Antithymocyte globulin for graft-versus-host disease prophylaxis in transplants from unrelated donors: 2 randomized studies from Gruppo Italiano Trapianti Midollo Osseo (GITMO)

Engineering the best transplant outcome for high-risk acute myeloid leukemia: the donor, the graft and beyond

Allogeneic hemopoietic cell transplantation remains the goal of therapy for high-risk acute myeloid leukemia (AML). However, treatment failure in the form of leukemia relapse or severe graft-versus-host disease remains a critical area of unmet need. Recently, significant progress has been made in the cell therapy-based interventions both before and after transplant. In this review, the Stem Cell Engineering Committee of the International Society for Cell and Gene Therapy summarizes the literature regarding the identification of high risk in AML, treatment approaches before transplant, optimal transplant platforms and measures that may be taken after transplant to ideally prevent, or, if need be, treat AML relapse. Although some strategies remain in the early phases of clinical investigation, they are built on progress in pre-clinical research and cellular engineering techniques that are already improving outcomes for children and adults with high-risk malignancies.

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.

Clinical effects of tacrolimus blood concentrations early after allogeneic hematopoietic stem cell transplantation

BACKGROUND AIMS

Tacrolimus (TAC) plus short-term methotrexate (stMTX) is used for graft-versus-host disease (GVHD) prophylaxis after allogeneic hematopoietic stem cell transplantation (allo-HSCT). TAC blood concentrations are frequently adjusted to enhance the graft-versus-leukemia/lymphoma effect or attenuate severe GVHD. Limited information is available on the clinical impact of these adjustments and the optimal time to perform them in order to achieve good clinical outcomes.

METHODS

We retrospectively analyzed 211 patients who underwent allo-HSCT at our institutes.

RESULTS

Higher TAC concentrations in week 3 correlated with a significantly higher cumulative incidence of relapse (CIR) (P = 0.03) and lower nonrelapse mortality (P = 0.04). The clinical impact of high TAC concentrations in week 3 on CIR was detected in the refined disease risk index: low/intermediate (P = 0.04) and high (P < 0.01), and conditioning regimens other than cyclophosphamide/total body irradiation and busulfan/cyclophosphamide (P = 0.07). Higher TAC concentrations in week 1 correlated with a lower grade 2-4 acute GVHD rate (P = 0.01). Higher TAC concentrations in weeks 2 and 3 correlated with slightly lower (P = 0.05) and significantly lower (P = 0.02) grade 3-4 acute GVHD rates, respectively. Higher TAC concentrations in weeks 1 and 3 were beneficial for severe acute GVHD in patients with a human leukocyte antigen-matched donor (P = 0.03 and P < 0.01, respectively), not treated with anti-thymocyte globulin (P = 0.02 and P = 0.02, respectively), and receiving three stMTX doses (P = 0.03 and P = 0.02, respectively).

CONCLUSIONS

The clinical impact of TAC concentrations varied according to patient characteristics, including disease malignancy, conditioning regimens, donor sources, and GVHD prophylaxis. These results suggest that TAC management needs to be based on patient profiles.

Optimizing Access to Unrelated Donors in Canada: Re-Examining the Importance of Donor Factors on Outcomes Following Hematopoietic Cell Transplantation

HLA-matched allogeneic hematopoietic cell transplantation (HCT) is a curative therapy for many patients. Unrelated HLA-matched donors are the most frequently used donor for HCT. When more than one donor transplant option is available, transplant centers can select donors based on non-HLA factors. With improved ability to prevent and treat immune complications, such as graft-versus-host disease and infections, it may be possible to proceed more often using HLA-mismatched donors, allowing greater consideration of non-HLA factors, such as donor age, CMV serostatus, and ABO blood group matching, which have demonstrated important impacts on transplant outcomes. Additional factors to consider are donor availability rates and the usage of domestic donors to optimize outcomes. A review of non-HLA factors and considerations on the selection of optimal unrelated donors for HCT are provided within this updated current context.

Post-Transplant Cyclophosphamide versus Anti-Thymocyte Globulin in Patients with Hematological Malignancies Treated with Allogeneic Hematopoietic Stem Cell Transplantation from Haploidentical and Matched Unrelated Donors: A Real-Life Experience

Background: Post-transplant cyclophosphamide (PTCY) is widely used as graft versus host disease (GvHD) prophylaxis in allogeneic hematopoietic stem cell transplant (HSCT) recipients, with reported clinical benefits in patients who underwent transplant from a matched unrelated donor (MUD). However, real-life data on clinical efficacy and safety of PTCY in haploidentical and MUD transplantations are still poor. Methods: In our real-life retrospective observational study, we included a total of 40 consecutive adult patients who underwent haploidentical or MUD HSCT for various hematological malignancies and who received PTCY (n = 24) or ATG (n = 16) as GvHD prophylaxis at Hematology Units from hospitals of Salerno and Avellino, Italy, and clinical outcomes were compared. Results: We showed protective effects of PTCY against disease relapse with the relapse rate after transplantation of 16% versus 50% in the ATG arm (p = 0.02). All-cause mortality was lower (36% vs. 75%; p = 0.02) and the 2-year overall survival was slightly superior in patients administered PTCY (61% vs. 42%; p = 0.26). Conclusions: We support the use of PTCY, even in a real-life setting; however, the optimization of this protocol should be further investigated to better balance relapse prevention and GvHD prophylaxis.

Post-transplant cyclophosphamide, calcineurin inhibitor, and mycophenolate mofetil compared to anti-thymocyte globulin, calcineurin inhibitor, and methotrexate combinations as graft-versus-host disease prophylaxis post allogeneic stem cell transplantation from sibling and unrelated donors in patients with acute myeloid leukemia: a study on behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Post-transplant cyclophosphamide plus calcineurin inhibitor (CNI)(tacrolimus or cyclosporine A) plus mycophenolate mofetil (PTCy/TAC or CSA/MMF) and anti-thymocyte globulin plus CNI (tacrolimus or cyclosporine A) plus methotrexate (ATG/TAC or CSA/MTX) are common graft-versus-host disease (GVHD) prophylaxis regimens. We compared the two regimens in patients with acute myeloid leukemia (AML) undergoing allogeneic transplantation from matched siblings or unrelated donors. 402 received PTCy/TAC or CSA/MMF and 5648 received ATG/TAC or CSA/MTX. Patients in the PTCy-based group were younger (48.7 vs. 51.5 years, p = 0.024) and there was a higher frequency of patient cytomegalovirus seropositivity and female donor to male patient combination in this group (77.8% vs. 71.8%, p = 0.009 and 18.4% vs. 14.4%, p = 0.029, respectively). More patients in the PTCy-based group received reduced-intensity conditioning (51.5% vs. 41%, p < 0.0001). No differences were observed in the incidence of acute GVHD grade II-IV and III-IV (21.2% vs. 20.4%, p = 0.92 and 8.1% vs. 6%, p = 0.1) or 2-year total and extensive chronic GVHD (33.7% vs. 30%, p = 0.09 and 10.7% vs. 11.2%, p = 0.81) between the groups. In the multivariate analysis, all transplant outcomes did not differ between the groups. PTCy/CNI/MMF and ATG/CNI/MTX are alternative regimens for GVHD prophylaxis in AML patients.

Busulfan with 400 centigray of total body irradiation and higher dose fludarabine: An alternative regimen for hematopoietic stem cell transplantation in pediatric acute lymphoblastic leukemia

BACKGROUND

Hematopoietic stem cell transplantation can be curative for children with difficult-to-treat leukemia. The conditioning regimen utilized is known to influence outcomes. We report outcomes of the conditioning regimen used at the Alberta Children's Hospital, consisting of busulfan (with pharmacokinetic target of 3750 μmol*min/L/day ±10%) for 4 days, higher dose (250 mg/m2 ) fludarabine and 400 centigray (cGy) of total body irradiation.

PROCEDURE

This retrospective study involved children receiving transplant for acute lymphoblastic leukemia (ALL). It compared children who fell within the target range for busulfan with those who were either not measured or were measured and fell outside this range. All other treatment factors were identical.

RESULTS

Twenty-nine children (17 within target) were evaluated. All subjects engrafted neutrophils with a median [interquartile range] time of 14 days [8-30 days]. The cumulative incidence of acute graft-versus-host disease was 44.8% [95% confidence interval, CI: 35.6%-54.0%], while chronic graft-versus-host disease was noted in 16.0% [95% CI: 8.7%-23.3%]. At 2 years, the overall survival was 78.1% [95% CI: 70.8%-86.4%] and event-free survival was 74.7% [95% CI: 66.4%-83.0%]. Cumulative incidence of relapse was 11.3% [95% CI: 5.1%-17.5%]. There were no statistically significant differences in between the group that received targeted busulfan compared with the untargeted group.

CONCLUSION

Our conditioning regiment for children with ALL resulted in outcomes comparable to standard treatment with acceptable toxicities and significant reduction in radiation dose. Targeting busulfan dose in this cohort did not result in improved outcomes.

Outcomes of haploidentical peripheral blood stem cell transplantation following myeloablative conditioning using two types of rabbit ATG: a propensity score-matched analysis

During hematopoietic stem cell transplantation (HSCT), ATG depletes T cells in-vivo to improve engraftment and prevent graft-versus-host disease (GVHD). Here, we compared the clinical efficacy of two different types of ATGs: thymoglobulin and anti-human T-lymphocyte immunoglobulin (Grafalon). A total of 469 patients who received haploidentical transplantation were enrolled in this retrospective study. We applied a propensity score (PS)-matched analysis and 209 patients were assigned to each group. Clinical outcomes were compared between two groups and primary outcome was overall survival (OS). There was no significant difference in OS between two groups. Within the first 180 days after HSCT, Grafalon was associated with lower incidences of Epstein-Barr virus (EBV) viremia (31.6 vs. 54.5%, P < 0.0001) and cytomegalovirus viremia (CMV) viremia (54.5 vs. 67.9%, P = 0.005) compared to thymoglobulin. Patients receiving Grafalon had a higher rate of moderate/severe chronic GVHD (26.3 vs. 18.2%, P = 0.046). However, the incidences of engraftment failure, grade II-IV acute GVHD, relapse, non-relapse mortality (NRM), and GVHD-free relapse-free survival (GRFS) did not differ greatly between groups. In the subgroup analysis, Grafalon improved the OS of lymphoid malignancies with young ages (< 40 years old) (HR, 0.55; P = 0.04) or with a high/very high disease risk index (HR, 0.36; P = 0.04). In the myeloid cohort, Grafalon reduced NRM in the patients who received non-female for male transplantation grafts (HR, 0.17; P = 0.02). Our results suggest the two types of ATG may differentially influence transplant outcomes and it may optimize ATG selection according to the condition of patients.

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).

Long term results of a prospective multicenter observational study on the use of anti-human T-lymphocyte immunoglobulin (ATLG) in unrelated donor transplantation (ATOS study)

ATOS is a prospective observational study evaluating the outcome of patients receiving anti-human T-lymphocyte immunoglobulin (ATLG) in unrelated donor transplantation. Primary endpoint was severe GvHD and relapse-free survival (SGRFS). GvHD prophylaxis consisted of ATLG and CSA/ MTX or MMF. Outcome was compared to the ATLG arm of our prospective randomized phase III multicenter trial trial (RCT) [1, 2]. 165 patients, median age 54 (18; 77) years, with haematological malignancies with early (45.5%), intermediate (17.6%), and advanced (37.0%) disease were included. ATLG dose differed between centers according to local practise (median total ATLG dose of 46 (IQR 32-60, range 15-91) mg/kg). Median follow-up was 70 months. Estimated probabilities at 5 years follow up were for SGRFS 0.27, OS 0.52, DFS 0.43, NRM 0.23, relapse 0.34, acute GvhD °III/IV 0.13, severe chronic GvHD 0.27. OS rates differed dependent on disease status. An effect of the given ATLG dose could not be separated from potential center effects. Despite higher age and more advanced disease in ATOS, outcome was similar to the ATLG arm of our RCT. This long-term, multicenter, experience in routine clinical practice confirms the GvHD-protective effect of ATLG without compromising relapse and non-relapse mortality rates.Clinical Trial Registry: German clinical trials register DRKS00004581.

Acute graft versus host disease 1976-2020: reduced incidence and predictive factors

We studied the incidence of acute graft versus host disease (GvHD) and its outcome in three consecutive time frames (year <2000; 2000-2010; >2010), in 3,120 patients allografted in two transplant Centers between 1976 and 2020. The median age increased over the three periods from 32 to 42 to 54 years (p < 0.00001). The median day of onset of GvHD in the three periods was day +14, day +16, and day +30, respectively (p < 0.0001). The cumulative incidence (CI) of GvHD grades II-IV in the three periods was 47, 24, and 16%, respectively (p < 0.00001). The CI of GvHD grades III-IV was 13, 5, and 4% (p < 0.001). In multivariate analysis, significant predictive factors for GvHD II-IV, on top of year of transplant, were anti-thymocyte globulin (ATG) (RR 0.67, p > 0.001); post-transplant cyclophosphamide (PTCY) (RR 0.41, p < 0.001), a family mismatched donor (RR 1.31, p = 0.03) a matched unrelated donor (RR 2.1, p < 0.001), an unrelated mismatched donor (RR1.8, p = 0.001), donor age above 40 years (RR 1.27, p < 0.001), hematological malignancy-as compared to aplastic anemia (RR 2.3, p < 0.001). When selecting only GvHD grade II, in a multivariate analysis, there was a significant reduction of transplant-related mortality (TRM) for patients grafted in 2001-2010 (RR 0.62, p < 0.0001) and for patients grafted in 2011-2020 (RR 0.35, p < 0.0001) as compared to grafts before the year 2000. A similar reduction in time was seen for patients with GvHD grades III-IV. The overall TRM in the three periods was 30, 22, and 16% (p < 0.0001) and survival was 47, 51, and 58% (p < 0.0001). Relapse risk was unchanged. In conclusion, we showed improved prevention of acute GvHD with time, together with a significant delay in the onset of the disease. Treatment of GvHD has also improved over time, as suggested by both reduced TRM and improved survival in more recent transplant periods.

Post-transplant сyclophosphamide after matched donor hematopoietic stem cell transplantation in children with acute leukemia

INTRODUCTION

The data on post-transplant cyclophosphamide (PTCy) in pediatric acute leukemia after matched allo-HSCT are limited to case series. The present study aimed to assess the results of PTCy-based GVHD prophylaxis in a large cohort of children with acute leukemia after matched allo-HSCT.

METHODS

A retrospective analysis of 190 pediatric patients with acute leukemia who had a first allograft between 2008 and 2020 from a matched sibling donor (MSD) or matched unrelated donor (MUD) was carried out. In the MSD setting, GVHD prophylaxis consisted of PTCy alone (n = 28) for the study group, and calcineurin inhibitor (CNI) ± antimetabolite (n = 30) for the control group. In MUD setting, most patients in the study group received GVHD prophylaxis with PTCy+CNI+mycophenolate mofetil (n = 42, 66.7%) or PTCy+CNI+sirolimus (n = 12, 19%). All patients (n = 69) in the control group received ATG+CNI+antimetabolite.

RESULTS

After MUD allo-HSCT, the incidences of acute GVHD grade III-IV and moderate/severe chronic GVHD were significantly lower in the PTCy group compared to control (6.6% vs. 35.0% and 12.7% vs. 47.1%, respectively, p < .0001). Five-year GVHD-free, relapse-free survival (GRFS) after MUD allo-HSCT was higher in the PTCy group compared to control (35.1% vs. 7.3%, p < .0001). At the same time, there was no significant difference between both groups after MSD allo-HSCT.

CONCLUSIONS

In pediatric acute leukemia, PTCy-based GVHD prophylaxis for MUD allo-HSCT is a feasible and effective option that results in a low incidence of GVHD. Compared to the ATG-based approach, PTCy provides better control of GVHD in children. In pediatric allo-HSCT from MSD, PTCy demonstrates comparable effectiveness to conventional GVHD prophylaxis.

Indication and management of allogeneic haematopoietic stem-cell transplantation in myelofibrosis: updated recommendations by the EBMT/ELN International Working Group

New options for medical therapy and risk scoring systems containing molecular data are leading to increased complexity in the management of patients with myelofibrosis. To inform patients' optimal care, we updated the 2015 guidelines on indications for and management of allogeneic haematopoietic stem-cell transplantation (HSCT) with the support of the European Society for Blood and Marrow Transplantation (EBMT) and European LeukemiaNet (ELN). New recommendations were produced using a consensus-building methodology after a comprehensive review of articles released from January, 2015 to December, 2022. Seven domains and 18 key questions were selected through a series of questionnaires using a Delphi process. Key recommendations in this update include: patients with primary myelofibrosis and an intermediate-2 or high-risk Dynamic International Prognostic Scoring System score, or a high-risk Mutation-Enhanced International Prognostic Score Systems (MIPSS70 or MIPSS70-plus) score, or a low-risk or intermediate-risk Myelofibrosis Transplant Scoring System score should be considered candidates for allogeneic HSCT. All patients who are candidates for allogeneic HSCT with splenomegaly greater than 5 cm below the left costal margin or splenomegaly-related symptoms should receive a spleen-directed treatment, ideally with a JAK-inhibitor; HLA-matched sibling donors remain the preferred donor source to date. Reduced intensity conditioning and myeloablative conditioning are both valid options for patients with myelofibrosis. Regular post-transplantation driver mutation monitoring is recommended to detect and treat early relapse with donor lymphocyte infusion. In a disease where evidence-based guidance is scarce, these recommendations might help clinicians and patients in shared decision making.

Evaluating the Impact of Post-Transplant Cyclophosphamide and Anti-Thymocyte Globulin on CMV Reactivation Following Allogeneic Hematopoietic Stem Cell Transplantation: A Systematic Literature Review

Anti-thymocyte globulin (ATG) and post-transplantation cyclophosphamide (PTCy) are two frequently utilised strategies in graft-versus-host disease (GvHD) prophylaxis following allogeneic hematopoietic cell transplantation (allo-HCT), currently approved for different recipient-donor settings. In addition, being efficacious in preventing GvHD owing to their T-cell depleting capacity, the employment of these two agents increases the risk of infections, including CMV reactivation, which stands as one of the most common and serious infections following allo-HCT. We performed a systematic literature review of articles published until 1 September 2023, through PubMed, MEDLINE, and Scopus, with the main endpoint being CMV reactivation after PTCy or ATG allo-HCT. The majority of the studies included in the analysis provide supporting evidence for a reduced risk of CMV reactivations following the use of PTCy compared to ATG, although not all findings reached statistical significance. Additionally, it appears that utilising a haploidentical donor leads to a higher incidence of CMV infections and clinically significant CMV infections (CS-CMVis) compared to other donor settings in PTCy allo-HCT. This study aims to compare the risk of CMV infections following allo-HCT in patients who have received either ATG or PTCy as GvHD prophylaxis and discuss other factors that could influence the infectious outcomes of patients who have undergone allo-HCT.

Posttransplant cyclophosphamide versus antithymocyte globulin in patients with acute lymphoblastic leukemia treated with allogeneic hematopoietic cell transplantation from matched unrelated donors: A study from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

BACKGROUND

The aim of this study was to compare two immunosuppressive strategies, based on the use of either rabbit antithymocyte globulin (ATG) or posttransplant cyclophosphamide (PTCY), as a prophylaxis of graft-versus-host disease (GVHD) for patients with acute lymphoblastic leukemia (ALL) in first complete remission who underwent hematopoietic cells transplantation from matched unrelated donors.

METHODS

Overall, 117 and 779 adult patients who received PTCY and ATG, respectively, between the years 2015 and 2020 were included in this retrospective study. The median patient age was 40 and 43 years in the PTCY and ATG groups, respectively, and 37% and 35% of patients, respectively, had Philadelphia chromosome-positive ALL.

RESULTS

In univariate analysis, the cumulative incidence of acute and chronic GVHD did not differ significantly between the study groups. The cumulative incidence of relapse at 2 years was reduced in the PTCY group (18% vs. 25%; p = .046) without a significant impact on nonrelapse mortality (11% vs. 16% in the ATG group; p = .29). The rates of leukemia-free survival (LFS) and overall survival were 71% versus 59%, respectively (p = .01), and 82% versus 74%, respectively (p = .08). In multivariate analysis, the receipt of ATG compared with PTCY was associated with a reduced risk of extensive chronic GVHD (hazard ratio, 0.54; 95% confidence interval, 0.3-0.98; p = .04) and an increased risk of low LFS (hazard ratio, 1.57; 95% confidence interval, 1.01-2.45; p = .045).

CONCLUSIONS

The receipt of ATG compared with PTCY, despite the reduced risk of extensive chronic GVHD, is associated with inferior LFS in adults with ALL who undergo hematopoietic cell transplantation from 10/10 human leukocyte antigen-matched unrelated donors. These findings warrant verification in prospective trials.

Targeted dosing of anti-thymocyte globulin in adult unmanipulated haploidentical peripheral blood stem cell transplantation: A single-arm, phase 2 trial

Anti-thymocyte globulin (ATG) is widely used in allogeneic hematopoietic stem cell transplantation to prevent severe graft-versus-host disease (GVHD) and graft failure. However, overexposure to ATG may increase cytomegalovirus (CMV), Epstein-Barr virus (EBV) reactivation, non-relapse mortality, and disease recurrence. To investigate the optimal dosing of ATG, we established a targeted dosing strategy based on ATG concentration monitoring for haploidentical peripheral blood stem cell transplantation (haplo-PBSCT). The aim of this phase 2 trial is to evaluate the safety and efficacy of the ATG-targeted dosing strategy in adult unmanipulated haplo-PBSCT. ATG was administered for 4 days (-5 days to -2 days) during conditioning. The ATG doses on -3 days and -2 days were adjusted by our dosing strategy to achieve the optimal ATG exposure. The primary endpoint was CMV reactivation on +180 days. Between December 2020 and January 2022, 66 haplo-PBSCT patients were enrolled and 63 of them were evaluable with a median follow-up of 632 days. The cumulative incidence of CMV reactivation was 36.7% and that of EBV was 58.7%. The 1-year disease-free survival was 82.5%, overall survival was 92.1%, and CD4+ T-cell reconstruction on +100 days was 76.8%. The most common severe regimen-associated toxicities (> grade 3) were infections (51.5%) and gastrointestinal toxicity (25.5%). A total of 102 haplo-PBSCT patients who received the conventional fixed ATG dose (cumulative 10 mg/kg) comprised historical control. The outcomes in historical control were inferior to those of phase 2 trial cohort (CMV reactivation: 70.8%, p < .001; EBV reactivation: 76.0%, p = .024; CD4 + T-cell reconstruction: 54.1%, p = .040). In conclusion, ATG-targeted dosing strategy reduced CMV/EBV reactivation and improved survival without increasing GVHD after haplo-PBSCT. These advantages may be associated with accelerated immune reconstitution.

A fully validated flow cytometry method to quantitatively analyze active rATG in human serum and its application in pharmacokinetic study for therapeutic drug monitoring

Rabbit anti-thymocyte globulin (rATG) has been widely used to prevent graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The therapeutic window of rATG is narrow, and it may increase the risk of relapse, viral reactivation, delayed immune reconstitution and GvHD when overexposed or underexposed. Therefore, a reliable method for detecting the rATG concentration in human serum by flow cytometry was established and fully validated for therapeutic drug monitoring. In this method, Jurkat T cells were used to capture active rATG in human serum, and PE-labeled donkey anti-rabbit IgG was used as a secondary antibody. The method showed good specificity, selectivity and excellent linearity at concentration of 0.00300-20.0 AU/mL. The intra- and interday precision values were all within 20% at four concentration levels for the analyte. The stock solutions of rATG showed no significant degradation after storage at ambient temperature for 8 h and at - 80 °C for 481 days. No significant degradation of rATG in serum was observed at ambient temperature for 6 h, during six freezethaw cycles and at - 80 °C for at least 373 days. This method was fully validated and successfully applied to monitor active rATG concentration in serum of patients with haploid-identical hematopoietic stem cell transplantation.

Comparison of Different Rabbit Anti-Thymocyte Globulin Formulations in the Prophylaxis of Graft-Versus-Host Disease: A Systematic Review

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is a potentially curative treatment modality, frequently used for patients suffering from haematological malignancies. In the last two decades, there have been multiple randomised controlled trials (RCTs), review articles, and meta-analyses addressing the efficacy of rabbit anti-thymocyte globulin (r-ATG) as a graft-versus-host disease (GvHD) prophylaxis. Nevertheless, only a few aimed to compare the effectiveness of different r-ATG formulations. Since the last article we retrieved comparing different r-ATGs in GvHD prophylaxis dates back to 2017, we performed a systematic literature review of articles published since 2017 to this day, utilising PubMed, Scopus, Cochrane, and MEDLINE, with the main endpoints being prophylaxis of acute GvHD (aGvHD) and chronic GvHD (cGvHD). We subjected to scrutiny a total of five studies, of which four compared the differences between Thymoglobulin (ATG-T) and Grafalon (ATG-G), and one discussed the impact of ATG-T dose. Overall, cGvHD, aGvHD grades II-IV, TRM, OS, NRM, LFS, relapse, overall infections, and EBV reactivation do not seem to be affected by the type of utilised rATG. However, data on aGvHD grades III-IV, GRFS, moderate-severe cGvHD, and CMV reactivation is conflicting. Through our research, we sought to summarise the most recent findings concerning r-ATGs in allo-HCT, and provide insight into the differences between the targets and origin of various ATG formulations.

Impact of the Recipient's Pre-Treatment Blood Lymphocyte Count on Intended and Unintended Effects of Anti-T-Lymphocyte Globulin in Allogeneic Hematopoietic Stem Cell Transplantation

Background: In allogeneic hematopoietic stem cell transplantation (HSCT), Anti-T-Lymphocyte Globulin (ATLG) may be used for the prevention of severe graft-versus-host disease (GVHD). ATLG targets both the recipient's lymphocytes and those transferred with the graft. Assuming an inverse relation between the recipient's absolute lymphocyte count (ALC) and exposure of remaining ATLG to the graft, we aim to evaluate the impact of the recipient's ALC before the first ATLG administration on the benefits (prevention of GVHD and GVHD-associated mortality) and potential risks (increased relapse incidence) associated with ATLG. Methods: In recipients of HLA-matched, ATLG-based HSCT (n = 311), we assessed the incidence of acute GVHD, GVHD-related mortality and relapse, as well as other transplant-related outcomes, in relation to the respective ALC (divided into tertiles) before ATLG. Results: The top-tertile ALC group had a significantly increased risk of aGVHD (subhazard ratio (sHR) 1.81; [CI 95%; 1.14-2.88]; p = 0.01) and aGVHD-associated mortality (sHR 1.81; [CI 95%; 1.03-3.19]; p = 0.04). At the highest ATLG dose level (≥45 mg/kg), recipients with lowest-tertile ALC had a trend towards increased relapse incidence (sHR 4.19; [CI 95%; 0.99-17.7]; p = 0.05, n = 32). Conclusions: ATLG dosing based on the recipient's ALC may be required for an optimal balance between GVHD suppression and relapse prevention.

The delicate balance of graft versus leukemia and graft versus host disease after allogeneic hematopoietic stem cell transplantation

INTRODUCTION

The curative basis of allogeneic hematopoietic stem cell transplantation (HSCT) relies in part upon the graft versus leukemia (GvL) effect, whereby donor immune cells recognize and eliminate recipient malignant cells. However, alloreactivity of donor cells against recipient tissues may also be deleterious. Chronic graft versus host disease (cGvHD) is an immunologic phenomenon wherein alloreactive donor T cells aberrantly react against host tissues, leading to damaging inflammatory symptoms.

AREAS COVERED

Here, we discuss biological insights into GvL and cGvHD and strategies to balance the prevention of GvHD with maintenance of GvL in modern HSCT.

EXPERT OPINION/COMMENTARY

Relapse remains the leading cause of mortality after HSCT with rates as high as 40% for some diseases. GvHD is a major cause of morbidity after HSCT, occurring in up to half of patients and responsible for 15-20% of deaths after HSCT. Intriguingly, the development of chronic GvHD may be linked to lower relapse rates after HSCT, suggesting that GvL and GvHD may be complementary sides of the immunologic foundation of HSCT. The ability to fine tune the balance of GvL and GvHD will lead to improvements in survival, relapse rates, and quality of life for patients undergoing HSCT.

Post-Transplantation Cyclophosphamide-Based Graft-versus-Host Disease Prophylaxis

BACKGROUND

In patients undergoing allogeneic hematopoietic stem-cell transplantation (HSCT), a calcineurin inhibitor plus methotrexate has been a standard prophylaxis against graft-versus-host disease (GVHD). A phase 2 study indicated the potential superiority of a post-transplantation regimen of cyclophosphamide, tacrolimus, and mycophenolate mofetil.

METHODS

In a phase 3 trial, we randomly assigned adults with hematologic cancers in a 1:1 ratio to receive cyclophosphamide-tacrolimus-mycophenolate mofetil (experimental prophylaxis) or tacrolimus-methotrexate (standard prophylaxis). The patients underwent HSCT from an HLA-matched related donor or a matched or 7/8 mismatched (i.e., mismatched at only one of the HLA-A, HLA-B, HLA-C, and HLA-DRB1 loci) unrelated donor, after reduced-intensity conditioning. The primary end point was GVHD-free, relapse-free survival at 1 year, assessed in a time-to-event analysis, with events defined as grade III or IV acute GVHD, chronic GVHD warranting systemic immunosuppression, disease relapse or progression, and death from any cause.

RESULTS

In a multivariate Cox regression analysis, GVHD-free, relapse-free survival was significantly more common among the 214 patients in the experimental-prophylaxis group than among the 217 patients in the standard-prophylaxis group (hazard ratio for grade III or IV acute GVHD, chronic GVHD, disease relapse or progression, or death, 0.64; 95% confidence interval [CI], 0.49 to 0.83; P = 0.001). At 1 year, the adjusted GVHD-free, relapse-free survival was 52.7% (95% CI, 45.8 to 59.2) with experimental prophylaxis and 34.9% (95% CI, 28.6 to 41.3) with standard prophylaxis. Patients in the experimental-prophylaxis group appeared to have less severe acute or chronic GVHD and a higher incidence of immunosuppression-free survival at 1 year. Overall and disease-free survival, relapse, transplantation-related death, and engraftment did not differ substantially between the groups.

CONCLUSIONS

Among patients undergoing allogeneic HLA-matched HSCT with reduced-intensity conditioning, GVHD-free, relapse-free survival at 1 year was significantly more common among those who received cyclophosphamide-tacrolimus-mycophenolate mofetil than among those who received tacrolimus-methotrexate. (Funded by the National Heart, Lung, and Blood Institute and others; BMT CTN 1703 ClinicalTrials.gov number, NCT03959241.).

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.

Acute graft-versus-host disease

Acute graft-versus-host disease (GVHD) is a common immune complication that can occur after allogeneic haematopoietic cell transplantation (alloHCT). Acute GVHD is a major health problem in these patients, and is associated with high morbidity and mortality. Acute GVHD is caused by the recognition and the destruction of the recipient tissues and organs by the donor immune effector cells. This condition usually occurs within the first 3 months after alloHCT, but later onset is possible. Targeted organs include the skin, the lower and upper gastrointestinal tract and the liver. Diagnosis is mainly based on clinical examination, and complementary examinations are performed to exclude differential diagnoses. Preventive treatment for acute GVHD is administered to all patients who receive alloHCT, although it is not always effective. Steroids are used for first-line treatment, and the Janus kinase 2 (JAK2) inhibitor ruxolitinib is second-line treatment. No validated treatments are available for acute GVHD that is refractory to steroids and ruxolitinib, and therefore it remains an unmet medical need.

Acute Graft-versus-Host Disease: An Update on New Treatment Options

Acute graft-versus-host disease (GVHD) occurs in approximately 50% of patients and remains a primary driver of non-relapse and transplant-related mortality. The best treatment remains prevention with either in vivo or ex vivo T-cell depletion, with multiple strategies used worldwide based on factors such as institution preference, ability to perform graft manipulation, and ongoing clinical trials. Predicting patients at high risk for developing severe acute GVHD based on clinical and biomarker-based criteria allows for escalation or potential de-escalation of therapy. Modern therapies for treatment of the disease include JAK/STAT pathway inhibitors, which are standard of care in the second-line setting and are being investigated for upfront management of non-severe risk based on biomarkers. Salvage therapies beyond the second-line remain suboptimal. In this review, we will focus on the most clinically used GVHD prevention and treatment strategies, including the accumulating data on JAK inhibitors in both settings.

Graft-Versus-Host Disease Prophylaxis with Antithymocyte Globulin in Patients Receiving Stem Cell Transplantation from Unrelated Donors: An Observational Retrospective Single-Center Study

Graft-versus-host disease (GVHD) is one of the most important complications of allogeneic hematopoietic stem cell transplantation. Rabbit antilymphocyte serum (ATG/ATLG) is recommended for GVHD prophylaxis, while its appropriate dosing is debated. We performed a retrospective single-center study to examine the outcome of patients receiving ATG at the dose of 5 mg/kg as GVHD prophylaxis for unrelated donor (URD) HSCT. We collected data from all consecutive adult patients with hematological malignancies who had undergone allogeneic HSCT from URDs at the Stem Cell Transplant Center of the Città della Salute e della Scienza Hospital of Torino between July 2008 and July 2021. The primary aim was to ascertain the cumulative incidence (CI) for acute GVHD (aGVHD) and chronic GVHD (cGVHD); the secondary aim was to ascertain the CI for NRM (Non-Relapse Mortality) and RI (Relapse Incidence), as well the overall survival (OS) and infection incidence within 30 days of transplantation. We included in the analysis 226 patients who collectively underwent 231 HSCTs. The CI of grade II-IV aGVHD was found to be 29.9%, while that of moderate to severe cGVHD was 29.8%. The CI of NRM recorded at 1, 2, and 3 years after transplant was 18.2%, 19.6%, and 20.2%, respectively. The CI of RI at 1, 2, and 3 years from transplant was recorded to be 17.8%, 21.0%, and 21.6%, respectively. The median follow-up was 56 months, while the median OS for the whole cohort was not established; the OS at 1, 3, and 5 years from transplant was 69.6%, 59.3%, and 57.2%, respectively. We registered 88 bacteremias in 82/231 patients (35.5%), while invasive fungal infections occurred in 12/231 patients (5.2%). Our study suggests that the use of ATG at 5 mg/kg is highly effective in limiting the occurrence of both aGVHD and cGVHD, ensuring a low NRM, RI, and infection incidence.

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.

A critical review of belumosudil in adult and pediatric patients with chronic graft-versus-host disease

INTRODUCTION

Chronic graft-versus-host disease (cGVHD) is a complication of allogeneic hematopoietic cell transplantation (allo-HCT) and is the main cause of late non-relapse mortality (NRM). Three new agents are now approved to treat cGVHD, of which belumosudil has a unique and dual mechanism of action of i) targeting the Rho-GTPase-associated coiled-coil kinase 2 (ROCK2) in T helper follicular cells (TFH) and TH17 cells, this results in downregulation of proinflammatory cytokines (interleukin -21 and 17), the former in a STAT3-dependent mechanism, ii) inhibition of tissue fibrosis by targeting stress-induced polymerization of G-actin fibrils by inhibiting the Rho-ROCK-MRTF pathway.

AREAS COVERED

In this review we describe the epidemiology of cGVHD, its cardinal symptoms, preventive and therapeutic options, including second-line approved therapies in the United States (US). Clinical trial data that led to approval of belumosudil is discussed, in addition to the clinical scenarios in which the approved drugs may be most applicable.

EXPERT OPINION

Belumosudil is approved for treatment of adult and pediatric patients ≥ 12 years with cGVHD after failing two lines of therapy based on results of the ROCKstar study that showed high overall response rates (ORR), favorable adverse effect profiles, and low rates of severe infections. With the availability of three new agents for treatment of cGVHD, treating physicians have more therapeutic options for patients and have additional options of development new clinical trials using a combination of recently approved drugs.

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.

Comparison of Benefits and Risks Associated with Anti-T-Lymphocyte Globulin (ATLG) Serotherapy in Methotrexate (MTX)- versus Mycophenolate Mofetil (MMF)-Based Hematopoietic Stem Cell Transplantation

Background: Serotherapy with anti-T lymphocyte globulin (ATLG, Grafalon, formerly ATG-Fresenius) is established for the prevention of severe graft-versus-host disease (GVHD) after hematopoietic stem cell transplantation (HSCT). The evidence from prospective studies is predominantly derived from a setting where methotrexate (MTX) and a calcineurin inhibitor (CNI) are used as the backbone of GVHD prophylaxis. The efficacy of ATLG in combination with CNI and mycophenolate mofetil (MMF) has not been investigated as much, particularly in terms of a direct comparison with its effects when combined with CNI/MTX. A total of 401 HSCTs from two Austrian transplant centers were retrospectively evaluated. We included peripheral blood transplants from early- or intermediate-stage (excluding advanced/refractory) hematological diseases from matched siblings or 10/10 or 9/10 matched unrelated donors with CNI/MTX or CNI/MMF prophylaxis, either without (n = 219) or with ATLG (n = 182). Overall, ATLG significantly reduced the risk for all-cause mortality by multivariate Cox analysis (HR 0.53; p = 0.002). Stratification by postgrafting prophylaxis type revealed a significant survival advantage for ATLG in the CNI/MMF cohort (HR 0.49; p = 0.001; n = 193), while its effect on survival in the CNI/MTX cohort was not significant (HR 0.87; p = 0.56; n = 208). In unrelated HSCT with CNI/MMF prophylaxis, ATLG exhibited its greatest survival benefit (HR 0.34; p = 0.001; n = 104). In the context of CNI/MMF, ATLG may provide even greater benefits than in the setting of CNI/MTX for post-grafting immunosuppression. Future prospective studies on ATLG should therefore focus on CNI/MMF-based transplants, which are widely performed in elderly or comorbid patients not expected to tolerate a standard course of MTX.

Clinical Benefit of Low-Dose Antithymocyte Globulin-Thymoglobulin as Graft-versus-Host Disease Prophylaxis in Patients Receiving Allogeneic Peripheral Blood Stem Cell Transplantation from HLA-Identical Donors

Graft-versus-host disease (GVHD) is a major complication of allogeneic peripheral blood stem cell transplantation (PBSCT). Previous randomized studies have already shown that the use of several types of antihuman T lymphocyte immune globulin (ATG) as GVHD prophylaxis can reduce the incidence of acute GVHD and chronic GVHD. However, the efficacy and safety of PBSCT from HLA-identical donors with low-dose ATG remain unclear. This study aimed to clarify the efficacy and safety of PBSCT from HLA-identical donors with low-dose ATG compared with PBSCT from HLA-identical donors without ATG. To do so, we retrospectively analyzed the outcomes of patients who underwent allogeneic PBSCT from HLA-identical donors with low-dose ATG-thymoglobulin (ATG-T; 2.5 mg/kg) versus those who did not receive ATG-T. Patient data were collected retrospectively from the medical records of Anjo Kosei Hospital. This study was conducted from 2009 to the final follow-up in October 2022. Forty-seven of 91 patients received ATG-T between January 2009 and March 2020. ATG-T reduced the incidence rates of moderate-to-severe chronic GVHD (hazard ratio [HR], .15; 95% confidence interval [CI], .057 to .41; P < .0010) and nonrelapse mortality (HR, .21; 95% CI, .0058 to.75, P = .016) without increasing the risk of relapse. Overall survival did not differ significantly between the 2 groups; however, the low-dose ATG-T group had better moderate-to-severe chronic GVHD-free, relapse-free survival rates (HR, .47; 95% CI, .27 to .80, P = .0054) than the non-ATG-T group. In addition, multistate analysis revealed that the low-dose ATG-T group had better current GVHD-free, relapse-free survival at 24 months after transplantation (45% [95% CI, 29% to 63%)] versus 21% [95% CI, 9.1% to 34%]; P = .015). Low-dose ATG-T was not associated with increased incidence of infections or adverse events. Our findings suggest that low-dose ATG-T can be beneficial for patients receiving PBSCT from HLA-identical donors. © 2023 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

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.

Pre-Transplant Total Lymphocyte Count Determines Anti-Thymocyte Globulin Exposure, Modifying Graft-versus-Host Disease Incidence and Post-Transplant Thymic Restoration: A Single-Center Retrospective Study

The use of anti-thymocyte globulin (ATG) as part of conditioning to prevent graft-versus-host disease (GVHD) may severely impair immune reconstitution (IR). We analyzed relationships between ATG exposure, the recipient lymphocyte count, IR, and transplant outcome. We retrospectively reviewed patients aged ≤ 18 years who underwent allogeneic HSCT between April 2005 and April 2020. The outcomes of interest included the incidence of GVHD, overall survival (OS), and IR. IR was analyzed through thymic magnetic resonance imaging (MRI) and by quantifying T CD4+ and recent thymic emigrants (RTEs). The ATG-exposed group was split into a low ATG/lymphocyte ratio subgroup (ratio < 0.01) and a high ATG/lymphocyte ratio subgroup (ratio > 0.01). The low ratio subgroup had a higher incidence of GVHD (29 [59%] vs. 7 [16.6%]) but a better IR in both laboratory and MRI imaging assessments (p < 0.0001). The median thymic volume in the low ratio subgroup was significantly higher (14.7 cm3 vs. 4.5 cm3, p < 0.001). This was associated with a better OS and lower transplant-related mortality (TRM) (80.4% vs. 58.0%, p = 0.031) and (13.1% vs. 33.0%, p = 0.035). An individualized approach to ATG dosing allows for the obtainment of rapid thymic reconstitution and the best transplant-related outcomes.

Impact of oral microbiota on pathophysiology of GVHD

Allogeneic transplantation of hematopoietic cells is the only curative therapy for several hematopoietic disease in which patients receive cytotoxic conditioning regimens followed by infusion of hematopoietic stem cells. Although the outcomes have improved over the past decades, graft-versus-host-disease (GVHD), the most common life-threatening complication, remains a major cause of non-relapse morbidity and mortality. Pathophysiology of acute GVHD characterized by host antigen-presenting cells after tissue damage and donor T-cells is well studied, and additionally the importance of recipient microbiota in the intestine is elucidated in the GVHD setting. Oral microbiota is the second most abundant bacterial flora in the body after the intestinal tract, and it is related to chronic inflammation and carcinogenesis. Recently, composition of the oral microbiome in GVHD related to transplantation has been characterized and several common patterns, dysbiosis and enrichment of the specific bacterial groups, have been reported. This review focuses on the role of the oral microbiota in the context of GVHD.

Engraftment syndrome following Hematopoietic stem cell transplantation: a systematic approach toward diagnosis and management

Engraftment syndrome (ES) is a non-infectious complication seen both in autologous and allogeneic hematopoietic stem cell transplants and is characterized by the presence of non-infectious fever, diarrhea, skin rash, pulmonary infiltration, pulmonary edema, and deranged renal and liver function tests This review will be delineating the incidence of ES, important differential diagnoses to be considered and management options. The literature search was done through various databases like PubMed, Google scholar, Cochrane library, and EMBASE. The incidence of engraftment syndrome was ranging from 8 to 50% in patients undergoing Autologous stem cell transplantation while the incidence was 10-77% in patients undergoing Allogeneic stem cell transplantation. Fever was the most commonly observed symptom of ES in both Autologous and Allogeneic stem cell transplantation while the second most frequently reported symptom was non-infectious diarrhea in patients undergoing autologous stem cell transplantation and Skin rash in patients with Allogeneic stem cell transplantation. Pro-inflammatory cytokines and immune response dysregulation were highlighted as the mechanism behind ES development. The significant difference between ES and aGVHD was observed based on cytokines, with IL-12, IL-1β, IL-6, TNF-α, and IFN-γ levels in plasma being higher in patients with ES as compared to patients with aGVHD. Intravenous methylprednisolone was used as the treatment of choice in the majority of the studies. Overall the incidence of ES was high in patients undergoing allogeneic hematopoietic stem cells transplantation. The survival in patients developing ES was less compared to those who did not develop ES. Engraftment syndrome is one of the complications following hematopoietic stem cell transplantation that need early identification, differentiation from infectious complications, and aGVHD and timely initiation of corticosteroids 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.

Impact of Anti-T-lymphocyte globulin dosing on GVHD and Immune reconstitution in matched unrelated myeloablative peripheral blood stem cell transplantation

Data on the influence of different Anti-lymphocyte globulin (ATLG) doses on graft versus host disease (GVHD) incidence and immune reconstitution in matched unrelated (MUD) allogeneic Stem cell transplantation (allo-SCT) is limited. This retrospective study conducted at the University Medical-Center Hamburg compares GVHD and Immune reconstitution after myeloablative MUD (HLA 10/10) PBSC allogeneic stem cell transplant between 30 mg/Kg (n = 73) and 60 mg/Kg (n = 216) ATLG. Detailed phenotypes of T, B natural killer (NK), natural killer T (NKT) cells were analyzed by multicolor flow at day 30, 100, and 180 posttransplant. Neutrophil and platelet engraftments were significantly delayed in the 60 mg/kg group with a higher Cumulative incidence of Infections (67% vs 75% p = 0.049) and EBV (21% vs 41% p = 0.049) reactivation at day 100 in this group. In the 30 mg/kg group, we observed a faster reconstitution of naïve-B cells (p < 0.0001) and γδ T cells (p = 0.045) at day+30 and a faster naïve helper T-cell (p = 0.046), NK-cells (p = 0.035), and naïve B-cell reconstitution (p = 0.009) at day+180. There were no significant differences in aGVHD, cGVHD, NRM, RI, PFS, and OS between the groups. The choice of ATLG dose has significant impact on IR but not on GVHD after MUD-allo-SCT. Higher doses are associated with delayed engraftment and increased infections.

Advantages of peripheral blood stem cells from unrelated donors versus bone marrow transplants in outcomes of adult acute myeloid leukemia patients

BACKGROUND AIMS

In allogeneic stem cell transplantation, unrelated donors are chosen in cases where appropriate related donors are not available. Peripheral blood stem cells (PBSCs) are more often selected as a graft source than bone marrow (BM). However, the prognostic benefits of PBSCs versus BM transplants from unrelated donors have not been carefully examined in patients with acute myeloid leukemia (AML). This study compared outcomes of adult AML patients who underwent unrelated PBSC and BM transplantation, evaluating post-transplant complications, including engraftment, graft-versus-host disease (GVHD) and infections, and determined subgroups of patients who are most likely to benefit from unrelated PBSCs compared with BM transplants.

METHODS

The authors analyzed 2962 adult AML patients who underwent unrelated PBSC or BM transplants between 2011 and 2018 (221 PBSC and 2741 BM) using the Japanese nationwide registry database, in which graft source selection is not skewed toward PBSCs.

RESULTS

In 49.7% of patients, disease status at transplantation was first complete remission (CR1). In 57.1% of cases, HLA-matched donors were selected. Myeloablative conditioning was performed in 75.1% of cases, and anti-thymocyte globulin (ATG) was added to conditioning in 10.5%. Multivariate analyses showed a trend toward favorable non-relapse mortality (NRM) in PBSC recipients compared with BM recipients (hazard ratio [HR], 0.731, P = 0.096), whereas overall survival (OS) (HR, 0.959, P = 0.230) and disease-free survival (DFS) (HR, 0.868, P = 0.221) were comparable between PBSC and BM recipients. Although the rate of chronic GVHD (cGVHD) was significantly higher in PBSC patients (HR, 1.367, P = 0.016), NRM was not increased, mainly as a result of significantly reduced risk of bacterial infections (HR, 0.618, P = 0.010), reflecting more prompt engraftments in PBSC recipients. Subgroup analyses revealed that PBSC transplantation was advantageous in patients transplanted at CR1 and in those without ATG use. PBSC recipients experienced significantly better OS and/or DFS compared with BM recipients in this patient group.

CONCLUSIONS

The authors' results confirmed the overall safety of unrelated PBSC transplantation for adult AML patients and suggested an advantage of PBSCs, especially for those in CR1. Further optimization of the prophylactic strategy for cGVHD is required to improve the overall outcome in transplantation from unrelated PBSC donors.

Anti-T-Lymphocyte Immunoglobulin (Grafalon) as an Induction Agent for Renal Transplantation: A Real-World, Retrospective, Single-Center Experience

OBJECTIVES

Polyclonal antithymocyte globulins are widely used in the induction regimens of solid-organ transplant recipients; however, their doses and outcomes remain to be standardized in Indian patients. We report our clinical experience from the real-world use of Grafalon (an anti-T-lymphocyte globulin; ATG-Fresenius) as an induction agentin renal transplant recipients from India.

MATERIALS AND METHODS

In this retrospective, single- center, observational study, we analyzed the medical records of 177 consecutive, kidney-only transplant recipients who received induction therapy with Grafalon from September 2016 to March 2018 at our center. Incidences of biopsy-proven acute rejection and graft dysfunction, immunosuppression protocol, Grafalon dosage, 18-month post-transplant graft and patient survival, treatment-related adverse events, and infective complications were reported.

RESULTS

Mean age of patients was 41.46 years (range, 14-68 years), (85% were males). The average dose of Grafalon was 5.81 ± 1.95 mg/kg (range, 2.41 to 10.07 mg/kg). Graft dysfunction (ie, at least 20% increase in serum creatinine from baseline) was observed in 26 patients (14%): 11 patients (6.2%) had biopsy-proven acute rejections, 11 patients (6.2%) had acute tubular necrosis, and 4 patients (2.2%) had calcineurin inhibitor toxicity. Seven deaths were recorded: 2 each from fungal pneumonia, bacterial pneumonia, and acute coronary syndrome and 1 with urinary tract infection with septicemia. Death-censored graft survival was 100% at 12 months and 98% at 18-month follow-up; overall patient survival was 96%. Infective complications occurred in 40 patients (22.5%), with the most common being urinary tract infection in 32 patients (18%). No malignancies were reported.

CONCLUSIONS

Use of a potent induction therapy like anti-T-lymphocyte globulin (Grafalon) is often restricted by the risk of side effects and lack of local clinical evidence supporting its role in long-term graft survival. Real-world evidence support the safe and effective use of anti-T-lymphocyte globulin as an induction agent in renal transplant recipients with an individualized dosing approach.

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.

HLA 1-3 antigen-mismatched related peripheral blood stem cells transplantation using low-dose antithymocyte globulin versus unrelated cord blood transplantation

Little information is available regarding whether unrelated cord blood transplantation (CBT) or an HLA 1-3 antigen-mismatched related donor peripheral blood stem-cell transplantation (PBSCT) using low-dose anti-thymocyte globulin (ATG) is superior as an alternative transplantation for patients who lack an HLA-matched sibling or unrelated donor. Therefore, we evaluated 7861 patients with hematologic malignancies (aged 0 to 70 years) who received either a CBT without ATG (CBT-no ATG, n = 7034) or an HLA 1-3 antigen-mismatched related donor PBSCT using low-dose ATG (PBSCT-ATG, n = 827). CBT-no ATG was associated with significantly better overall survival (OS) than the use of a PBSCT-ATG (hazard ratio [HR], 0.77; p < .001), although PBSCT-ATG patients with an HLA 1 antigen-mismatch showed OS comparable to that in the CBT-no ATG group. Neutrophil and platelet engraftment was significantly delayed, whereas the incidences of nonrelapse mortality, and severe graft-versus-host disease (GVHD) were significantly lower in the CBT-no ATG group. The incidences of relapse and chronic GVHD were comparable between these donors. In conclusion, CBT-no ATG may be a better alternative than HLA-mismatched related donor PBSCT using low-dose ATG. Notably, HLA 2-3 antigen mismatch-related transplantation with low-dose ATG had significant adverse effects on transplantation outcomes.

Outcomes of Allogeneic Hematopoietic Cell Transplantation in T-cell Prolymphocytic Leukemia: A Contemporary Analysis from the Center for International Blood and Marrow Transplant Research

T cell prolymphocytic leukemia (T-PLL) is a rare, aggressive malignancy with limited treatment options and poor long-term survival. Previous studies of allogeneic hematopoietic cell transplantation (alloHCT) for T-PLL are limited by small numbers, and descriptions of patient and transplantation characteristics and outcomes after alloHCT are sparse. In this study, we evaluated outcomes of alloHCT in patients with T-PLL and attempted to identify predictors of post-transplantation relapse and survival. We conducted an analysis of data using the Center for International Blood and Marrow Transplant Research database on 266 patients with T-PLL who underwent alloHCT between 2008 and 2018. The 4-year rates of overall survival (OS), disease-free survival (DFS), relapse, and treatment-related mortality (TRM) were 30.0% (95% confidence interval [CI], 23.8% to 36.5%), 25.7% (95% CI, 20% to 32%), 41.9% (95% CI, 35.5% to 48.4%), and 32.4% (95% CI, 26.4% to 38.6%), respectively. In multivariable analyses, 3 variables were associated with inferior OS: receipt of a myeloablative conditioning (MAC) regimen (hazard ratio [HR], 2.18; P < .0001), age >60 years (HR, 1.61; P = .0053), and suboptimal performance status, defined by Karnofsky Performance Status (KPS) <90 (HR, 1.53; P = .0073). Receipt of an MAC regimen also was associated with increased TRM (HR, 3.31; P < .0001), an elevated cumulative incidence of grade II-IV acute graft-versus-host disease (HR, 2.94; P = .0011), and inferior DFS (HR, 1.86; P = .0004). Conditioning intensity was not associated with relapse; however, stable disease/progression was correlated with increased risk of relapse (HR, 2.13; P = .0072). Both in vivo T cell depletion (TCD) as part of conditioning and KPS <90 were associated with worse TRM and inferior DFS. Receipt of total body irradiation had no significant effect on OS, DFS, or TRM. Our data show that reduced-intensity conditioning without in vivo TCD (ie, without antithymocyte globulin or alemtuzumab) before alloHCT was associated with long-term DFS in patients with T-PLL who were age ≤60 years or who had a KPS >90 or chemosensitive disease.

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.

Low-dose thymoglobulin for prevention of chronic graft-versus-host disease in transplantation from an HLA-matched sibling donor

Despite the proven efficacy of anti-T-cell or antithymocyte globulin (ATG) for chronic graft-versus-host disease (GVHD) prevention in transplantation from an unrelated donor, dosing protocols and the effects of ATG on relapse and infection remain controversial. In the setting of transplantation from an HLA-matched sibling (MSD-T), few randomized studies have been conducted. We conducted a prospective, single-center, open-label, randomized study of low-dose thymoglobulin (2.5 mg/kg) for chronic GVHD prevention. A total of 120 patients with acute leukemia were randomly assigned in a 1:1 ratio. After a median follow-up of 27 months, the cumulative incidence of chronic GVHD in the ATG and non-ATG groups was 25.0% and 65.4% (p < 0.001), respectively. The ATG group had an increased relapse rate compared with the non-ATG-group (20.0% vs. 9.3%; p = 0.055), with risks that differed according to cytogenetic subgroup (high-risk, 29.6% vs. 9.3%, p = 0.042; non-high-risk, 12.2% vs. 9.2%, p = 0.596). Chronic GVHD-free and relapse-free survival (cGRFS) was higher in the ATG group (46.7% vs. 19.4%; p = 0.070), and the difference was significant in a cytogenetic non-high-risk subgroup (45.5% vs. 0%; p = 0.038). No differences were observed in other survival outcomes. Improved physical components in quality-of-life scores were observed in the ATG group at 12 months after transplantation. A higher rate of Epstein-Barr virus reactivation was observed in the ATG group (21.8% vs. 5.1%; p = 0.013), whereas no between-group differences for other complications. In conclusion, the low-dose thymoglobulin effectively prevented chronic GVHD in MSD-T, resulting in improvement in quality-of-life and cGRFS, whereas the necessity of caution for high-risk acute leukemia.

Anti-Thymocyte Globulin Prophylaxis in Patients With Hematological Malignancies Undergoing Allogeneic Hematopoietic Stem Cell Transplantation: An Updated Meta-Analysis

Background

Anti-thymocyte globulin (ATG) prophylaxis reduces graft-versus-host disease (GVHD) incidence. This meta-analysis aimed to explore the long-term efficacy of ATG and the influencing factors in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT).

Methods

PubMed, Embase, and Cochrane databases were searched for the relevant studies published up to August 2020. Data from randomized controlled trials (RCTs) on ATG prophylaxis for GVHD prevention in allo-HSCT patients were extracted.

Results

A total of eight relevant RCTs (1,348 patients) were included. ATG significantly reduced the incidence of grade III–IV aGVHD (P = 0.001) and cGVHD (P < 0.001). ATG significantly improved the GVHD relapse-free survival (GRFS) (P < 0.001). The immunosuppressive regimen (number and dose of immunosuppressants) was significantly reduced when using ATG (P = 0.005). Epstein-Barr virus (EBV) reactivation was high in patients receiving ATG (P = 0.003). No significant differences were detected in relapses, overall survival (OS), relapse-free survival (RFS), and non-relapse mortality (NRM) between the ATG and no ATG groups. Subgroup analyses revealed that the donor type and ATG formulation might be the possible sources of heterogeneity among the included studies. Meta-regression analysis showed that the cumulative dose of ATG did not affect GVHD, OS, relapse, RFS, and NRM.

Conclusion

Although ATG had no significant effect on relapse, RFS, and NRM, it significantly reduced the occurrence and severity of GVHD, improved the GRFS, and reduced the number and dose of immunosuppressants in patients undergoing allo-HSCT.

Graft-Versus-Host Disease Prophylaxis Using Low-Dose Antithymocyte Globulin in Peripheral Blood Stem Cell Transplantation-A Matched-Pair Analysis

Antithymocyte globulin (ATG) decreases chronic graft-versus-host disease (cGVHD) in peripheral blood stem cell transplantation (PBSCT); however, the optimal ATG dose has not been elucidated. We conducted a matched-pair analysis to evaluate whether low-dose ATG could inhibit cGVHD in HLA-matched PBSCT after myeloablative conditioning. A total of 70 patients who were enrolled in the JSCT-ATG15 study, a multicenter phase II clinical trial of 2 mg/kg of ATG (thymoglobulin) given on days -2 and -1, were compared with 210 patients not receiving ATG, who were matched for age, sex, disease, and calcineurin inhibitor selected from the database in Japan. The primary endpoint, cumulative incidence of extensive cGVHD at 2 years was significantly less in the ATG group than that in the non-ATG group (8.7% [95% CI, 3.5%-16.8%] versus 26.2% [95% CI, 20.3%-32.5%], P = .002). ATG significantly reduced the incidence of overall cGVHD and inhibited multiple organ involvement. The ATG group had favorable outcome compared to the non-ATG group in GVHD-free, and relapse-free survival at 2 years. In conclusion, low-dose ATG effectively inhibits chronic GVHD in PBSCT.