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Targeted lymphodepletion with a CD45-directed antibody radioconjugate as a novel conditioning regimen prior to adoptive cell therapy

ABSTRACT: Chimeric antigen receptor (CAR) T cell therapies, and adoptive cell therapy (ACT) in general, represent one of the most promising anti-cancer strategies. Conditioning has been shown to improve the immune homeostatic environment to enable successful ACT or CAR-T engraftment and expansion in vivo following infusion, and represents potential point of intervention to decrease serious toxicities following CAR-T treatment. In contrast to relatively non-specific chemotherapy-derived lymphodepletion, targeted lymphodepletion with radioimmunotherapy (RIT) directed to CD45 may be a safer and more effective alternative to target and deplete immune cells. Here we describe the results of preclinical studies with an anti-mouse CD45 antibody 30F11, labeled with two different beta-emitters 131Iodine (131I) and 177Lutetium (177Lu), to investigate the effect of anti-CD45 RIT lymphodepletion on immune cell types and on tumor control in a model of adoptive cell therapy. Treatment of mice with 3.7 MBq 131I-30F11 or 1.48 MBq 177Lu-30F11 safely depleted immune cells such as spleen CD4+ and CD8+ T Cells, B and NK cells as well as Tregs in OT I tumor model while sparing RBC and platelets and enabled E. G7 tumor control. Our results support the application of CD45-targeted RIT lymphodepletion with a non-myeloablative dose of 131I-30F11 or 177Lu-30F11 antibody prior to adoptive cell therapy.

SUBMITTER: Dawicki W

PROVIDER: S-EPMC7533072 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Project description:IntroductionReducing toxicities while preserving efficacy in allogeneic stem cell transplant (allo-HCT) remains a particularly challenging problem. Different strategies to enhance the antitumor activity without increasing early and late adverse toxicities of the conditioning regimens have been investigated.MethodsThe aim of "AlloTreo" prospective phase 2 clinical trial was to evaluate the efficacy and safety of a conditioning regimen based on Treosulfan (42 g/m2) and fludarabine (https://clinicaltrials.gov/ct2/show/NCT00598624). We enrolled 108 patients with hematological diseases who received a first allo-HCT between June 2005 and January 2011, inside the frame of this trial at our center. Median age at allo-HCT was 49 (21-69) years. Disease Risk Index was low in 14 (13%) patients, intermediate in 73 (67.7%), high in 17 (15.7%), and very high in 4 (3.7%). Donors were human leukocyte antigen (HLA)-matched related in 50 cases, 10/10-matched unrelated in 36, and 9/10-mismatched unrelated in 22. Graft-versus-host disease (GvHD) prophylaxis consisted of cyclosporine-A and methotrexate. Anti-T-lymphocyte globulin (ATLG) was administered in patients receiving unrelated allo-HCT. Stem cell source was mainly peripheral blood stem cells (95%).ResultsConditioning regimen was well tolerated. Full donor chimerism was documented for most patients (88%) at day +30. At 12 years, overall survival (OS) was 41.7% (32.2%-50.9%), progression-free survival (PFS) was 31.7% (23%-40.7%), GvHD-free/relapse-free survival was 20.9% (13.7%-29.1%), cumulative incidence (CI) of relapse was 44.5% (34.9%-53.6%), and transplant-related mortality (TRM) was 22.5% (15.1%-30.9%). CI of acute GvHD grades II-IV was 27.8% (19.7%-36.5%) at 100 days; 12-year CI of chronic GvHD was 40.7% (31.3%-49.9%). Relevant long-term adverse effects were 10 secondary malignancy, 3 fatal cardiovascular events, and 1 late-onset transplant-associated thrombotic microangiopathy. Ten successful pregnancies were reported after allo-HCT. In multivariate analysis, older age (≥60 years) at transplant [hazard ratio (HR), 2.157; p = 0.004] and a high/very high disease risk index (HR, 1.913; p = 0.026) were significantly associated with a lower OS.ConclusionsOverall, our data confirmed the myeloablative potential and safe toxicity profile of full dose Treo (42 g/m2) especially for the younger population.

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Targeted lymphodepletion with a CD45-directed antibody radioconjugate as a novel conditioning regimen prior to adoptive cell therapy

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