Optimal dose of rabbit thymoglobulin in conditioning regimens for unmanipulated, haploidentical, hematopoietic stem cell transplantation: Long-term outcomes of a prospective randomized trial

Dual T-cell depletion with individually tailored anti-thymocyte globulin and attenuated dose of post-transplant cyclophosphamide in haploidentical peripheral stem cell transplantation

This study aimed to assess the efficacy of dual T-cell suppression using individually tailored doses of antithymocyte globulin (ATG) and attenuated dose of post-transplant cyclophosphamide (PTCy) in haploidentical hematopoietic stem cell transplantation (haplo-HSCT). We conducted a retrospective analysis of 78 adults with acute leukemia or myelodysplastic syndrome who underwent haplo-HSCT using intravenous busulfan and fludarabine conditioning. Thirty-two patients received attenuated ATG/PTCy, while 46 patients received ATG (7.5 mg/kg) as GVHD prophylaxis. The 100-day cumulative incidence of grade III-IV (9.7% vs. 32.4%, P = 0.018) acute GVHD, as well as 2-year moderate-severe chronic GVHD (13.9% vs. 43.9%, P = 0.018) in the ATG/PTCy group were significantly lower than those in the ATG group. The 2-year overall survival was comparable between the two groups. However, 2-year GVHD-free, relapse-free survival in the ATG/PTCy group was significantly higher compared to that in the ATG group (38.9% vs. 21.7%, P = 0.021). Moreover, during post-engraftment period, the ATG/PTCy group exhibited lower incidences of life-threatening bacterial (12.5% vs. 37%, P = 0.033) and viral infection (0% vs. 17.4%, P = 0.035) than the ATG group. In conclusion, the combination of individually tailored ATG and low-dose PTCy appears to be a promising strategy in haplo-HSCT.

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).

Haploidentical transplants with a G-CSF/ATG-based protocol: Experience from China

Haploidentical donor stem cell transplantation (haplo-SCT) has made great advances in recent decades. The granulocyte colony-stimulating factor (G-CSF)- and antithymocyte globulin (ATG)-based protocol, which is known as the Beijing Protocol, represents one of the current T-cell repletion strategies in haplo-SCT. The key elements of the Beijing Protocol for graft versus host disease (GvHD) prophylaxis include G-CSF inducing T-cell tolerance and altering graft cell components, as well as ATG administration exerting an immunoregulatory effect for intensive prophylaxis. This review will summarize the GvHD incidence, the underlying novel mechanism for GvHD prophylaxis, how to optimize GvHD prophylaxis, and the recent advances of the Beijing Protocol, mainly focusing on the issues of GvHD.

Mini-dose methotrexate combined with methylprednisolone as a first-line treatment for acute graft-versus-host disease: A phase 2 trial

Background and Objectives

Acute graft-versus-host disease (aGvHD) remains a major complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Methylprednisolone (MP; 1-2 mg/kg/day) remains the standard first-line therapy for aGvHD, although no response is detected in nearly one-half of the patients with aGvHD. This study aimed to investigate the feasibility of mini-dose methotrexate (MTX) combined with standard-dose MP as a front-line therapy for aGvHD.

Materials and Methods

A prospective Phase 2 clinical trial was performed to evaluate the safety and efficacy of 5 mg/m2 MTX combined with 1 mg/kg/day MP as the initial therapy in 31 patients with aGvHD. Moreover, the effects of MTX combined with MP were explored in a humanized xenogeneic murine model of aGvHD.

Results

The overall response and complete response rate at 7 days after the initial treatment were 100% and 83%, respectively. The overall response rate on day 28 was 87%. The complete response rates for aGvHD grades I, II, and III were 100% (6/6), 82% (18/22), and 66% (2/3), respectively. Grade 3 toxicities occurred in only three patients presenting with cytopenia. Importantly, MTX and MP demonstrated synergistic effects on ameliorating aGvHD in humanized xenogeneic murine model.

Conclusion

The current study suggests that mini-dose MTX combined with standard-dose MP could potentially become a novel first-line therapy for patients with aGvHD.

Polyclonal anti-thymocyte globulins for the prophylaxis of graft-versus-host disease after allogeneic stem cell or bone marrow transplantation in adults

BACKGROUND

Allogeneic haematopoietic stem cell transplantation (SCT) is an established treatment for many malignant and non-malignant haematological disorders. Graft-versus-host disease (GVHD), a condition frequently occurring after an allogeneic SCT, is the result of host tissues being attacked by donor immune cells. It affects more than half of the patients after transplant either as acute and or chronic GVHD. One strategy for the prevention of GVHD is the administration of anti-thymocyte globulins (ATGs), a set of polyclonal antibodies directed against a variety of immune cell epitopes, leading to immunosuppression and immunomodulation.

OBJECTIVES

To assess the effect of ATG used for the prevention of GVHD in patients undergoing allogeneic SCT with regard to overall survival, incidence and severity of acute and chronic GVHD, incidence of relapse, non-relapse mortality, graft failure and adverse events.

SEARCH METHODS

For this update we searched the CENTRAL, MEDLINE, Embase, trial registers and conference proceedings on the 18th November 2022 along with reference checking and contacting study authors to identify additional studies. We did not apply language restrictions.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) investigating the impact of ATG on GVHD prophylaxis in adults suffering from haematological diseases and undergoing allogeneic SCT. The selection criteria were modified from the previous version of this review. Paediatric studies and studies where patients aged < 18 years constituted more than 20 % of the total number were excluded. Treatment arms had to differ only in the addition of ATG to the standard GVHD prophylaxis regimen.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by the Cochrane Collaboration for data collection, extraction and analyses.

MAIN RESULTS

For this update we included seven new RCTs, leading to a total of ten studies investigating 1413 participants. All patients had a haematological condition which warranted an allogeneic SCT. The risk of bias was estimated as low for seven and unclear for three studies. ATG probably has little or no influence on overall survival (HR (hazard ratio) 0.93 (95 % confidence interval (CI) 0.77 to 1.13, nine studies, n = 1249, moderate-certainty evidence)). Estimated absolute effect: 430 surviving people per 1000 people not receiving ATG compared to 456 people surviving per 1000 people receiving the intervention (95 % CI 385 to 522 per 1000 people). ATG results in a reduction in acute GVHD II to IV with relative risk (RR) 0.68 (95 % CI 0.60 to 0.79, 10 studies, n = 1413, high-certainty evidence). Estimated absolute effect: 418 acute GVHD II to IV per 1000 people not receiving ATG compared to 285 per 1000 people receiving the intervention (95 % CI 251 to 331 per 1000 people). Addition of ATG results in a reduction of overall chronic GvHD with a RR of 0.53 (95 % CI 0.45 to 0.61, eight studies, n = 1273, high-certainty evidence). Estimated absolute effect: 506 chronic GVHD per 1000 people not receiving ATG compared to 268 per 1000 people receiving the intervention (95 % CI 228 to 369 per 1000 people). Further data on severe acute GVHD and extensive chronic GVHD are available in the manuscript. ATG probably slightly increases the incidence of relapse with a RR of 1.21 (95 % CI 0.99 to 1.49, eight studies,  n =1315, moderate-certainty evidence). Non relapse mortality is probably slightly or not affected by ATG with an HR of 0.86 (95 % CI 0.67 to 1.11, nine studies, n=1370, moderate-certainty evidence).   ATG prophylaxis may result in no increase in graft failure with a RR of 1.55 (95 % CI 0.54 to 4.44, eight studies, n = 1240, low-certainty evidence).  Adverse events could not be analysed due to the serious heterogeneity in the reporting between the studies, which limited comparability (moderate-certainty evidence) and are reported in a descriptive manner.   Subgroup analyses on ATG types, doses and donor type are available in the manuscript.

AUTHORS' CONCLUSIONS

This systematic review suggests that the addition of ATG during allogeneic SCT probably has little or no influence on overall survival. ATG results in a reduction in the incidence and severity of acute and chronic GvHD. ATG intervention probably slightly increases the incidence of relapse and probably does not affect the non relapse mortality. Graft failure may not be affected by ATG prophylaxis. Analysis of data on adverse events was reported in a narrative manner. A limitation for the analysis was the imprecision in reporting between the studies thereby reducing the confidence in the certainty of evidence.

Outcomes of patients with hematological malignancies who undergo unrelated donor hematopoietic stem cell transplantation with ATG-Fresenius versus ATG-Genzyme

To compare the outcomes of patients with hematological malignancies who received ATG-Fresenius (ATG-F) 20 mg/kg versus those who received ATG-Genzyme (ATG-G) 10 mg/kg in an unrelated donor hematopoietic stem cell transplantation (HSCT) procedure, a total of 186 patients who underwent their first allogeneic HSCT with an unrelated donor were retrospectively analyzed. One hundred and seven patients received ATG-F, and seventy-nine patients received ATG-G. Multivariate analysis showed that the type of ATG preparation had no effect on neutrophil engraftment (P = 0.61), cumulative incidence of relapse (P = 0.092), nonrelapse mortality (P = 0.44), grade II-IV acute graft-versus-host disease (GVHD) (P = 0.47), chronic GVHD (P = 0.29), overall survival (P = 0.795), recurrence-free survival (P = 0.945) or GVHD-free relapse-free survival (P = 0.082). ATG-G was associated with a lower risk of extensive chronic GVHD and a higher risk of cytomegaloviremia (P = 0.01 and HR = 0.41, P < 0.001 and HR = 4.244, respectively). The results of this study suggest that the preparation of rabbit ATG used for unrelated HSCT should be selected based on the incidence of extensive chronic GVHD of each center, and the posttransplant management strategy should be adjusted according to the ATG preparation.

Glucocorticoid and glycolysis inhibitors cooperatively abrogate acute graft-versus-host disease

Although glucorticosteroids (GCs) are the standard first-line therapy for acute graft-versus-host disease (aGvHD), nearly 50% of aGvHD patients have no response to GCs. The role of T cell metabolism in murine aGvHD was recently reported. However, whether GCs and metabolism regulators could cooperatively suppress T cell alloreactivity and ameliorate aGvHD remains to be elucidated. Increased glycolysis, characterized by elevated 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), and higher rates of glucose consumption and lactate production were found in T cells from aGvHD patients. Genetic upregulation of PFKFB3 induced T cell proliferation and differentiation into proinflammatory cells. In a humanized mouse model, PFKFB3-overexpressing or PFKFB3-silenced T cells aggravated or prevented aGvHD, respectively. Importantly, our integrated data from patient samples in vitro, in a humanized xenogeneic murine model of aGvHD and graft-versus-leukaemia (GVL) demonstrate that GCs combined with a glycolysis inhibitor could cooperatively reduce the alloreactivity of T cells and ameliorate aGvHD without loss of GVL effects. Together, the current study indicated that glycolysis is critical for T cell activation and induction of human aGvHD. Therefore, the regulation of glycolysis offers a potential pathogenesis-oriented therapeutic strategy for aGvHD patients. GCs combined with glycolysis inhibitors promises to be a novel first-line combination therapy for aGvHD patients.

Cytokine profiling during conditioning in haploidentical stem cell transplantation and its prognostic impact on early transplant outcomes

Cytokine storm development is a major cause of many transplant-related complications, especially during the conditioning regimen. This study aimed to characterize the cytokine profile and determine its prognostic impact during conditioning in patients undergoing subsequent haploidentical stem cell transplantation. A total of 43 patients were enrolled in this study. Sixteen cytokines associated with cytokine release syndrome (CRS) during anti-thymocyte globulin (ATG) treatment were quantified in patients undergoing haploidentical stem cell transplantation. Thirty-six (83.7%) patients developed CRS during ATG treatment; most of those cases (33/36; 91.7%) were classified as grade 1 CRS, whereas only three (7.0%) developed grade 2 CRS. CRS was observed more frequently on the first (15/43; 34.9%) and second day (30/43; 69.8%) of ATG infusion. No factors were identified that could predict the development of CRS on the first day of ATG treatment. Five of the 16 cytokines (interleukins 6, 8, and 10 (IL-6, IL-8, and IL-10), C-reactive protein (CRP), and procalcitonin (PCT)) were significantly elevated during ATG treatment, although only the level of IL-6, IL-10, and PCT were associated with the severity of CRS. However, neither CRS nor the cytokine levels significantly impacted the development of acute graft-versus-host disease (GVHD) or cytomegalovirus (CMV) infection or affected overall survival.

Different effects of thymoglobulin on acute leukemia with pre-transplant residual blasts in HLA mismatch transplantation

Anti-thymocyte globulin (ATG) is widely used to reduce acute and chronic graft-versus-host disease (a/cGVHD), one of the leading causes of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). As the removal of alloreactive T cells by ATG may also reduce the graft-versus-leukemia effect, the question of whether ATG use affects relapse incidence and survival outcomes in acute leukemia patients with pre-transplant bone marrow residual blasts (PRB) remains controversial. Here, we evaluated the impact of ATG on transplant outcomes in acute leukemia patients with PRB (n = 994) who underwent HSCT from HLA 1-allele mismatched unrelated donors (MMUD) or HLA 1-antigen mismatched related donors (MMRD). In MMUD with PRB (n = 560), multivariate analysis demonstrated that ATG use significantly decreased grade II-IV aGVHD (hazard ratio [HR], 0.474; P = 0.007) and non-relapse mortality (HR, 0.414; P = 0.029) and marginally improved extensive cGVHD (HR, 0.321; P = 0.054) and GVHD-free/relapse-free survival (HR, 0.750; P = 0.069). We concluded that ATG had different effects on transplant outcomes using MMRD and MMUD, and its use would be beneficial to decrease a/cGVHD without increasing non-relapse mortality and relapse incidence in acute leukemia patients with PRB following HSCT from MMUD.

Unique Reduced-Intensity Conditioning Haploidentical Peripheral Blood Stem Cell Transplantation Protocol for Patients with Hematologic Malignancy

Reduced-intensity conditioning (RIC) haploidentical (haplo-) hematopoietic stem cell transplantation (HSCT) requires more hematopoietic progenitor and stem cells (HPSCs) to promote engraftment and immune reconstitution and needs a stronger graft-versus-leukemia effect. Peripheral blood stem cells (PBSCs) offer advantages over bone marrow; however, the use of higher-dose non-T cell-depleted (non-TCD) in vitro PBSCs may increase the occurrence of severe graft-versus-host disease (GVHD). This prospective, single-arm clinical study was performed to investigate using high-dose non-TCD in vitro PBSCs as the graft source, using fludarabine/Ara-C/busulfan (FAB) as the conditioning regimen, using rabbit antithymocyte globulin to remove T cells in vivo, and enhancing GVHD prophylaxis with an IL-2 receptor antagonist in RIC-haplo-HSCT in patients with hematologic malignancies age 50 to 70 years or <50 years with comorbidities (Hematopoietic Cell Transplantation Comorbidity Index score ≥2) classified as intermediate to high risk. The primary endpoint was day 100 acute GVHD (aGVHD). A total of 47 patients were enrolled; the median age was 52 years (range, 30 to 68 years), the median duration of follow-up was 34 months (range, 2 to 99 months), and the medium-infused doses of mononuclear cells, CD34⁺ cells, and CD3⁺ cells were 15.93 × 10⁸/kg, 8.68 × 10⁶/kg, and 5.57 × 10⁸/kg, respectively. The cumulative incidence of grade II-IV aGVHD at day 100 was 30.3% (95% confidence interval [CI], 15.9% to 44.8%), and that of grade III-IV aGVHD was 10.2% (95% CI, .6% to 19.8%). The 2-year cumulative incidence of chronic GVHD (cGVHD) was 34.9% (95% CI, 19.0% to 50.8%). The 2-year cumulative incidences of localized and extensive cGVHD were 26.1% (95% CI, 11.80% to 40.40%) and 8.7% (95% CI, 3.26% to 20.65%), respectively. The 2-year cumulative incidence of relapse was 17.3% (95% CI, 5.1% to 29.5%), the 2-year overall survival rate was 71.2% (95% CI, 57.9% to 84.5%), and the 2-year disease-free survival rate was 66.2% (95% CI, 52.1% to 80.3%). The incidence of aGVHD was not high, and the overall efficacy was good. This study demonstrates that this unique RIC-haplo-PBSC transplantation protocol was effective in treating hematologic malignancies. Nonetheless, larger prospective multicenter clinical trials and experimental studies should be performed to further confirm our findings.

Comparison of haploidentical hematopoietic stem cell transplantation with chemotherapy in older adults with acute myeloid leukemia

Acute myeloid leukemia (AML) outcomes are very poor in older patients. Haploidentical stem cell transplantation (haplo-SCT) helps to achieve long-term survival. However, the benefit of haplo-SCT versus chemotherapy is unclear in older adults with AML. Outcomes were retrospectively compared among patients aged 55‒65 years for chemotherapy consolidation or haplo-SCT for AML in the first complete remission with intermediate to high-risk disease. Forty-six patients who underwent chemotherapy and 38 patients who underwent haplo-SCT were evaluated in the final analysis. Compared with the chemotherapy group, patients in the haplo-SCT group had significantly better overall survival (OS) (74.0% versus 23.9% at 36 months, p = 0.005) and leukemia-free survival (LFS) (74.0% versus 21.6%, p < 0.001). The cumulative incidence of relapse (CIR) was significantly lower in the haplo-SCT group (17.3% versus 75.4%, p < 0.001). Treatment-related mortality (TRM) was similar in the haplo-SCT and chemotherapy groups (7.9% versus 4.8%, p = 0.587). In the multivariate analysis, haplo-SCT was associated with improved OS, LFS, and decreased CIR. Haplo-SCT did not affect TRM. In conclusion, our data suggest that haploidentical transplant may be an alternative to consolidation chemotherapy as post-remission therapy in patients with intermediate or high-risk AML aged 55‒65 years. Further well-designed studies are needed to validate this result.

The role of allogeneic hematopoietic cell transplantation for chronic lymphocytic leukemia: A review

Although the use of allogeneic hematopoietic cell transplantation (HCT) for chronic lymphocytic leukemia (CLL) has declined with the development of novel targeted agents, it continues to play an important role for eligible patients with high-risk or heavily pretreated CLL who lack other treatment options. CLL is susceptible to a potent graft-versus-leukemia (GVL) effect which produces long-lasting remissions in 30-50% of transplanted patients. While allogeneic HCT is associated with significant risks of graft-versus-host disease (GVHD), infection, and non-relapse mortality (NRM), improvements in patient and donor selection, reduced intensity conditioning (RIC), GVHD prophylaxis, and supportive care have rendered this an increasingly safe and effective procedure in the current era. In this review, we discuss recent advances in allogeneic HCT for CLL, with a focus on the optimal evidence-based strategies to maximize benefit and minimize toxicity of this potentially curative cellular therapy.

Incomplete chimerism following myeloablative and anti-thymocyte globulin-conditioned hematopoietic cell transplantation is a risk factor for relapse and chronic graft-versus-host disease

BACKGROUND AIMS

The value of routine chimerism determination after myeloablative hematopoietic cell transplantation (HCT) is unclear, particularly in the setting of anti-thymocyte globulin (ATG)-based graft-versus-host disease (GVHD) prophylaxis.

METHODS

Blood samples were collected at 3 months post-HCT from 558 patients who received myeloablative conditioning and ATG-based GVHD prophylaxis. Chimerism was assessed using multiplex polymerase chain reaction of short tandem repeats in sorted T cells (CD3+) and leukemia lineage cells (CD13+CD33+ for myeloid malignancies and CD19+ for B-lymphoid malignancies). ATG exposure was determined using a flow cytometry-based assay. The primary outcomes of interest were relapse and chronic GVHD (cGVHD).

RESULTS

Incomplete (<95%) T-cell chimerism and leukemia lineage chimerism were present in 17% and 4% of patients, respectively. Patients with incomplete T-cell chimerism had a significantly greater incidence of relapse (36% versus 22%, subhazard ratio [SHR] = 2.03, P = 0.001) and lower incidence of cGVHD (8% versus 25%, SHR = 0.29, P < 0.001) compared with patients with complete chimerism. In multivariate modeling, patients with high post-transplant ATG area under the curve and any cytomegalovirus (CMV) serostatus other than donor/recipient seropositivity (non-D+R+) had an increased likelihood of incomplete T-cell chimerism. Patients with incomplete leukemia lineage chimerism had a significantly greater incidence of relapse (50% versus 23%, SHR = 2.70, P = 0.011) and, surprisingly, a greater incidence of cGVHD (45% versus 20%, SHR = 2.64, P = 0.003).

CONCLUSIONS

High post-transplant ATG exposure and non-D+R+ CMV serostatus predispose patients to incomplete T-cell chimerism, which is associated with an increased risk of relapse. The increased risk of cGVHD with incomplete B-cell/myeloid chimerism is a novel finding that suggests an important role for recipient antigen-presenting cells in cGVHD pathogenesis.

Lower dose of ATG combined with basiliximab for haploidentical hematopoietic stem cell transplantation is associated with effective control of GVHD and less CMV viremia

Currently, the graft-versus-host disease (GVHD) prophylaxis consists of an immunosuppressive therapy mainly based on antithymocyte globulin (ATG) or post-transplant cyclophosphamide (PTCy). GVHD remains a major complication and limitation to successful allogeneic haploidentical hematopoietic stem cell transplantation (haplo-HSCT). We modified the ATG-based GVHD prophylaxis with the addition of basiliximab in the setting of haplo-HSCT and attempted to explore the appropriate dosages. We conducted a retrospective analysis of 239 patients with intermediate- or high-risk hematologic malignancies who received haplo-HSCT with unmanipulated peripheral blood stem cells combined or not with bone marrow. All patients received the same GVHD prophylaxis consisting of the combination of methotrexate, cyclosporine or tacrolimus, mycofenolate-mofetil, and basiliximab with different doses of ATG (5-9mg/kg). With a median time of 11 days (range, 7-40 days), the rate of neutrophil engraftment was 96.65%. The 100-day cumulative incidences (CIs) of grade II-IV and III-IV aGVHD were 15.8 ± 2.5% and 5.0 ± 1.5%, while the 2-year CIs of total cGVHD and extensive cGVHD were 9.8 ± 2.2% and 4.1 ± 1.5%, respectively. The 3-year CIs of treatment-related mortality (TRM), relapse, overall survival (OS), and disease-free survival (DFS) were 14.6 ± 2.6%, 28.1 ± 3.4%, 60.9 ± 3.4%, 57.3 ± 3.4%, respectively. Furthermore, the impact of the reduction of the ATG dose to 6 mg/kg or less in combination with basiliximab on GVHD prevention and transplant outcomes among patients was analyzed. Compared to higher dose of ATG(>6mg/kg), lower dose of ATG (≤6mg/kg) was associated with a significant reduced risk of CMV viremia (52.38% vs 79.35%, P<0.001), while the incidences of aGVHD and cGVHD were similar between the two dose levels. No significant effect was found with regard to the risk of relapse, TRM, and OS. ATG combined with basiliximab could prevent GVHD efficiently and safely. The optimal scheme of using this combined regimen of ATG and basiliximab is that administration of lower dose ATG (≤6mg/kg), which seems to be more appropriate for balancing infection control and GVHD prophylaxis.

Optimal Active Anti-Thymocyte Globulin Exposure Associated with Minimum Risk of Virus Reactivation and Comparable Acute Graft-Versus-Host Disease Under Adult Myeloablative Haploidentical Peripheral Blood Stem Cell Transplantation

Anti-thymocyte globulin (ATG) is often included in the conditioning regimen to prevent graft-versus-host disease (GVHD) in allogeneic hematopoietic cell transplantation (allo-HCT). However, the risk of virus reactivation increases significantly. We conducted a single-center prospective study to identify the optimal ATG exposure that ensures engraftment, effectively prevents acute GVHD, and reduces the risk of virus reactivation without increasing relapse of malignant diseases in haploidentical peripheral blood stem cell transplantation (haplo-PBSCT). From September 2018 to June 2020, 106 patients (median age, 32 years) with malignant hematological diseases who received haplo-PBSCT for the first time were enrolled. All patients received 10 mg/kg rabbit ATG (thymoglobulin) divided for 4 days (days -5 to -2). Pre-transplant, post-transplant, and total areas under the concentration-time curve (AUCs) of active ATG were calculated. Total AUC of active ATG was shown to be the best predictor for virus reactivation and acute GVHD of grades II to IV or grades III and IV. The optimal total AUC range of active ATG was 100 to 148.5 UE/mL/day. The median time was 14 versus 13 days (P = .184) for myeloid engraftment and 13 versus 13 days (P = .263) for platelet engraftment in the optimal and non-optimal AUC groups, respectively. The optimal AUC group showed a lower cumulative incidence of cytomegalovirus (CMV) reactivation and persistent CMV viremia than the non-optimal AUC group: 60.6% (95% confidence interval [CI], 48.3%-73.1%) versus 77.1% (95% CI, 64.5%-87.7%; P = .016) and 31.5% (95% CI, 21.2%-45.3%) versus 56.3% (95% CI, 42.9%-70.4%; P = .007), respectively. The cumulative incidence of persistent Epstein-Barr virus (EBV) viremia in the optimal AUC group was significantly lower than the non-optimal total AUC group: 33.1% (95% CI, 22.5%-46.8%) versus 52.6% (95% CI, 39.3%-67.2%; P = .048). However, there was no difference in EBV reactivation (P = .752). Similar outcomes were observed for grade II to IV and grade III and IV acute GVHD between the two groups: 48.6% (95% CI, 36.8%-62.0%) versus 37.0% (95% CI, 24.8%-52.5%; P = .113) and 10.4% (95% CI, 4.8%-21.7%) versus 4.2% (95% CI, 1.0%-15.6%; P = .234, respectively. Relapse, non-relapse mortality, and disease-free survival demonstrated no significant differences between the two groups. But, overall survival at 2 years tended to increase in the optimal AUC group: 75.7% (95% CI, 62.4%-84.8%) versus 57.8% (95% CI, 42.4%-70.4%; P = .061). These data support an optimal active ATG exposure of 110 to 148.5 UE/mL/day in haplo-PBSCT. Individualized dosing of ATG in allo-HCT might reduce the risk of virus reactivation and effectively prevent acute GVHD simultaneously.

Optimizing antithymocyte globulin dosing in haploidentical hematopoietic cell transplantation: long-term follow-up of a multicenter, randomized controlled trial

Given that randomized studies testing the long-term impact of antithymocyte globulin (ATG) dosing are scarce, we report the results of an extended follow-up from the original trial. In our prospective, multicenter, randomized trial, 408 leukemia patients 14-65 years of age who underwent haploidentical hematopoietic cell transplantation (haplo-HCT) under our original "Beijing Protocol" were randomly assigned one-to-one to ATG doses of 7.5 mg/kg (n = 203, ATG-7.5) or 10 mg/kg (n = 205, ATG-10.0) at four sites. Extended follow-up (median 1968 d (range: 1300-2710 d) indicated comparable 5-year probabilities of moderate-to-severe chronic graft-versus-host disease (GVHD) (hazard ratio (HR): 1.384, 95% confidence interval (CI): 0.876-2.189, P = 0.164), nonrelapse mortality (HR: 0.814, 95% CI: 0.526-1.261, P = 0.357), relapse (HR: 1.521, 95% CI: 0.919-2.518, P = 0.103), disease-free survival (HR: 1.074, 95% CI: 0.783-1.473, P = 0.658), and GVHD-free/relapse-free survival (HR: 1.186, 95% CI: 0.904-1.555, P = 0.219) between groups (ATG-7.5 vs. ATG-10.0). The 5-year rate of late effects did not differ significantly. However, the cytomegalovirus/Epstein-Barr virus-related death rate was much higher in the ATG-10.0 cohort than in the ATG-7.5 cohort (9.8% vs. 1.5%; P = 0.003). In summary, patients undergoing haplo-HCT benefit from 7.5 mg/kg ATG compared to 10.0 mg/kg ATG based on a balance between GVHD and infection control. ATG (7.5 mg/kg) is potentially regarded as the standard regimen in the platform. These results support the optimization of ATG use in the "Beijing Protocol", especially considering the potential economic advantage in developing countries.

The impact of different doses of antithymocyte globulin conditioning on immune reconstitution upon hematopoietic stem cell transplantation

INTRODUCTION

Anti-thymocyte globulin (ATG) is used prior to allogeneic hematopoietic stem cell transplantation (allo-HSCT) for graft-versus-host disease (GVHD) prophylaxis. Two different ATG doses (7.5 or 10 mg/kg) were evaluated in comparison with a group without ATG therapy.

METHODS

We retrospectively analyzed 132 patients who were transplanted with HSCT without ATG (non-ATG), or who received 7.5 mg/kg ATG (ATG-7.5) or 10 mg/kg ATG (ATG-10) prior to transplantation. The immune cells (CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, CD19⁺ B cells and CD16⁺CD56⁺ NK cells) were examined in peripheral blood every three months post-HSCT for 12 months.

RESULTS

Compared with non-ATG group, combined ATG-7.5/ATG-10 groups had significantly lower CD3⁺CD4⁺ T cells and higher CD3⁺CD8⁺ T cells at 3, 6, 9, 12 months post-HSCT; thus, displaying a lower CD4/CD8 ratio in the ATG groups compared to non-ATG group. The ratio of CD19⁺ B cells was statistically lower (at 3rd month, p = .014; at 6th month, p = .025) in combined ATG-7.5/ATG-10 groups at 3 and 6 months post-HSCT, but not at 9 and 12 months after HSCT. The ratios of CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, CD19⁺ B cells and CD16⁺CD56⁺ NK cells were similar between the ATG-7.5 and ATG-10 groups at all examined time points. The overall survival (OS), progression-free survival (PFS), relapse and acute GVHD (aGVHD) were comparable among recipients without ATG therapy and with ATG-7.5 or/and ATG-10 therapies. Multivariate analysis revealed that immune cells ratios were not independent factors affecting prognosis.

CONCLUSION

The ATG therapy at higher and lower doses led to a delayed reconstitution of T cells and the inversion of CD4/CD8 ratio for at least one year after HSCT.

Incidence of refractory cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation

Post-transplant cytomegalovirus (CMV) disease can be almost completely avoided by current infection control procedures. However, CMV reactivation occurs in more than half of patients, and some patients can develop clinically resistant CMV infections. Whether resistance is due to the host's immune status or a viral resistance mutation is challenging to confirm. Therefore, a prospective observational analysis of refractory CMV infection was conducted in 199 consecutive patients who received allogeneic hematopoietic stem cell transplantation at a single institution. Among them, 143 (72%) patients received anti-CMV drugs due to CMV reactivation, and only 17 (8.5%) exhibited refractory CMV infection. These patients had clinically refractory infection. However, viral genome analysis revealed that only one patient exhibited a mutation associated with the anti-CMV drug resistance. Clinical resistance was mainly correlated with host immune factors, and the incidence of resistance caused by gene mutations was low at the early stage after a transplantation.

The consensus from The Chinese Society of Hematology on indications, conditioning regimens and donor selection for allogeneic hematopoietic stem cell transplantation: 2021 update

The consensus recommendations in 2018 from The Chinese Society of Hematology (CSH) on indications, conditioning regimens and donor selection for allogeneic hematopoietic stem cell transplantation (allo-HSCT) facilitated the standardization of clinical practices of allo-HSCT in China and progressive integration with the world. There have been new developments since the initial publication. To integrate recent developments and further improve the consensus, a panel of experts from the CSH recently updated the consensus recommendations, which are summarized as follows: (1) there is a new algorithm for selecting appropriate donors for allo-HSCT candidates. Haploidentical donors (HIDs) are the preferred donor choice over matched sibling donors (MSDs) for patients with high-risk leukemia or elderly patients with young offspring donors in experienced centers. This replaces the previous algorithm for donor selection, which favored MSDs over HIDs. (2) Patients with refractory/relapsed lymphoblastic malignancies are now encouraged to undergo salvage treatment with novel immunotherapies prior to HSCT. (3) The consensus has been updated to reflect additional evidence for the application of allo-HSCT in specific groups of patients with hematological malignancies (intermediate-risk acute myeloid leukemia (AML), favorable-risk AML with positive minimal residual disease, and standard-risk acute lymphoblastic leukemia). (4) The consensus has been updated to reflect additional evidence for the application of HSCT in patients with nonmalignant diseases, such as severe aplastic anemia and inherited diseases. (5) The consensus has been updated to reflect additional evidence for the administration of anti-thymocyte globulin, granulocyte colony-stimulating factors and post-transplantation cyclophosphamide in HID-HSCT.

A prognostic model (BATAP) with external validation for patients with transplant-associated thrombotic microangiopathy

Transplant-associated thrombotic microangiopathy (TA-TMA) is a potentially life-threatening complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT). Information on markers for early prognostication remains limited, and no predictive tools for TA-TMA are available. We attempt to develop and validate a prognostic model for TA-TMA. A total of 507 patients who developed TA-TMA following allo-HSCT were retrospectively identified and separated into a derivation cohort and a validation cohort according to the time of transplantation to perform external temporal validation. Patient age (OR 2.371, 95% CI 1.264-4.445), anemia (OR 2.836, 95% CI 1.566-5.138), severe thrombocytopenia (OR 3.871, 95% CI 2.156-6.950), elevated total bilirubin (OR 2.716, 95% CI 1.489-4.955) and proteinuria (OR 2.289, 95% CI 1.257-4.168) were identified as independent prognostic factors for the 6-month outcome of TA-TMA. A risk score model termed BATAP (Bilirubin, Age, Thrombocytopenia, Anemia, Proteinuria) was then constructed according to the regression coefficients. The validated c-statistics were 0.816 (95% CI 0.766-0.867) and 0.756 (95% CI 0.696-0.817) in the internal and external validation, respectively. Calibration plots indicated that the model-predicted probabilities correlated well with the actual observed frequencies. This predictive model may facilitate the prognostication of TA-TMA and contribute to the early identification of high-risk patients.

Comparison of 2 Different Doses of Antithymocyte Globulin in Conditioning Regimens for Haploidentical Hematopoietic Stem Cell Transplantation

OBJECTIVES

Antithymocyte globulin is extensively used for prophylaxis of graft-versus-host disease in patients undergoing haploidentical hematopoietic stem cell transplantation. However, different doses of antithymocyte globulin are administered in clinical practice. This study aimed to identify the optimal dose of antithymocyte globulin (thymoglobulin) in haploidentical hematopoietic stem cell transplantation.

MATERIALS AND METHODS

We retrospectively analyzed the effects of 10 mg/kg (2.5 mg/kg on days -5 to -2) versus 7.5 mg/kg thymoglobulin (2.5 mg/kg on days -4 to -2) on patients receiving haploidentical hematopoietic stem cell transplantation with myeloablative conditioning.

RESULTS

We observed significant differences between the 2 treatment groups with regard to cumulative incidence of grade II to IV acute graft-versus-host disease (15.3% vs 14.6%; P = .93) and 3-year chronic graft-versus-host disease (12.1% vs 14.3%; P = .77). The probabilities of 3-year overall survival (68.9% vs 73.5%; P = .98) and graft-versus-host disease-free/relapse-free survival (66.7% vs 53.1%; P = .14) were comparable between the 2 groups. However, there was a trend for lower cumulative incidence of hemorrhagic cystitis in the 7.5 mg/kg treatment group compared with the 10 mg/kg treatment group (40.7% vs 24.4%; P = .07).

CONCLUSIONS

For patients who received a reduced dose of antithymocyte globulin (7.5 vs 10 mg/kg), there was no impaired effect on prophylaxis of graft-versus-host disease, with a trend of reduced incidence of hemorrhagic cystitis. Further studies of the 7.5 mg/kg dose of antithymocyte globulin are warranted for patients receiving haploidentical hematopoietic stem cell transplantation.

A biomarker-guided, prospective, phase 2 trial of pre-emptive graft-versus-host disease therapy using anti-thymocyte globulin

BACKGROUND AIMS

Intensified immunosuppressive prophylaxis for graft-versus-host disease (GVHD) may be toxic and therefore warranted only in patients at high risk of developing GVHD. In patients who underwent allogeneic hematopoietic cell transplant at the authors' center, high serum soluble IL-2 receptor alpha (sIL-2Rα) and low IL-15 levels on day 7 post-transplant were found to predict a high risk of developing clinically significant GVHD (sGVHD), defined as grade 2-4 acute GVHD or moderate to severe chronic GVHD.

METHODS

This was a prospective, phase 2 trial in which high-risk patients (serum sIL-2Rα >4500 ng/L or IL-15 <31 ng/L) received rabbit anti-thymocyte globulin (ATG) 3 mg/kg on day 8 post-transplant. Controls consisted of patients who had their sIL-2Rα/IL-15 levels measured but did not participate in the trial. A total of 68 trial patients and 143 controls were accrued to this study. The primary endpoint was incidence of sGVHD.

RESULTS

There was a reduction in sGVHD in high-risk trial patients (received day 8 ATG) compared with high-risk controls (did not receive day 8 ATG) (sub-hazard ratio [SHR] = 0.48, P < 0.05). There was no significant difference between the groups in overall survival or relapse; however, there was a greater incidence of non-GVHD-associated non-relapse mortality in high-risk trial patients (SHR = 3.73, P < 0.05), mostly related to infections. This may be due in part to the biomarkers ineffectively stratifying GVHD risk.

CONCLUSIONS

Pre-emptive ATG therapy is both feasible and effective at reducing sGVHD without increasing relapse. Further mitigation strategies are needed to reduce the risk of infection associated with intensified GVHD prophylaxis. This study was registered at ClinicalTrials.gov (NCT01994824).

The time-dependent effects of early-onset Epstein-Barr viremia on adult acute leukemia patients following allo-HSCT with ATG-containing MAC regimen

Epstein-Barr virus (EBV) viremia is a common complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The purpose of this study was to evaluate the impacts of early-onset EBV viremia in acute leukemia (AL) patients who underwent allo-HSCT with anti-thymocyte globulin (ATG)-containing myeloablative conditioning (MAC) regimen. Two hundred and ninety-six patients were included between January 2013 and December 2015. In 126 patients (42.6%) who developed early-onset EBV viremia, with a median time of 48 (range 18~99) days after allo-HSCT. The cumulative incidence of EBV viremia at 30 and 90 days after allo-HSCT were 4.1 and 39.9%, respectively. Prognostic analysis showed that the adjusted overall survival in early-EBV^pos group was significantly lower than early-EBV^neg group within the first 26.7 months after allo-HSCT [hazard ratio (HR), 1.63, P = 0.012], but significantly higher than those afterward (after 26.7 months: HR 0.11, P = 0.035); for the adjusted event-free survival, early-EBV^pos group was significantly inferior in early-EBV^pos group within the first 10.8 months after transplantation (HR: 1.55, P = 0.042), and this adverse effect was not detected any more after 10.8 months (HR: 0.58, P = 0.107). Compared with early-EBV^neg group after adjusting by aGVHD and CMV viremia, HR for death from transplant-related mortality was 2.78-fold higher in patients with early-EBV viremia in piecewise constant Cox analysis (P = 0.006), and this adverse effect was not detected any more after the cut-point time (HR: 0.67, P = 0.361). No differences in terms of relapse and relapse mortality were observed between early-EBV^pos and early-EBV^neg group (P > 0.05). In conclusion, the impacts on transplant outcomes of early-EBV viremia were time-dependent, which may help to optimize management strategies for early-EBV viremia after allo-HSCT, especially in AL patients with ATG-containing MAC regimen.

GVHD Prophylaxis 2020

Graft-vs. host disease (GVHD), both acute and chronic are among the chief non-relapse complications of allogeneic transplantation which still cause substantial morbidity and mortality despite significant advances in supportive care over the last few decades. The prevention of GVHD therefore remains critical to the success of allogeneic transplantation. In this review we briefly discuss the pathophysiology and immunobiology of GVHD and the current standards in the field which remain centered around calcineurin inhibitors. We then discuss important translational advances in GVHD prophylaxis, approaching these various platforms from a mechanistic standpoint based on the pathophysiology of GVHD including in-vivo and ex-vivo T-cell depletion alongwith methods of selective T-cell depletion, modulation of T-cell co-stimulatory pathways (checkpoints), enhancing regulatory T-cells (Tregs), targeting T-cell trafficking as well as cytokine pathways. Finally we highlight exciting novel pre-clinical research that has the potential to translate to the clinic successfully. We approach these methods from a pathophysiology based perspective as well and touch upon strategies targeting the interaction between tissue damage induced antigens and T-cells, regimen related endothelial toxicity, T-cell co-stimulatory pathways and other T-cell modulatory approaches, T-cell trafficking, and cytokine pathways. We end this review with a critical discussion of existing data and novel therapies that may be transformative in the field in the near future as a comprehensive picture of GVHD prophylaxis in 2020. While calcineurin inhibitors remain the standard, post-transplant eparinsphamide originally developed to facilitate haploidentical transplantation is becoming an attractive alternative to traditional calcinuerin inhibitor based prophylaxis due to its ability to reduce severe forms of acute and chronic GVHD without compromising other outcomes, even in the HLA-matched setting. In addition T-cell modulation, particularly targeting some important T-cell co-stimulatory pathways have resulted in promising outcomes and may be a part of GVHD prophylaxis in the future. Novel approaches including targeting early events in GVHD pathogenesis such as interactions bvetween tissue damage associated antigens and T-cells, endothelial toxicity, and T-cell trafficking are also promising and discussed in this review. GVHD prophylaxis in 2020 continues to evolve with novel exicitng therapies on the horizon based on a more sophisticated understanding of the immunobiology of GVHD.

Comparison of alemtuzumab, anti-thymocyte globulin, and post-transplant cyclophosphamide for graft-versus-host disease and graft-versus-leukemia in murine models

Graft-versus-host disease is a major complication after allogeneic hematopoietic stem cell transplantation for hematological malignancies. Immunosuppressive drugs, such as anti-thymocyte globulin, alemtuzumab, and post-transplant cyclophosphamide, have been used to prevent graft-versus-host disease in HLA-mismatched haploidentical hematopoietic stem cell transplantation. Here, we investigated whether these drugs could ameliorate graft-versus-host disease without diminishing the graft-versus-leukemia effect by using a xenogeneic transplanted graft-versus-host disease/graft-versus-leukemia model. Anti-thymocyte globulin treatment diminished graft-versus-host disease symptoms, completely depleted the infiltration of inflammatory cells in the liver and intestine, and led to prolonged survival. By contrast, improvement after post-transplant cyclophosphamide treatment remained minimal. Alemtuzumab treatment modestly prolonged survival despite an apparent decrease of Tregs. In the graft-versus-leukemia model, 1.5 to 2.0 mg/kg of anti-thymocyte globulin and 0.6 to 0.9 mg/kg of alemtuzumab reduced graft-versus-host disease with minimal loss of graft-versus-leukemia effect. Mice treated with 400 mg/kg of post-transplant cyclophosphamide did not develop graft-versus-host disease or leukemia, but it was difficult to evaluate the graft-versus-leukemia effect due to the sensitivity of A20 cells to cyclophosphamide. Although the current settings provide narrow optimal therapeutic windows, further studies are warranted to maximize the benefits of each immunosuppressant.

Efficacy of low dose antithymocyte globulin on overall survival, relapse rate, and infectious complications following allogeneic peripheral blood stem cell transplantation for leukemia in children

Antithymocyte globulin (ATG) and anti-T lymphocyte globulin (ATLG) have been widely used to prevent graft-versus-host disease (GvHD), each with distinct properties and noninterchangeable doses. However, the optimal dose of ATG in children undergoing allo-PBSCT for leukemia has not yet been established. Therefore, the impact of ATG dose on overall survival (OS), relapse, GvHD, and infectious complications was investigated. Patients administered high dose (unrelated: 7.5 mg/kg, haploidentical: 10.0 mg/kg) and low dose (unrelated: 3.75 mg/kg, haploidentical: 5.0 mg/kg) ATG during two consecutive time periods were compared. There were 78 (39.8%) patients in the low dose group and 118 (60.2%) in the high dose group. OS was superior in the low dose group compared to the high dose group (P = 0.017), and relapse incidence was significantly lower in the low dose group (P = 0.022). Cumulative incidences of acute and chronic GvHD were similar between the groups (P = 0.095 and P = 0.672, respectively). Cytomegalovirus reactivation (70.3% vs. 51.3%, P = 0.007), Epstein-Barr virus reactivation (81.4% vs. 39.7%, P < 0.001), and invasive bacterial infections (12.7% vs. 0%, P = 0.001) post transplant were more frequent in the high dose group compared to the low dose group. Therefore, low dose ATG is more optimal in pediatric allo-PBSCT providing better OS while lowering the risk of relapse and infectious complications.

[Optimization of ATG dose in haploid hematopoietic stem cell transplantation for hematologic malignancies]

Objective: To compare the clinical efficacy of different doses of rabbit antithymocyte globulin (rATG) in haplo-HSCT in the treatment of hematologic malignancies. Methods: Malignant hematological patients treated at our hospital from March 2013 to December 2018 were retrospectively analyzed. These patients were divided into three groups as per three doses of ATG (6 mg/kg, 7.5 mg/kg, and 9 mg/kg) in the conditioning regimens. The transplant outcomes were compared in terms of the occurrence of acute graft versus host disease (GVHD) , infection, and survival. Results: ①Total 288 patients were enrolled in the study, including 182 men and 106 women, with a median age of 18 (6-62) years. Total 110 patients were diagnosed with acute lymphoblastic leukemia (ALL) , 128 with acute myelogenous leukemia (AML) , 8 with chronic myeloid leukemia (CML) , 28 with myelodysplastic syndrome (MDS) , and 14 with mixed cell leukemia (MAL) . There were 159 patients in the ATG-6 group, 72 in the ATG-7.5 group, and 57 in the ATG-9 group. The median follow-up time of post transplantation was 14 (0.2-74) months. ②The incidence of neutrophil engraftment (96.9% , 97.2% , and 96.5% , respectively) and platelet engraftment (92.5% , 87.5% , and 86% , respectively) did not significantly differ among the ATG-6, ATG-7.5, and ATG-9 groups (P=0.972, P=0.276) . The incidence of grades 2-4 acute GVHD was 14.5% , 11.1% , and 8.8% in the three groups, respectively (P=0.493) , chronic GVHD incidence in the three group was 8.8% , 14.3% and 12.0% , respectively (P=0.493) . The infection rates of CMV and EBV in the ATG-9 group (77.2% and 12.5% ) were significantly higher than those in the ATG-6 (43.3% and 3.5% ) , and ATG -7.5 group (44.4% and 1.5% ) (P<0.001 and P=0.033, respectively) . ③Among the three groups, there were no significant difference in the 3-year overall survival [68.5% (95% CI 60.3% -77.9% ) , 60.1% (95% CI 48.3% -74.8% ) , 64.7% (95% CI 51.9% -80.7% ) ], cumulative incidences of relapse [34.6% (95% CI 34.3% -35.1% ) , 38.0% (95% CI 37.3% -38.7% ) , 20.6% (95% CI 20.0% -21.3% ) ], disease-free survival [53.3% (95% CI 44.9% -63.4% ) , 51.9% (95% CI 41% -65.8% ) , 63.9% (95% CI 51.9% -78.7% ) ] and non-relapse mortality [24.2% (95% CI 23.8% -24.5% ) , 26.0% (95% CI 25.4% -26.6% ) , 23.6% (95% CI 26.3% -28.2% ) ] (P=0.648, P=0.165, and P=0.486 and P=0.955) . Conclusion: Low dose (6 mg/kg) of rATG may increase the risk of grade Ⅱ-Ⅳ aGVHD, and a high dose (9 mg/kg) of ATG could significantly increase the risk of CMV and EBV infection. Median dose (7.5 mg/kg) of ATG is expected to reduce the incidence of moderate to severe aGVHD and viral infections without increasing the mortality.

Antithymocyte Globulin for Matched Sibling Donor Transplantation in Patients With Hematologic Malignancies: A Multicenter, Open-Label, Randomized Controlled Study

PURPOSE

The role of antithymocyte globulin (ATG) in preventing acute graft-versus-host disease (aGVHD) after HLA-matched sibling donor transplantation (MSDT) is still controversial.

PATIENTS AND METHODS

We performed a prospective, multicenter, open-label, randomized controlled trial (RCT) across 23 transplantation centers in China. Patients ages 40-60 years with standard-risk hematologic malignancies with an HLA-matched sibling donor were randomly assigned to an ATG group (4.5 mg/kg thymoglobulin plus cyclosporine [CsA], methotrexate [MTX], and mycophenolate mofetil [MMF]) and a control group (CsA, MTX, and MMF). The primary end point of this study was grade 2-4 aGVHD on day 100.

RESULTS

From November 2013 to April 2018, 263 patients were enrolled. The cumulative incidence rate of grade 2-4 aGVHD was significantly reduced in the ATG group (13.7%; 95% CI, 13.5% to 13.9%) compared with the control group (27.0%; 95% CI, 26.7% to 27.3%; P = .007). The ATG group had significantly lower incidences of 2-year overall chronic GVHD (27.9% [95% CI, 27.6% to 28.2%] v 52.5% [95% CI, 52.1% to 52.9%]; P < .001) and 2-year extensive chronic GVHD (8.5% [95% CI, 8.4% to 8.6%] v 23.2% [95% CI, 22.9% to 23.5%]; P = .029) than the control group. There were no differences between the ATG and control groups with regard to cytomegalovirus reactivation, Epstein-Barr virus reactivation, 3-year nonrelapse mortality (NRM), 3-year cumulative incidence of relapse (CIR), 3-year overall survival, or 3-year leukemia-free survival. Three-year GVHD relapse-free survival was significantly improved in the ATG group (38.7%; 95% CI, 29.9% to 47.5%) compared with the control group (24.5%; 95% CI, 16.9% to 32.1%; P = .003).

CONCLUSION

Our study is the first prospective RCT in our knowledge to demonstrate that ATG can effectively decrease the incidence of aGVHD after MSDT in the CsA era without affecting the CIR or NRM.

Hematopoietic cell transplant outcomes after myeloablative conditioning with fludarabine, busulfan, low-dose total body irradiation, and rabbit antithymocyte globulin

Optimal conditioning and graft-vs-host disease (GVHD) prophylaxis for hematopoietic cell transplantation (HCT) are unknown. Here, we report on outcomes after low toxicity, myeloablative conditioning consisting of fludarabine, busulfan, and 4 Gy total body irradiation, in combination with thymoglobulin and post-transplant methotrexate and cyclosporine. We retrospectively studied 700 patients with hematologic malignancies who received blood stem cells from 7 to 8/8 HLA-matched unrelated or related donors. Median follow-up of surviving patients was 5 years. At 5 years, overall survival (OS), relapse-free survival (RFS), and chronic GVHD/relapse-free survival (cGRFS) were 58%, 55%, and 40%. Risk factors for poor OS, RFS, and cGRFS were (1). high to very high disease risk index (DRI), (2). high recipient age, and (3). cytomegalovirus (CMV)-seropositive recipient with seronegative donor (D-R+). The latter risk factor applied particularly to patients with lymphoid malignancies. Neither donor other than HLA-matched sibling (7-8/8 unrelated) nor one HLA allele mismatch was risk factors for poor OS, RFS, or cGRFS. In conclusion, the above regimen results in excellent long-term outcomes. The outcomes are negatively impacted by older age, high or very high DRI, and CMV D-R+ serostatus, but not by donor unrelatedness or one HLA allele mismatch.

Antirelapse effect of pretransplant exposure to rabbit antithymocyte globulin

It remains unknown why rabbit antithymocyte globulin (ATG; Thymoglobulin) has not affected relapse after hematopoietic cell transplantation (HCT) in randomized studies. We hypothesized that high pre-HCT ATG area under the curve (AUC) would be associated with a low incidence of relapse, whereas high post-HCT AUC would be associated with a high incidence of relapse. We measured serum levels of ATG capable of binding to mononuclear cells (MNCs), lymphocytes, T cells, CD4 T cells, or CD33 cells. We estimated pre- and post-HCT AUCs in 152 adult recipients of myeloablative conditioning and blood stem cells. High pre-HCT AUCs of MNC- and CD33 cell-binding ATG were associated with a low incidence of relapse and high relapse-free survival (RFS). There was a trend toward an association of high post-HCT AUC of lymphocyte-binding ATG with a high incidence of relapse and low RFS. High pre-HCT AUCs were also associated with faster engraftment and had no impact on graft-versus-host disease (GVHD) or fatal infections. High post-HCT AUCs were associated with a low risk of GVHD, seemed associated with an increased risk of fatal infections, and had no impact on engraftment. In conclusion, pre-HCT AUC seems to have a positive, whereas post-HCT AUC seems to have a negative, impact on relapse.

Similar transplant outcomes between haploidentical and unrelated donors after reduced-intensity conditioning with busulfan, fludarabine, and anti-thymocyte globulin in patients with acute leukemia or myelodysplastic syndrome

Background

Although T-cell-replete hematopoietic cell transplantation (HCT) from haploidentical donors (HIDs) using anti-thymocyte globulin (ATG) has shown promising outcomes, previous studies often adopted heterogenous graft sources and conditioning.

Methods

We retrospectively compared HCT outcomes from 62 HIDs, 36 partially-matched unrelated donors (PUDs), and 55 matched unrelated donors (MUDs) in patients with acute leukemia or myelodysplastic syndrome using the same graft source of peripheral blood and a reduced intensity conditioning of busulfan, fludarabine, and ATG.

Results

The estimates of 3-yr disease-free survival (DFS) and overall survival (OS) rates were not significantly different among the MUD, HID, and PUD groups, at 46%, “41%, and 36%” for the DFS rate (P=0.844), and 55%, 45%, and 45% for the OS rate (P=0.802), respectively. Cumulative incidence of relapse and non-relapse mortality at 3 yr was similar among different donor types. Subsequent multivariable analyses showed that the sex of the patient (male) and a high/very high disease risk index were independently associated with poorer DFS and OS, while the donor type was not.

Conclusion

T-cell replete HCT from HIDs using an ATG-containing reduced intensity conditioning regimen may be a reasonable option in the absence of matched related donors in patients with acute leukemia or myelodysplastic syndrome.

[Risk factors analysis for steroid-resistant acute graft versus host disease after haploidentical hematopoietic stem cell transplantation]

目的

分析单倍型造血干细胞移植（haplo-HSCT）后糖皮质激素耐药急性移植物抗宿主病（GVHD）的危险因素。

方法

回顾性分析2010年1月至2011年12月在北京大学血液病研究所接受haplo-HSCT后并发急性GVHD的成人急性髓系白血病/骨髓增生异常综合征患者的临床资料。

结果

共有85例急性GVHD患者纳入研究，男55例，女30例，中位年龄30（19~67）岁。糖皮质激素治疗后达到完全缓解（CR）53例（62.4%），部分缓解（PR）6例（7.1%），未缓解（NR）26例（30.6%）。Ⅰ/Ⅱ、Ⅲ/Ⅳ度急性GVHD组糖皮质激素治疗的CR率分别为66.2%（51/77）、25.0%（2/8）（χ²=3.639，P=0.048）；累及1个、2个靶器官急性GVHD组糖皮质激素治疗的CR率分别为77.4%（48/62）、21.7%（5/23）（χ²=22.157，P<0.001）；明尼苏达危险度积分标危、高危组糖皮质激素治疗的CR率分别为67.5%（52/77）、12.5%（1/8）（χ²=7.153，P=0.004）。单因素和多因素分析均显示明尼苏达危险度积分高危和移植物单个核细胞量≥8.33×10⁸/kg是发生糖皮质激素耐药急性GVHD的独立危险因素。明尼苏达积分标危组（77例）、高危组（8例）移植后22个月总生存率分别为（90.3±3.8）%、（75.0±15.3）%（χ²=2.831，P=0.092）；糖皮质激素治疗CR组（53例）、非CR组（32例）移植后22个月总生存率分别为（95.2±3.4）%、（78.6±7.9）%（χ²=5.287，P=0.021）。

结论

明尼苏达危险度积分和移植物单个核细胞数可以预测haplo-HSCT后糖皮质激素耐药的急性GVHD。

Impacts of thymoglobulin in patients with acute leukemia in remission undergoing allogeneic HSCT from different donors

Antithymocyte globulin (ATG) is widely used to reduce acute graft-versus-host disease (aGVHD) and chronic GVHD (cGVHD). To clarify the different impacts of ATG for conditioning across different donor types, we retrospectively analyzed patients with acute leukemia (n = 6617) who underwent hematopoietic stem cell transplantation between 2008 and 2015 with ATG (n = 279) or without ATG (n = 6338). Because thymoglobulin is the only ATG drug approved for GVHD prophylaxis in Japan since September 2008, we included thymoglobulin alone in the present analysis. The survivors' median follow-up time was 1081 days. Patients were categorized into 5 groups: cord blood (CB; n = 1915), matched related donor (n = 1772), 1-antigen mismatched related donor (1-MMRD; n = 225), matched unrelated donor (MUD; n = 1742), and 1-allele mismatched unrelated donor (1-MMUD; n = 963). In multivariate analysis, ATG decreased overall survival (hazard ratio [HR], 1.403; P = .054) and GVHD-free/relapse-free survival (GRFS) (HR, 1.458; P = .053) in association with increased nonrelapse mortality (NRM) (HR, 1.608; P =03) with CB, whereas it improved GRFS (HR, 0.515; P < .01) and decreased grades II to IV aGVHD (HR, 0.576; P < .01), extensive cGVHD (HR, 0.460; P = .02), and NRM (HR, 0.545; P = .03) with 1-MMUD. ATG did not impact survival with 1-MMRD and MUD. The use of ATG in conditioning is beneficial due to the reduction in acute/chronic GVHD without increasing NRM or disease relapse only in 1-MMUD transplantation. On the other hand, ATG is not recommended for CB transplantation.

High incidence of Pneumocystis jirovecii pneumonia in allogeneic hematopoietic cell transplant recipients in the modern era

BACKGROUND

International guidelines for Pneumocystis jirovecii pneumonia (PJP) prevention recommend prophylaxis for ≥6 months following allogeneic hematopoietic cell transplantation, and longer in patients with graft-versus-host disease (GVHD) or on immunosuppressive therapy (IST). These recommendations are based on cohorts of patients who did not routinely receive anti-thymocyte globulin (ATG) for GVHD prophylaxis.

METHODS

We performed a retrospective chart review of 649 patients, all of whom received ATG as part of GVHD prophylaxis.

RESULTS

The cumulative incidence of definite PJP was 3.52% at both 3 and 5 years (median follow up, 1648 days for survivors). PJP occurred in 13 non-GVHD patients between days 207 and 508, due in part to low CD4 T-cell counts (<200 CD4 T cells/µL). PJP occurred in eight GVHD patients between days 389 and 792, due in part to non-adherence to PJP prophylaxis guidelines (discontinuation of PJP prophylaxis at <3 months after discontinuation of IST). Breakthrough PJP infection was not observed in patients receiving prophylaxis with cotrimoxazole, dapsone or atovaquone, whereas three cases were observed with inhaled pentamidine.

DISCUSSION

In conclusion, for non-GVHD patients receiving ATG-containing GVHD prophylaxis, 6 months of PJP prophylaxis is inadequate, particularly if the CD4 T-cell count is <200 cells/µL or if there is a high incidence of PJP in the community. For patients with GVHD receiving ATG-containing GVHD prophylaxis, continuing PJP prophylaxis until ≥3 months post-discontinuation of IST is important. Cotrimoxazole, dapsone and atovaquone are preferred over inhaled pentamidine.

Reduced risk of chronic GVHD by low-dose rATG in adult matched sibling donor peripheral blood stem cell transplantation for hematologic malignancies

The optimal rabbit anti-thymocyte globulin (rATG) graft-versus-host disease (GVHD) prophylaxis regimen in matched sibling donor peripheral blood stem cell transplantation (MSD-PBSCT) remains to be elucidated. In this prospective study, we used low-dose rATG for GVHD prophylaxis in patients or donors aged ≥ 40 years with hematological malignancies receiving MSD-PBSCT. rATG was administered to 40 patients at an intravenous dose of 5 mg/kg divided over day 5 and day 4 before graft infusion. No graft failure occurred. Median times to leukocyte engraftment and platelet engraftment were 11.0 days and 13.9 days. The cumulative incidence of grades 2–4 and grades 3–4 acute GVHD at day +100 was 30.0% and 2.6%. The 2-year cumulative incidence of extensive chronic GVHD and severe chronic GVHD was 11.4% and 14.7%. 93.5% (29/31) of patients had discontinued immunosuppressive medication within 3 years after transplantation. The 2-year cumulative incidence of transplant-related mortality (TRM) and relapse was 14.0% and 22.6%. The cumulative incidence of cytomegalovirus reactivation, Epstein–Barr virus reactivation, and fungal infection was 22.3%, 12.9%, and 12.5%. Kaplan–Meier estimates for overall survival, disease-free survival, and GVHD-free and relapse-free survival 3 years after transplantation were 68.9%, 68.9%, and 54.0%. rATG for GVHD prophylaxis is tolerable and efficacious at a 5 mg/kg total dose administered over 2 days (days −5 to −4) in patients receiving allogeneic MSD-PBSCT.

Unmanipulated haploidentical hematopoietic stem cell transplantation using very low-dose antithymocyte globulin and methylprednisolone in adults with relapsed/refractory acute leukemia

Allogeneic hematopoietic stem cell transplantation (HSCT) could be the only curative therapy for patients with relapsed/refractory acute leukemia (RRAL). Many reports have described unmanipulated haploidentical HSCT (HID-HSCT) using high-dose antithymocyte globulin (ATG). However, the transplant outcomes of HID-HSCT using very low-dose ATG (thymoglobulin, 2-2.5 mg/kg) and methylprednisolone (mPSL, 1 mg/kg) for patients with RRAL have not been reported. We compared the outcomes of 46 patients with RRAL who underwent HID-HSCT using very low-dose ATG (thymoglobulin) and mPSL with the outcomes of 72 patients who underwent non-HID-HSCT. Patient characteristics differed regarding conditioning intensity (myeloablative; 19.6% in HID-HSCT vs. 61.1% in non-HID-HSCT, P < 0.001) and having undergone multiple HSCT (26.1% vs. 11.1%, P = 0.045). However, we found no significant differences in the 1-year overall survival (OS, 31.7% vs. 29.1%; P = 0.25), disease-free survival (DFS, 20.5% vs. 23.7%; P = 0.23), cumulative incidence of relapse (CIR, 40.0% vs. 42.8%; P = 0.92), non-relapse mortality (NRM, 39.5% vs. 33.5%; P = 0.22), or 100-day grade II-IV acute graft-versus-host disease (32.6% vs. 34.7%; P = 0.64) following HID-HSCT vs. non-HID-HSCT, respectively. Subgroup analysis stratified by disease and intensity of conditioning regimen demonstrated the same results between HID-HSCT and non-HID-HSCT. Furthermore, multivariate analysis showed that HID-HSCT was not an independent prognostic factor for OS (hazard ratio (HR) = 0.95 [95% confidence interval (CI), 0.58-1.58]), DFS (HR = 1.05 [95%CI, 0.67-1.68]), CIR (HR = 0.84 [95%CI, 0.48-1.47]), or NRM (HR = 1.28 [95%CI, 0.66-2.46]). In summary, transplant outcomes for RRAL were comparable in the HID-HSCT and non-HID-HSCT groups. HID-HSCT using very low-dose ATG and mPSL for RRAL may be a viable alternative to non-HID-HSCT.

Risk factors for chronic graft-versus-host disease after anti-thymocyte globulin-based haploidentical hematopoietic stem cell transplantation in acute myeloid leukemia

Chronic graft-versus-host disease (cGVHD) is a major complication following unmanipulated haploidentical hematopoietic stem cell transplantation (haplo-HSCT). We aimed to identify the risk factors for cGVHD in patients who underwent anti-thymocyte globulin-based haplo-HSCT for acute myeloid leukemia (n = 280). The diagnosis of cGVHD was in accordance with the National Institutes of Health consensus criteria. A total of 169 patients suffered from cGVHD. The patients who had 3 loci mismatched had a higher 8-year incidence of cGVHD (total, 66.0% vs. 53.7%, P = 0.031; moderate to severe, 42.4% vs. 30.1%, P = 0.036) than the patients who had 1 to 2 loci mismatched. The patients who had maternal donors had a higher 8-year incidence of moderate to severe cGVHD (49.2% vs. 32.9%, P = 0.024) compared with the patients who had other donors. The patients who had grades III to IV acute GVHD (aGVHD) had higher 8-year incidence of cGVHD (total, 88.0% vs. 50.4%, P < 0.001; moderate to severe, 68.0% vs. 27.0%, P < 0.001) compared with the patients without aGVHD. In multivariate analysis, grades III to IV aGVHD was the only independent risk factor for cGVHD. Thus, further interventions should be considered in patients with severe aGVHD to prevent cGVHD.

Two dose levels of rabbit antithymocyte globulin as graft-versus-host disease prophylaxis in haploidentical stem cell transplantation: a multicenter randomized study

BACKGROUND

The optimal dose of rabbit antithymocyte globulin (ATG, ImtixSangstat) minimizing infections without increasing graft-versus-host disease (GVHD) is unknown in T cell-replete, G-CSF-primed haploidentical hematopoietic stem cell transplantation (haplo-HSCT).

METHODS

Four hundred and eight patients were enrolled in this multicenter study to evaluate the effect of 7.5 mg/kg and 10.0 mg/kg rabbit ATG on viral infections and GVHD prophylaxis after haplo-HSCT. The primary endpoint was EBV DNAemia within 1 year posttransplantation.

RESULTS

The 1-year incidence of EBV DNAemia was 20.7% (95% confidence interval, 15.4-26.5) and 40.0% (33.3-46.6) in the 7.5 mg/kg and 10.0 mg/kg groups, respectively (P < 0.001). The 100-day cumulative incidence of grade II to IV aGVHD was 27.1% (21.1-33.4) and 25.4% (19.6-31.5) in the 7.5 mg/kg and 10.0 mg/kg ATG groups, respectively (P = 0.548). The 2-year incidence of chronic GVHD was 34.6% (27.8-41.4) and 36.2% (29.1-43.2) in the 7.5 mg and 10.0 mg groups (P = 0.814). The 1-year incidence of CMV DNAemia was 73.4% (67.2-79.4) and 83.4% (77.5-87.9) in the 7.5 mg/kg and 10.0 mg/kg groups (P = 0.038). The 3-year overall survival posttransplantation was 69.5% (63.2-75.8) and 63.5% (56.2-70.8), and the disease-free survival was 62.2% (55.3-69.1) and 60.3% (53.0-67.6) in the 7.5 mg/kg and 10.0 mg/kg groups, respectively (OS: P = 0.308; DFS: P = 0.660). The counts of EBV- and CMV-specific cytotoxic T cells (CTLs) were higher in the 7.5 mg/kg group than in the 10.0 mg/kg group early posttransplantation.

CONCLUSIONS

Compared with 10.0 mg/kg, 7.5 mg/kg ATG for GVHD prophylaxis was associated with reduced EBV and CMV infections without increased incidence of GVHD in haplo-HSCT, probably by affecting EBV- and CMV-specific CTLs.

TRIAL REGISTRATION

clinicaltrials.gov, NCT01883180 . Registered 14 June 2013.

Prophylaxis and treatment of relapse after haploidentical stem cell transplantation: What is known vs unknown?

In recent years, the human leukocyte antigen-haploidentical stem cell transplantation (haplo-SCT) approach is an attractive option for patients who require transplantation, but relapse is still the main reason that affects the curative effect of transplantation. Some studies have shown that haplo-SCT is superior to sibling or unrelated matching donor transplantation in preventing leukemia relapse after transplantation. In this review, we discussed the known and unknown aspects of relapse post haplo-SCT. Encouragingly, haplo-SCT experienced lower or similar incidence of relapse. But there is currently a lack of multicenter prospective studies evaluating the outcomes of different haplo-SCT strategies. The combination of common prophylactic strategies and pre-emptive interventions might help prevent relapse after transplantation. Novel methods such as target drugs therapy and chimeric antigen receptor T cell therapy may be useful in treatment of relapse.

New Strategy of Acute Graft-vs-Host Disease: Investigation of a Reduced Dose of Antithymocyte Globulin in Haploidentical Hematopoietic Stem Cell Transplantation

Graft-vs-host disease (GVHD) is one of the biggest challenges in haploidentical hematopoietic stem cell transplantation. Antithymocyte globulins (ATGs) are widely used to overcome GVHD, but excessive immunosuppression increases the chances of relapse and infection following transplantation. No defined standard of the appropriate dose of ATG usage is recognized. The study included 11 patients who were treated with a reduced dose of ATG to prevent GVHD in haploidentical hematopoietic stem cell transplantation. A reduced dose of ATG-Thymoglobulin (total dose of 5 mg/kg) was used in the pretreatment protocol for 2 consecutive days. All patients had successful transplantation. The median time of neutrophil engraftment was 12 days. All chimerism tests passed on day 30, 60, and 90 post transplantation. None of the patients had acute GVHD, while only 2 patients had I to II degree chronic GVHD (18.2%). No transplantation-related deaths were observed. The current findings suggest that the reduced dose of ATG can effectively prevent the incidence of acute GVHD in haploidentical hematopoietic stem cell transplantation.

Antithymocyte globulin improves GVHD-free and relapse-free survival in unrelated hematopoietic stem cell transplantation

Antithymocyte globulin (ATG) is an important component of conditioning regimens to prevent graft-versus-host disease (GVHD) in unrelated hematopoietic stem cell transplantation (HSCT), but the optimal dose of ATG remains unknown. We prospectively analyzed 205 unrelated HSCTs in patients with malignant hematological disorders. HSCTs were classified as follows: HLA-matched transplant without ATG (n = 53, group A), HLA-mismatched transplant treated with 6.0 mg/kg thymoglobulin (n = 77, group B), and HLA-matched transplant treated with 4.5 mg/kg thymoglobulin (n = 75, group C). For groups A and B, the 5-year moderate/severe chronic GVHD rates were 31.9% and 24.2%, the 5-year GVHD-free and relapse-free survival (GRFS) rates were 28.3 and 47%, and the 2-year immunosuppressive therapy (IST)-free survival rates were 8.6% and 40.2% (p = 0.0016), respectively. Furthermore, group C had lower incidences of grade II-IV acute GVHD (18.7%) and 5-year moderate/severe chronic GVHD (16.6%) than group A did. Group C had higher 5-year GRFS (52.1% vs 28.3%, p = 0.002), 2-year IST-free survival (51.7% vs 8.6%, p = 0.00004), and 5-year overall survival (OS) (68.3% vs 41.5%, p = 0.007) rates than group A did. Thus, ATG was associated with better GVHD prevention, a higher rate of IST-free survival, lower transplant-related mortality (TRM), and superior OS and GRFS in unrelated HSCTs.

Differential Elimination of Anti-Thymocyte Globulin of Fresenius and Genzyme Impacts T-Cell Reconstitution After Hematopoietic Stem Cell Transplantation

Anti-thymocyte globulin (ATG) is a lymphocyte depleting agent applied in hematopoietic stem cell transplantation (HSCT) to prevent rejection and Graft-vs.-Host Disease (GvHD). In this study, we compared two rabbit ATG products, ATG-Genzyme (ATG-GENZ), and ATG-Fresenius (ATG-FRES), with respect to dosing, clearance of the active lymphocyte binding component, post-HSCT immune reconstitution and clinical outcome. Fifty-eigth pediatric acute leukemia patients (n = 42 ATG-GENZ, n = 16 ATG-FRES), who received a non-depleted bone marrow or peripheral blood stem cell graft from an unrelated donor were included. ATG-GENZ was given at a dosage of 6-10 mg/kg; ATG-FRES at 45-60 mg/kg. The active component of ATG from both products was cleared at different rates. Within the ATG-FRES dose range no differences were found in clearance of active ATG or T-cell re-appearance. However, the high dosage of ATG-GENZ (10 mg/kg), in contrast to the low dosage (6-8 mg/kg), correlated with prolonged persistence of active ATG and delayed T-cell reconstitution. Occurrence of serious acute GvHD (grade III-IV) was highest in the ATG-GENZ-low dosage group. These results imply that dosing of ATG-GENZ is more critical than dosing of ATG-FRES due to the difference in clearance of active ATG. This should be taken into account when designing clinical protocols.