloB+/-ATG conditioning regimen. CloB consisted in clofarabine 30 mg/m²/day (d) from d-6 to d-2, cyclophosphamide 14.5 mg/kg/d on d-6 and d-5, and cyclophosphamide 50mg/kg/d on d+4 and d+5 after Allo-HSCT. In CloB+ATG, pts additionally received ATG 2.5mg/kg/d on d-2. GVHD prophylaxis consisted in the administration of cyclosporine A and mycophenolate mofetil to all patients. Graft source was exclusively peripheral blood stem cells. We determined overall (OS), disease-free (DFS) and GVHD relapse-free (GRFS) survivals, as well as non-relapse mortality (NRM) and relapse incidences. RESULTS Sixty-six pts (median age 61 years old, range 32-74) were included, with 36 pts treated with CloB conditioning between 2014 and 2017, and 30 with CloB+ATG between 2019 and 2022. Between the two periods other conditioning regimens were used in our Department. Diagnoses comprised acute myeloblastic leukemia (AML, n=32), myelodysplastic syndromes (MDS, n=18), myeloproliferative neoplasms (MPN, n=5), or MDS/MPN (n=10). The disease risk index (DRI) was low in 7 (11%) pts, intermediate in 43 (66%), and high in 15 (23%). The median HSCT-specific comorbidity index was 3 (range 0-7). Donors were haploidentical in 54 (82%) cases, and matched in 12. In the whole cohort, 18-months(m) OS, DFS and GRFS were 71±6%, 65±6%, and 55±6%, and 18-m NRM and relapse incidences were 14±4% and 21±5% respectively. A higher proportion of high DRI was observed in the CloB group (36 vs 10%, p=0.03). The median follow-up was 68 months (m) in the CloB cohort and 19.5 m in the CloB+ATG cohort. These two groups were otherwise comparable (Table 1). A lower proportion of acute GVHD was observed in the CloB+ATG group (23.3 vs 50%, p=0.05), with no statistical differences in terms of chronic GVHD (p=0.49). Of note, no extensive chronic GVHD was observed in the CloB+ATG group (vs 11% in CloB patients, p=0.17) In multivariate analysis, the addition of ATG to CloB conditioning was associated with a significant increase in 18-m GRFS (70±8% vs 43±8%, HR 0.38 [95%CI 0.17-0.85], p=0.02; Figure1). No differences were observed in terms of OS (HR 0.74, p=0.51), DFS (HR 0.58 p=0.22), NRM (HR 0.84, p=0.79), relapse rate (HR 0.51, p=0.25), median time of neutrophil (>1 109/L) and platelet (> 50 109/L) recovery (respectively 19d [range 12-27] vs 18d [8-32], p=0.69, and 36d [22-471] vs 31d [12-134], p=0.09). The results were similar when considering only patients with a haploidentical donor (n=54), with a benefit in terms of GRFS in the ATG group in multivariate analysis: HR 0.30 (95%CI 0.12-0.73; p=0.008). CONCLUSION Addition of ATG to the Clo-Baltimore RIC regimen with PTCY improved GRFS rates in this cohort without increasing infection-related mortality nor relapse rate in pts with myeloid malignancies and matched or haplo-donors. This strategy should be more widely implemented. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Association between gene polymorphisms in the cyclophosphamide metabolism pathway with complications after haploidentical hematopoietic stem cell transplantation.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment for patients with hematologic malignances. Haploidentical HSCT (Haplo-HSCT) is an alternative option for patients who do not have an HLA-matched donor. The use of post-transplantation high dose cyclophosphamide (PT-Cy) is commonly employed for graft-versus-host disease (GVHD) prophylaxis in haplo-HSCT. Cyclophosphamide (Cy) is an alkylating agent with antineoplastic and immunosuppressive activity, whose bioactivation requires the activity of polymorphic enzymes in the liver to produce phosphoramide mustard, which is a DNA alkylating agent. To identify polymorphisms in the genes of Cy metabolism and correlate them with post-HSCT complications [GVHD, sinusoidal obstruction syndrome (SOS), hemorrhagic cystitis (HC) and transplant-related mortality (TRM)], we designed a custom next-generation sequencing panel with Cy metabolism enzymes. We analyzed 182 patients treated with haplo-HSCT with PT-Cy from 2007 to 2019, detecting 40 variants in 11 Cy metabolism genes. Polymorphisms in CYP2B6, a major enzyme involved in Cy activation, were associated with decreased activity of this enzyme and a higher risk of Graf-versus-host disease (GVHD). Variants in other activation enzymes (CYP2A6, CYP2C8, CYP2C9, CYP2C19) lead to decreased enzyme activity and were associated with GVHD. Polymorphisms in detoxification genes such as glutathione S-transferases decreased the ability to detoxify cyclophosphamide metabolites due to lower enzyme activity, which leads to increased amounts of toxic metabolites and the development of III-IV acute GVHD. GSMT1*0 a single nucleotide polymorphism previously recognized as a risk factor for SOS was associated with a higher risk of SOS. We conclude that polymorphisms of genes involved in the metabolism of cyclophosphamide in our series are associated with severe grades of GVHD and toxicities (SOS and TRM) after haplo-HSCT and could be used to improve the clinical management of transplanted patients.

Outcomes of haploidentical peripheral stem cell transplantation with combination of post-transplant cyclophosphamide (PTCy) and anti-thymocyte globulin (ATG) compared to unrelated donor transplantation in acute myeloid leukemia: A retrospective 10-year experience

In the evolution of haploidentical hematopoietic stem cell transplantation (haplo-HSCT), In vivo T-cell modulation with concomitant use of anti-thymocyte globulin (ATG) and high-dose post-transplant cyclophosphamide (PTCy) provides a novel promising method on transplant outcomes; however, the long-term effects of this therapy are mostly unknown. We retrospectively compared the long-term outcomes of adult acute myeloid leukemia (AML) patients undergoing a haplo-HSCT (n = 92) with a new modified combination of ATG and PTCy in the context of peripheral blood stem cell (PBSC) and myeloablative conditioning (MAC) with an otherwise similar group of AML patients who received an unrelated donor (URD) HSCT (n = 57) with ATG protocol from February 2010 to December 2020 at our single-center (HORCSCT). Median follow-up was 3.73 and 4.28 years for haploidentical and URD-HSCT, respectively. In haplo-HSCT, the cumulative incidence of grades II-IV and III-IV acute graft versus host disease (aGvHD) and extensive chronic GvHD (cGvHD) was much lower than in URD (27% versus 56% for grades II-IV, 8.7% versus 24.5% for grades III-IV, and 15.4% versus 34.7% for extensive cGvHD, respectively). Five-year overall survival (OS) was 54.03% for haplo and 54.48% for URD (p = 0.927); GvHD-free relapse-free survival (GRFS) was 44.1% and 29.86% (p = 0.149); relapse incidence was 15.79% and 26.95% (p = 0.72); and non-relapse mortality (NRM) was 29.48% and 26.32% (p = 0.73), respectively. Using multivariable analyses, when compared to Haplo, URD was a significant predictor of relapse (HR=1.80, p = 0.039); however, no difference in OS, GRFS, and NRM was noted between haplo and URD. Therefore, given the favorable results with haplo-HSCT and considering donor availability promptly with low cost, it conservatively suggested that haplo-HSCT with the introduced protocol could be viewed as the first alternative for patients with AML in the absence of matched sibling donors.

Extracellular Vesicles as Biomarkers of Acute Graft-vs.-Host Disease After Haploidentical Stem Cell Transplantation and Post-Transplant Cyclophosphamide.

Even with high-dose post-transplant cyclophosphamide (PT-Cy) which was initially introduced for graft-versus-host disease (GvHD) prevention in the setting of HLA-haploidentical transplantation, both acute and chronic GvHDs remain a major clinical challenge. Despite improvements in the understanding of the pathogenesis of both acute and chronic GvHDs, reliable biomarkers that predict their onset have yet to be identified. We recently studied the potential correlation between extracellular vesicles (EVs) and the onset of acute (a)GvHD in transplant recipients from related and unrelated donors. In the present study, we further investigated the role of the expression profile of membrane proteins and their microRNA (miRNA) cargo (miRNA100, miRNA155, and miRNA194) in predicting the onset of aGvHD in haploidentical transplant recipients with PT-Cy. Thirty-two consecutive patients were included. We evaluated the expression profile of EVs, by flow cytometry, and their miRNA cargo, by real-time PCR, at baseline, prior, and at different time points following transplant. Using logistic regression and Cox proportional hazard models, a significant association between expression profiles of antigens such as CD146, CD31, CD140a, CD120a, CD26, CD144, and CD30 on EVs, and their miRNA cargo with the onset of aGvHD was observed. Moreover, we also investigated a potential correlation between EV expression profile and cargo with plasma biomarkers (e.g., ST2, sTNFR1, and REG3a) that had been associated with aGVHD previously. This analysis showed that the combination of CD146, sTNFR1, and miR100 or miR194 strongly correlated with the onset of aGvHD (AUROC >0.975). A large prospective multicenter study is currently in progress to validate our findings.

Post-Transplant Cyclophosphamide after HLA Identical Compared to Haploidentical Donor Transplant in Acute Myeloid Leukemia: A Study on Behalf of Geth-TC

Introduction: High-dose post transplant cyclophosphamide (PTCY) effectively prevents graft-versus-host disease (GVHD) after unmanipulated HLA-haploidentical hematopoietic stem cell transplant (HSCT) and offer low rates of GVHD in the setting of HLA identical transplant. The objective of our study was to compare the outcomes of haplo vs HLA identical HSCT in patients undergoing HSCT for acute myeloid leukemia (AML) using PTCY.Patients and methods: We conducted a retrospective study of 229 patients undergoing a first HSCT for AML using PTCY, 130 from an haploidentical donor between 2013 and 2018 (median follow up 62.5 months) and 99 from a matched sibling (MSD) (n=38) or unrelated donor (MUD) (n=61) (median follow up 27 months) between 2013 and 2019, in 20 centers in Spain. Last update of the cohort was performed in March 2021.Results: Baseline characteristics are summarized in Table 1. There were more patients with active disease at transplant (5% MSD/MUD vs. 20% haplo, p=0.001), high/very high DRI (32% vs. 67%, p=0.000) and prior autologous HSCT (2% vs. 11%, p=0.010) in the haplo group. Mobilized peripheral blood stem cells was the most frequent stem cell source in both groups. Most patients received myeloablative conditioning (55% vs. 64%, p=0.170). All Patients in the haplo group received PTCY days +3+4 followed by a calcineurin inhibitor (CNI) and MMF from +5. In the MSD/MUD group, 37% received both CNI+MMF, 33% only CNI and 30% PTCY with sirolimus+MMF (this group included only MUD donors). None of the patients received ATG. Cumulative incidence of neutrophil recovery at day 28 was 97% in both groups, with a median of 16 and 17 days respectively (p=0.948). Both 2-year overall survival (OS) (72% vs. 62%, p=0.07) and event-free survival (EFS) (70% vs. 54%, p=0.055) were higher in the MSD/MUD group, but the difference was not statistically significant (Figure 1). Multivariate analysis only identified age and pre-transplant status as independent risk factors for OS, and pre-transplant status for EFS. No differences were found in the cumulative incidence of relapse at 2 years (19% vs. 25%, p=0.13) and non-relapse mortality (14% vs. 19%, p=0.145). Cumulative incidence of grade II-IV acute GVHD was lower in MSD/MUD (14% vs. 47%, p=0.000, Figure 2), while III-IV aGVHD was similar (4% vs. 9%, p=0.14). Cumulative incidence of chronic GVHD and moderate-severe cGVHD at 2 years was similar for both groups (42% vs. 33% (p=0.051); 22% vs. 19% (p=0.28)). No differences were found in GRFS (48% vs. 46% (p=0.506)). Most frequent cause of death in the early post-transplant period was non-GVHD related infection in both groups.Conclusions: in our experience, PTCY as GVHD prophylaxis in both MSD/MUD and Haplo transplant in AML using mostly PBSC effectively prevents GVHD and offers similar NRM, relapse and survival rates. Poor control of the disease before transplant was the only factor affecting OS and EFS in this setting. Prospective studies are needed to confirm our results. [Display omitted] DisclosuresBailen: Pfizer, Kite-Gilead, Gilead: Honoraria. Guerreiro: Novartis, Gilead: Consultancy, Honoraria. Oarbeascoa: Gilead: Honoraria, Speakers Bureau. Kwon: Novartis, Celgene, Gilead, Pfizer: Consultancy, Honoraria.

Post-Transplant High Dose Cyclophosphamide and Bortezomib As Graft-Versus-Host Disease Prophylaxis Following Allogeneic Hematopoietic Stem Cell Transplantation

Introduction. Prevention of graft-versus-host disease (GvHD) following allogeneic hematopoietic cell transplantation (AHCT) remains a major challenge. The combination of methotrexate (MTX) and a calcineurin inhibitor has been the standard regimen for prophylaxis in patients receiving matched sibling donor (MSD) or matched unrelated donor (MUD) transplants for the past few decades. However, over 50% of patients undergoing AHCT still develop acute or chronic GvHD or even both, causing high rates of morbidity and mortality. Moreover, calcineurin inhibitors also have untoward toxic side effects. High dose post-transplant cyclophosphamide (PTCy), initially introduced for GvHD prevention in the setting of haploidentical transplantation, has now been studied in MSD and MUD transplants. We adopted a novel approach to prevent GvHD using a short course of PTCy and bortezomib. We hypothesized that such combination is safe and effective and omits the need for calcineurin or m-TOR inhibitors.Study Design. We report the outcomes of a prospective cohort of patients who received PTCy and bortezomib for GvHD prevention following MSD or MUD transplants. Twenty-eight patients were treated in a phase I-II trial and their clinical outcomes were previously reported (al-Homsi AS et al, BBMT 2019). Most of the remaining patients were treated on an extension trial. GvHD prevention consisted of PTCy 50 mg/kg IV on day +3 and +4, and bortezomib 1.3mg/m 2 IV 6 hours after transplant and again 72 hours after. Patients receiving MUD transplants also received rabbit ATG (thymoglobulin®) 5mg/kg total IV fractionated on day -4 to -2. All patients received peripheral blood grafts and standard supportive care as per Institutional policy. G-CSF was administered routinely until neutrophil engraftment.Results. Fifty-eight patients are included in this analysis. Median age was 60 (range 22-78) years. Fifty-three percent of patients were male. Underlying malignancies consisted of myeloid and lymphoid malignancies in 79.3% and 20.6%, respectively. Acute myeloid leukemia (50%) and myelodysplastic syndromes (24.1%) were the most common diseases. At transplant, disease risk index was low, intermediate, high and very high in 19.0%, 48.3%, 31.0% and 1.7% of patients, respectively. Median Pretransplant Assessment of Mortality Score (PAM) was 16.7 (5.4-29.4). Grafts were from MSD in 24.1% or MUD in 75.9% of patients. Recipient (R)/Donor (D) CMV status at transplant was as follows: R+/D+: 43%; R+/D-: 21%; R-/D+: 14% and R-/D-: 22%. Conditioning regimens consisted of reduced intensity fludarabine and busulfan in all but 2 patients who were conditioned with myeloablative fludarabine and busulfan. Overall, the regimen was remarkably well tolerated. Median times to neutrophil and platelet engraftment were 16 (13-28) and 26 (15-57) days respectively. No patient experienced primary graft failure. CMV and EBV reactivation rates were 46.6% and 24%. Cumulative incidences of grade II-IV and grade III-IV acute GVHD were 35% (95% CI: 22%-47%) and 15% (95% CI: 7%-25%) at day +120, respectively. Cumulative incidence of chronic GvHD was 14% at 1 year . Overall, 34% of patients required immunosuppression with systemic steroids after day +4 either for grade III-IV acute or chronic GvHD. Disease relapse rate was 26%. One-year cumulative incidence of transplant-related mortality was 14% (95% CI: 6%-25%). Median overall survival was 30.7 (95% CI: 15.7-not yet reached) months. One-year overall survival was 72% (95% CI: 57%-82%). One-year composite GvHD (acute and chronic) free and relapse free survival (GRFS) was 41.6% (95% CI: 28.9%-54%).Conclusion. PTCy and bortezomib combination for GvHD prophylaxis following MSD and MUD transplants is well tolerated and effective. It offers an alternative regimen to calcineurin and m-TOR inhibitor-containing regimens and may be preferred in certain settings including patients with limited resources, poor medication compliance, and with impaired renal function. A comparison of this cohort to a matched control group of patients receiving methotrexate and cyclosporine for GvHD prevention is ongoing. DisclosuresAbdul-Hay: Amgen: Membership on an entity's Board of Directors or advisory committees; Servier: Other: Advisory Board, Speakers Bureau; Jazz: Other: Advisory Board, Speakers Bureau; Abbvie: Consultancy; Takeda: Speakers Bureau. Al-Homsi: Celyad: Other: Advisory Board; Daichii Sanyko: Consultancy. OffLabel Disclosure:Cyclophosphamide and Bortezomib are used for GvHD prevention

Nonmyeloablative Allogeneic Transplantation in First Remission for Philadelphia Chromosome-Negative B-Cell Acute Lymphoblastic Leukemia with Post-Transplantation Cyclophosphamide: Outcomes By Receipt of Pre-Transplant Blinatumomab

Nonmyeloablative Allogeneic Transplantation in First Remission for Philadelphia Chromosome-Negative B-Cell Acute Lymphoblastic Leukemia with Post-Transplantation Cyclophosphamide: Outcomes By Receipt of Pre-Transplant Blinatumomab

Experience of Low Dose (25mg/Kg) of Cyclophosphamide (Chennai-Chezhian-Kishore PTCy Protocol) As Post Transplant Cyclophosphamide (PTCy) Dose in Haploidentical Bone Marrow Transplant

Introduction:-Haploidentical Bone marrow transplantation has become one of the most commonly employed alternative donor techniques, with many centers applying T-cell-replete strategies developed by the Baltimore group using high-dose post-transplant cyclophosphamide. The usefulness of this technique is to reduce graft acquisition cost, lesser grade of GVHD, and reduction in non-relapse mortality. One problem we face in a country like India is the worry of engraftment delay leading to refractory multi-drug resistant gram-negative sepsis increasing the risk of transplant-related mortality. We took up this pilot study to check for the feasibility of a low dose (50%) 25mg/kg of cyclophosphamide as PTCy and its impact on transplant outcomes especially GVHD.Methodology:-This study was done from January 2016 to June 2019. 41 Haploidentical bone marrow transplants were done for Acute Myeloid leukemia at this time under this protocol. 23 Cases had Busulfan / Fludarabine as conditioning and in 18 cases; we used Treosulfan / Fludarabine-based conditioning regimen. The study protocol PTCy dose was 25mg/kg on Day +3 and Day +4. Cyclosporine / Tacrolimus was used from day -1 in all patients as GVHD prophylaxis. The parameters analyzed are engraftment dynamics, rates of gram-negative sepsis, hemorrhagic cystitis, rates of acute and chronic GVHD, and 2-year Non-relapse mortality.Results:Parents were the haploidentical donors in 22 cases whereas siblings in the rest 19 cases. Peripheral blood stem cell collection was chosen in all cases. The average CD34 dose was 6.8 x 10 6/Kg of the recipient. The mean number of days to achieve engraftment was around day 11. Culture-proven gram-negative sepsis was seen in 11 cases (26.8%). Two patients died within Day +30. Both due to sepsis. The rates of acute GVHD of grade I/2 was 18 (43.9%) and grade 3/4 acute GVHD was seen only in 2 patients (5%). No mortality was due to GVHD. With a median follow-up of two years, chronic skin and liver grade 1/2 GVHD was noted in 29 patients (74.3%) but were manageable with oral and topical medications not needing admission. Three patients had hemorrhagic cystitis. CMV reactivation needing medications was seen in 5(12.2%) patients indicating a higher incidence of post-transplant viral reactivation with PTCy. At data cut-off, we had lost 12 patients due to relapse and there was no non-relapse mortality except for the two sepsis-related death.Conclusion:The results of this pilot study indicate the feasibility of using a low dose PTCy (25mg/kg) in Haploidentical transplant as a methodology for in vivo T cell depletion without increased incidence of GVHD and Non-relapse mortality in Indian patients. This is a small study and it needs further follow-up with drug metabolism analysis and a bigger cohort to make this Chennai-Chezhian-Kishore PTCy Protocol a validated standard in Haplo-identical transplants. This is a pilot study and we are planning to incorporate genetic polymorphism in drug metabolism to validate the proposed protocol more scientifically.Reference:1. Wang, Y et al. Low-dose post-transplant cyclophosphamide and anti-thymocyte globulin as an effective strategy for GVHD prevention in haploidentical patients. J Hematol Oncol 12, 88 (2019). https://doi.org/10.1186/s13045-019-0781-y2. Shannon R. McCurdy, Leo Luznik How we perform haploidentical stem cell transplantation with posttransplant cyclophosphamide Blood (2019) 134 (21): 1802-1810. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

A Prospective Phase 2 Study Testing High Dose Post-Transplant Cyclophosphamide As Sole Ghvd Prophylaxis after Matched Allotransplant Using Baltimore-Based Reduced-Intensity Conditioning Regimens and PBSC As Source of Graft

Introduction: The use of high-dose post-transplant cyclophosphamide (PTCY) has revolutionized graft-versus-host disease (GVHD) prophylaxis and allowed to successfully reconsider haplotransplant in recent years. As this strategy significantly reduces the incidence of both acute and chronic GVHD, PTCY has been thereafter considered not only in matched settings but also as sole GVHD prophylaxis, at least when considering myeloablative allotransplant using matched sibling (MSD) or unrelated (MUD) donors and bone marrow as source of graft. Here, PTCY, as a sole GVHD prophylaxis, was tested in a reduced-intensity conditioning (RIC) setting, using peripheral blood stem cells (PBSC) as source of graft considering that this platform is currently broadly used worldwide in adults.Methods: This prospective monocentric phase 2 study was designed with the main objective to demonstrate the feasibility and safety of using only PTCY (without cyclosporine A nor mycophenolate mofetyl after transplant) in adults (18-70 years old) eligible for a RIC PBSC transplant with MSD or MUD. The Baltimore platform with 2 days of PTCY 50mg/kg/day on days 3 and 4 post infusion was considered as conditioning regimen, using fludarabine for lymphoid disease or clofarabine for myeloid disease. The primary objective was to appreciate the incidence of corticosteroid-resistant acute grade 3-4 GVHD (CR 3-4 GVHD) within 100 days post-transplant. According to statistical rules, patients have to be included in a step by step fashion (3, 3, 6, 15, 15 and 17 patients) for a total of 59 evaluable patients (meaning having received PTCY), in order to stop the protocol soon enough in case of excessive rate of deleterious severe acute GVHD (graded according to Mount Sinai International Consortium). Thus, the trial had to be stopped in case of documentation of > 2 CR 3-4 GVHD for the first 3 patients, >3 CR 3-4 GVHD for the first 6 patients, > 4 CR 3-4 GVHD for the first 12 patients, > 6 3-4 CR GVHD for the first 27 patients, > 8 CR 3-4 GVHD for the first 42 patients and finally as soon as > 9 CR 3-4 GVHD for the last included patients. All patients gave informed consent. The trial was registered at ClinicalTrials.gov Identifier: NCT03263767.Results: The results of the first 27 first patients (males n=17 and female n=10; median age: 59 years old (yo), range: 26-70) are reported here. They were included between February 2018 and November 2020. Diagnoses were AML (N=8), MDS (N=5), CMML (N=2), myelofibrosis (N=5), CML (N=1), DLBCL (N=1), T-cell lymphoma (N=1), Philadelphia positive B-ALL (N=1), CLL (N=1), lymphoblastic lymphoma (N=1) and mixed phenotype acute leukemia (N=1). Donors were MSD in 10 cases and MUD in 17.Only one primary graft failure was documented in a 61 yo MDS patient with active disease at transplant. He is however still alive in response after autologous reconstitution. With a median follow-up of 17.6 months (range: 10-42) for alive patients at the time of analysis (July 2021), 1-year and 2-year survivals were 80.9+7% and 74.7+9%, respectively, for both OS et DFS. GVHD-free/relapse-free survival (GRFS) at 1-year and 2-year was 58.7+9% and 52.2+10%, respectively. Three relapses (11%) and 6 deaths occurred. Deaths were due to acute GVHD in 4 patients (including 1 with sepsis and 1 with SARS-COVID 19 infection) and relapse in 2. Grade 2, 3 and 4 acute GVHD occurred in 11, 1 and 4 patients, respectively, for a total of 59% of grade 2-4 acute GVHD. CR 3-4 GVHD was observed in all of 5 patients with acute grade 3-4 GVHD and 4 died related to GVHD. Moderate/severe chronic GVHD occurred in 5/22 (22.7%) evaluable patients, including 4 still on immunosuppressive therapy at 40, 28, 25 and 16 months post-transplant. Overall non-relapse mortality (NRM) was 14.8% and related to acute GVHD. However, the number of cases conducting to stop the protocol was not reached.Conclusion: PTCY as a sole GVHD prophylaxis is here demonstrated as possible and relatively safe for adults receiving a matched PBSC Baltimore-based RIC allograft. The very good survivals reported here may be related to a strong GVL effect associated with the high incidence of acute GVHD. However, because of this high incidence and the fact that NRM was related to GVHD after this first analysis, we have now made an amendment to test the addition to PTCY of one day of anti-thymoglobulin (ATG) 2.5 mg/kg on day-2 for the next 32 patients to be included. This second cohort receiving PTCY+ATG as a sole prophylaxis is ongoing. DisclosuresMoreau: Celgene BMS: Honoraria; Sanofi: Honoraria; Abbvie: Honoraria; Janssen: Honoraria; Amgen: Honoraria; Oncopeptides: Honoraria.

De-Escalation of Ptcy Dosing in Matched Allogenic Transplants: A Single Institution Retrospective Study

IntroductionThe role of post-transplant cyclophosphamide (PTCy) in preventing acute GVHD (aGVHD) and chronic GVHD (cGVHD) has been well established in the haploidentical setting (Al-Homsi AS et al., Post-transplant high-dose cyclophosphamide for the prevention of graft-versus-host disease. Biol Blood Marrow Transplant. 2015;21(4):604-611). More recently, several studies are also supporting its use in matched related and unrelated donors (Williams L et al., Post-transplantation Cyclophosphamide: From HLA-Haploidentical to Matched-Related and Matched-Unrelated Donor Blood and Marrow Transplantation. Front Immunol. 2020;11(April):1-7). But as new emerging data are starting to show some toxicities from that regimen, a reevaluation of the optimal PTCy dose is highly valuable (Duléry R et al., Early Cardiac Toxicity Associated with Post-Transplant Cyclophosphamide in Allogeneic Stem Cell Transplantation. JACC CardioOncology. 2021;3(2):250-259; Goldsmith et al., Posttransplant cyclophosphamide is associated with increased cytomegalovirus infection: a CIBMTR analysis. Blood. 2021;137(23):3291-3305).PTCy dose de-escalation in preventing GvHD was also evaluated in a phase I/II study (NCT03983850) with initial results indicating that de-escalation of PTCy (DL2, 25 mg/kg/day given in Days 3−4) may provide a feasible and effective approach in preventing severe aGvHD(McAdams MJ et al., Phase I Study De-Intensifying Exposure of Post-Transplantation Cyclophosphamide (PTCy) after HLA-Haploidentical Hematopoietic Cell Transplantation (HCT) for Hematologic Malignancies. Transplant Cell Ther Off Publ Am Soc Transplant Cell Ther. 2021;27(3): S9-S11). However, this was in the setting of haplo-identical transplants. Currently there are no studies that investigate the safety and efficacy of a lower dose of PTCy in matched allogenic transplants.MethodsWe retrospectively selected 37 consecutive patients who underwent transplant at our center from January 2017 to April 2021. Patients who received a mismatched or haploidentical transplants were excluded. 26 matched sibling or matched unrelated donor transplants were further analyzed. These were divided into 3 cohorts according to GVHD prophylaxis: cohort 1 (No-PTCy) received standard calcineurin inhibitor-methotrexate based GVHD prophylaxis (n=16), cohort 2 (PTCy-50) received PTCy at 50 mg/kg (D+3 and D+4) in combination other immunosuppressive drugs (ISD) (n=6), and cohort 3 (PTCy-25) received PTCy at 25 mg/kg (D+3 and D+4) in combination with other ISD (n=4). The reduced PTCy dosing was based on physician discretion due to various reasons (2 cardiac risk, 1 heavy pre-treatment, 1 unknown).ResultsBaseline characteristics are summarized in table 1. Median follow up for all survivors was 523 days (range, 97-1463) while it was shorter for PTCy cohorts at 152 days (97-534). There were zero grade 3 aGVHD in PTCy groups compared to 12.5% (2/16) in No-PTCy cohort (p=0.30). cGVHD was significantly lower in PTCy-50 and PTCy-25 as compared to No-PTCy (0/6, 0/4, 5/16 respectively, p=0.04). The 100-day treatment-related mortality (TRM) was significantly lower in PTCy-25 as compared to PTCy-50 and No-PTCy (0/4, 2/6, 2/16 respectively, p<0.001). There was no viral reactivation (EBV/CMV) in PTCy-25 as compared to 1/6 in PTCy-50 and 5/16 in No-PTCy (p=0.54). The length of hospital stay (LOS) for transplant and the median days for neutrophil recovery (NR) were shorter in PTCy-25 as compared to PTCy-50 and No-PTCy (25.5 days, 31 days and 28.5 days respectively for LOS, p=0.60; 15.5 days, 22 days and 17.5 days for NR, p=0.87). Although the overall survival (OS) seems to favor PTCy-25 (Figure 1), it is limited by short follow up.ConclusionDe-escalating the dose of PTCy to 25mg/kg x 2 in GVHD prophylaxis regimens appears to be efficacious and safe in patients receiving matched allogenic transplant. Further prospective studies including a larger patient sample and longer follow-up is warranted to investigate lower PTCy dosing in matched transplants over the current standard dosing. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Nonmyeloablative, HLA-Mismatched Unrelated Peripheral Blood Transplantation with High-Dose Post-Transplantation Cyclophosphamide

High-dose post-transplantation cyclophosphamide (PTCy) is an effective platform for prevention of severe graft-versus-host disease (GVHD) after allogeneic bone marrow (BM) transplantation with mismatched unrelated donors (mMUDs). Previous studies evaluating PTCy with mMUDs favored BM allografts over peripheral blood stem cell transplantation (PBSCT) due to concerns that PBSCT may be associated with an increased risk of acute and chronic GVHD. In addition, haploidentical PBSCT is associated with high rates of cytokine release syndrome (CRS), which is another concern with mMUD PBSCT. This study was conducted to determine the feasibility and safety of using mMUD PBSCT with PTCy as GVHD prophylaxis. Patients who received mMUD PBSCT using a PTCy-based GVHD prophylaxis at Johns Hopkins Hospital as part of a prospective clinical trial of mMUD and non-first-degree relative haploidentical transplantation with PTCy (ClinicalTrials.gov identifier NCT01203722) were included. All patients underwent T cell-replete PBSCT between November 2012 and August 2020. Statistical analyses were performed using the Kaplan-Meier method and proportional subdistribution hazard regression model for competing risks. The 29 patients in the study had a median age of 54 years, with 10 patients (34%) age ≥60 years. Nineteen grafts (66%) were matched for 9/10 HLA loci, 6 (21%) were match for 8/10, and 4 (14%) were matched for 7/10. No primary or secondary graft failure occurred. The median time to neutrophil recovery (≥500/µL) was 17 days, and that to platelet recovery (≥20,000/µL) was 28 days. Full donor chimerism was achieved in all patients by day +60. The cumulative incidence (CuI) of grade II-IV acute GVHD at 180 days was 15% (90% confidence interval [CI], 3% to 26%). There were no cases of severe chronic GVHD, 3 cases of mild chronic GVHD, and 1 case of moderate chronic GVHD. The CuI of nonrelapse mortality (NRM) was 7% (90% CI, NA to 18%) at 1 year. Eighteen patients (62%) experienced mild CRS (grade 1-2), and 1 patient (3%) experienced severe CRS (grade 3-5). At 1 year, the CuI of relapse was 29% (90% CI, 8% to 50%), overall survival was 93% (90% CI, 85% to 100%), progression-free survival was 64% (90% CI, 46% to 88%), GVHD-free relapse-free survival was 41% (90% CI, 23% to 73%), and chronic GVHD-free relapse-free survival was 64% (90% CI, 46% to 88%). Our data indicate that mMUD PBSCT using PTCy-based GVHD prophylaxis is safe and feasible. All patients engrafted, and rates of NRM (7%) and acute GVHD (15%) at 1 year were low. There was only 1 case (3%) of severe CRS. Compared with previously published outcomes, mMUD PBSCT using PTCy-based GVHD prophylaxis has a safety and efficacy profile that may not be different from that of PBSCT from matched donors. These results further solidify that all patients who require blood or BM transplantation should be able to find an acceptable donor.

FLAMSA-Busulfan-Melphalan as a Sequential Conditioning Regimen in HLA-Matched or Haploidentical Hematopoietic Stem Cell Transplantation for High-Risk Myeloid Diseases

Given the poor prognosis of relapsed/refractory myeloid malignancies, the concept of sequential conditioning before allogeneic hematopoietic stem cell transplantation (allo-HSCT) has proven to be an effective approach. We sought to evaluate a sequential scheme combining fludarabine, amsacrine, and cytarabine (FLAMSA) for cytoreduction, followed by reduced-intensity conditioning with busulfan and melphalan (FLAMSA-BuMel), which was designed to be suitable for both HLA-matched and haploidentical HSCT. This single-center retrospective study included 36 adult patients with high-risk myeloid malignancies who underwent allo-HSCT from HLA-matched (n=19) or haploidentical (n=17) donors. Along with the standard prophylaxis for graft-versus-host disease (GVHD), patients with a haploidentical donor received post-transplantation high-dose cyclophosphamide. A post-transplantation consolidation treatment with low-dose 5-azacytidine and prophylactic donor lymphocyte infusions was provided whenever possible. Thirty patients (83%) achieved complete remission on day +30. With a median follow-up of 30.0 months, the 2-year overall survival was 89% in the HLA-matched group versus 34% in the haploidentical group (P=.0018). The 2-year disease-free survival in these 2 groups was 68% and 34%, respectively (P=.013). At 2 years, the probability of relapse was 32% and 20%, respectively, and nonrelapse mortality was 0% and 58%, respectively (P=.0003). The leading cause of death was relapse in the HLA-matched group (3 of 19) and hemorrhagic events (5 of 17) in the haploidentical group, favored by significantly delayed platelet reconstitution and a severe GVHD context. These data confirm the feasibility of FLAMSA-BuMel as a sequential conditioning in allo-HSCT for high-risk myeloid malignancies. The use of bone marrow as the preferred graft source might reduce the incidence of acute GVHD and nonrelapse mortality in the haploidentical transplantation setting.

Impact of Post-Transplant High-Dose Cyclophosphamide on Reconstitution in Bone Marrow Recipients

Introduction: Hematopoetic stem cell transplantation (HSCT) is the only curative therapy for many patients with hematologic malignancies. Occurrence of complications and mortality after allo HSCT is still high and it's strongly associated with immune reconstitution. Despite the wide-spread of Post-Transplant High-Dose Cyclophosphamide (PTCy) immune reconstitution and immunological safety of this method is still poorly understood.Aim: to evaluate immune reconstitution profile in patients who was underwent HSCT with a bone marrow as a stem cell source and with or without PTCy.Patients and methods: In National Research Center for Hematology 41patients after allogeneic HSCT were analyzed in 2 groups; patients with PTCy (n=17) and without PTCy (n=24). The total cohort had 12 males and 29 females, and had a median age of 33 years (range 19-61). All patients were diagnosed with a hematological malignancy. 14 patients were underwent myeloablative conditioning and 27 patients - non-myeloalative prior HSCT.The GVHD prophylaxis consisted of ATG-PTCy-CsA-MMF (n=10), ATG-PTCy (n=5), Mono-PTCy (n=1), ATG-CsA-MMF-MTX (n=20), CsA-MTX (n=2), ATG-CsA-MTX (n=2), CsA-MMF-MTX(n=1). The patients who only had received ATG were included on the analysis.Immune reconstitution profile was tested via serial flow cytometry analysis of peripheral blood on day +14, +30, +60 and +90 after allo-HSCT. Anti-CD3 FITC, anti-CD16PE, anti-CD56 PE, anti-CD45 Per-CP-CYTM5.5, anti-CD4 PE-CyTM7, anti-CD19 APC, anti-CD8 APC-Cy7; anti-CD62L FITC (BD Biosciences, USA); anti-CD14PE, anti-CD16PE, anti-HLA-DR APC (eBiosciences, USA) were used to define white blood cell subsets.Results: Reported detailed data is presented in Table 1. In bone marrow recipients the number of CD4+- cells was significantly lower on day +14 and +30, NK-cells on day +30 and CD8+-cells on day +60 in case of using PTCy versus immunosuppression without PTCy.The number of classical monocytes on day +30 and patrol monocytes on day +30 and +90 was significantly lower in case of using PTCy versus a standard protocol.Conclusion:Lymphocyte and monocyte reconstitution was impaired for the PTCy groups in the immediate post-HSCT period but quickly recovered. The mechanism of tolerance induction with PTCy on day+ 3, + 4 is not limited only to deletion of alloreactive T-cell clones, but also affects other leukocyte subpopulations (B cells, monocytes, granulocytes). The use of PTCy on day+ 3, + 4 is an immunologically safe method for prevention of GVHD.Table 1. Short-term reconstitution in BM recipients with and without PTCy [Display omitted] DisclosuresNo relevant conflicts of interest to declare.