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Data on the influence of different Anti-lymphocyte globulin (ATLG) doses on graft versus host disease (GVHD) incidence and immune reconstitution in matched unrelated (MUD) allogeneic Stem cell transplantation (allo-SCT) is limited. This retrospective study conducted at the University Medical-Center Hamburg compares GVHD and Immune reconstitution after myeloablative MUD (HLA 10/10) PBSC allogeneic stem cell transplant between 30 mg/Kg (n = 73) and 60 mg/Kg (n = 216) ATLG. Detailed phenotypes of T, B natural killer (NK), natural killer T (NKT) cells were analyzed by multicolor flow at day 30, 100, and 180 posttransplant. Neutrophil and platelet engraftments were significantly delayed in the 60 mg/kg group with a higher Cumulative incidence of Infections (67% vs 75% p = 0.049) and EBV (21% vs 41% p = 0.049) reactivation at day 100 in this group. In the 30 mg/kg group, we observed a faster reconstitution of naïve-B cells (p < 0.0001) and γδ T cells (p = 0.045) at day+30 and a faster naïve helper T-cell (p = 0.046), NK-cells (p = 0.035), and naïve B-cell reconstitution (p = 0.009) at day+180. There were no significant differences in aGVHD, cGVHD, NRM, RI, PFS, and OS between the groups. The choice of ATLG dose has significant impact on IR but not on GVHD after MUD-allo-SCT. Higher doses are associated with delayed engraftment and increased infections., (© 2022. The Author(s).)

Anti-T-cell lymphocyte globulin (ATLG) and posttransplant cyclophosphamide (PTCy) are now widely used strategies to prevent graft-versus-host disease (GVHD) after allogeneic stem cell transplantation. Data comparing immune reconstitution (IR) between ATLG and PTCy is scarce. This retrospective study conducted at the University Medical Center Hamburg-Eppendorf (UKE) compares PTCy (n=123) and ATLG (n=476) after myeloablative allogeneic peripheral blood stem cell transplant. Detailed phenotypes of T, B natural killer (NK), natural killer T (NKT) cells were analyzed by multicolor flow at day 30, 100 and 180 posttransplant. Incidence of infections, viral reactivations, GVHD and relapse were collected. Neutrophil engraftment was significantly delayed in the PTCy group (median day 12 vs. day 10, P<0.001) with a high incidence of infection before day+100 in the PTCy arm but a higher Epstein-Barr virus reactivation in the ATLG arm and comparable cytomegalovirus reactivation. Overall incidence of acute GVHD was similar but moderate/severe chronic GVHD was seen more often after PTCy (44% vs. 38%, P=0.005). ATLG resulted in a faster reconstitution of CD8+ T, NK, NKT and gdT cells while CD4 T cells and B cells reconstituted faster after PTCy. Similar reconstitution was observed for T-regulatory cells and B cells. Non-relapse mortality relapse incidence, disease-free survival, and overall survival did not differ significantly between both arms. Even though differences in IR were related to a decreased incidence of infection and moderate/severe cGVHD in the ATLG group they had no impact on any of the other long-term outcomes. However, it remains undetermined which regimen is better as GVHD prophylaxis.

Since 2000, various phase III randomized controlled trials (RCTs) have investigated the efficacy of rabbit antithymocyte globulin (ATG) in patients following allogeneic stem cell transplantation (allo-SCT). Comparisons of different ATG formulations are lacking, however. Our aim was to synthesize all published efficacy evidence to enable a comparison of all available formulations of rabbit ATG in the allo-SCT setting. We performed a systematic literature review to identify all available phase III RCT evidence. We searched the Cochrane Library, MEDLINE, MEDLINE In-Process, and the website www.ClinicalTrials.gov . In addition, a trial presented at the Annual Meeting of the American Society of Hematology 2016 was added to include the most recent evidence. We identified a total of 6 RCTs, including 2 formulations: anti–T lymphocyte globulin (ATLG; Grafalon, Neovii Biotech, Lexington, MA) and polyclonal globulin immunized with human thymocytes (Thymoglobulin [Thymo]; Genzyme-Sanofi, Cambridge, MA). The evidence was synthesized using a conventional network meta-analysis (NMA). The best treatment for preventing graft-versus-host disease (GVHD) was ATLG, which had a more favorable hazard ratio (HR) compared with standard treatment (chronic GVHD: HR, .42; 95% confidence interval [CI], .31 to .56; acute GVHD grade II-IV: HR, .54; 95% CI, .39 to .73; acute GVHD grade III-IV: HR, .50; 95% CI, .29 to .86), whereas both ATLG and Thymo were at least similarly effective in terms of transplantation-related mortality (TRM) (ATLG: HR, .90; 95% CI, .61 to 1.32; Thymo: HR, .90; 95% CI, .56 to 1.44). Thymo tended to be the better treatment option regarding overall survival (OS) (HR, .86; 95% CI, .59 to 1.26). Our NMA provides the first report of the relative efficacy of all available rabbit ATG formulations in patients undergoing allo-SCT. Until additional data from randomized head-to-head comparisons are available, based on the present analysis, ATLG seems to be the best option to prevent chronic and acute GVHD. Both formulations show similar efficacy in terms of TRM, whereas Thymo appears to be the better treatment option in terms of OS. [ABSTRACT FROM AUTHOR]

Polyclonal antithymocyte globulins (ATGs) are used in organ and allogeneic stem cell transplantation mainly due to their immunomodulatory potential. Since ATGs contain antibodies against antigens expressed on various hematopoetic cells, it is not surprising that they induce cell death not only in healthy T-, B-, NK, and dendritic cells but also in malignant cells of lymphatic and to a lesser extent of myeloid lineage. The cytotoxic and antiproliferative effects of ATGs in malignant B-cells have been known for many years, without attracting clinical attention due to the advent of monoclonal antibodies like rituximab. Recent data indicate a potential role of ATGs in the therapy of multiple myeloma, a disease in which monoclonal serotherapy has been rather unsuccessful. This review discusses available data demonstrating the cytotoxic effects of ATGs and envisages a possible new role of these polyclonal antibodies in the therapy of hematological malignancies. [ABSTRACT FROM AUTHOR]

Objective: Allogeneic stem cell transplantation is a potentially curative therapy for patients with multiple myeloma. Polyclonal antithymocyte globulins (ATG) or monoclonal anti-CD52 (Alemtuzumab) are included in conditioning regimens to enhance engraftment and reduce risk of severe graft-vs-host disease. Because both agents have been reported to induce depletion of B cells, we sought to investigate their cytotoxic activity on myeloma cells. Materials and Methods: Complement-mediated and complement-independent activity of ATG-Fresenius and Alemtuzumab was investigated on four myeloma cell lines (RPMI-8226, U266, KMS-12-BM, and EJM) and bone marrow samples from six myeloma patients. Cytotoxicity was determined by staining with annexin V-fluorescein isothiocyanate and 7-amino-actinomycin D followed by flow cytometry. Results: ATG at a concentration of 500 μg mL−1 induced up to 100% and 85% complement-dependent killing of myeloma cell lines and primary myeloma samples respectively. In the absence of complement ATG still could induce up to 50% and 80% apoptosis in myeloma cell lines and primary myeloma samples, respectively. Preincubation of myeloma cells with a general caspase inhibitor abrogated ATG-induced complement-independent cell death. Alemtuzumab-mediated myeloma cytotoxicity was only observed in KMS-12-BM cells, and in none of the patient samples. Conclusion: ATG induces marked cytotoxic activity both in myeloma cell lines and in primary myeloma samples. Further elucidation of antibodies and antigens involved may pave the way for antibody-based myeloma therapy. [Copyright &y& Elsevier]

Summary:We investigated toxicity and efficacy of in vivo T-cell depletion with anti-thymocyte globulin (ATG) as part of an intensified myeloablative conditioning regimen followed by allogeneic stem cell transplantation in patients with advanced multiple myeloma. The conditioning regimen consisted of modified total body irradiation, busulfan and cyclophosphamide (n=15) or in the case of prior dose-limiting radiotherapy of busulfan and cyclophosphamide (n=3). The median age was 44 years (range, 29-53) and the median time from diagnosis to transplant was 12 months (range, 6-144). Grade II-IV acute graft-versus-host disease (GvHD) occurred in six patients (35%). Severe grade III/IV GvHD developed in one patient (6%). Three patients died of therapy-related causes (17%). A complete remission (CR) with negative immunofixation after allogeneic transplantation was seen in eight of the evaluable patients (53%). After a median follow-up of 41 months (range, 8-84), the estimated overall survival at 6 years for all patients is 77% (CI 95%: 58-96%). The estimated progression-free survival at 6 years for all patients is 31% (CI 95%: 2-59%) and 46% (CI 95%: 9-83%) for patients with CR. In vivo T-cell depletion with ATG resulted in a low rate of severe GvHD with low treatment-related mortality, and a substantial number of long-term survivors.Bone Marrow Transplantation (2003) 31, 973-979. doi:10.1038/sj.bmt.1704049 [ABSTRACT FROM AUTHOR]

Lymphocyte depletion with antithymocyte globulin (ATG) can be complicated by systemic coagulation activation. We found that ATG activated tissue factor procoagulant activity (TF PCA) on monocytic cells more potently than other stimuli that decrypt TF, including cell disruption, TF pathway inhibitor inhibition, and calcium lonophore treatment. Induction of TF PCA by ATG was dependent on lipid raft integrity and complement activation. We showed that ATG-mediated TF activation required complement activation until assembly of the C5b-7 membrane insertion complex, but not lytic pore formation by the membrane attack complex C5b-9. Consistently, induction of TF PCA by ATG did not require maximal phosphatidylserine membrane exposure and was not correlated with the magnitude of complement-induced lytic cell injury. Blockade of free thiols, an inhibitory monoclonal antibody to protein clisulfide isomerase (PDI), and the small-molecule PDI antagonist quercetin-3-rutinoside prevented ATG-mediated TF activation, and C5 complement activation resulted in oxidation of cell surface PDI. This rapid and potent mechanism of cellular TF activation represents a novel connection between the complement system and cell surface PDI-mediated thiol-disulfide exchange. Delineation of this clinically relevant mechanism of activation of the extrinsic coagulation pathway during immunosuppressive therapy with ATG may have broader implications for vascular thrombosis associated with inflammatory disorders. (Blood. 201 3;121 (1 2):2324-2335) [ABSTRACT FROM AUTHOR]

Abstract: Between August 1996 and December 2004, 369 patients with a median age of 41 years (range: 1-68 years) received stem cell transplantation (SCT) from unrelated donors after an antithymocyte-globulin (ATG)-containing conditioning regimen. In 268 patients, complete molecular typing (4-digit) of HLA-A, -B, -C, -DRB1, and -DQB1 was available: 110 patients were completely matched for 10 alleles, 91 patients had 1 allele-mismatch (9/10), and 67 patients were mismatched for 2-4 alleles (6-8/10). The incidence of grade II-IV acute graft-versus-host disease (aGVHD) was 33% in the 10/10, 41% in the 9/10, and 40% in the 6-8/10 group, respectively (P = .1). The cumulative incidence of treatment-related mortality (TRM) and relapse among the groups were similar (27%, 31%, and 32%, P = .2; and 28%, 27%, and 26%, P = .9. After a median follow-up of 35 months (range: 3-120 months), the estimated 5-year disease-free survival (DFS) was 42% and did not differ among the 10/10, the 9/10, and the 6-8/10-mismatched groups (45% versus 42% versus 39%) (P = .5). In multivariate analysis, only age (hazard ratio [HR] 1.013) (P = .004) and bad-risk disease (HR 1.975) (P < .001) were independent risk factors for DFS. In conclusion, pretransplant ATG allows allogeneic SCT from unrelated donors with HLA disparities. [Copyright &y& Elsevier]