Role Of Antithymocyte Globulin Research Articles

The role of anti-thymocyte globulin in allogeneic stem cell transplantation (HSCT) from HLA-matched unrelated donors (MUD) for secondary AML in remission: a study from the ALWP /EBMT.

We compared outcomes, of 1609 patients with secondary acute myeloid leukemia (sAML) undergoing allogeneic transplantation (HSCT) in first complete remission (CR1) from matched unrelated donors (MUD) from 2010 to 2021, receiving or not receiving anti-thymocyte globulin (ATG) (ATG-1308, no ATG-301). Median age was 60.9 (range, 18.5-77.8) and 61.1 (range, 21.8-75.7) years, (p = 0.3). Graft versus host disease (GVHD) prophylaxis was cyclosporin-A with methotrexate (41%) or mycophenolate mofetil (38.2%), without significant differences between groups. Day 28, engraftment (ANC > 0.5 × 109/L) was 92.3% vs 95.3% (p = 0.17), respectively. On multivariate analysis, ATG was associated with lower incidence of grade II-IV and grade III-IV acute GVHD (p = 0.002 and p = 0.015), total and extensive chronic GVHD (p = 0.008 and p < 0.0001), and relapse incidence (RI) (p = 0.039), while non-relapse mortality (NRM) did not differ (p = 0.51). Overall survival (OS), and GVHD-free, relapse-free survival (GRFS) were significantly higher in the ATG vs no ATG group, HR = 0.76 (95% CI 0.61-0.95, p = 0.014) and HR = 0.68 (95% CI 0.57-0.8, p < 0.0001), with a tendency for better leukemia-free survival (LFS), HR = 0.82 (95% CI 0.67-1, p = 0.051). The main causes of death were the original disease, infection, and GVHD. In conclusion, ATG reduces GVHD and improves LFS, OS, and GRFS in sAML patients without increasing the RI, despite sAML being a high-risk disease.

The Role of Anti-Thymocyte Globulin in Peri-Operative Desensitization for Donor Specific Antibody Positive Lung Transplants

<h3>Purpose</h3> Among programs who perform lung transplants in the presence of pre-formed donor specific antibodies (DSA), peri-operative desensitization protocols may include anti-thymocyte globulin (ATG). However, the role of ATG in peri-operative desensitization is unknown. We conducted a retrospective cohort study to determine the impact of receiving ATG as part of our program's peri-operative desensitization protocol on allograft survival (death/re-transplant) and chronic lung allograft dysfunction (CLAD)-free survival among lung transplant recipients (LTRs) with DSA at the time of transplant. <h3>Methods</h3> All adult, first-time LTRs from January 2014 to December 2019 who had DSA at the time of transplant and received plasmapheresis (PLEX) and intravenous immune globulin (IVIG) as per our protocol were included in this study. Our protocol also includes peri-operative ATG, but it may be withheld for infection concern. Patients were divided into 2 groups: those who received peri-operative PLEX/IVIG/ATG and those who received PLEX/IVIG only. Kaplan Meier estimates of allograft survival and CLAD-free survival were compared using the log-rank test. Patient characteristics were compared using Fisher's exact test. Patients were followed until October 2021. <h3>Results</h3> At total of 125 LTRs were included: 96 (77%) received peri-operative PLEX/IVIG/ATG and 29 (23%) received PLEX/IVIG only. Compared to patients who received peri-operative ATG, patients who did not were more likely to be younger (p=0.003) and have cystic fibrosis/bronchiectasis (p=0.002), but they did not have significantly different allograft survival (p=0.1504) or CLAD-free survival (p=0.7043) (Figure 1). <h3>Conclusion</h3> Based on this data, likely confounded by small sample size and ATG contraindications, the benefit of ATG in peri-operative desensitization for DSA positive LTRs remains unclear. Adjustment analyses are ongoing, but a randomized controlled trial of peri-operative ATG for DSA positive LTRs is needed.

Role of antithymocyte globulin in matched sibling donor peripheral blood stem cell transplantation for hematologic malignancies.

Background:High incidence of chronic graft-versus-host disease (GVHD) has been a major drawback of matched sibling donor peripheral blood stem cell transplantation (MSD -PBSCT). This study aimed to investigate the safety and efficacy of antithymocyte globulin (ATG) as a standardized part of GVHD prophylaxis in patients receiving MSD -PBSCT.Methods:A total of 72 patients with hematological malignancies receiving MSD -PBSCT who displayed similar baseline characteristics were either given rabbit ATG ( n = 42) or no ATG (n = 30), in addition to cyclosporine, methotrexate, and mycophenolate mofetil as a standard GVHD prophylaxis regimen. Either patients or donors aged ≥40 years were included in the study. Thymoglobulin was administered at a daily dose of 1.5 mg/kg on day −5 and 3.5 mg/kg on day −4 prior to transplant (the total dose was 5 mg/kg)Results:After a median follow-up of 874 days, the 3-year cumulative incidence of chronic GVHD (cGVHD) was 37.3% in the ATG group and 52.1% in the non -ATG group. The 3-year overall and disease-free survival probability were 71.0% and 62.0% (ATG versus non -ATG, P = .262) and 66.7% and 58.4% (ATG versus non -ATG, P = .334). No difference was found in the 2-year cumulative incidence of nonrelapse mortality and relapse between the ATG and non -ATG groups. This significant reduction in the incidence of cGVHD without increased relapse risk and nonrelapse mortality led to a 3-year GVHD-free, relapse-free survival probability of 66.7% and 40.0% in the ATG and non-ATG groups, respectively.Conclusions:These data suggested that rabbit antithymocyte globulin in the current protocol for GVHD prophylaxis was well tolerable and efficacious.The clinical trial was registered on January 1, 2016 (ClinicalTrials.gov Identifier NCT02677181). https://clinicaltrials.gov/ct2/show/NCT02677181.

Role of antithymocyte globulin in patients with hematologic diseases undergoing umbilical cord blood transplantation: A systematic review and meta-analysis.

The role of antithymocyte globulin (ATG) in patients with hematologic diseases undergoing umbilical cord blood transplantation (UCBT) remains controversial. This systematic review and meta-analysis was conducted to comprehensively evaluate this issue. PubMed, Embase, and the Cochrane Library were systematically searched. Clinical studies reporting the impact of ATG- vs non-ATG-containing conditioning regimens on transplantation outcomes were identified. Twenty-five studies were included. ATG significantly prevented grade II-IV and grade III-IV acute graft-vs-host disease (GVHD) (11 studies, 5020 patients, HR: 0.49, 95% CI: 0.42-0.56, P<.001; 5 studies, 5490 patients, HR: 0.60, 95% CI: 0.46-0.80, P<.001) but not chronic GVHD (8 studies, 5952 patients, HR: 0.78, 95% CI: 0.51-1.20, P=.266). However, use of ATG was associated with increased transplantation-related mortality and inferior overall survival (9 studies, 4244 patients, HR: 1.79, 95% CI: 1.38-2.33, P<.001; 8 studies, 5438 patients, HR: 1.96, 95% CI: 1.56-2.46, P<.001). Our study did not recommend routine use of ATG in UCBT. Individualizing the ATG timing and dose based on patient characteristics to retain the prophylactic effects of ATG on GVHD without compromising the survival of UCBT recipients may be reasonable.

The Role of Anti-Thymocyte Globulin (ATG) in Patients with AML Transplanted in CR1 from Sibling and Unrelated Donors with or without Measurable Residual Disease (MRD) at the Time of Allogeneic Stem Cell Transplantation:a Study on Behalf of the Acute Leukemia Working Party (ALWP) of the European Society for Blood and Marrow Transplantation (EBMT)

Background Measurable residual disease (MRD) status pre- transplantation (alloSCT) predicts transplant outcome. Nonetheless, the impact of MRD persistence (MRD+) might be modulated by the use of anti thymocyte globulin (ATG) to prevent graft versus host disease (GVHD). Since GVHD is usually associated with the graft versus leukemia effect (GVL), there is a concern that ATG may increase relapse incidence (RI) in patients (pts) with a higher risk of relapse. We therefore investigated whether MRD status pre-alloSCT could impact the outcome in AML patients receiving alloSCT with ATG in CR1. Methods Study included adult AML pts undergoing alloSCT in CR1 during 2005-2016 period. First, we assessed the impact of MRD status, cytogenetics, FLT3-ITD and ATG in the whole population. Then, we studied the impact of ATG in relation to the MRD status at time of alloSCT. Results 1509 pts (1083 MRD negative (MRD-) and 426 MRD+) were included. In the MRD- group, 552 (48%) pts did not receive ATG (MRD− /no ATG) and 561 (52%) received ATG (MRD−/ATG), whereas within MRD+ cohort, 187 (44%) received no ATG (MRD+/no ATG) and 239 (58%) received ATG (MRD+/ATG). Median age was 51 (range 18-73) years, 51% were females. Acute GVHD grade III-IV and cGVHD were significantly lower in pts who received ATG in comparison to those who did not, translating into better GVHD-free, relapse-free survival (GRFS). Non-relapse mortality (NRM), RI, LFS and OS did not differ statistically. Focusing on the influence of MRD status, the overall RI was higher in MRD+ patients prior to alloSCT (38.7% vs. 22.8%, p Conclusions ATG reduces acute and cGVHD incidence and severity in AML pts undergoing alloSCT in CR1, resulting in improved GRFS. AML relapse risk remained unmodified by ATG use, even in the high risk subset of MRD+ patients' pre-alloSCT. Therefore, the use of ATG is not detrimental, and can allow for a significant clinical benefit in all CR1 AML patients who are candidate for alloSCT.

The Role of Anti-Thymocyte Globulin (ATG) in Patients with AML Transplanted in CR1 from Sibling and Unrelated Donors with or without Measurable Residual Disease (MRD) at the Time of Allogeneic Stem Cell Transplantation: A Study on Behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Background: Measurable residual disease (MRD) status pre-allogeneic stem cell transplantation (alloSCT) has been shown to predict outcome after transplant. Nonetheless, the impact of MRD persistence pre-alloSCT (MRD+) on transplant outcome might be modulated by relevant procedure features, such as conditioning intensity (Am J Hem 2018) or the use of anti thymocyte globulin (ATG) to prevent chronic graft versus host disease (cGVHD). Thus, since cGVHD is associated with graft versus leukemia effect (GVL), there is a concern that ATG may hamper GVL and increase relapse after transplant, especial in patients (pts) with a higher risk such as MRD+. For this purpose, we investigated whether MRD status pre-alloSCT modifies the effect of ATG on AML relapse post alloSCT in a large cohort of pts undergoing alloSCT in CR1, adjusting for other important variables on outcome.Methods: Inclusion criteria were adult AML pts with intermediate or adverse risk cytogenetics according to MRC and known FLT3-ITD status undergoing alloSCT in CR1 from either a HLA matched sibling (MSD) or (10/10) matched unrelated donors (MUD) during 2006-2017 period. First, we assessed the impact of MRD status, cytogenetics, FLT3-ITD and ATG as part of the conditioning in the whole population. Then, we studied the impact of ATG in accordance to MRD status at time of transplantation. Results are given at 2 years.Results: 1509 pts (1083 MRD negative (MRD-) and 426 MRD+) met the inclusion criteria. In the MRD- group, 552 (48%) pts did not receive ATG and 561 (52%) received ATG, whereas within MRD+ cohort, 187 (44%) received no ATG and 239 (58%) received ATG. Median age was 51 (range 18-73) years, 51% were females. Median year of alloSCT was 2014; 85% and 15% of the pts harbored intermediate and adverse risk cytogenetics, respectively. FLT3-ITD was identified in 51% of the pts, and NPM1 was mutated in 689 (56%). 59% of the pts underwent alloSCT from MSD while 41% from MUD. 82% of the pts received PB grafts; 58% received myeloablative (MAC) while 42% reduced intensity conditioning (RIC). The GVHD prophylaxis was CSA/MTX followed by CSA/MMF in the majority of the pts (75 %). 24% of pts developed grade II-IV while 7% grade III-IV acute (a) GVHD. cGVHD occurred in 30% of the pts, being extensive in half of them.In the overall population, aGVHD grade III-IV, cGVHD total and extensive were significantly lower in pts who received ATG in comparison to those who did not (6% vs 9%, p=0.04; 30% vs 45%, p<10-5; 15% vs 25%, p<10-4, respectively), translating into better GVHD-relapse-free survival (GRFS; 52% vs 43%, p=0.007). Non relapse mortality (NRM), relapse (RI), leukemia-free survival (LFS) and overall survival (OS) did not differ statistically between pts who received or did not receive ATG. Focusing on the influence of MRD status, RI was higher in MRD+ (39% vs. 23%, p<10-5), and LFS, OS and GRFS were all significantly superior in the MRD- cohort (66% vs 51% p<10-5; 73% vs 60% p=<10-5 and 51% vs 37% p<10-5, respectively). In contrast, NRM and GVHD did not differ between the groups.Then, we investigated the effect of ATG separately in MRD- and MRD+pts. By multivariate analysis, in MRD- pts, ATG did not affect RI (24% vs. 21% in no ATG and ATG; HR 0.80, P=0.17), but was associated with lower incidence of grade II-IV aGVHD, grade III-IV aGVHD, cGVHD, extensive cGVHD and NRM (HR 0.71 P=0.04, HR 0.37 P<10-3; HR 0.55 p<10-4, HR 0.42 P<10-4 and HR 0.66 p=0.05, respectively). As a consequence, ATG was associated with improved LFS, OS and GRFS (HR 0.74 P=0.02, HR 0.69 P=0.01 and HR 0.62 P<10-3). In MRD+ pts, ATG was associated with lower incidence of cGVHD and extensive cGVHD (HR 0.56 p= 0.03, HR 0.40 P=0.01, respectively), without a significant impact on any other alloSCT outcome parameters, including RI (39% vs 39% in no ATG and ATG; HR 1.02 P=0.92). FLT3 was associated with a higher RI in both MRD- and MRD+ pts. Finally, in both MRD- and MRD+groups, there was no interaction between ATG and cytogenetics, FLT3 and donor type as neither of these 3 factors influenced significantly the effect of ATG.Conclusions: ATG reduces severe (grade II-IV) acute and both chronic and extensive chronic GVHD in AML pts undergoing alloSCT in CR1, resulting in improved GRFS. Most importantly, the clinical benefit of ATG in terms of GVHD prevention was not achieved at the expense of an increased relapse incidence including in MRD+ pts pre-alloSCT. [Display omitted] DisclosuresMohty:MaaT Pharma: Consultancy, Honoraria.

Comparable 3-Year Disease-Free Survival Regardless of Anti-Thymocyte Globulin Inclusion in Pediatric Myeloablative Cord Blood Transplantation for Acute Lymphoblastic Leukemia

Background: Cord blood (CB) is routinely used as an alternative stem cell source for the treatment of children with acute leukemia and has been associated with high rates of disease-free survival (DFS). However, one controversial issue in pediatric CB transplantation is the role of anti-thymocyte globulin (ATG) as immunoprophylaxis. While inclusion of ATG in the conditioning may decrease the risk of graft-versus-host disease (GVHD), it could potentially abrogate graft-versus-leukemia effects and increase the risk of opportunistic infections. Thus, we compared outcomes in a uniform group of pediatric patients with acute lymphoblastic leukemia (ALL) who underwent myeloablative CB transplantation with or without ATG.Methods: Patients with ALL in morphologic remission (CR1 n=106, CR2 n=146, CR3 n=45) aged ≤ 20 years transplanted between 01/2007-12/2011 with high-dose total body irradiation-based conditioning and single or double unit CB grafts were eligible for analysis. CB units were 4-6/6 HLA-A,-B at the antigen-level, -DRB1 allele matched to the recipient and had CB unit with cryopreserved total nucleated cell dose of ≥ 2.5 x107/kg/unit. Cox regression models were built to evaluate potential differences in outcome in ATG versus non-ATG CB transplant recipients. The primary endpoint was 3-year DFS.Results: Of 297 patients, 92 received ATG and 205 did not. Age and disease status were similar in each group whereas ATG recipients were less likely to be CMV seropositive and more likely to receive single unit CB grafts. While neutrophil engraftment was similar in each group, the risk of day 100 grade II-IV acute GVHD [30% (95%CI: 21-40) versus 54% (95%CI: 47-61), p = 0.0002] and 3-year chronic GVHD [22% (95% CI: 14-31) versus 43% (95% CI: 36-50), p = 0.0008] were decreased in ATG recipients. However, day 100 grade III-IV aGVHD was comparable: 11% (95%CI: 5-18) in ATG versus 17% (95%CI: 12-23) in non-ATG recipients, p = 0.15]. The 3-year TRM was similar in both groups: 16% (95%CI: 10-25) in ATG versus 17% (95%CI: 13-23) in non-ATG recipients (p = 0.98). Relapse was also similar in ATG and non-ATG recipients: 17% (95%CI: 10-23) versus 27% (95%CI: 21-34, p = 0.12), respectively. In multivariate analysis, negative CMV serostatus was associated with reduced TRM risk [HR 0.55 (95%CI: 0.30-0.98), p = 0.004] whereas remission status CR2 or CR3 significantly increased relapse risk [HR 2.18 (95%CI: 1.22-3.89), p = 0.008], but inclusion of ATG had no effect on either outcome. With a median follow-up of survivors of 36 months (range 5-72), the 3-year DFS was 66% (95%CI: 56-76) and 55% (95%CI: 48-62) in ATG and non-ATG recipients, respectively (p = 0.23, Figure 1). The distribution of causes of death was similar in each group. In multivariate analysis, treatment failure risk was increased in patients transplanted in CR2 or CR3, but the inclusion of ATG had no effect (p = 0.24) (Table 1).Conclusion: Inclusion of ATG in pediatric myeloablative CB transplant for ALL is associated with a decreased risk of grade II-IV acute GVHD and chronic GVHD but not severe grade III-IV acute GVHD. There was no difference in 3-year DFS in each group and multivariate analysis revealed ATG inclusion had no impact upon treatment failure risk. These results indicate that optimization of both ATG and non-ATG conditioning platforms are needed in order to further improve CB transplantation survival in children with ALL. Unanswered questions include the impact of the formulation, dose and timing of ATG administration. These findings cannot be extrapolated for other diagnoses, reduced intensity conditioning, or adults.Table 1Hazard ratio(95% confidence interval)p-valueATG useConditioning without ATG Conditioning with ATG1.00 0.78 (0.52 – 1.18)0.24 Disease statusCR1 CR2, CR31.00 2.01 (1.31 – 3.08)0.001 [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Impact of antithymocyte globulin on new HLA groups for unrelated donor allogeneic stem cell transplantation.

e18017 Background: The outcomes of unrelated donor transplantation have improved with refinements in HLA testing. Recently, grouping of HLA matching for unrelated donor was suggested, defining by well-matched, partially-matched, and mismatched. In the current study, the role of anti-thymocyte globulin (ATG) for each group was evaluated. Methods: A total of 120 patients diagnosed as hematologic diseases and received allogeneic stem cell transplantation (SCT) from unrelated donor were retrospectively analyzed. Results: 28 patients were classified as well-matched, 52 as partially-matched, and 40 as mismatched. Among them, 73 patients received ATG as graft-versus-host disease (GVHD) prophylaxis. The overall survival (OS) rate was higher for well-matched group (82%) compared to partially-matched (53%) and mismatched (34%, p=0.076). For partially-matched group, the OS was significantly improved with ATG (83.3% vs. 38.6%, p=0.018). But, the OS was not different between groups with or without ATG for well-matched (87.5% vs. 66.7%, p=0.487) and mismatched (32.4% vs. 41.7%, p=0.215). ATG decreased the cumulative incidence of grade 3-4 acute GVHD (10% vs. 40.2%, p=0.068) and severe chronic GVHD (21.2% vs. 52.2%, p=0.037). The use of ATG (HR=0.248, p=0.029) was related with favorable OS for partially-matched group. However, the favorable effect of ATG was not observed in well-matched and mismatched groups. Conclusions: ATG effectively improved survival rate for partially-matched group in unrelated donor transplantation. However, the positive effect of ATG was not observed in well-matched and mismatched group.

Impact of ATG on new HLA groups for unrelated donor allogeneic stem cell transplantation.

6536 Background: The outcomes of unrelated donor transplantation have improved with refinements in HLA testing. Recently, grouping of HLA matching for unrelated donor was suggested, defining by well-matched, partially-matched, and mismatched. In the current study, the role of ATG for each group was evaluated. Methods: A total of 92 patients diagnosed as hematologic diseases and received allogeneic stem cell transplantation (SCT) from unrelated donor were retrospectively analyzed. Results: Nineteen patients were classified as well-matched, 42 as partially-matched, and 31 as mismatched. Among them, 57 patients received anti-thymocyte globulin (ATG) as graft-versus-host disease (GVHD) prophylaxis. The overall survival (OS) rate was higher for well-matched group (83%) compared to partially-matched (54%) and mismatched (34%, p=0.076). For partially-matched group, the OS was significantly improved with ATG (83.3% vs. 38.6%, p=0.018). But, the OS was not different between groups with or without ATG for well-matched (87.5% vs. 66.7%, p=0.487) and mismatched (32.4% vs. 41.7%, p=0.215). ATG decreased the cumulative incidence of grade 3-4 acute GVHD (10% vs. 40.2%, p=0.068) and severe chronic GVHD (21.2% vs. 52.2%, p=0.037). The use of ATG (HR=0.248, p=0.029) was related with favorable OS for partially-matched group. However, the favorable effect of ATG was not observed in well-matched and mismatched groups. Conclusions: ATG effectively improved survival rate for partially-matched group in unrelated donor transplantation. However, the positive effect of ATG was not observed in well-matched and mismatched group.

Role of Anti Thymocyte Globulin (ATG) Prior to Unrelated Donor Stem Cell Transplantation (URD SCT) in Patients with Hematologic Malignancies: A Single Center Experience

Role of Anti Thymocyte Globulin (ATG) Prior to Unrelated Donor Stem Cell Transplantation (URD SCT) in Patients with Hematologic Malignancies: A Single Center Experience

Role of Antithymocyte Globulin and Granulocyte-Colony Stimulating Factor-Mobilized Bone Marrow in Allogeneic Transplantation for Patients with Hematologic Malignancies

The main obstacle for allogeneic transplantation is delayed hematologic reconstitution and serious graft-versus-host disease (GVHD). The results of 128 patients with hematologic malignancies undergoing HLA -identical (n = 52) or HLA-haploidentical/mismatched (n = 76) hematopoietic stem cell transplantation (HSCT) performed during the same time period were compared. Patients with HLA-identical HSCT received unmanipulated granulocyte-colony stimulating factor -mobilized peripheral blood stem cells (G-PBSCs). Forty-six patients with HLA-haploidentical related HSCT received antithymocyte globulin (ATG) in conditioning regimens followed by the transplantation of the combination of unmanipulated G-PBSCs and granulocyte-colony stimulating factor -mobilized bone marrow (G-BM) and 30 patients with HLA-mismatched unrelated HSCT received ATG in conditioning regimens followed by the transplantation of unmanipulated G-PBSCs. All patients got successful hematopoietic engraftment. The cumulative incidences of grades I to II acute GVHD (aGVHD) on day 100 in the identical, haploidentical related and mismatched unrelated cohorts were 21.2%, 43.5%, and 53.3%, respectively. The cumulative incidences of chronic GVHD (cGVHD) in the identical, mismatched unrelated, and haploidentical related cohorts were 34.6%, 33.3%, and 10.9%, respectively. The 2-year relapse and treatment-related mortality (TRM) rates were 19.2%, 23.9%, 23.3%, and 9.6%, 8.7%, 10% for patients who underwent identical, HLA-haploidentical related, and mismatched unrelated transplantation, respectively. The 2-year probabilities of leukemia-free survival and overall survival were 72.2%, 70.6%, 68.1%, and 76.5%, 77.8%, 70.0% after identical, haploidentical related and mismatched unrelated transplantations, respectively. Multivariate analyses showed that only advanced disease stage and a diagnosis of disease had increased risk of relapse, treatment failure, and overall mortality. In conclusion, it is a feasible approach with acceptable outcomes for patients undergoing HLA-haploidentical related HSCT by the combination of G-PBSCs and G-BM with conditioning regimens including ATG.

Thymoglobulin ® Rabbit Anti-Thymocyte Globulins (r-ATG) Induces Faster Platelet Recovery and Does Not Suppress Granulocyte Engraftment in a Non-Myeloablative Stem Cell Transplantation Setting.

Introduction: The role of anti thymocyte globulin in GVHD prevention is well established, but it is also known that anti thymocyte globulin induces leucopenia and thrombocytopenia and as such might theoretically delay engraftment. Additionally, fast platelet engraftment is a marker for good hematopoietic stem cell graft function. We have prospectively compared the effect of Thymoglobulin on engraftment of granulocytes and platelets following a single non-myeloablative conditioning protocol in a randomized study.Methods: 28 consecutive patients undergoing SCT were conditioned with the NST protocol (I.V.fludarabine 30mg/m2/day (days −10 to −5) and I.V. busulfex (3.2 mg\\kg on days −6 and −5), with or without I.V. Thymoglobulin according to randomization (days −4 to −1). Thymoglobulin dosing schedule: a cumulative dose of 7.5 mg/kg r-ATG was given with the following program 0.5 mg/kg day −4, 2.0 mg/kg day −3, 2.5 mg/kg day −2, 2.5 mg/kg day −1. Patients were followed for engraftment of leukocytes and platelets.Results: only one patient rejected the graft (conditioned without Thymoglobulin, NS). In 4 patients underlying disease progression prevented engraftment of either ANC or platelets (2 per group). The median time to ANC engraftment was similar between the groups, 15±2.8 and 14±2.9 days for the Thymoglobulin and control groups respectively (figure 1, p=0.21). However, the median time for platelet engraftment was significantly shorter in patients receiving Thymoglobulin as part of the conditioning. Platelet recovery occurred 9.5±1.2 and 11±2.5 days for the Thymoglobulin and control groups respectively (figure 2, p=0.018).Conclusions: in the non-myeloablative setting, Thymoglobulin induces faster platelet recovery and does not delay ANC engraftment. [Display omitted] [Display omitted]