A Chemo-enzymatically Linked Bispecific Antibody Retargets T Cells to a Sialylated Epitope on CD43 in Acute Myeloid Leukemia.
Acute myeloid leukemia (AML) is a high-risk disease with a poor prognosis, particularly in elderly patients. Because current AML treatment relies primarily on untargeted therapies with severe side effects that limit patient eligibility, identification of novel therapeutic AML targets is highly desired. We recently described AT1413, an antibody produced by donor B cells of a patient with AML cured after allogeneic hematopoietic stem cell transplantation. AT1413 binds CD43s, a unique sialylated epitope on CD43, which is weakly expressed on normal myeloid cells and overexpressed on AML cells. Because of its selectivity for AML cells, we considered CD43s as a target for a bispecific T-cell-engaging antibody (bTCE) and generated a bTCE by coupling AT1413 to two T-cell-targeting fragments using chemo-enzymatic linkage. In vitro, AT1413 bTCE efficiently induced T-cell-mediated cytotoxicity toward different AML cell lines and patient-derived AML blasts, whereas endothelial cells with low binding capacity for AT1413 remained unaffected. In the presence of AML cells, AT1413 bTCE induced upregulation of T-cell activation markers, cytokine release, and T-cell proliferation. AT1413 bTCE was also effective in vivo. Mice either coinjected with human peripheral blood mononuclear cells or engrafted with human hematopoietic stem cells [human immune system (HIS) mice] were inoculated with an AML cell line or patient-derived primary AML blasts. AT1413 bTCE treatment strongly inhibited tumor growth and, in HIS mice, had minimal effects on normal human hematopoietic cells. Taken together, our results indicate that CD43s is a promising target for T-cell-engaging antibodies and that AT1413 holds therapeutic potential in a bTCE-format. SIGNIFICANCE: These findings offer preclinical evidence for the therapeutic potential of a bTCE antibody that targets a sialylated epitope on CD43 in AML.
Bartels L
，de Jong G
，Gillissen MA
，Yasuda E
，Kattler V
，Bru C
，Fatmawati C
，van Hal-van Veen SE
，Cercel MG
，Moiset G
，Bakker AQ
，van Helden PM
，Villaudy J
，Hazenberg MD
，Spits H
，Wagner K
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Cytomegalovirus Reactivation after Allogeneic Hematopoietic Stem Cell Transplantation is Associated with a Reduced Risk of Relapse in Patients with Acute Myeloid Leukemia Who Survived to Day 100 after Transplantation: The Japan Society for Hematopoietic C
Cytomegalovirus (CMV) infection is a major infectious complication after allogeneic hematopoietic cell transplantation (allo-HSCT). Recently, it was reported that CMV reactivation is associated with a decreased risk of relapse in patients with acute myeloid leukemia (AML). The aim of this study was to evaluate the impact of early CMV reactivation on the incidence of disease relapse after allo-HSCT in a large cohort of patients. The Japan Society for Hematopoietic Cell Transplantation's Transplantation-Related Complication Working Group retrospectively surveyed the database of the Transplant Registry Unified Management Program at the Japan Society for Hematopoietic Cell Transplantation. Patients with AML (n = 1836), acute lymphoblastic leukemia (ALL, n = 911), chronic myeloid leukemia (CML, n = 223), and myelodysplastic syndrome (MDS, n = 569) who underwent their first allo-HSCT from HLA-matched related or unrelated donors between 2000 and 2009 and who survived without disease relapse until day 100 after transplantation were analyzed. Patients who received umbilical cord blood transplantation were not included. Patients underwent surveillance by pp65 antigenemia from the time of engraftment, and the beginning of preemptive therapy was defined as CMV reactivation. Cox proportional hazards models were used to evaluate the risk factors of relapse, nonrelapse, and overall mortality. CMV reactivation and acute/chronic graft-versus-host disease (GVHD) were evaluated as time-dependent covariates. CMV reactivation was associated with a decreased incidence of relapse in patients with AML (20.3% versus 26.4%, P = .027), but not in patients with ALL, CML, or MDS. Among 1836 patients with AML, CMV reactivation occurred in 795 patients (43.3%) at a median of 42 days, and 436 patients (23.7%) relapsed at a median of 221 days after allo-HSCT. Acute GVHD grades II to IV developed in 630 patients (34.3%). By multivariate analysis considering competing risk factors, 3 factors were significantly associated with a decreased risk of AML relapse and 1 factor with an increased risk of AML relapse: CMV reactivation (hazard ratio [HR], .77; 95% confidence interval [CI], .59 to .99), unrelated donor compared with related donor (HR, .59; 95% CI, .42 to .84), development of chronic GVHD (HR, .77; 95% CI, .60 to .99), and pretransplantation advanced disease status compared with standard disease status (HR, 1.99; 95% CI, 1.56 to 2.52). However, CMV reactivation was associated with increased nonrelapse mortality (HR, 1.60; 95% CI, 1.18 to 2.17) and overall mortality (HR, 1.37; 95% CI, 1.11 to 1.69). A beneficial effect of CMV reactivation on subsequent risk of relapse was observed in patients with AML but not in those with other hematological malignancies. However, this benefit was nullified by the increased nonrelapse mortality. The underlying mechanism is unclear; however, immunological activation against CMV reactivation plays an essential role in this association. Thus, immune augmentation treatment options, including vaccination and adoptive T cell transfer, may be useful to take advantage of the efficacy of CMV reactivation with minimal increase in nonrelapse mortality.
Takenaka K
，Nishida T
，Asano-Mori Y
，Oshima K
，Ohashi K
，Mori T
，Kanamori H
，Miyamura K
，Kato C
，Kobayashi N
，Uchida N
，Nakamae H
，Ichinohe T
，Morishima Y
，Suzuki R
，Yamaguchi T
，Fukuda T
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Patient-individualized CD8⁺ cytolytic T-cell therapy effectively combats minimal residual leukemia in immunodeficient mice.
Adoptive transfer of donor-derived cytolytic T-lymphocytes (CTL) has evolved as a promising strategy to improve graft-versus-leukemia (GvL) effects in allogeneic hematopoietic stem-cell transplantation. However, durable clinical responses are often hampered by limited capability of transferred T cells to establish effective and sustained antitumor immunity in vivo. We therefore analyzed GvL responses of acute myeloid leukemia (AML)-reactive CD8(+) CTL with central and effector memory phenotype in a new allogeneic donor-patient specific humanized mouse model. CTL lines and clones obtained upon stimulation of naive CD45RA(+) donor CD8(+) T cells with either single HLA antigen-mismatched or HLA-matched primary AML blasts, respectively, elicited strong leukemia reactivity during cytokine-optimized short to intermediate (i.e., 2-8 weeks) culture periods. Single doses of CTL were intravenously infused into NOD/scidIL2Rcg(null) mice when engraftment with patient AML reached bone marrow infiltration of 1-5%, clinically defining minimal residual disease status. This treatment resulted in complete regression of HLA-mismatched and strong reduction of HLA-matched AML infiltration, respectively. Most importantly, mice receiving AML-reactive CTL showed significantly prolonged survival. Transferred CTL were detectable in murine bone marrow and spleen and demonstrated sustained AML-reactivity ex vivo. Moreover, injections with human IL-15 clearly promoted CTL persistence. In summary, we show that naive donor-derived CD8(+) CTL effectively combat patient AML blasts in immunodeficient mice. The donor-patient specific humanized mouse model appears suitable to evaluate therapeutic efficacy of AML-reactive CTL before adoptive transfer into patients. It may further help to identify powerful leukemia rejection antigens and T-cell receptors for redirecting immunity to leukemias even in a patient-individualized manner.
Distler E
，Albrecht J
，Brunk A
，Khan S
，Schnürer E
，Frey M
，Mottok A
，Jordán-Garrote AL
，Brede C
，Beilhack A
，Mades A
，Tomsitz D
，Theobald M
，Herr W
，Hartwig UF
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