Dose Of rATG Research Articles

Comparative Efficacy and Safety of Low-Dose Versus Standard-Dose Rabbit Antithymocyte Globulin Induction Strategy in Kidney Transplant Recipients: Insights From a Single-Center Experience in North India.

Background Rabbit antithymocyte globulin (rATG) is frequently utilized as an induction therapy in kidney transplant recipients (KTRs). Full-dose rATG induction therapy (7-10 mg/kg) has been associated with increased morbidity. However, definitive data on the appropriate rATG dosage remains scarce. In this study, we evaluated the efficacy and tolerability of varying rATG doses in KTRs. Methodology A single-center, retrospective, observational study was conducted between 2009 and 2014 in a cohort of 208 KTRs who received rATG induction therapy. Patients included in the study had received two to three consecutive doses of rATG as part of their planned induction protocol. Participants were categorized into the following two groups based on the cumulative dosage of rATG received during induction therapy: group A received 2 or 2.5 mg/kg, while group B received ≥3 mg/kg. The five-year follow-up data were analyzed. Results A cumulative rATG dose of 2 or 2.5 mg/kg and ≥3 mg/kg was given to 122 and 86 patients, respectively. The incidence of delayed graft function (DGF), acute rejection episodes, total graft loss, death, and death-censored graft loss was 6.25%, 3.84%, 7.21%, 4.32%, and 2.88%, respectively. Two malignancies and 141 infectious complications were noted. There was no significant difference between the groups regarding DGF, total graft loss, death, death-censored graft loss, infectious complications, and incidence of acute rejection episodes. Deceased donor kidney transplantation was identified as a significant predictor of acute rejection episodes (odds ratio = 9.19, 95% confidence interval = 1.567-53.907; p = 0.014). Conclusions The dosage for rATG induction therapy for KTRs should be tailored based on immunological and other factors impacting graft survival, along with a comprehensive risk assessment for potential infectious complications. A cumulative dose of 2.0 or 2.5 mg/kg could be optimal, offering effective induction therapy in KTRs with excellent graft survival rates and potentially fewer infectious complications.

Patients Beyond the Optimal Range of rATG-AUC Still Benefit from the Targeted Dosing Strategy in Unmanipulated Haplo-PBSCT

Rabbit antithymocyte globulin (rATG) is widely used in allogeneic hematopoietic stem cell transplantation to prevent graft failure and severe graft-versus-host disease (GVHD). We developed a rATG-targeted dosing strategy based on the optimal areas under the concentration-time curve (AUC) of active rATG. This study compared the outcomes of the optimal AUC arm with nonoptimal AUC arm to assess the effect of the rATG-targeted dosing strategy. Eighty patients (median age: 32 years) with hematological malignancies who received their first haplo-PBSCT were enrolled successively. With rATG-targeted dosing, the AUC values of 60 patients (75%, optimal AUC arm) fell within the optimal range (100-148.5 UE/mL/day) and 20 fell beyond this range (nonoptimal AUC arm). In the historical control group of 102 haplo-PBSCT patients who received a fixed dose of rATG (10 mg/kg), less patients fell within the optimal range (57.8%, P = .016). Looking at the nonoptimal AUC arms in both groups, lower cumulative incidence of CMV was noted in the targeted dosing group compared with the historical control group(50.0%, 95% CI, 30.8%-72.9% versus 81.4%, 95% CI, 68.6%-91.3%; P = .004). The cumulative incidences of EBV, relapse, overall survival and disease-free survival tended to be superior in the nonoptimal AUC arm in the targeted dosing group compared with the historical control. In the targeted dosing group, the cumulative incidence of cytomegalovirus (CMV) reactivation on day +180 tended to be lower in the optimal AUC arm (30.0%, 95% CI, 20.1%-43.3%) compared with the nonoptimal AUC arm (50.0%, 95% CI, 30.8%-72.9%, P = .199) without statistical difference. There were no significant differences of acute or chronic GVHD, relapse, nonrelapse mortality, overall survival, disease-free survival or lymphocyte reconstitution between the two arms. In conclusion, the rATG-targeted dosing strategy made the exposure of active rATG in more patients with the optimal AUC range. Even patients who fell beyond this range would still benefit from the strategy.

Induction immunosuppression strategies and outcomes post-lung transplant: A single center experience

PurposeCurrently 80% of lung transplant centers use induction immunosuppression. However, there is a lack of standardization of induction protocols within and across lung transplant centers. This study explores the association of two different induction immunosuppression strategies used at our center [single dose rabbit antithymocyte globulin (rATG) vs. alemtuzumab] compared to no induction with immunologic and clinical outcomes after lung transplantation. MethodsA total of 174 consecutive lung transplant recipients (LTR) between 2016 and 2019 were included in the analysis. Twenty nine LTR (16.7%) received no induction, 22 LTR (12.6%) received alemtuzumab, 123 LTR (70.6%) received a single dose of rATG; 1.5 mg/kg within 24 h of transplant for induction. All LTR had a negative flow cytometry crossmatch on the day of the transplant. All LTR were assessed for de novo HLA donor-specific antibodies (DSA) development and clinical outcomes, including the risk of acute cellular rejection (ACR), antibody-mediated rejection (AMR), chronic lung allograft dysfunction (CLAD), and overall survival post-transplant. ResultsThe median lung allocation score (LAS) was significantly higher in LTR that did not receive Induction immunosuppression (76; range = 35.3–94.3) compared to induction with rATG (41.6; range = 31.6–91) and alemtuzumab (51; range = 33.1–88.2) (p < 0.001). De novo HLA DSA were detected in 50/174 (28.7%) LTR within 12 months post-transplant. They were detected in 13/29 (44.8%) LTR without induction immunosuppression compared to 28/123 (22.8%) and 9/22 (40.9%) LTR with rATG and alemtuzumab induction, respectively (p = 0.02). The percent freedom from ACR rates between LTR who received alemtuzumab induction was significantly higher compared to LTR who received rATG or no induction at 1 (p = 0.02), 2 (p = 0.01) and 3 (p = 0.05) years post-transplant. In addition, the overall 1-year survival rates were significantly higher in LTR who received rATG or alemtuzumab induction compared to LTR without induction immunosuppression (p = 0.02). ConclusionInduction immunosuppression strategies utilizing rATG or Alemtuzumab have unique and contrasting benefits in LTR. Combination of alemtuzumab induction and a lower dose of maintenance immunosuppression may reduce the incidence of ACR in LTR. Single-dose rATG or alemtuzumab induction immunosuppression may also improve the 1 year overall LTR survival compared to no induction.

Efficacy and safety of single-dose anti-thymocyte globulin versus basiliximab induction therapy in pediatric kidney transplant recipients: A retrospective comparative cohort study.

This study aimed to compare the efficacy and safety of basiliximab (BAS) versus a single dose of anti-thymocyte globulin (r-ATG) induction therapy in pediatric kidney transplant recipients (KTRs). This single-center retrospective comparative cohort study included all pediatric KTRs from May 2013 to April 2018 and followed up to 12 months. In the first period, all recipients received BAS, while from May 2016, a single 3 mg/kg dose of r-ATG was instituted. Maintenance therapy consisted of a calcineurin inhibitor plus prednisone plus azathioprine or mycophenolate. A total of 227 patients were included (BAS, n = 113; r-ATG, n = 114). The main combination of immunosuppressive drugs was tacrolimus, prednisone, and azathioprine in both groups (87% vs. 88%, p = .718). Patients receiving r-ATG showed superior survival-free of the composite endpoint (acute rejection, graft loss, or death; 76% vs. 61%, p = .003; HR 2.08, 1.29-3.34, p = .003) and lower incidence of biopsy-proven acute rejection (10% vs. 21%, p = .015). There was no difference in the overall incidence of CMV infection (33% vs. 37%, p = .457), PTLD (1% vs. 3%, p = .309), 30-day hospital readmissions (24% vs. 23%, p = .847), and kidney function at 12 months (86 ± 29 vs. 84 ± 30 mL/min/1.73m2, p = .614). These data suggest that induction therapy with a single 3 mg/kg dose of r-ATG is associated with higher efficacy for preventing acute rejection and similar safety profile compared to BAS.

Impact of rabbit anti-thymocyte globulin (ATG) exposure on outcomes after ex vivo T-cell–depleted hematopoietic cell transplantation in pediatric and young adult patients

Background aimsTraditional weight-based dosing of rabbit anti-thymocyte globulin (rATG) used in allogeneic hematopoietic cell transplantation (HCT) to prevent graft-versus-host disease (GVHD) and graft rejection leads to variable exposures. High exposures induce delayed CD4+immune reconstitution (CD4+IR) and greater mortality. We sought to determine the impact of rATG exposure in children and young adults receiving various types of EX-VIVO T-cell–depleted (EX-VIVO-TCD) HCT. MethodsPatients receiving their first EX-VIVO-TCD HCT (CliniMACS CD34+, Isolex or soybean lectin agglutination), with removal of residual T cells by E-rosette depletion (E-) between 2008 and 2018 at Memorial Sloan Kettering Cancer Center were retrospectively analyzed. rATG exposure post-HCT was estimated (AU*d/L) using a validated population pharmacokinetic model. Previously defined rATG-exposures, <30, 30–55, ≥55 AU*d/L, were related with outcomes of interest. Cox proportional hazard and cause-specific models were used for analyses. ResultsIn total, 180 patients (median age 11 years; range 0.1–44 years) were included, malignant 124 (69%) and nonmalignant 56 (31%). Median post-HCT rATG exposure was 32 (0–104) AU*d/L. Exposure <30 AU*d/L was associated with a 3-fold greater probability of CD4+IR (P < 0.001); 2- to 4-fold lower risk of death (P = 0.002); and 3- to 4-fold lower risk of non-relapse mortality (NRM) (P = 0.02). Cumulative incidence of NRM was 8-fold lower in patients who attained CD4+IR compared with those who did not (P < 0.0001). There was no relation between rATG exposure and aGVHD (P = 0.33) or relapse (P = 0.23). Effect of rATG exposure on outcomes was similar in three EX-VIVO-TCD methods. ConclusionsIndividualizing rATG dosing to target a low rATG exposure post-HCT while maintaining total cumulative exposure may better predict CD4+IR, reduce NRM and increase overall survival, independent of the EX-VIVO-TCD method.

Effectiveness of In Vivo T-Cell Depleted Regimen Containing Porcine Antilymphocyte Globulin and Rabbit Antithymocyte Globulin in Preventing Acute Gvhd after Haploid Hematopoietic Stem Cell Transplantation

Objective To compare the clinical efficacy of porcine antilymphocyte globulin (p-ALG) and rabbit antithymocyte globulin (r-ATG) in the treatment of hematologic malignancies using haploid hematopoietic stem cell transplantation (haplo- HSCT), this study was conducted. Methods This was a single center retrospective analysis of 178 subjects who received haplo-HSCT with p-ALG or r-ATG from January 2020 to December 2022. The patients were divided into three groups according to the doses of p-ALG or r-ATG used in the conditioning regimens. The study evaluated and compared the occurrence of early fever, graft versus host disease (GVHD), infection, and survival among the three groups of patients. Results A total of 178 patients were enrolled in the study with a median age of 30 (14-61) years, including 95 men and 83 women. The median follow-up time post-transplantation was 20.1 (1.7-36.9) months. The study included 57 patients in the p-ALG 75mg/kg group, 49 patients in the p-ALG 90mg/kg group, and 72 patients in the r-ATG 7.5mg/kg group, respectively. The incidences of neutrophil and platelet engraftment, respectively, were 100%,93.5%, and 91.3% (p=0.133); 100%, 93.6%, 90.3% (p=0.033) in P-ALG 75mg/kg, P-ALG 90mg/kg and r-ATG 7.5mg/kg. The median time to neutrophil engraftment was 11 days for the P-ALG 75mg/kg group, 12 days for the P-ALG 90mg/kg group, and 12 days for the r-ATG 7.5mg/kg group (p=0.133). The median time to platelet engraftment was 12 days for the P-ALG 75mg/kg group, 14 days for the P-ALG 90mg/kg group, and 13 days for the r-ATG 7.5mg/kg group (p=0.033). In the p-ALG 75mg/kg, p-ALG 90mg/kg, and r-ATG 7.5mg/kg groups, 16 patients (28.1%), 24 patients (49.0%) and 35 patients (48.6%) developed fever within 14 days after transplantation, respectively. Cytokine release syndrome was found to be the most common cause of fever. The incidence of grades Ⅱ-Ⅳ acute GVHD (aGVHD) and grades Ⅲ-Ⅳ aGVHD, respectively, were 15.8%, 12.2%, and 12.5% (p=0.853); 5.3%, 2.0%, and 5.6% (p=0.523) in P-ALG 75mg/kg, P-ALG 90mg/kg and r-ATG 7.5mg/kg. The cumulative incidence of chronic GVHD at 1 year was 14.0%, 10.2%, and 15.3% (p=0.731) in the three groups. 43.9%, 71.4%, and 61.1% of patients in the p-ALG 75mg/kg, p-ALG 90mg/kg and r-ATG 7.5mg/kg groups, respectively, experienced at least one infection within 1 year after haplo-HSCT (p=0.0.13). Notably, the CMV infection rate in the p-ALG 75mg/kg group was significantly lower than in the p-ALG 90mg/kg and r-ATG 7.5mg/kg groups. The 2-year overall survival (OS) rates of p-ALG 75mg/kg, p-ALG 90mg/kg and r-ATG 7.5mg/kg groups were 78.2%, 70.6%, and 72.3% (p=0.491). The cumulative incidence of 2-year relapse were 33.0%, 29.8%, and 30.0% (p=0.834). ConclusionsCompared with r-ATG group, the p-ALG 75mg/kg group showed a lower incidence of infection. However, there were no significant differences between the two groups in terms of the incidence of grades Ⅱ-Ⅳ aGVHD, 2-year overall survival (OS), and 2-year cumulative incidence of relapse. p-ALG (75mg/kg) has a comparable effect on the prevention of GVHD after haplo-HSCT with a lower incidence of infection. Keywords: Porcine antilymphocyte globulin; Rabbit antithymocyte Globulin; Haploidentical hematopoietic cell transplantation; Graft versus host disease; Infection

#6888 COMPARISON OF COMBINATION OF RITUXIMAB WITH LOW DOSE THYMOGLOBULIN VERSUS LOW DOSE THYMOGLOBULIN ALONE AS INDUCTION AGENT IN RENAL TRANSPLANTATION

Abstract Background and Aims Current immunosuppressive therapies and protocols have led to significant improvements in early patient and graft survival rates following kidney transplantation. However full dose rATG induction therapy (7-10 mg/kg) has been associated with increased morbidity. There is not much data available on the use of single dose low dose rATG and rituximab, a Anti CD 20 chimeric antibody in low sensitized Indian transplant recipients. To compare the efficacy of low dose single dose rATG(1–1.2mg/kg) versus combination of rituximab with low dose single dose rATG in ABO compatible low sensitization renal transplant recipients. Method Retrospective analysis of all renal transplant recipients between 2010 and 2022 in our center who received low dose rATG(1-1.2mg/kg) or a combination of single dose rituximab(375mg/m2) and low dose thymoglobulin were studied. Demographic data, donor characterstics, HLA matches, infections,rejections was collected Graft function at 3,6 and 12 months post transplant if available was collected. Data was analysed using SPSS 16. Results Of 86 patients studied, 58(67.4%) received single dose of low dose rATG(1-1.2 mg/kg/day) (Grp1) and 28 received a combination of single low dose rATG &amp; Rituximab(375mg/m2)(Grp 2)(32.5%). There was no significant difference between the Grp 1 and Grp 2 in terms of age,gender,vintage of dialysis, PRA status prior to transplant, no of HLA Matches, donor age and Donor GFR. There were 9(15%) of Acute cellular rejections (ACR) in Group1 when compared to 8 (28%) in-group 2(p = 0.263). The number of steroid resistant ACR were 2 (3%)in Grp 1 when compared to 3 (10%)in grp 2(p = 0.365) The number of ABMR were 5(8.6%) in group 1 when compared to 1(3.5%)in grp 2(p = 0.658) 15.5% had graft loss by 1 year in group 1 compared to none in grp 2(p = 0.322)CMV and BKV infections were seen in 1 and no pts and 1 patient in each group respectively.Overall infection rate was 24% when compared to 46.4% in grp 2(p = 0.03). The mean egfr(ml/min/1.73m2) at the end of 3 months, 6 months and 1 year was &amp;95.6,93,95 respectively in grp 1 when compared to 92, 89.4 &amp; 84.3 in grp 2. Conclusion The % of steroid resistant ACR and the number of infections were higher in the 1 year in the Single low dose rATG+Rituximab induction when compared to low single dose rATG alone. However ABMR was lower in the combination grp. Further prospective RCT s are required to establish the role of Rituximab in ABO Compatible transplants.

Population Pharmacokinetics of Total Rabbit Anti-thymocyte Globulin in Non-obese Adult Patients Undergoing Hematopoietic Cell Transplantation for Hematologic Malignancy.

Rabbit anti-thymocyte globulin (rATG), a therapeutic polyclonal antibody against human T cells, is commonly used in conditioning therapy prior to allogeneic hematopoietic cell transplantation (HCT). Previous studies successfully developed an individualized rATG dosing regimen based on "active" rATG population PK (popPK) analysis, while "total" rATG can be a more logistically favorable alternative for early HCT outcomes. We conducted a novel popPK analysis of total rATG. Total rATG concentration was measured in adult human-leukocyte antigen (HLA) mismatched HCT patients who received a low-dose rATG regimen (total 2.5-3mg/kg) within 3days prior to HCT. PopPK modeling and simulation was performed using nonlinear mixed effect modeling approach. A total of 504 rATG concentrations were available from 105 non-obese patients with hematologic malignancy (median age 47years) treated in Japan. The majority had acute leukemia or malignant lymphoma (94%). Total rATG PK was described by a two-compartment linear model. Influential covariate relations include ideal body weight [positively on both clearance (CL) and central volume of distribution], baseline serum albumin (negatively on CL), CD4+ T cell dose (positively on CL), and baseline serum IgG (positively on CL). Simulated covariate effects predicted that early total rATG exposures were affected by ideal body weight. This novel popPK model described the PK of total rATG in the adult HCT patients who received a low-dose rATG conditioning regimen. This model can be used for model-informed precision dosing in the settings with minimal baseline rATG targets (T cells), and early clinical outcomes are of interest.

The impact of universal induction therapy on early hospital readmission of kidney transplant recipients.

Early hospital readmission (EHR) is associated with worse outcomes. The use of anti-thymocyte globulin (rATG) induction therapy is associated with increased efficacy in preventing acute rejection, although safety concerns still exist. This retrospective single-center study compared the incidence, causes of EHR, and one-year clinical outcomes of patients receiving a kidney transplant between August 18, 2011 and December 31, 2012 (old era), in which only high-risk patients received 5 mg/kg rATG, with those transplanted between August 18, 2014 and December 31, 2015 (new era), in which all patients received a single 3 mg/kg dose of rATG. There were 788 patients from the Old Era and 800 from the New Era. The EHR incidence in the old era patients was 26.4% and in the new era patients, 22.5% (p = 0.071). The main cause of EHR in both eras was infection (67% vs. 68%). The incidence of acute rejection episodes was lower (22.7% vs 3.5%, p < 0.001) and the one-year patient survival was higher (95.6% vs. 98.1%, vs. p = 0.004) in new era patients. The universal use of 3 mg/kg rATG single-dose induction therapy in the new era was associated with a trend towards reduced EHR and a reduction in the incidence of acute rejection and mortality.

Bodyweight and Absolute Lymphocyte Count Based Dosing of Rabbit Anti-Thymocyte Globulin Results in Early CD4+ Immune Reconstitution in Patients with Inborn Errors of Metabolism Undergoing Umbilical Cord Blood Transplantation

Background Rabbit anti-thymocyte globulin (rATG) is used in allogeneic hematopoietic cell transplantation (HCT) to prevent graft failure through depletion of host T cells and decrease the risk of graft-versus-host disease (GVHD) through partial depletion of donor T cells. However, it has highly variable pharmacokinetics. Previous reports suggest rATG dosing should be based on recipient bodyweight and absolute lymphocyte count (ALC) prior to initiating rATG. This new dosing nomogram reduces rATG overexposure, potentially leading to faster immune reconstitution and subsequently superior overall outcomes. Methods Since January 12, 2017, we use a previously described rATG dosing nomogram based on bodyweight and ALC before administering rATG in patients with inborn errors of metabolism receiving an umbilical cord blood transplant at the University of Minnesota Masonic Children's Hospital. The proposed rATG dosing varied from 2 to 10 mg/kg based on bodyweight and recipient ALC prior to initiating rATG, starting 8 or 9 days before HCT. The myeloablative conditioning regimen was Busulfan based, with addition of Fludarabine and Cyclophosphamide for lymphodepletion, as well as Rituximab and/ or Bortezomib for prevention of immune-mediated cytopenia. For GVHD prophylaxis cyclosporin A or tacrolimus were used with methylprednisolone. The primary endpoint was CD4+ immune reconstitution (>50 CD4+ T-cells/mL) within 100 days after transplantation. Secondary endpoints included overall survival, graft failure, acute and chronic GVHD, myeloid and T cell donor chimerism at one year post transplant, time to neutrophil engraftment and viral reactivations of cytomegalovirus, adenovirus and Epstein Barr virus. The study protocol was approved by the Institutional Review Board of University of Minnesota. Results Between February 20, 2017, and June 28, 2021, 27 patients were included in the study. Median follow-up time was 31 months (IQR 22.0 to 38.5) and median age was 1.45 years (IQR 0.7 to 3.9). Ten (37%) of 27 patients were female. The baseline characteristics are presented in Table 1. rATG dose was adjusted below 10 mg/kg recipient body weight in 7 (26%) of 27 patients on average by 29% (SD 14.9%). The CD4+ recovery at 100 days post HCT was reached in 22 (85%) of 26 patients (Figure 1A). Overall, four (15%) patients died resulting in overall survival of 83% (95%CI 67% to 100%). Causes of death were intracranial bleeding due to immune-mediated thrombocytopenia (this patient was transplanted before introduction of bortezomib and rituximab for immune-mediated cytopenia prevention), diffuse alveolar hemorrhage, respiratory syncytial virus infection and disease progression. Median time to neutrophil engraftment was 14 days (IQR 12.5 to 18.0), and no graft failure was observed. All surviving patients had full myeloid chimerism and 14 of 23 (61%) of patients had full T cell donor chimerism at one year post HCT. Two (7%) patients developed acute GVHD grade II to IV (Figure 1B), and no patients had chronic GVHD. Six patients (22%) had cytomegalovirus viremia, five of them were seropositive before transplant, one patient was seronegative as was the mother of the donor. One patient, who was seronegative before transplant, had Epstein-Barr virus reactivation requiring treatment, no patient had adenovirus reactivation. Conclusion In pediatric patients with inborn errors of metabolism individualized dosing of rATG was associated with a robust and early CD4+ immune reconstitution, with low therapy related mortality, low GVHD incidence compared to historical findings and stable full myeloid chimerism. These results are in line to the findings of the PARACHUTE trial previously published. However, the PARACHUTE trial included only small number of patients with inborn errors of metabolism. Table 1. Baseline characteristicsFigure 1A. Cumulative incidence of CD4+ immune reconstitutionFigure 1B. Cumulative incidence of acute Graft-versus-host disease Grade 2 to 4Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Low dose rabbit antithymocyte globulin is non-inferior to higher dose in low-risk pediatric kidney transplant recipients.

Currently, there is no consensus among pediatric kidney transplant centers regarding the use and regimen for immunosuppressive induction therapy. In this single center, retrospective cohort study, pediatric kidney transplant recipients transplanted between 1 May 2013 and 1 May 2018 with rabbit antithymocyte globulin (rATG) induction were included. We stratified patients based on immunological risk, with high risk defined as those with repeat transplant, preformed donor specific antibody, current panel-reactive antibodies > 20%, 0 antigen match and/or African-American heritage. Outcome of interest was the incidence of biopsy proven acute rejection by 1year. A total of 166 patients met inclusion criteria. Age of patients was 12years (11 mo-21 y), (median, range), 21.5% received a living donor transplant and 50.6% were female. Low-immunologic-risk patients were divided into 2 groups, those who received the lower cumulative rATG dose of ≤ 3.5mg/kg (n = 52) versus the higher cumulative dose of > 3.5mg/kg (n = 47). The median total dose in the lower dose group was 3.1 (IQR 0.3) and 4.4 (IQR 0.8) in the higher dose group, P < 0.001. Rejection rate did not differ significantly between the 2 treatment groups (7/52 vs. 6/47). None in the lower dose group developed BK nephropathy versus 3 in the higher dose group. Graft loss due to BK nephropathy occurred in 1 patient in the higher dose group. Graft loss in the whole cohort at 12months was a rare event (n = 1) with 99.5% graft survival and 100% patient survival. Reduced rATG dosing (≤ 3.5mg/kg) when compared to higher dosing (> 3.5mg/kg) is safe and effective in low-risk pediatric kidney transplant recipients without increasing risk of rejection. A higher resolution version of the Graphical abstract is available as Supplementary information.

Antithymocyte globulin exposure in CD34+ T-cell–depleted allogeneic hematopoietic cell transplantation

AbstractTraditional weight-based dosing results in variable rabbit antithymocyte globulin (rATG) clearance that can delay CD4+ T-cell immune reconstitution (CD4+ IR) leading to higher mortality. In a retrospective pharmacokinetic/pharmacodynamic (PK/PD) analysis of patients undergoing their first CD34+ T-cell–depleted (TCD) allogeneic hematopoietic cell transplantation (HCT) after myeloablative conditioning with rATG, we estimated post-HCT rATG exposure as area under the curve (arbitrary unit per day/milliliter [AU × day/mL]) using a validated population PK model. We related rATG exposure to nonrelapse mortality (NRM), CD4+ IR (CD4+ ≥50 cells per µL at 2 consecutive measures within 100 days after HCT), overall survival, relapse, and acute graft-versus-host disease (aGVHD) to define an optimal rATG exposure. We used Cox proportional hazard models and multistate competing risk models for analysis. In all, 554 patients were included (age range, 0.1-73 years). Median post-HCT rATG exposure was 47 AU × day/mL (range, 0-101 AU × day/mL). Low post-HCT area under the curve (<30 AU × day/mL) was associated with lower risk of NRM (P < .01) and higher probability of achieving CD4+ IR (P < .001). Patients who attained CD4+ IR had a sevenfold lower 5-year NRM (P < .0001). The probability of achieving CD4+ IR was 2.5-fold higher in the <30 AU × day/mL group compared with 30-55 AU × day/mL and threefold higher in the <30 AU × day/mL group compared with the ≥55 AU × day/mL group. In multivariable analyses, post-HCT rATG exposure ≥55 AU × day/mL was associated with an increased risk of NRM (hazard ratio, 3.42; 95% confidence interval, 1.26-9.30). In the malignancy subgroup (n = 515), a tenfold increased NRM was observed in the ≥55 AU × day/mL group, and a sevenfold increased NRM was observed in the 30-55 AU × day/mL group compared with the <30 AU × day/mL group. Post-HCT rATG exposure ≥55 AU × day/mL was associated with higher risk of a GVHD (hazard ratio, 2.28; 95% confidence interval, 1.01-5.16). High post-HCT rATG exposure is associated with higher NRM secondary to poor CD4+ IR after TCD HCT. Using personalized PK-directed rATG dosing to achieve optimal exposure may improve survival after HCT.

Malignancy among adult heart transplant recipients following patient-tailored dosing of anti-thymocyte globulin: a retrospective, nested case-control study of individualized dosing.

Post-transplant malignancy is diagnosed in approximately 18% of heart transplant patients and is a leading cause of death post-transplant. One modifiable risk factor is the type and amount of immunosuppression received. Contemporary rabbit anti-thymocyte globulin (rATG) dosing strategy using T-cell-guided dosing, and its effect on malignancy in heart transplant patients is unclear. This was a single-center, retrospective chart review of heart transplant recipients receiving rATG for induction. Patients diagnosed with malignancy post-transplant were matched 1:2 to controls using a nested case-control design. The primary endpoint was to determine the relative risk of rATG exposure with the actual incidence of malignancy post-transplant. The secondary endpoint was the impact of maintenance immunosuppression on malignancy risk. Of the 126 patients included in the study, 25 developed malignancy and were matched to 50 control patients. The median cumulative rATG dose in milligrams (mg) between groups was 365 mg in malignancy cases and 480 mg in controls (OR 0.90, 95% CI 0.75-1.08, P = 0.28). In both the univariate and multivariable analysis, there was no statistically significant difference in malignancy risk found with any maintenance immunosuppressant. The results of this study showed that patient-tailored rATG dosing strategies may not be associated with malignancy development as previously thought.

Relationship between plasma rabbit anti-thymocyte globulin concentration and immunosuppressive therapy response in patients with severe aplastic anemia.

Patients with acquired aplastic anemia (AA) without HLA-matched sibling donors or aged >40years receive immunosuppressive therapy (IST) with anti-thymocyte globulin (ATG). We investigated the relationship between plasma rabbit ATG (r-ATG) concentration and IST response. From May 2012 to October 2017, 81 patients with severe AA who required initial IST were included. A 1:1 block randomization was employed for 2.5 and 3.5mg/kg doses of r-ATG. No significant difference in response rates was observed between the 2.5 and 3.5mg/kg groups (63% vs. 58%, P=.894). Median r-ATG concentrations on days 14 and 28 after IST were 15.2 (0.0-97.7) and 1.8 (0.0-74.9µg/mL), respectively. According to r-ATG concentration, response rates were significantly higher in the group with higher r-ATG concentration than in those with lower r-ATG concentration (day 14, 88% vs. 52%; P=.006 and day 28, 79% vs. 46%; P=.005). In multivariate analysis, higher r-ATG concentrations at day 28 were independent predictors of favorable response to IST at 6months (odds ratio, 0.29; 95% confidence interval, 0.09-0.93; P=.037). The present data indicate that higher r-ATG concentration at day 28 resulted in improved IST response.

MO992RABBIT ANTITHYMOCYTE GLOBULIN (RATG) AS INDUCTION THERAPY IN INDIAN PATIENTS UNDERGOING RENAL TRANSPLANTATION: CLINICAL EXPERIENCE FROM RISE REGISTRY

Abstract Background and Aims Induction therapy with rabbit anti-thymocyte globulin (rATG) in patients with renal transplantation prevents early graft failure due to immunologic rejection. In India, due to the lack of a robust national transplant registry, limited real-world evidence is available on induction immunosuppression. The RISE study aimed to evaluate the safety and effectiveness of induction immunosuppression using rATG in patients undergoing renal transplantation in India. Method In this multicenter, prospective, observational cohort study (CTRI/2017/09/009/009700) adult patients (≥18 years) were included if they were due to have a renal transplant and physicians’ decision to use rATG as an induction therapy was independent of this registry and based on routine clinical practice. Acute rejection and infections over 12 months, graft survival and renal function at the end of 6 and 12 months and safety (adverse events [AEs] and serious AEs [SAEs]) were evaluated over 12 months. Results Of the 325 patients enrolled, 314 met the eligibility criteria, 313 patients received at least one dose of rATG (safety population) and 299 patients (evaluable population) received at least one dose of rATG and had no critical protocol deviation (ongoing infection, transplantation date deviation, and ABO incompatibility). Of the 299 donors, 81.3% were live donors and the remaining 18.7% deceased. The mean (SD [standard deviation]) age of participants was 42.8 (11.7) years and 76.3% of patients were men. The cumulative mean (SD) rATG dose was 155.06 (91.12) mg. A total of 23 (7.7%) patients experienced graft rejection; of which 21 (91.3%) patients reported acute rejections; one patient had a hyperacute rejection and another patient had accelerated rejection. These rejections occurred within a median time duration of 0.49 months (range: 0.1 to 7.75 months). The diagnosis of graft rejection was most often done by renal biopsy (n=21, 91.3%; 20 of these patients had acute rejection) and clinical diagnosis in two patients. Cellular rejection was the predominant pathology (n=17, 77.3%), followed by mixed rejection (n=3) and antibody-mediated rejection (n=2). The corresponding mean (SD) time to first graft rejection were 5.45 (1.59) and 10.37 (3.58) months, respectively. The graft survival was 93.3% (n=279) at 6 months and 92.3% (n=276) at 12 months (Figure). The mean (SD) glomerular filtration rate was 64.59 (19.57) and 64.93 (20.26) mL/min/1.73m2 at 6 and 12 months, respectively, suggesting normal post-transplant kidney function. Fifty-three patients (17.7%) reported a total of 74 infections, the most common being bacterial (n=37) followed by viral (n=8) and fungal infections (n=5). Urinary tract infection was the most common site of infection (25 events in 23 patients) followed by sepsis (3 events in 2 patients). A total of 342 AEs were reported in 154 (49.2%) patients during 12 months. The majority of AEs (n=195) were of mild intensity, followed by 124 and 22 events of moderate and severe intensity, respectively. SAEs (n=111) were reported in 56 patients. Pyrexia was the most commonly reported SAE in 10 patients (12 events). A total of seven deaths were reported during the study (acute coronary syndrome, left ventricular dysfunction, neutropenic sepsis, septic shock, sudden sepsis, n=1 each and undetermined, n=2). Conclusion The study demonstrated low rejection rate, better survival and function at 6 months and 1 year and an acceptable safety profile of rATG with overall infection incidence less than 18%. Additional follow-up data is warranted to understand factors associated with rejection of graft. This study was funded by Sanofi, India.

Anti-Thymocyte Globulin Exposure in CD34+T Cell Depleted Allogeneic Hematopoietic Cell Transplantation

Background: Traditional weight-based dosing results in variable rabbit anti-thymocyte-globulin (rATG) clearance that can delay CD4+Tcell immune reconstitution (CD4+IR) leading to higher mortality. Methods: In a retrospective, pharmacokinetic (PK)/pharmacodynamic analysis of patients undergoing their first CD34+ T-cell depleted (TCD) Allogeneic Hematopoietic Cell Transplantation (HCT) after myeloablative conditioning with rATG, we estimated post-HCT rATG exposure as area-under-the-curve (AUC;AU*d/L) using a validated population-PK model. We related rATG exposure to non-relapse mortality (NRM), CD4+IR (CD4+≥50/µL at two consecutive measures within 100 days after HCT), overall survival, relapse, and acute-graft versus host disease (GVHD) to define an optimal rATG-exposure. Cox-proportional hazard models, and multi-state competing risk models were used. Results: 554 patients were included (age 0.1-73 years). Median post-HCT rATG exposure was 47AU*d/L (range 0–101). Low post–HCT AUC ( 55AU*d/L and 30-55AU*d/L groups, respectively, compared to <30AU*d/L group. Post-HCT rATG exposure ≥55AU*d/L was associated with higher risk of acute GVHD (HR 2.28,95%CI 1.01-5.16). Conclusions: High post-HCT rATG-exposure is associated with higher NRM secondary to poor CD4+IR after TCD-HCT. Using personalized PK-directed rATG dosing to achieve optimal exposure may improve survival after HCT. Funding Information: MSK authors acknowledge the support of the NCI Cancer Center Support Grant P30 CA008748. Declaration of Interests: Madhavi Lakkaraja, MD, MPH, Audrey Mauguen, PhD, Christina Cho, MD, Sean Devlin, PhD, Scott T Avecilla, MD PhD, Farid Boulad, MD, Maria I. Cancio, MD, Ann A. Jakubowski, MD PhD, , Andrew L. Kung, MD, PhD, Esperanza B. Papadopoulos, MD, Ichelle Roessel, Josel D Ruiz, MPH, Brian C. Shaffer, MD, Gunjan Shah, MD, Barbara Spitzer, MD, Roni Tamari, MD : No Disclosures Michael Scordo, MD - Research support: Angiocrine Bioscience, Inc.; Omeros Corporation. Consultancy: Angiocrine Bioscience, Inc.; Omeros Corporation; McKinsey & Company. Ad-hoc advisory board: Kite – A Gilead Company. One-time speaking commitment: i3Health (CME). Kevin J. Curran, MD- Consultancy: Mesoblast, Consultancy and Research funding: Novartis, Research funding: Celgene. Nancy A. Kernan, MD - Equity in Amgen, Johnson and Johnson, Pfizer and Merck. Richard J O'Reilly, MD - Consultancy, Patents & Royalties: EBV-specific T-cell bank and Research Funding : Atara Biotherapeutics Susan Prockop, MD – Support for the conduct of clinical trials, Atara Biotherapeutics, Jasper Pharmaceuticals, AlloVir. Advisory Boards - Mesoblast, Neovii. S.E.P. is an inventor of intellectual property licensed to Atara Biotherapeutics by MSKCC; S.E.P. assigned all rights to MSKCC and has no financial interest in Atara Biotherapeutics. Andromachi Scaradavou, MD - Membership on an entity's Board of Directors or advisory committees: Excellthera Sergio A. Giralt, MD- Consultancy, Honoraria and Research funding : Celgene, Novartis, Consultancy and Research funding: Amgen, Actinuum, Miltenyi, Consultancy and Honoraria: Jazz, Omeros, Research funding: Takeda, Consultancy: Kite Miguel-Angel Perales, MD- Dr. Perales reports honoraria from Abbvie, Astellas, Bristol-Myers Squibb, Celgene, Equilium, Incyte, Karyopharm, Kite/Gilead, Merck, Miltenyi Biotec, MorphoSys, Novartis, Nektar Therapeutics, Omeros, Takeda, and VectivBio AG, Vor Biopharma. He serves on DSMBs for Cidara Therapeutics, Medigene, Sellas Life Sciences, and Servier, and the scientific advisory board of NexImmune. He has ownership interests in NexImmune and Omeros. He has received research support for clinical trials from Incyte, Kite/Gilead, Miltenyi Biotec, and Novartis. He serves in a volunteer capacity as a member of the Board of Directors of the American Society for Transplantation and Cellular Therapy (ASTCT) and Be The Match (National Marrow Donor Program, NMDP), as well as on the CIBMTR Cellular Immunotherapy Data Resource (CIDR) Executive Committee. Jaap Jan Boelens, MD, PhD -Consultancy: Race Oncology, Omeros, Avrobio, Takeda, Advanced Clinical, Bluerock. Ethics Approval Statement: The study protocol was approved by the institutional review board at Memorial Sloan Kettering Cancer Center (MSKCC).

The influence of the antithymocyte globulin dose on clinical outcomes of patients undergoing kidney retransplantation

Optimizing antithymocyte globulin (rATG) dosage is critical for high immunological risk patients undergoing a repeat kidney transplant. This natural retrospective cohort study compared clinical outcomes of two successive cohorts of consecutive recipients of retransplants receiving 5 x 1 mg/kg (rATG-5, n = 100) or a single 3 mg/kg (rATG-3, n = 110) dose of rATG induction therapy. All patients had negative complement-dependent cytotoxicity crossmatch and no anti-HLA A, B, DR donor-specific antibodies (DSA). The primary endpoint was efficacy failure (first biopsy-proven acute rejection, graft loss, or death) at 12 months. There was no difference in the cumulative incidence of efficacy failure (18.0% vs. 21.8%, HR = 1.22, 95% CI 0.66-2.25), respectively. There were no differences in 3-years freedom from biopsy proven acute rejection, and patient, graft, and death-censored graft survivals. There were no differences in the incidence of surgical complications (25.0% vs. 18.2%; p 0.151), early hospital readmission (27.8% vs. 29.5%; p = 0.877) and CMV infections (49% vs. 40%; p = 0.190). There were also no differences in the incidence (59.6% vs. 58.7%, p = 0.897) and duration of delayed graft function but a stable difference in estimate glomerular filtration rate was observed from month 1 (54.7±28.8 vs. 44.1±25.3 ml/min/1.73 m2, p = 0.005) to month 36 (51.1±27.7 vs. 42.5±24.5, p = 0.019). Mean urinary protein concentration (month 36: 0.38±0.81 vs. 0.70±2.40 g/ml, p = 0.008) and mean chronic glomerular Banff score in for cause biopsies (months 4-36: 0.0±0.0 vs. 0.04±0.26, p = 0.044) were higher in the rATG-3 group. This cohort analysis did not detect differences in the incidence of efficacy failure and in safety outcomes at 12 months among recipients of kidney retransplants without A, B, and DR DSA, receiving induction therapy with a single 3 mg/kg rATG dose or the traditional 5 mg/kg rATG.

The Optimal Cumulative Dose of Rabbit Antithymocyte Globulin Induction in Adult Heart Transplantation

Purpose To determine the optimal cumulative dose of rabbit antithymocyte globulin (rATG) regarding its efficacy and safety and to evaluate the target level of CD3+ T cell count for induction therapy in adult heart transplantation. Methods This retrospective cohort study enrolled adult patients undergoing heart transplantation in a medical center between January 2016 and July 2019. The rATG induction was initiated postoperatively at a dose of 0.75-1 mg/kg/day for 3-5 days to maintain CD3+ counts Results A total of 62 patients with 189 doses of rATG were enrolled. The first dose and the cumulative dose of rATG were 0.67 ± 0.18 mg/kg and 1.44 ± 0.40 mg/kg. The cut-off point for the cumulative dose of rATG in achieving CD3+ count Conclusion A cumulative rATG dose of 1.2 mg/kg may be effective in achieving CD3+ counts

Retrospective Evaluation of Rabbit Anti-Thymocyte Globulin (rATG) Induction in Heart Transplant Patients

<h3>Purpose</h3> The use and dosing intensity of rATG as induction therapy in heart transplantation remains controversial. We sought to evaluate the efficacy and safety of rATG at a total dose of 4.5mg/kg compared to less than 4.5mg/kg. <h3>Methods</h3> This study was a cross-sectional retrospective chart review of adults who underwent heart transplantation from January 1, 2016 - December 31, 2018 at a single quaternary care center. Exposure was defined as a full rATG (4.5mg/kg total) induction per institutional protocol compared to partial (less than 4.5mg/kg) induction. The primary outcome was the incidence of ISHLT 1990 defined acute cellular rejection (ACR) at two years. Secondary outcomes were all-cause mortality, proportion of infections, and time to therapeutic tacrolimus levels. <h3>Results</h3> A total of 201 patients met inclusion criteria. 61 received partial rATG induction and 140 received full rATG induction. When comparing partial vs full induction, there was no difference in any-grade of ACR (78.7% vs 88.6%, p=0.11). There was a trend toward a higher cumulative incidence of ACR grade 2 or above over two years in the partial as compared to the full induction group (18% vs 11.4%, p=0.21). On multivariate Cox PH analysis, partial vs full induction, the estimated hazard ratio was 1.45 (CI 0.62-3.37, p=0.39). Adjusted landmark survival analysis conditional on survival to 1 month showed no difference between the two groups. The number of patients with at least one infection within 3 months of transplant was similar between the groups (partial 29.5% vs full 20.0% p=0.20). Both groups achieved therapeutic tacrolimus levels by day 7 after initiation. <h3>Conclusion</h3> The dose of rATG does not appear to affect the overall incidence of biopsy-proven rejection, though there appears to be a trend towards severe rejection with rATG induction doses less than 4.5mg/kg. The total cumulative dose of rATG induction did not impact medium-term survival. Prospective, randomized, controlled trials are needed to validate these observations.

Coronary Thrombosis after Rabbit-ATG in LTx Recipient

Introduction Rabbit anti-thymocyte globulin (rATG) is a polyclonal antibody that targets human T lymphocytes; it can be used as an induction agent at the time of lung transplant (LTx) or as treatment for steroid refractory allograft rejection. rATG-induced platelet activation and hypercoagulability has been reported. Herein, we report a case of acute thrombotic myocardial infarction (MI) after the first dose of rATG in an LTx recipient with steroid refractory rejection. Case Report The patient is a 60-year-old man with COPD who underwent a bilateral LTx in May 2018. He had an uneventful post-LTx course, but presented 18 months later with dyspnea and a 600-cc decline in FEV1. A CT scan of the chest showed diffuse bronchial thickening and a bronchoscopy with bronchoalveolar lavage and transbronchial biopsies showed rhinovirus, but no evidence of acute cellular rejection. Donor specific antibodies were absent. The patient was empirically treated with high-dose corticosteroids, but presented a month later with another 400-cc decline in FEV1, prompting admission and treatment with rATG for presumed steroid refractory rejection. During admission, his labs were remarkable for mild anemia and thrombocytosis (781 K/µL). Thirty minutes into his rATG infusion, the patient complained of shortness of breath, chest discomfort, diaphoresis, and right-arm numbness. The infusion was stopped. His labs revealed elevated troponin (0.382 ng/mL), and his EKG showed an ST elevation in leads II, III and aVF along with ST depression in leads I and aVL suggestive of inferior wall MI. Emergent cardiac catheterization and ventriculogram showed 100% occlusion of the mid-distal right coronary artery with heavy clot burden, inferior wall hypokinesis, and a mildly reduced ejection fraction. A drug-eluting stent was placed, which resulted in near resolution of ST elevation. Of note, his prior pre-LTx cardiac catheterization had no angiographic evidence of coronary artery disease (CAD). Summary rATG activates platelets and establishes a link between complement and coagulation cascades, which may explain the clinically observed phenomenon of rATG-induced hypercoagulability. To the best of our knowledge, this is the first report of rATG-induced coronary arterial thrombosis in an LTx recipient with no prior CAD, but with thrombocytosis at the time of rATG infusion.