Modeling Sézary Syndrome for Immunophenotyping and Anti-Tumor Effect of Ucart and Long-Acting Interleukin-7 Combination Therapy

Abstract

Background Sezary syndrome (SS) is a highly-morbid T cell leukemic lymphoma with no widely-effective treatments and few preclinical models. SS T cells typically lose CD7 but maintain ubiquitous high CD2 expression. Thus, we generated CD2- and TRAC-deleted anti-CD2 universal CARTs (UCART2) and multiple SS xenograft models (PDXs) as preclinical UCART2 testing platforms. We further tested a stable homodimeric interleukin-7 molecule, the long-acting form of recombinant human interleukin-7 fused with hybrid Fc (rhIL-7-hyFc, NT-I7), to potentiate UCART2 killing of an SS xenograft in vivo. Methods To generate SS PDX models, we injected NSG-SGM3 mice with ∼2\u202f×\u202f106 mononuclear cells derived from SS patients. We immunophenotyped SS patient blood and PDX engraftment with two 21-color flow cytometry panels assessing major immune subsets, CTCL, and exhaustion markers. To generate UCART2s, we CRISPR/Cas9 multiplexed edited CD2 and TRAC from CART2. For initial testing, we injected NSG mice with 5\u202f×\u202f105 cells from a human Sezary cell line (HH) on day -4 from UCART2 treatment, followed by NT-I7 (10mg/kg SC) on days +1, +15 and +29. Results SS patient blood showed specific defects in monocyte, monocytic dendritic cell, and natural killer cell differentiation, increased skewing toward granulocytes and non-classical CD16+ monocytes (p 90% vs ∼20%, p UCART2-treated HHCBR-GFP mice showed dramatically reduced tumor burden as compared to control UCART19-treated HHCBR-GFP mice (BLI; 10^7 vs. 10^11 photon flux/s at 3 weeks, p Discussion We describe the generation of physiologically-relevant SS preclinical models and the highly effective anti-tumor activity of UCART2- plus NT-I7-mediated killing of SS cells in vivo using an NSG xenograft model.