Dose Of Antithymocyte Globulin Research Articles

302.2: Comparison of actual versus ideal body weight based dosing of anti-thymocyte globulin in kidney transplant recipients.

302.2: Comparison of actual versus ideal body weight based dosing of anti-thymocyte globulin in kidney transplant recipients.

Outcomes with low dose anti-thymocyte globulin based graft versus host disease prophylaxis after mismatched unrelated donor allogeneic hematopoietic cell transplantation.

Anti-thymocyte globulin (ATG) based graft versus host disease (GVHD) prophylaxis is widely used for mismatched unrelated donor allogeneic hematopoietic cell transplantation (HCT) although optimal dose remains unclear. Although recent literature suggested improved outcomes with PTCy-based regimens when compared to ATG-based regimens these studies used doses of ATG ≥5 mg/kg. Thus, we analyzed outcomes of HLA 9/10 MMUD allogeneic HCTs using lower-dose ATG-based regimens at our center. We retrospectively analyzed outcomes of HLA 9/10 MMUD allogeneic HCTs using lower dose ATG-based regimens for all adults undergoing allogeneic HCT at The Ottawa Hospital from 2015 to 2022. Data regarding demographics, conditioning regimen, dose of ATG, rates of GVHD, duration of remission, and survival, were collected and analyzed. Seventy-seven (n = 77) patients (males 62.3%; median age 50 years) underwent allogeneic HCT from MMUD. Majority(81%; n = 63) received 2.5 mg/kg of rabbit ATG and remaining 18.2% (n = 14) received 4.5 mg/kg. Grade II-IV acute GVHD occurred in 24.7% (n = 19) while any chronic GVHD occurred in 32.5% (n = 25) patients. After a median follow-up of 21 months, relapse occurred in 28.6% of patients. Two-year OS, GRFS, CIR, and NRM were 60.6%, 45.3%, 16.9%, and 18.2% respectively. Dose of ATG (2.5 mg/kg vs. 4.5 mg/kg) was not associated with outcomes in either univariate or multivariate analyses. When compared to published studies using ATG doses ≥5 mg/kg, GVHD prophylaxis using lower dose ATG may potentially lead to improved outcomes in patients undergoing MMUD allogeneic HCT. Further studies are needed to directly compare lower dose ATG to PTCy-based regimens to determine ideal GVHD prophylaxis for these patients.

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

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

Immune reconstitution after single-unit umbilical cord blood transplantation using anti-thymoglobulin and myeloablative conditioning in adults with hematological malignancies.

This study aimed to investigate the kinetics of immune recovery following umbilical cord blood transplantation (UCBT) in adults who received a myeloablative conditioning (MAC) regimen and antithymocyte globulin (ATG). While the immune recovery kinetics has been extensively studied in pediatric UCBT recipients, limited data exist for adults. We conducted a comprehensive analysis of 221 consecutive adult patients who underwent UCBT with MAC and ATG at a single institution. Our objective was to evaluate the influence of patient, disease, and transplant factors, along with acute graft-versus-host disease (aGVHD), on immune reconstitution and overall survival. Our findings confirm a delayed recovery of T cells, while B and NK cell reconstitution exhibited rapid progress, with NK cell counts reaching normal levels within 3 months post-transplantation and B cells within 6 months. Within CD3+ T cells, CD8+ T cells also experienced a delayed recovery (12 months), but to a lesser extent compared to CD4+ T cells (18 months). Delayed immune recovery of T-cell subsets was associated with the development of aGVHD grade II-IV, older age, CMV negativity, and a female donor. Patients with lymphoproliferative diseases showed slower NK cell recovery. Our study demonstrates that adult patients undergoing MAC with ATG and receiving a single unit UCBT for hematologic malignancies experienced rapid reconstitution of NK and B cells. However, T cell recovery, particularly CD4+ T cells, was significantly delayed. To enhance T cell recovery, it may be crucial to consider UCB units with higher cellularity and optimize ATG doses in conditioning.

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.

Comparable outcomes with low-dose and standard-dose horse anti-thymocyte globulin in the treatment of severe aplastic anemia

BackgroundThe standard dose (SD) of horse anti-thymocyte globulin (hATG) ATGAM (Pfizer, USA) or its biosimilar thymogam (Bharat Serum, India) for the treatment of Aplastic Anemia (AA) is 40 mg/kg/day for 4 days in combination with cyclosporine. Data on the impact of hATG dose on long-term outcomes are limited. Here, we describe our comparative experience using 25 mg/kg/day (low-dose [LD]) hATG for 4 days with SD for the treatment of AA.MethodsWe retrospectively studied patients with AA (age > 12 years) who received two doses of hATG combined with cyclosporine. Among 93 AA patients who received hATG, 62 (66.7%) and 31 (33.3%) patients received LD and SD hATG with cyclosporine, respectively. Among these,seventeen(18.2%) patients also received eltrombopag with hATG and cyclosporine. Overall response rates [complete response (CR) and partial response (PR)] of LD and SD hATG groups at 3 months (50% vs. 48.4%; p = 0.88), 6 months (63.8% vs. 71.4%; p = 0.67), and 12 months (69.6% vs. 79.2%; p = 0.167) were comparable. The mean (Standard Deviation) 5-year Kaplan–Meier estimate of overall survival and event-free survival was 82.1 (4.6)% and 70.9 (5.5)% for the study population. The mean (standard deviation) 5-year Kaplan–Meier estimate of overall survival and event-free survival of those who received LD hATG versus SD hATG dose was 82.9 (5·3)% versus 74.8 (10·3)% (P = 0·439), and 75.2 (6.2)% versus 61.4(11.2)% (P = 0·441).ConclusionOur study revealed that the response rates of patients with AA and LD were similar to those of patients with SD to hATG combined with cyclosporine in a real-world setting.

High-dose individualized antithymocyte globulin with therapeutic drug monitoring in high-risk cord blood transplant

BackgroundGraft-versus-host disease (GvHD) and rejection are main limitations of cord blood transplantation (CBT), more so in patients with severe inflammation or previous rejections. While rigorous T-cell depletion with antithymocyte globulin (ATG) is needed to prevent GvHD and rejection, overexposure to ATG leads to slow T-cell recovery after transplantation, especially in CBT. ObjectiveTo evaluate high-dose, upfront ATG with individualized dosing and therapeutic drug monitoring (TDM) in pediatric CBT for patients at high risk for GvHD and rejection. Study designHeavily inflamed patients and patients with a recent history of rejection were eligible for individualized high-dose ATG with real-time TDM. The ATG dosing scheme was adjusted to target a post-CBT exposure of <10 AU*day/mL, while achieving a pre-CBT exposure of 60–120 AU*day/mL; exposure levels previously defined for optimal efficacy and safety in terms of reduced GvHD and rejection, respectively. Main outcomes of interest included efficacy (target exposure attainment) and safety (incidence of GvHD and rejection). Other outcomes of interest included T-cell recovery and survival. ResultsTwenty-one patients were included ranging from 2 months to 18 years old, receiving an actual median cumulative dose of ATG of 13.3 mg/kg (range 6–30 mg/kg) starting at a median 15 days (range 12–17) prior to CBT. Dosing was adjusted in 14 patients (increased in 3 and decreased in 11 patients). Eighteen (86%) and 19 (91%) patients reached the target pre-CBT and post-CBT exposure, respectively. Cumulative incidence for acute GvHD was 34% (95% CI 23–45) and 5% (95% CI 0–10%) for grade 2–4 and grade 3–4, respectively; cumulative incidence of rejection was 9% (95% CI 2–16%). Overall survival was 75% (95% CI 65–85%). ConclusionIndividualized high-dose ATG with TDM is feasible and safe for patients with hyperinflammation in a CBT setting. We observe high target ATG exposure attainment, good immune reconstitution (despite very high doses of ATG) and acceptable rates of GvHD and rejection.

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.

Favorable Outcomes with Low Dose Anti Thymocyte Globulin Based Graft Versus Host Disease Prophylaxis after Mismatched Unrelated Donor Allogenic Hematopoietic Cell Transplantation

Favorable Outcomes with Low Dose Anti Thymocyte Globulin Based Graft Versus Host Disease Prophylaxis after Mismatched Unrelated Donor Allogenic Hematopoietic Cell Transplantation

Model-Based Dosing of Anti-Thymocyte Globulin in Pediatric Allogeneic Hematopoietic Cell Transplantation Improves Survival Chances: Updated Results from the Single Arm Phase II Parachute-Trial Combined with Real-World Data

Model-Based Dosing of Anti-Thymocyte Globulin in Pediatric Allogeneic Hematopoietic Cell Transplantation Improves Survival Chances: Updated Results from the Single Arm Phase II Parachute-Trial Combined with Real-World Data

Individualized dose of anti-thymocyte globulin based on weight and pre-transplantation lymphocyte counts in pediatric patients: a single center experience.

Anti-thymocyte globulin (ATG) has become a standard in preventing GVHD in related and unrelated donor transplantation, but there is no consensus on the best administration schedule. The PARACHUTE trial reported excellent CD4 immune reconstitution (CD4 IR) using a dosing schedule based on the patient's weight and pre-conditioning absolute lymphocyte count (ALC). In 2015 we introduced the PARACHUTE dosing schedule for pediatric patients at our center. One hundred one patients were transplanted for malignant and non-malignant diseases. In this non-concurrent cohort CD4 IR+, defined by a single CD4 count >50/µL on day 90, was seen in 81% of patients. The incidence of grade II-IV and III to IV aGvHD was 26.6% and 15.3% and 5% for cGvHD with no severe cases. We found no difference in aGvHD between donor type and stem cell sources. Five-year EFS and OS were 77.5% and 83.5%. Grade III-IV GFRS was 75.2%. CD4 IR+ patients had better EFS (93.1% vs. 77.7%, p = 0.04) and lower non-relapse mortality (2.7% vs. 22.2%, p = 0.002). The PARACHUTE ATG dosing schedule individualized by weight and ALC results in good early immune reconstitution, low incidence of cGvHD, and favorable survival for patients with different disease groups, donor types, and stem cell sources.

Anti-thymocyte globulin for treatment of T-cell-mediated allograft rejection.

Anti-thymocyte globulin (ATG) is a pivotal immunosuppressive therapy utilized in the management of T-cell-mediated rejection and steroid-resistant rejection among renal transplant recipients. Commercially available as Thymoglobulin (rabbit-derived, Sanofi, United States), ATG-Fresenius S (rabbit-derived), and ATGAM (equine-derived, Pfizer, United States), these formulations share a common mechanism of action centered on their interaction with cell surface markers of immune cells, imparting immunosuppressive effects. Although the prevailing mechanism predominantly involves T-cell depletion via the com plement-mediated pathway, alternate mechanisms have been elucidated. Optimal dosing and treatment duration of ATG have exhibited variance across ran domised trials and clinical reports, rendering the establishment of standardized guidelines a challenge. The spectrum of risks associated with ATG administration spans from transient adverse effects such as fever, chills, and skin rash in the acute phase to long-term concerns related to immunosuppression, including susceptibility to infections and malignancies. This comprehensive review aims to provide a thorough exploration of the current understanding of ATG, encom passing its mechanism of action, clinical utility in the treatment of acute renal graft rejections, specifically steroid-resistant cases, efficacy in rejection episode reversal, and a synthesis of findings from different eras of maintenance immunosuppression. Additionally, it delves into the adverse effects associated with ATG therapy and its impact on long-term graft function. Furthermore, the review underscores the existing gaps in evidence, particularly in the context of the Banff classification of rejections, and highlights the challenges faced by clinicians when navigating the available literature to strike the optimal balance between the risks and benefits of ATG utilization in renal transplantation.

Incidence and Risk Factors for Central Nervous System Relapse after Allogeneic Hematopoietic Stem Cell Transplantation in Adult Patients with Acute Lymphoblastic Leukemia

Background Acute lymphoblastic leukemia (ALL) is frequently accompanied with the involvement of the central nervous system (CNS). The clinical prognosis for ALL patients with CNS disease is generally unfavorable, and prophylactic measures such as intrathecal chemotherapy are highly recommended. In adult ALL patients, hematopoietic stem cell transplantation (HSCT) presents a potential curative approach. However, there are currently only a few reports available on the risk factors and epidemiology of CNS relapse after HSCT. Method We conducted a retrospective single-center cohort study involving 1043 patients diagnosed with either acute lymphoblastic leukemia (ALL) or mixed phenotype acute leukemia (MPAL). These patients were treated at our center using the same treatment protocol between 2009 and 2022. During the remission induction phase, we utilized a modified hyper-CVAD regimen, along with six rounds of prophylactic intrathecal (IT) chemotherapy. High-risk patients who had suitable donors underwent allogeneic hematopoietic stem cell transplantation (HSCT) as part of their post-remission therapy. Diagnosis of central nervous system (CNS) leukemia was established when neurologic symptoms were observed in correlation with CNS lesions on imaging studies, or when leukemic blasts were detected in the cerebrospinal fluid (CSF). In our study, we examined the incidence, risk factors, and survival outcomes of patients who experienced CNS relapse after transplantation. Results Among the entire cohort of 1043 patients, CNS involvement was observed in 3 (0.3%) patients at initial diagnosis and 12 (1.2%) during chemotherapy. We proceeded with allogeneic hematopoietic stem cell transplantation (allo-HSCT) in 755 consecutive patients. Among these 755 patients, 3 had CNS leukemia prior to transplantation. Among the group of 755 patients, a total of 224 (29.6%) experienced relapse. Of these relapses, 142 (18.8%) were bone marrow relapses alone, 54 (7.1%) were extramedullary relapses alone (with CNS involvement in 21 [38.8%]), and 28 (3.7%) had both bone marrow and extramedullary relapses (with CNS involvement in 13 [46.4%]). Overall, extramedullary relapse was observed in 82 (10.8%) patients, with CNS involvement in 34 (4.5%) cases, following allo-HSCT. The 5-year cumulative incidence of CNS relapse was 4.6%, which was significantly higher in patients with Philadelphia chromosome-positive (Ph-positive) ALL (9.4% vs. 1.0%, p &amp;lt;0.001), as well as those with a high leukocyte count at diagnosis (8.3% vs. 2.6%, p = 0.001). Among the Ph-positive ALL cases, a high leukocyte count (n=151) was associated with a higher prevalence of pre-HSCT minimal residual disease (MRD) &amp;gt; 0.1% (n=88), which exhibited a significantly increased incidence of CNS relapse (16.6% vs. 6.8%, p = 0.009). Factors such as age, number of intrathecal chemotherapy treatments, conditioning intensity, and dose of anti-thymocyte globulin did not have a significant impact. Among the 34 patients with CNS relapse, 21 (61.7%) had isolated CNS relapse, and 7 of them showed evidence of positive MRD. With the exception of one patient who refused further treatment, the remaining 33 patients received initial CNS local therapy, including intrathecal chemotherapy combined with radiotherapy in 27 (82.0%) cases, intrathecal chemotherapy alone in 6 cases, and radiotherapy alone in 4 cases. Out of these patients, 22 were treated with dasatinib or ponatinib, while 6 received salvage chemotherapy. The median overall survival for patients with CNS relapse was 11.2 months, which was 19.8 months for those with isolated CNS relapse and 10.9 months for those with CNS relapse accompanied by bone marrow relapse (p = 0.077). The subsequent 2-year cumulative incidence of CNS relapse was 30%. Conclusion Based on our findings, the current prophylaxis strategy employed for the prevention of post-HSCT CNS relapse in adult ALL appears to be effective. However, our data indicates that MRD-positive Ph-positive ALL requires distinct management due to its significantly elevated risk of CNS relapse. New strategies including prophylactic radiotherapy for this high-risk subgroup must be considered to prevent post-HSCT CNS disease.

Radiation and Busulfan-Free Hematopoietic Stem Cell Transplantation Using Briquilimab (JSP191) Anti-CD117 Antibody-Conditioning, Transient Immunosuppression and TCRαβ + T-Cell/CD19 + B-Cell Depleted Haploidentical Grafts in Patients with Fanconi Anemia

Introduction: Fanconi anemia (FA) is a rare, genetic disorder clinically characterized by congenital abnormalities, progressive bone marrow failure (BMF), and a predisposition to malignancies. Allogeneic hematopoietic stem cell transplantation (HSCT) is currently the only curative treatment for BMF. In patients with FA who do not have a matched sibling donor, HSCT conditioning regimens typically use reduced doses of cyclophosphamide, fludarabine and anti-thymocyte globulin (ATG) with total body irradiation (TBI) or busulfan. However, treatment is complicated by conditioning related toxicities, graft vs host disease (GvHD) and increased predisposition to malignancies later in life. Prior attempts to remove TBI from FA conditioning regimens have been unsuccessful due to increased risk of graft rejection - and alternative approaches have replaced TBI with busulfan which is still genotoxic. Objective: To reduce acute and long-term treatment-related toxicities, we have developed a first of its kind treatment intended to improve the safety of allo-HSCT through: 1) a TBI- and busulfan-free conditioning regimen consisting of briquilimab, rabbit ATG (rATG - Thymoglobulin), fludarabine, cyclophosphamide and rituximab - briquilimab (formerly called JSP191) is a monoclonal antibody (mAb) that targets human CD117 to deplete host HSCs enabling blood and immune reconstitution with minimal toxicity with the other agents being used for transient immune suppression to prevent immunologic rejection; 2) transplantation of TCRαβ + T-cell/CD19 + B-cell hematopoietic grafts - a stem cell therapy that enhances donor hematopoietic and immune reconstitution while decreasing GvHD; and 3) a pre- and post-transplant monitoring protocol to maximize engraftment. This is the first HSCT regimen to use anti-CD117 mAb-based conditioning in immunocompetent patients without concurrent use of irradiation. Methods: Patients with FA in BMF were eligible to be enrolled in this Phase 1b/2a trial to receive allo-HSCT with TCRαβ + T-cell/CD19 + B-cell depleted hematopoietic grafts from 10/10 unrelated, 9/10 unrelated or haploidentical family donors. Per the treatment schema, in this regimen a fixed dose of briquilimab was administered at 0.6 mg/kg in combination with standard FA dosing of rATG, fludarabine, cyclophosphamide and rituximab as lymphodepletion (Figure 1). Prospective pharmacokinetic measurements of briquilimab, rATG and fludarabine are included in the protocol. Results: Treatment of all of the patients on the Phase 1b portion of the study has been completed with each of the three patients showing promising safety and efficacy results (Table 1). Importantly, briquilimab treatment was well tolerated without any complications with appropriate antibody clearance of &amp;lt; 500 ng/ml prior to HSCT in all three patients. Each of the patients achieved full blood count recovery by Day +14 post HSCT with haploidentical grafts that were within specifications of the protocol. Total, CD34 +, and CD15 + donor chimerism of &amp;gt; 98% in the bone marrow has been observed in all patients with &amp;gt; 91% chimerism in all immune subsets (CD3, CD19 and CD56) at the last follow-up with 1 year of follow-up post HSCT in the first patient. None of the patients have developed acute or chronic GvHD at the time of reporting. Conclusions: All three patients in the Phase 1b portion of the study show early safety and efficacy of this approach. Briquilimab was well tolerated and all patients have shown prompt and durable donor engraftment. This data indicates that it might be possible to remove irradiation or alkylator chemotherapy from the conditioning regimen in patients with FA without matched sibling donors thus decreasing the chances for cancer predisposition in these patients that have inherited DNA repair defects.

Favorable Outcomes with Low Dose Anti Thymocyte Globulin Based Graft Versus Host Disease Prophylaxis after Mismatched Unrelated Donor Allogenic Hematopoietic Cell Transplantation

DISCUSSION INTRODUCTION Anti thymocyte globulin (ATG) based Graft versus Host disease (GVHD) prophylaxis is widely used for unrelated donor allogeneic hematopoietic cell transplantation (HCT) although the optimal dose remains unclear. Recently, registry based and single centre retrospective analyses have suggested superior outcomes with the PTCy based GVHD prophylaxis regimens when compared to ATG based regimens in mismatched unrelated donor (MMUD) allogeneic HCT, however, these studies all used doses of ATG ≥ 5mg/kg. Outcomes following MMUD allogeneic HCT with lower dose ATG based GVHD prophylaxis regimens have not been extensively studied. Thus, we analysed outcomes of HLA 9/10 MMUD allogeneic HCTs using two low dose ATG based regimens as GVHD prophylaxis at our centre. All adult patients undergoing standard of care allogenic hematopoietic cell transplant at The Ottawa Hospital from January 1 st 2015- December 31, 2022 were included. Data regarding demographics, HLA mismatched allele, conditioning regimen, dose of ATG, time to engraftment, and rates of acute and chronic GVHD was collected. The primary outcome evaluated was overall survival (OS) and secondary outcomes were GVHD-free relapse-free survival (GRFS), cumulative incidence of relapse (CIR) and non-relapse mortality (NRM). Survival outcomes were analyzed using Kaplan Meier analysis. Predictors of survival were identified using Cox-proportional hazards regression model. 77 patients (Males 62.3% (n=48); Median age - 50 years) underwent allogeneic HCT from MMUD. Most common indication for transplant was MDS/AML in 66.2% (n=51) followed by ALL in 11.3% (n=9) patients. Most frequently mismatched locus was HLA A in 37.7% (n= 29) followed by HLA B in 14.3% (n=11). Myeloablative conditioning regimen was received by 76.6% (n=59) while reduced intensity regimens were used in 23.4% (n=18) patients. Rabbit ATG was part of the GVHD prophylaxis regimen in all patients with majority (81%; n=63) receiving 2.5mg/kg and remaining 18.2% (n=14) receiving 4.5mg/kg of the drug. Grade II-IV acute GVHD occurred in 24.7% (n=19) while chronic GVHD occurred in 32.5% (n= 25) patients. After a median follow up of 21 months, relapse occurred in 28.6% (n=22) patients. Two year OS (Fig 1), and GRFS of the whole cohort were 60.6% and 45.3% respectively. 2-year incidence of non-relapse mortality (NRM) and cumulative incidence of relapse (CIR) were 16.9% and 18.2% respectively. Dose of ATG (2.5 mg/kg vs 4.5 mg/kg) was not a predictor of outcomes in either univariate and multivariate analyses. Age more than 50 years, primary diagnosis of lymphoma, reduced intensity conditioning and mismatch in loci other than HLA C were significant predictors of poor OS after univariate analysis. Only primary diagnosis of lymphoma (Hazard Ratio (HR) - 7.76; p=0.045) and mismatch in loci other than HLA C (HR - 9.53; p=0.03) were significant predictors of poor OS after multivariate analysis. When compared to published single centre and registry-based studies using ATG doses ≥ 5 mg/kg, GVHD prophylaxis using ATG doses ≤4.5 mg/kg seems to provide improved outcomes in patients undergoing allogeneic HCT from mismatched unrelated donors (Table 1). Our findings suggest that further studies are needed directly comparing lower dose ATG based regimens to PTCy based regimens to determine the ideal GVHD prophylaxis regimen for patients undergoing allogeneic HCT from HLA mismatched unrelated donors.

Analysis of the Impact of Body Mass Index (BMI) on the Durability of Response in Patients with Aplastic Anemia Treated with Weight-Adjusted Horse Anti-Thymocyte Globulin (hATG)

Introduction: Immunosuppressive therapy (IST) with anti-thymocyte globulin (ATG), cyclosporine A (CsA) and Eltrombopag (Epag) has recently been established as standard of care in adult patients (pts.) with severe (sAA) or very severe (vsAA) aplastic anemia &amp;gt; 40-50 years or ineligible for transplant for other reasons. ATG works via immunosuppressive properties including T-cell depletion and induction of immune tolerance. Horse ATG (hATG) is applied for 4 days with 40 mg/kg/day based on the patient's current body weight. Thus, obese pts., defined by a body mass index (BMI) ≥ 30, receive higher absolute hATG dosages than non-obese pts. (BMI &amp;lt; 30). To date, it is unknown whether increased hATG dosages in obese pts. might have beneficial or adverse effects on AA treatment. To address the role of obesity in AA, we investigated (1) the prevalence of obesity in 334 pts. with (suspected) AA and (2) compared the overall survival (OS) and response of 89 obese and non-obese AA pts. to the treatment with hATG/CsA ±Epag. Methods: Retrospective analysis of data from pts. enrolled in the German Registry for Aplastic Anemia and Bone Marrow Failure (AA-BMF). 334 pts. with (suspected) AA and available BMI data (49% (n=164) male/ 51% (n=170) female, 83% (n=278) BMI &amp;lt; 30, 17% (n=56) BMI ≥ 30) were identified of which 89 pts. (43 male/ 46 female, mean age 50 ± 17 years, 75 BMI &amp;lt; 30/ 14 BMI ≥ 30 at hATG administration) with confirmed diagnosis of AA (4 mAA/ 49 sAA/ 18 vsAA/ 14 AA not otherwise specified/ 4 AA-PNH Overlap) and treatment with hATG/CSA were analyzed in detail. 14 pts. received hATG/CSA/Epag (all BMI &amp;lt; 30). Follow-up data were compiled over 35 ± 38.5 months between 2000 and 2023, whereby follow-up data of 12 pts. were incomplete. Results are given as mean ± standard deviation. Results: Analysis of the age distribution of the 343 pts. with (suspected) AA showed a mean age of 50 ±17 years with a biphasic peak at age approx. 25 and 65 years. The average BMI stratified by age (20-30y: 22.9, 31-40y: 24.5, 41-50y: 26.8, 51-60y: 26.4, 61-70y: 27.5, &amp;gt;70y: 27.8) corresponded to the BMI distribution of the German population surveyed by the German Federal Statistical Office. In accordance with the expected survival rates, the 89 AA pts. treated with hATG/CSA (including 14 pts. with Epag) revealed a 5-year overall survival (OS) of 93%/ 86%/ 67 % at &amp;lt; 40/ 40-60/ &amp;gt; 60 years. Regarding BMI, no significant difference was observed in 5-year OS between obese (BMI ≥ 30, 5y-OS 67%) and non-obese pts. (BMI &amp;lt; 30, 5y-OS 85%, p = 0.51). In pts. responding to IST, hematological response at six months after ATG was reached in 67 % (n=7/11) of the obese and 63 % (n=21/33, in 9 pts. exact timepoint not available) of the non-obese pts. (p = 0.85). The proportion of primary IST refractory pts. was numerically lower in obese (21 %, n=3/14) than in non-obese pts. (32 %, n=21/65, p=0.53). Among all 53 responders (2 pts. had incomplete follow-up to assess relapse), a significantly lower relapse rate of 9 % (n=1/11) in obese (median follow-up: 16 months, range 3 to 120 months) compared to 55 % (n=22/40) in non-obese pts. was observed (median follow-up: 19 months, range 1 to 87 months, p=0.008). Conclusion: BMI distribution of AA pts. by age is comparable to that of the general population with a higher rate of obesity in older pts.. Pts. with a BMI ≥ 30 thus receiving higher ATG dosages do appear to have comparable OS and hematological response rates compared to pts. with BMI &amp;lt;30. However, pending validation in a larger patient cohort, we hypothesize, based on our analysis, that a higher cumulative total ATG dose may have a beneficial impact on relapse rates in pts. with BMI ≥ 30 compared to those with BMI &amp;lt; 30.

Peripheral Blood Grafts Vs Bone Marrow Grafts in Young Acute Myeloid Leukemia Patients with HLA-Matched Sibling Donors Undergoing Myeloablative Conditioning

In allogeneic hematopoietic cell transplantation (allo-HSCT), graft source has been changed from bone marrow grafts (Bone marrow stem cell, BMSC) to peripheral blood grafts (Peripheral blood stem cell, PBSC) mobilized by granulocyte colony-stimulating factor. PBSC transplantation is known to have numerous advantages over BMSC, including faster engraftment, improved survival outcomes, and for the donor, the elimination of invasive marrow harvesting procedure under general anesthesia. However, previous studies regarding graft source included various hematologic malignancies and lacked consistency in conditioning intensity and disease status at allo-HSCT. Still, there are limited data on the comparison of graft sources specifically in patients with acute myeloid leukemia (AML) undergoing myeloablative conditioning. In this background, we conducted an analysis to investigate the impact of graft source on transplant outcomes in AML patients who underwent HLA A, B, C, DR-matched sibling donor (MSD) HSCT with myeloablative conditioning. This study was a retrospective, single-center study for patients with AML who received first allo-HSCT from 2002 to 2022. We included the patients aged &amp;lt; 60 at the time of allo-HSCT, in a state of complete remission (CR) or CR with incomplete hematologic recovery, from a MSD, and underwent myeloablative conditioning. We classified the patients into three groups: the BMSC graft group (BMSC group), the PBSC graft group without antithymocyte globulin (ATG) (PBSC/ATG- group), and the PBSC graft group with ATG (PBSC/ATG+ group). Patients who received both PBSC and BMSC grafts were excluded from the analysis. We examined the differences in overall survival (OS), relapse-free survival (RFS) among these three groups. A total of 480 patients were included in this analysis, with 234 patients in the BMSC group, 66 patients in the PBSC/ATG+ group, and 180 patients in the PBSC/ATG- group. BMSC transplantation was mostly performed before 2010, whereas PBSC transplantation started in 2007, and allo-HSCT with ATG administration were conducted after 2014. In the PBSC/ATG+ group, the median ATG dose was 2.5 mg/kg (Interquartile range, IQR: 1.6-2.5). The BMSC group tended to be younger at the time of HSCT (median 38 years [31-46]) compared to the other groups (median age of PBSC/ATG+ group: 44 years [37-51], PBSC/ATG- group: 46 years [39-51], p&amp;lt;0.01). Of total patients in the three groups, there was only 1 case of neutrophil engraftment failure (in the PBSC/ATG- group) and 5 cases of platelet engraftment failure (3 in the BMSC group and the other 2 in the PBSC/ATG- group). BMSC patients demonstrated superior OS compared to PBSC patients, with the most pronounced difference was observed over PBSC/ATG- group (Figure A). Similar trends were presented in relapse-free survival (RFS) as well. After adjusting for other covariates through multivariate Cox modeling, the difference caused by the graft source remained significant, particularly in terms of RFS (Figure B). The hazard ratios for RFS of PBSC comparing to BMSC were as follows; PBSC/ATG+: 1.64 [1.04-2.58], PBSC/ATG-: 1.95 [1.45-2.63]. In conclusion, Despite the clear differences in allo-HSCT era between groups, even BMSC patients underwent allo-HSCT at an earlier time, patients receiving BMSC grafts showed superior survival compared to those receiving PBSC grafts in young AML patients undergoing MSD myeloablative allo-HSCT. Parallel evaluation of the transplant outcomes between BMSC and PBSC would be crucial for assessing the advantages and disadvantages of PBSC and BMSC grafts in this setting.

T-Cell Depletion with Both Reduced Dose Anti-Thymocyte Globulin and Reduced Dose Post-Transplant Cyclophosphamide in Haploidentical Peripheral Blood Stem Cell Transplantation for Acute Leukemia and Myelodysplatic Syndrome

Graft-versus-host disease (GVHD) prophylaxis in allogeneic hematopoietic stem cell transplantation from HLA haplo-identical familial donor (haplo-HSCT) is based on in vivo T-cell depletion with either anti-thymocyte globulin (ATG) or post-transplant cyclophosphamide (PTCy). ATG has made significant contributions to enabling haplo-HSCT. However, the benefit of ATG may be often mitigated by higher risk of viral reactivation, including cytomegalovirus (CMV) and Epstein-Barr virus (EBV) due to a slower immune reconstitution. PTCy revolutionized HLA-mismatched HSCT and rapidly became the standard-of-care. However, it also has problems due to a cytokine release syndrome (CRS) -like symptoms and excessive cytotoxicity leading to the risk of acute cardiotoxicity and the possibility of alleviated graft-versus-leukemia effect. Considering a demand for more optimal in vivo T-cell depletion, we tried to combine both ‘lower-dose’ ATG and ‘lower-dose’ PTCy before and after stem cell infusion, respectively, hoping they can mitigate their individual limitations while maintaining the effectiveness of in vivo T-cell depletion. We retrospectively included 60 adults with acute leukemia or myelodysplastic syndrome who underwent haplo-HSCT following busulfan (3.2 mg/kg/day for 4 days as myeloablative and for 2 days as reduced intensity conditioning) and fludarabine (a total of 160 mg/m 2) between January 2019 and June 2023. Among them, 32 received a novel combination of ATG (a total of 3.0, 3.5, or 4.0 mg/kg depending on the absolute lymphocyte count level on days -3) and PTCy (50mg/kg on day +3 and 30mg/kg on day +4) compared to 28 patients who received ATG only (2.5 mg/kg/day from days -3 to -1, a total of 7.5 mg/kg) as in vivo T-cell depletion. Most patients received cyclosporine and mycophenolate mofetil as GVHD prophylaxis. The median follow-up duration for all patients was 8 months (median 9 months in the ATG/PTCy group and 7.5 months in the ATG group, respectively; P = 0.744). Baseline characteristics including age, sex, disease status, modified EBMT score, and the intensity of conditioning, were well-balanced except slightly higher infused CD34+ cells in the ATG/PTCy group (median 5.2 vs. 4.7 x 10 6/kg, P = 0.042). The cumulative incidence of acute GVHD at day +100 and moderate to severe chronic GVHD at 1 year were significantly lower in the ATG/PTCy group compared to the ATG group, respectively [grades II-IV acute GVHD: 20.4% (95% confidence interval [CI], 4.3-33.8%) vs. 48.4% (95% CI, 25.2-64.4%), P = 0.014; grades III-IV acute GVHD: 7.5% (95% CI, 0-17.1%) vs 31.1% (95% CI, 10.5-46.9%), P = 0.019; and moderate to severe chronic GVHD: 9.5% (95% CI, 0-21.2%) vs. 60% (95% CI, 23.3-79.1%), P = 0.007]. The ATG/PTCy group had a tendency of less incidence and severity of the haplo-fever. Multivariate analysis showed a significantly higher GRFS (hazard ratio 0.35, P = 0.002) and OS (hazard ratio 0.4, P = 0.014) for an ATG/PTCy group. The use of dual T-cell depletion with the reduced dose ATG in combination with the reduced dose PTCy showed a significantly superior early transplant outcome over with ATG of 7.5 mg/kg in terms of both GVHD and survival outcomes.

Real-world outcomes with immunosuppressive therapy for aplastic anemia in patients treated at the University of Michigan.

Aplastic anemia (AA) is a rare bone marrow failure disorder that is treated with either allogeneic stem cell transplant or immunosuppressive therapy (IST) consisting of antithymocyte globulin (ATG), cyclosporine (CSA), and eltrombopag. While outcomes are favorable in younger patients, older patients (>60) have significantly worse long-term survival. The dose of ATG is often reduced in older patients and those with multiple comorbidities given concerns for tolerability. The efficacy and safety of dose-attenuated IST in this population is largely undescribed. We performed a retrospective review of patients with AA treated with IST. Our analysis was confounded by changes in practice patterns and the introduction of eltrombopag. We identified 53 patients >60 years old, of which, 20 received dose-attenuated IST, with no statistically significant difference in overall survival between full and attenuated dose cohorts. Overall response rates in both cohorts were similar at 6 months at 71% and 68%. There were more documented infectious complications in the full dose cohort (13 vs. 3). This supports the consideration of dose-attenuated IST in older patients with concerns about tolerance of IST. Lastly, our data confirmed favorable outcomes of younger patients receiving IST, especially in combination with eltrombopag.

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.