Thiotepa, Busulfan, and Fludarabine Conditioning Regimen in T Cell-Replete HLA-Haploidentical Hematopoietic Stem Cell Transplantation

More about post-transplant cyclophosphamide in haploidentical grafts: full or reduced doses?

Haploidentical hematopoietic can be conducted on an outpatient basis but the two main reasons to accept into the hospital a patient in this setting are complications of the hematological toxicity and/or the cytokine-release syndrome. With the aim of reducing the post-transplant cyclophosphamide-dependent toxicity without compromising its effectivity, attempts to reduce the dose of post-transplant cyclophosphamide have been made: Decreases from the conventional total dose of post-transplant cyclophosphamide (100 mg/Kg) have been explored worldwide, showing that decreasing the total dose to even 50 mg/Kg significantly decreases the toxicity of the procedure without compromising its efficacy, safety and results. We present here the salient data of the attempts to diminish the doses of post-transplant cyclophosphamide which have been done and published worldwide, information that suggests that the conventional doses of post-transplant cyclophosphamide can be significantly reduced thus decreasing the toxicity, without compromising the effectiveness of the procedure, mainly the development of graft versus host disease.

Lower relapse incidence with haploidentical versus matched sibling or unrelated donor hematopoietic cell transplantation for core-binding factor AML patients in CR2: A study from the Global Committee and the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Allogeneic hematopoietic cell transplantation (allo-HCT) is recommended for core-binding factor mutated (CBF) AML patients achieving second complete remission (CR2). However, approximately 20% of patients may relapse after transplant and donor preference remains unclear. We compared in this EBMT global multicenter registry-based analysis the allo-HCT outcomes using either haploidentical (Haplo), matched siblings donors (MSD), or 10/10 matched unrelated donors (MUD). Data from 865 de novo adult CBF AML patients in CR2 receiving allo-HCT in 227 EBMT centers from 2010 to 2022 were analyzed, in which 329 MSD, 374 MUD, and 162 Haplo-HCTs were included. For the entire cohort, 503 (58%) patients were inv(16)/CBFB-MYH11 and 362 patients (42%) were t(8;21)/RUNX1-RUNX1T1 AML. On multivariate analysis, Haplo-HCT was associated with a lower Relapse Incidence (RI) compared to either MSD (hazard ratio [HR] = 0.56, 95% CI 0.32-0.97; p < .05) or MUD (HR = 0.57, 95% CI: 0.33-0.99, p < .05). No significant difference was observed among the 3 types of donors on LFS, OS and GRFS. CBF-AML with t(8;21) was associated with both higher RI (HR = 1.79, 95% CI 1.3-2.47; p < .01) and higher NRM (HR = 1.58, 95% CI 1.1-2.27; p < .01) than CBF-AML with inv(16), which led to worse LFS, OS and GRFS. To conclude, for CBF-AML patients in CR2, Haplo-HCTs were associated with a lower RI compared to MSD and MUD allo-HCTs. There was no difference on LFS, OS or GRFS. CBF AML patients with inv(16) had a better progonosis than those with t(8;21) after allo-HCT in CR2.

Outcomes of Antithymocyte Globulin-Post-Transplantation Cyclophosphamide-Cyclosporine-Based versus Antithymocyte Globulin-Based Prophylaxis for 10/10 HLA-Matched Unrelated Donor Allogeneic Hematopoietic Cell Transplantation

In 2015, dual T cell depletion with antithymocyte globulin (ATG) and post-transplantation cyclophosphamide (PTCy) combined with cyclosporine A (CsA) replaced our prior institutional graft-versus-host disease (GVHD) prophylaxis regimen of 4.5 mg/kg ATG, CsA, and mycophenolate mofetil (MMF) (ATG-based) in 10/10 HLA-matched unrelated donor (MUD) peripheral blood allogeneic hematopoietic stem cell transplantation (allo-HCT). The initial ATG dose of 4.5 mg/kg [ATG(4.5)/PTCy] was reduced to 2 mg/kg [ATG(2)/PTCy] in 2018. This study compares the results obtained from 444 adults undergoing MUD allo-HCT at our institution who received ATG(4.5)/PTCy (n = 127) or ATG(2)/PTCy (n = 223) with those who received ATG-based prophylaxis without PTCy (n = 84). The rates of grade II-IV and grade III-IV acute GVHD (aGVHD) at day +100 and moderate/severe chronic GVHD (cGVHD) at 1 year were 35.7%, 21.6%, and 14.7%, respectively, in patients receiving ATG-based prophylaxis without PTCy; 16.5%, 4.9%, and 4.3% in patients receiving ATG(4.5)/PTCy; and 23.3% (P = .004), 8.0% (P < .001), and 14.1% (P =.006) in patients receiving ATG(2)/PTCy. One-year overall survival (OS), nonrelapse mortality (NRM), and GVHD-free relapse-free survival (GRFS) were 69.8%, 25.3%, and 52.0%, respectively, for patients receiving ATG-based prophylaxis without PTCy; 82.7%, 17.3%, and 59.8% for patients receiving ATG(4.5)/PTCy; and 78.3% (P = .446), 14.7% (P = 101), and 56.2% (P = .448) for patients receiving ATG(2)/PTCy. On univariate analyses, the use of ATG(2)/PTCy was associated with a lower risk of NRM (hazard ratio, .54; P = .023) compared with the use of ATG-based prophylaxis without PTCy. ATG(2)/PTCy prophylaxis effectively prevents GVHD and is associated with comparable relapse risk, OS, and GRFS as seen with ATG(4.5)/PTCy and ATG-based prophylaxis without PTCy.

Dual T cell depletion for graft versus host disease prevention in peripheral blood haploidentical hematopoietic cell transplantation for adults with hematological malignancies

The ideal immunosuppressive agents to complement post-transplant cyclophosphamide (PTCy) in PBSC-based haploidentical hematopoietic cell transplantation (haplo-HCT) remain debated. This study looks at our experience with ATG-PTCy-Cyclosporine (CsA) prophylaxis in PB haplo-HCT since 2015. Between October 2015 and December 2021, 157 adults underwent haploidentical hematopoietic cell transplantation (haplo-HCT) using a GVHD prophylaxis regimen comprising rabbit-ATG, PTCy, and CsA. Among these patients, 76.4% received a total ATG dose of 4.5 mg/kg, and 23.5% received 2 mg/kg. T-cell replete peripheral blood stem cell (PBSC) grafts were infused on day 0. The study reported a median follow-up of 32 months (range 0.3-61.64) for survivors. The cumulative incidence of grade II-IV and grade III-IV acute GVHD at day +100 was 26.3% and 9.5%, respectively. Moderate/severe chronic GVHD at 1 year was 19.9%. The 2-year overall survival (OS) was 49.4%, with a relapse-free survival (RFS) of 44.6%. In multivariate analysis, older patients, and those with high/very-high disease risk indices (DRI) were at higher risk for worse OS and higher non-relapse mortality (NRM). The study confirms that using PTCy and ATG (4.5 mg/kg), alongside CsA is safe and effective in preventing GVHD when using peripheral blood as the stem cell source in haploidentical hematopoietic cell transplantation (haplo-HCT).

Stem cell therapy for HTLV-1 induced adult T-cell leukemia/lymphoma (ATLL): A comprehensive review

Adult T-cell leukemia/lymphoma (ATLL) is a rare and aggressive form of cancer associated with human T-cell lymphotropic virus type 1 (HTLV-1) infection. The emerging field of stem cell therapies for ATLL is discussed, highlighting the potential of hematopoietic stem cell transplantation (HSCT) and genetically modified stem cells. HSCT aims to eradicate malignant T-cells and restore a functional immune system through the infusion of healthy donor stem cells. Genetically modified stem cells show promise in enhancing their ability to target and eliminate ATLL cells. The article presents insights from preclinical studies and limited clinical trials, emphasizing the need for further research to establish the safety, efficacy, and long-term outcomes of stem cell therapies for ATLL and challenges associated with these innovative approaches are also explored. Overall, stem cell therapies hold significant potential in revolutionizing ATLL treatment, and ongoing clinical trials aim to determine their benefits in larger patient populations.

Phase I study of zoledronic acid combined with escalated doses of interleukine-2 for early in vivo generation of Vγ9Vδ2 T-cells after haploidentical stem cell transplant with posttransplant cyclophosphamide

The presence of donor Vγ9Vδ2 T-cells after haploidentical hematopoietic stem cell transplant (h-HSCT) has been associated with improved disease-free survival. These cells kill tumor cells in a non-MHC restricted manner, do not induce graft-versus-host disease (GVHD), and can be generated by stimulation with zoledronic acid (ZA) in combination with interleukin-2 (IL-2). This monocentric phase I, open-label, dose-escalating study (ClinicalTrials.gov: NCT03862833) aimed at evaluating the safety and possibility to generate Vγ9Vδ2 T-cells early after h-HSCT. It applied a standard 3 + 3 protocol to determine the maximum tolerated dose (MTD) of increasing low-doses of IL-2 (5 days [d] per week, 4 weeks) in combination with a single dose of ZA, starting both the first Monday after d + 15 posttransplant. Vγ9Vδ2 T-cell monitoring was performed by multiparameter flow cytometry on blood samples and compared with a control cohort of h-HSCT recipients. Twenty-six patients were included between April 2019 and September 2022, 16 of whom being ultimately treated and seven being controls who received h-HSCT only. At the three dose levels tested, 1, 0, and 1 dose-limiting toxicities were observed. MTD was not reached. A significantly higher number of Vγ9Vδ2 T-cells was observed during IL-2 treatment compared with controls. In conclusion, early in vivo generation of Vγ9Vδ2 T-cells is feasible after h-HSCT by using a combination of ZA and repeated IL-2 infusions. This study paves the way to a future phase 2 study, with the hope to document lesser posttransplant relapse with this particular adaptive immunotherapy.

Human herpesvirus type 6 reactivation after haploidentical hematopoietic cell transplantation with post-transplant cyclophosphamide and antithymocyte globulin: risk factors and clinical impact

Human herpesvirus type 6 (HHV6) reactivation after haploidentical hematopoietic cell transplantation (HCT) with post-transplant cyclophosphamide (PT-Cy) has been scarcely studied, especially when antithymocyte globulin (ATG) is added to the graft-versus-host disease (GvHD) prophylaxis. We conducted a retrospective cohort study in 100 consecutive patients receiving haploidentical HCT with PT-Cy. We systematically monitored HHV6 DNA loads in blood samples on a weekly basis using quantitative PCR until day +100. The 100-day cumulative incidence of HHV6 reactivation was 54%. Clinically significant HHV6 infections were rare (7%), associated with higher HHV6 DNA loads, and had favorable outcomes after antiviral therapy. The main risk factor for HHV6 reactivation was a low absolute lymphocyte count (ALC) \< 290/µL on day +30 (68% versus 40%, p = 0.003). Adding ATG to PT-Cy did not increase the incidence of HHV6 reactivation (52% with ATG versus 79% without ATG, p = 0.12). Patients experiencing HHV6 reactivation demonstrated delayed platelet recovery (HR 1.81, 95% CI 1.07-3.05, p = 0.026), higher risk of acute grade II-IV GvHD (39% versus 9%, p \< 0.001) but similar overall survival and non-relapse mortality to the other patients. In conclusion, our findings endorse the safety of combining ATG and PT-Cy in terms of the risk of HHV6 reactivation and infection in patients undergoing haploidentical HCT. Patients with a low ALC on day +30 face a higher risk of HHV6 reactivation and may require careful monitoring.

Thiotepa-Based Regimens Are Valid Alternatives to Total Body Irradiation-Based Reduced-Intensity Conditioning Regimens in Patients with Acute Lymphoblastic Leukemia: A Retrospective Study on Behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Total body irradiation (TBI) at myeloablative doses is superior to chemotherapy-based regimens in young patients with acute lymphoblastic leukemia (ALL) undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, in elderly and unfit patients, in whom reduced-intensity conditioning (RIC) regimens are preferred, whether a TBI-based or a chemotherapy-based approach is better is unexplored. Thiotepa can be used as part of ALL conditioning regimens. The current study aimed to compare transplantation outcomes after RIC with TBI-based or thiotepa-based regimens in patients with ALL. The study cohort comprised patients aged ≥40 years undergoing allo-HSCT for ALL in first complete remission between 2000 and 2020 who received an RIC regimen containing either TBI (4 to 6 Gy) or thiotepa. We identified a total of 265 patients, including 117 who received a TBI-based RIC regimen and 148 who received a thiotepa-based RIC regimen. Univariate analysis revealed no significant differences in the following transplantation outcomes for TBI versus thiotepa: relapse, 23% versus 28% (P = .24); nonrelapse mortality, 20% versus 26% (P = .61); leukemia-free survival, 57% versus 46% (P = .12); overall survival, 67% versus 56% (P = .18); graft-versus-host disease (GVHD]/relapse-free survival, 45% versus 38% (P = .21); grade II-IV acute GVHD, 30% in both groups (P = .84); grade III-IV acute GVHD, 9% versus 10% (P = .89). The sole exception was the incidence of chronic GVHD, which was higher in the recipients of TBI-based regimens (43% versus 29%; P = .03). However, multivariate analysis revealed no differences in transplantation outcomes between the 2 groups. In patients aged ≥40 years receiving RIC, use of a thiotepa-based regimen may represent a valid alternative to TBI-based regimens, as no differences were observed in the main transplantation outcomes.

Novel approaches to acute graft-versus-host disease prevention

The field of graft-versus-host disease (GvHD) has experienced significant growth, with increased number of clinical trials and the approval of several agents by the US Food and Drug Administration for both acute and chronic GvHD treatment. In addition, the development of prognostic biomarker algorithms has enabled risk stratification in acute GvHD. However, prevention remains the cornerstone of GvHD management. Notable recent changes include the expansion of donor options with the increased use of haploidentical donor and unrelated donor transplantation, the development of ex vivo selective T-cell depletion strategies, recent approval by the Food and Drug Administration of abatacept for GvHD prevention, and the application of posttransplant cyclophosphamide in matched and mismatched donor settings. In this article, we review the results of recent clinical trials in GvHD prophylaxis and discuss the changes in clinical practice and promising emerging strategies driving the field forward.

Combining post-transplant cyclophosphamide with antithymocyte globulin for graft-versus-host disease prophylaxis in hematological malignancies

In search of an ideal partner or alternative to conventional immunosuppressive agents, rabbit anti-thymocyte globulin (ATG) and, more recently, post-transplant cyclophosphamide (PT-Cy) have both emerged as valid and efficient options for preventing graft-versus-host disease (GvHD). To further reduce the risk of GvHD, strategies combining ATG and PT-Cy have recently been investigated. In a haploidentical setting, retrospective studies suggest that combining PT-Cy and ATG may result in a lower incidence of chronic GvHD without increasing the risks of infection or relapse, when compared to PT-Cy without ATG. In haploidentical or unrelated donor settings, adding reduced doses of PT-Cy to ATG may reduce the risk of acute and chronic GvHD and improve survival, particularly GvHD-free, relapse-free survival (GRFS), when compared to ATG without PT-Cy. Overall, the combination of PT-Cy and ATG is a safe and promising approach for patients with hematological malignancies undergoing allogeneic hematopoietic stem cell transplantation (HSCT).

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

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

Thiotepa-busulfan-fludarabine Compared to Treosulfan-based Conditioning for Haploidentical Transplant With Posttransplant Cyclophosphamide in Patients With Acute Myeloid Leukemia in Remission: A Study From the Acute Leukemia Working Party of the EBMT

We conducted a registry analysis including adult acute myeloid leukemia (AML) patients in remission who had received thiotepa, busulfan, and fludarabine (TBF) or treosulfan-based (Treo) conditioning for haplo-hematopoietic stem cell transplant (HSCT) with posttransplant cyclophosphamide (PTCy) between 2010 and 2020. A total of 1123 patients met the inclusion criteria (968 received TBF and 155 received Treo). A 1:1 matched-pair analysis was performed on 142 TBF and 142 Treo patients. In the Treo group, 68% of patients received treosulfan at a dose ≥36 g/m2 and 54% of patients received a second alkylator (thiotepa or melphalan). We observed a trend toward increased incidence of grade II-IV acute (a) graft-versus-host disease (GVHD) at 180 days in the TBF group compared with Treo (29% versus 20%; P = 0.08), while incidence of grade III-IV aGVHD was not statistically different. Similarly, the incidence of chronic (c) GVHD was not statistically different in the 2 groups. Incidence of nonrelapse mortality at 2 years was 19% in TBF and 14% in Treo (P = 0.4). Relapse incidence at 2 years was not statistically different in the 2 groups (16% and 18% in TBF and Treo, respectively; P = 0.9). Leukemia-free survival, overall survival, and GVHD-free, relapse-free survival was 65% versus 68% (P = 0.6), 73% versus 76% (P = 0.5), and 54% versus 53% (P = 0.8) in TBF versus Treo, respectively. In conclusion, we did not find a significant difference between the 2 conditioning in the present study; Treo and TBF represent 2 valid alternative regimens for haplo-HSCT with PTCy for AML in remission.

Reduced post-transplant cyclophosphamide doses in haploidentical hematopoietic cell transplantation for elderly patients with hematological malignancies

Although post-transplant cyclophosphamide (PT-Cy) is effective for graft-versus-host disease (GVHD) prophylaxis, it is associated with toxicities, which might be dose-dependent. We compared the outcomes with PT-Cy at 80 mg/kg to those with PT-Cy at 100 mg/kg in elderly patients undergoing haploidentical hematopoietic cell transplantation (HCT). Inclusion criteria included peripheral blood stem cells, hematological malignancy, and age>65 years (or age>60 years if cardiac event history). Thirty-eight patients received PT-Cy at 80 mg/kg and 55 100 mg/kg, divided in two doses. The cumulative incidences (CI) of acute grade II-IV, acute grade III-IV, and moderate/severe chronic GVHD were 32%, 16%, and 13% with PT-Cy at 80 mg/kg compared to 33%, 13%, and 16% with 100 mg/kg, respectively. In multivariable analysis, reducing PT-Cy dose had no significant impact on GVHD. Neutrophil and platelet engraftments were significantly improved, and CI of BK virus-associated hemorrhagic cystitis was reduced with 80 mg/kg of PT-Cy compared to 100 mg/kg. At 2 years, non-relapse mortality was 16% and 31%, progression-free survival 65% and 49%, overall survival 70% and 56%, and GVHD-free, relapse-free survival 52% and 36% with 80 mg/kg and 100 mg/kg, respectively. Reducing PT-Cy dose to 80 mg/kg is safe and associated with improved hematological recovery and lower CI of hemorrhagic cystitis in elderly patients undergoing haploidentical HCT.

Allogeneic hematopoietic stem cell transplantation with myeloablative conditioning regimen for blastic plasmacytoid dendritic cell neoplasm patients in complete remission: a single center study

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematopoietic malignancy characterized by poor prognosis even following an allogeneic hematopoietic stem cell transplantation (allo-HSCT). We retrospectively analyzed 15 patients diagnosed with BPDCN who underwent an allo-HSCT with myeloablative conditioning (MAC) at our center. The male to female ratio was 11:4. The median age of 36 (range: 6-70) years, all patients initially presented with extramedullary lesions (13 with cutaneous lesions, 1 in the breast and 1 in the lymph nodes) and involved the bone marrow, two cases were diagnosed as central nervous system leukemia (CNSL). Nine patients were in CR1 and six patients were in CR2 status prior to HSCT. All patients received the MAC regimen and an unmanipulated graft. All patients successfully engraftment and achieved full donor chimerism. One patient developed poor graft function, three patients developed aGVHD (Grade I, II, and IV), and seven patients developed cGVHD (mild in 6; moderate in 1). The median follow-up time for survival was 34 (range: 6-64) months. The primary endpoint, overall leukemia-free survival (LFS) rate and overall survival rate was 73.3 ± 10.5%. Allo-HSCT with MAC is a valid option for BPDCN patients in complete remission.

Clinical and healthcare burden of disease associated with cytomegalovirus in allogeneic hematopoietic stem cell transplantation - A retrospective single-center study

BACKGROUND

CMV infection is a common complication in allogeneic hematopoietic stem cell transplantation (HSCT). We investigated the association of clinically significant CMV (CS-CMV) infection with clinical outcomes and healthcare resource utilization in allogeneic HSCT patients in Finland.

METHODS

This retrospective study included adult patients who received their first allogeneic HSCT between January 1, 2013, and December 31, 2018, at the Turku University Hospital. Data were collected from the hospital data lake. Clinical and healthcare outcomes were investigated at one year and mortality up to three years.

RESULTS

The study included 251 patients. CMV seroprevalence was 69.7%. CS-CMV infection occurred in 59.0% of the patients, and of those, 14.2% had ≥2 infections. The median time to CS-CMV infection was 34.5 days (Q₁ -Q₃ , 27.0-45.0). Recipient and donor seropositivity, and lymphoproliferative diseases were associated with higher, and HLA identical sibling donors with lower CS-CMV infection risk. CS-CMV infection was not associated with mortality in three years of follow-up. One hundred thirty-three (89.8%) and 75 (72.8%) patients with and without CS-CMV infection, respectively, were readmitted to the hospital. Patients with CS-CMV infection had more hospital readmissions (incidence rate ratio [IRR] 1.38, 95% confidence interval [CI] 1.10-1.73, p = .005) and patients with one CS-CMV infection (IRR 1.48, 95% CI 1.12-1.94, p = .005) or ≥2 infections had longer length of hospital stay (IRR 2.71, 95% CI 1.76-4.35, p < .001).

CONCLUSION

CMV seroprevalence is relatively high among Finnish allogeneic HSCT patients. CS-CMV infection was common and associated with a higher readmission rate and longer length of hospital stay.

Controversies and expectations for the prevention of GVHD: A biological and clinical perspective

Severe acute and chronic graft versus host disease (GVHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation. Historically, cord blood and matched sibling transplantation has been associated with the lowest rates of GVHD. Newer methods have modified the lymphocyte components to minimize alloimmunity, including: anti-thymocyte globulin, post-transplant cyclophosphamide, alpha/beta T cell depletion, and abatacept. These agents have shown promise in reducing severe GVHD, however, can be associated with increased risks of relapse, graft failure, infections, and delayed immune reconstitution. Nonetheless, these GVHD prophylaxis strategies have permitted expansion of donor sources, especially critical for those of non-Caucasian decent who previously lacked transplant options. This review will focus on the biologic mechanisms driving GVHD, the method by which each agent impacts these activated pathways, and the clinical consequences of these modern prophylaxis approaches. In addition, emerging novel targeted strategies will be described. These GVHD prophylaxis approaches have revolutionized our ability to increase access to transplant and have provided important insights into the biology of GVHD and immune reconstitution.

Post-Transplant Cyclophosphamide after Matched Sibling and Unrelated Donor Hematopoietic Stem Cell Transplantation in Pediatric Patients with Acute Myeloid Leukemia

Non-relapse mortality due to GVHD and infections represents a major source of morbidity and mortality in pediatric HSCT recipients. Post-transplant cyclophosphamide (PTCy) has emerged as an effective and safe GVHD prophylaxis strategy, with improved GVHD and relapse-free survival in matched (related and unrelated) and mismatched haploidentical HSCT adult recipients. However, there are no published data in pediatric patients with acute myeloid leukemia who received matched-donor HSCT with PTCy. We demonstrate, in this case series, that the use of PTCy in this population is potentially safe, effective in preventing acute GVHD, does not impair engraftment, is associated with reduced non-relapse mortality, and does not hinder immune reconstitution post HSCT.

Lower dose of ATG combined with post-transplant cyclophosphamide for HLA matched RIC alloHCT is associated with effective control of GVHD and less viral infections

This study compares the outcomes before and after reducing the ATG dose from 4.5 to 2 mg/kg, in a combination of PTCy and CsA for GVHD prevention, in 250 patients treated with HLA matched RIC PB-alloHCT (70% received 4.5 mg/kg and 30% received 2 mg/kg). The incidences of grade II-IV and III-IV aGVHD at day +100, and moderate/severe cGVHD at 1-year were 12.6% vs. 20% (p = 0.431), 3.6% vs. 4.5% (p = 0.935), and 10.9% vs. 26.1% (p = 0.480), respectively. PTLD (9.1% vs. 1.3%, p = 0.026) and viral infections (30.3% vs. 12%; p = 0.001) were lower for those treated with 2 mg/kg of ATG. The reduction of the ATG dose resulted in a comparable OS (2-year: 64.7% vs. 64.7%), GRFS (2-year: 48.0% vs. 44.5%), RFS (2-year: 57.0% vs. 62.0%), and NRM (2-year: 17.8 vs. 14.9). The use of (2 mg/kg) ATG-PTCy-CsA for HLA matched RIC alloHCT results in lower viral infections, and incomparable GVHD preventive effect and survival rates.

Early Cardiac Toxicity Associated With Post-Transplant Cyclophosphamide in Allogeneic Stem Cell Transplantation

Background

Post-transplant cyclophosphamide (PT-Cy) has become a standard of care in haploidentical hematopoietic stem cell transplantation (HSCT) to reduce the risk of graft-versus-host disease. However, data on cardiac events associated with PT-Cy are scarce.

Objectives

This study sought to assess the incidence and clinical features of cardiac events associated with PT-Cy.

Methods

The study compared clinical outcomes between patients who received PT-Cy (n = 136) and patients who did not (n = 195), with a focus on early cardiac events (ECE) occurring within the first 100 days after HSCT. All patients had the same systematic cardiac monitoring.

Results

The cumulative incidence of ECE was 19% in the PT-Cy group and 6% in the no–PT-Cy group (p < 0.001). The main ECE occurring after PT-Cy were left ventricular systolic dysfunction (13%), acute pulmonary edema (7%), pericarditis (4%), arrhythmia (3%), and acute coronary syndrome (2%). Cardiovascular risk factors were not associated with ECE. In multivariable analysis, the use of PT-Cy was associated with ECE (hazard ratio: 2.7; 95% confidence interval: 1.4 to 4.9; p = 0.002]. Older age, sequential conditioning regimen, and Cy exposure before HSCT were also associated with a higher incidence of ECE. Finally, a history of cardiac events before HSCT and ECE had a detrimental impact on overall survival.

Conclusions

PT-Cy is associated with a higher incidence of ECE occurring within the first 100 days after HSCT. Patients who have a cardiac event after HSCT have lower overall survival. These results may help to improve the selection of patients who are eligible to undergo HSCT with PT-Cy, especially older adult patients and patients with previous exposure to Cy.

Myeloablative haploidentical BMT with posttransplant cyclophosphamide for hematologic malignancies in children and adults

Promising results have been reported for patients with high-risk hematologic malignancies undergoing HLA-haploidentical bone marrow transplantation (haploBMT) with posttransplantation cyclophosphamide (PTCy), but there are few data on outcomes with myeloablative conditioning in this context. We report the results of a single-institution, prospective phase 2 trial of myeloablative haploBMT using busulfan-based or total body irradiation-based conditioning in 96 children or adults (median age, 42 years; range, 1-65 years) with high-risk hematologic malignancies. Recovery of neutrophils and platelets occurred at a median of 24 and 29 days. Engraftment of donor cells with chimerism >95% was achieved in 91%. The cumulative incidence of acute graft-versus-host disease (GVHD) grades II to IV and grades III to IV at day 100 was 11% and 4%, and of chronic GVHD at 6 and 12 months was 4% and 15%, with 6% moderate to severe. The cumulative incidence of nonrelapse mortality was 6% at 100 days and 11% at 1 year (19% in those aged >55 years). The cumulative incidence of relapse at 1 year was 35%; at 3 years, it was 43%. In multivariable analysis, relapse was associated with increased age (P = .02 for age 20-55 years and P = .02 for age >55 years) and with minimal residual disease before transplantation (P = .05). The overall survival at 1 and 3 years is 73% and 54%, and event-free survival at 1 and 3 years is 57% and 49%. We show that haploBMT with PTCy after myeloablative conditioning is safe and efficacious for adult and pediatric patients with hematologic malignancies. Careful consideration must be given to using myeloablative conditioning in patients age >55 years. This trial was registered at www.clinicaltrials.gov as #NCT00796562.

Total Body Irradiation Forever? Optimising Chemotherapeutic Options for Irradiation-Free Conditioning for Paediatric Acute Lymphoblastic Leukaemia

Total-body irradiation (TBI) based conditioning prior to allogeneic hematopoietic stem cell transplantation (HSCT) is generally regarded as the gold-standard for children >4 years of age with acute lymphoblastic leukaemia (ALL). Retrospective studies in the 1990's suggested better survival with irradiation, confirmed in a small randomised, prospective study in the early 2000's. Most recently, this was reconfirmed by the early results of the large, randomised, international, phase III FORUM study published in 2020. But we know survivors will suffer a multitude of long-term sequelae after TBI, including second malignancies, neurocognitive, endocrine and cardiometabolic effects. The drive to avoid TBI directs us to continue optimising irradiation-free, myeloablative conditioning. In chemotherapy-based conditioning, the dominant myeloablative effect is provided by the alkylating agents, most commonly busulfan or treosulfan. Busulfan with cyclophosphamide is a long-established alternative to TBI-based conditioning in ALL patients. Substituting fludarabine for cyclophosphamide reduces toxicity, but may not be as effective, prompting the addition of a third agent, such as thiotepa, melphalan, and now clofarabine. For busulfan, it's wide pharmacokinetic (PK) variability and narrow therapeutic window is well-known, with widespread use of therapeutic drug monitoring (TDM) to individualise dosing and control the cumulative busulfan exposure. The development of first-dose selection algorithms has helped achieve early, accurate busulfan levels within the targeted therapeutic window. In the future, predictive genetic variants, associated with differing busulfan exposures and toxicities, could be employed to further tailor individualised busulfan-based conditioning for ALL patients. Treosulfan-based conditioning leads to comparable outcomes to busulfan-based conditioning in paediatric ALL, without the need for TDM to date. Future PK evaluation and modelling may optimise therapy and improve outcome. More recently, the addition of clofarabine to busulfan/fludarabine has shown encouraging results when compared to TBI-based regimens. The combination shows activity in ALL as well as AML and deserves further evaluation. Like busulfan, optimization of chemotherapy conditioning may be enhanced by understanding not just the PK of clofarabine, fludarabine, treosulfan and other agents, but also the pharmacodynamics and pharmacogenetics, ideally in the context of a single disease such as ALL.

Acute Myeloid Leukemia: From Biology to Clinical Practices Through Development and Pre-Clinical Therapeutics

Recent studies have provided several insights into acute myeloid leukemia. Studies based on molecular biology have identified eight functional mutations involved in leukemogenesis, including driver and passenger mutations. Insight into Leukemia stem cells (LSCs) and assessment of cell surface markers have enabled characterization of LSCs from hematopoietic stem and progenitor cells. Clonal evolution has been described as having an effect similar to that of microenvironment alterations. Such biological findings have enabled the development of new targeted drugs, including drug inhibitors and monoclonal antibodies with blockage functions. Some recently approved targeted drugs have resulted in new therapeutic strategies that enhance standard intensive chemotherapy regimens as well as supportive care regimens. Besides the progress made in adoptive immunotherapy, since allogenic hematopoietic stem cell transplantation enabled the development of new T-cell transfer therapies, such as chimeric antigen receptor T-cell and transgenic TCR T-cell engineering, new promising strategies that are investigated.

Comparable outcomes of haploidentical transplant with TBF conditioning versus matched unrelated donor with fludarabine/busulfan conditioning for acute myeloid leukemia

We compared transplant outcomes of 708 acute myeloid leukemia (AML) patients receiving haploidentical allogeneic hematopoietic-cell transplantation using thiotepa/busulfan/fludarabine (TBF) conditioning with posttransplant cyclophosphamide (ptCy), to 2083 patients receiving matched unrelated donor (MUD) transplantation using fludarabine/busulfan (FB) conditioning and in vivo T-cell depletion. For intermediate cytogenetic risk AML transplanted in first complete remission (CR1), multivariate analysis revealed that haplo-TBF significantly increased nonrelapse mortality (NRM) (HR 2.1; p = 0.0006) but did not affect relapse incidence (RI), leukemia-free survival (LFS), overall survival (OS), or graft-versus-host disease-free, relapse-free survival (GRFS). For high cytogenetic risk AML transplanted in CR1, haplo-TBF significantly increased NRM (HR = 2.7; p = 0.02), decreased RI (HR = 0.45; p = 0.03) but had no influence on LFS, OS, or GRFS. For AML transplanted in CR2, haplo-TBF significantly increased NRM (HR = 2.36; p = 0.008), decreased RI (HR = 0.38; p = 0.005), but had no influence on LFS, OS, or GRFS. Finally, for AML patients transplanted with active disease, haplo-TBF had no influence on transplant outcomes. In conclusion, compared to MUD-FB, haplo-TBF increased NRM, reduced RI in high-risk AML in CR, resulting in similar LFS, OS, and GRFS. These results comparing two different approaches support the use of a haploidentical family donor for high-risk AML patients lacking a matched sibling donor.

Review of conditioning regimens for haplo-identical donor transplants using post-transplant cyclophosphamide in recipients of G-CSF mobilised peripheral stem cell

Haplo-identical transplant is being increasingly used in patients who do not have a readily available matched related or unrelated donor. Post-transplant cyclophosphamide's use due to its simplicity and documented efficacy has made this approach readily employable across diverse transplant centres across the globe. The outcomes of regimens used for conditioning in recipients of bone marrow are at times in variance to that from more commonly employed G-CSF mobilised peripheral stem cell (PBSC). This review highlights various conditioning regimens used in PBSC recipients, with emphasis on toxicities, practicalities and transplant related outcomes of relapse, non-relapse mortality and graft versus host disease.

Impact of Adding Antithymocyte Globulin to Posttransplantation Cyclophosphamide in Haploidentical Stem-Cell Transplantation

BACKGROUND

Graft-versus-host disease (GVHD) is a major cause of mortality after allogeneic stem-cell transplantation. Posttransplantation cyclophosphamide (PT/CY) has become standard prophylaxis of GVHD in T-replete haploidentical transplantation. The question is whether adding antithymocyte globulin (ATG) to PT/CY may further reduce the incidence of GVHD compared to PT/CY only.

PATIENTS AND METHODS

We retrospectively studied 268 patients undergoing myeloablative haploidentical transplantation with thiotepa, busulfan, and fludarabine (TBF) conditioning. Sixty-nine patients (26%) received ATG.

RESULTS

In the ATG group, 3% died due to GVHD versus 8% in the no ATG group. The 100-day and 1-year nonrelapse mortality (NRM) was 0% and 19%, respectively, in the whole cohort. On univariate analysis, the 1-year NRM was 8% versus 23% in patients receiving ATG and no ATG, respectively (P = .005). The no ATG group had a higher incidence of acute GVHD at 12 months compared to the ATG group (22% vs. 12%, respectively, P = .029). The ATG group had better overall survival at 12 months compared to the no ATG group (79% vs. 69%, P = .029). On multivariate analysis, adding ATG to PT/CY had no significant impact on any of the outcomes. A low disease risk index was associated with better overall survival and lower NRM, while Hematopoietic Cell Transplantation-Specific Comorbidity Index (HCT-CI) score ≥ 3 was associated with higher NRM.

CONCLUSION

ATG can be safely used as part of the pretransplantation conditioning and does not increase the incidence of relapse or complications after transplantation.

Allogeneic Hemopoietic Stem Cell Transplants in Patients with Acute Myeloid Leukemia (AML) Prepared with Busulfan and Fludarabine (BUFLU) or Thiotepa, Busulfan, and Fludarabine (TBF): A Retrospective Study

This is a multicenter retrospective comparison of 2 myeloablative conditioning regimens in 454 patients with acute myeloid leukemia (AML) in remission: busulfan (4 days) and fludarabine (BUFLU) versus thiotepa, busulfan, and fludarabine (TBF). Eligible for this study were patients allografted between January 2008 and December 2018 in 10 transplant centers, with AML in first or second remission: 201 patients received BUFLU, whereas 253 received TBF. The 2 groups (BUFLU and TBF) were comparable for age (P = .13) and adverse AML risk factors (P = .3). The TBF group had more second remissions and more haploidentical grafts. The donor type included HLA-identical siblings, unrelated donors, and family haploidentical donors. The 5-year cumulative incidence of nonrelapse mortality (NRM) was 19% for BUFLU and 22% for TBF (P = .8), and the 5-year cumulative incidence of relapse was 30% and 15%, respectively (P = .0004). The 5-year actuarial survival was 51% for BUFLU and 68% for TBF (P = .002). In a multivariate Cox analysis, after correcting for confounding factors, the use of TBF reduced the risk of relapse compared with BUFLU (P = .03) and the risk of death (P = .03). In a matched pair analysis of 108 BUFLU patients matched with 108 TBF patients, with the exclusion of haploidentical grafts, TBF reduced the risk of relapse (P = .006) and there was a trend for improved survival (P = .07). Superior survival of patients receiving TBF as compared with BUFLU is due to a reduced risk of relapse, with comparable NRM. The survival advantage is independent of donor type and AML risk factors.

Haploidentical Stem Cell Transplantation in Children With Hematological Malignancies Using αβ+ T-Cell Receptor and CD19+ Cell Depleted Grafts: High CD56dim/CD56bright NK Cell Ratio Early Following Transplantation Is Associated With Lower Relapse Incidence and Better Outcome

We prospectively analyzed outcomes of haploidentical hematopoietic stem cell transplantation using αβ⁺ T-cell receptor/CD19⁺ depleted grafts. Sixty-three transplantations were performed in 60 patients. Twenty-eight patients were diagnosed with acute lymphoblastic leukemia (ALL), 27 patients were diagnosed with acute myelogenous leukemia, and in eight other hematological malignancies were diagnosed. Twenty-three were in first complete remission (CR), 20 in second CR, 20 beyond second CR. Four patients developed graft failure. Median time to neutrophil and platelet recovery was 14 (range 9–25) and 10 days (range 7–30), respectively. The probability of non-relapse mortality (NRM) by day +100 after transplantation was 10 ± 4%. With a median follow-up of 28 months, the probability of relapse was 32 ± 6% and disease-free survival was 52 ± 6%. Immune reconstitution was leaded by NK cells. As such, a high CD56^dim/CD56^bright NK cell ratio early after transplantation was associated with better disease-free survival (DFS) (≥3.5; 77 ± 8% vs. <3.5; 28 ± 5%; p = 0.001) due to lower relapse incidence (≥3.5; 15 ± 7% vs. <3.5; 37 ± 9%; p = 0.04). T-cell reconstitution was delayed and associated with severe infections after transplant. Viral reactivation/disease and presence of venooclusive disease of liver in the non-caucasian population had a significant impact on NRM. αβ⁺ T-cell receptor/CD19⁺ cell-depleted haploidentical transplant is associated with good outcomes especially in patients in early phase of disease. A rapid expansion of “mature” natural killer cells early after transplantation resulted on lower probability of relapse, suggesting a graft vs. leukemia effect independent from graft-vs.-host reactions.

Prospective Randomized Study Comparing Myeloablative Unrelated Umbilical Cord Blood Transplantation versus HLA-Haploidentical Related Stem Cell Transplantation for Adults with Hematologic Malignancies

In this prospective randomized study, we compared the outcomes of single-unit umbilical cord blood transplantation (UCBT) and unmanipulated haploidentical stem cell transplantation (haplo-SCT) with post-transplantation cyclophosphamide (PTCy) in adults with hematologic malignancies. All patients received a myeloablative conditioning (MAC) regimen consisting of thiotepa, busulfan, and fludarabine, with antithymocyte globulin (ATG) added for UCBT recipients. Nineteen patients were randomized to UCBT and the other 26 to haplo-HSCT. Four patients (15%) allocated to the haplo-HSCT arm lacked a suitable donor and were crossed over to the UCBT arm. Finally, 23 underwent UCBT and 22 underwent haplo-HSCT. The cumulative incidence of neutrophil recovery was 87% at a median of 19 days (range, 13 to 24 days) in the UCBT arm versus 100% at a median of 17 days (range, 13 to 25 days) in the haplo-SCT arm (P = .04). Platelet recovery was 70% at a median of 40 days (range, 18 to 129 days) in the UCBT arm versus 86% at a median of 24 days (range, 12 to 127 days) in the haplo-HCT arm (P = .02). Rates of acute graft-versus-host disease (GVHD) grade II-IV or grade III-IV, overall chronic GVHD, and extensive chronic GVHD in the UCBT and Haplo-SCT arms were 43% versus 36% (P = .8), 9% versus 9% (P = 1), 66% versus 43% (P = .04), and 41% versus 23% (P = .2), respectively. Two-year nonrelapse mortality and relapse in the 2 arms were 52% versus 23% (P = .06) and 17% versus 23% (P = .5), respectively. Two-year disease-free survival, overall survival, and GVHD/relapse-free survival in the 2 arms were 30% versus 54% (P = .2), 35% versus 59% (P = .1), and 17% versus 40% (P = .04), respectively. Our data show that in the context of an MAC regimen, haplo-SCT with PTCy provides improved outcomes compared with ATG-containing single-unit UCBT.