Characterization of a Bispecific FLT3 X CD3 Antibody in an Improved, Recombinant Format for the Treatment of Leukemia
Characterization of a Bispecific FLT3 X CD3 Antibody in an Improved, Recombinant Format for the Treatment of Leukemia
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DOI：
10.1038/mt.2015.2
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发表时间：
2015-04-01
影响因子：
12.4
通讯作者：
Jung, Gundram
中科院分区：
文献类型：
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作者：
Durben, Michael;Schmiedel, Dominik;Jung, Gundram
FLT3是一种受体酪氨酸激酶，在髓系和淋系白血病细胞上特异性表达。在此，我们报道了一种新型重组形式的双特异性FLT3×CD3抗体的构建和筛选，这种形式被称为Fabsc，它比已成熟的双特异性单链（bssc）形式更接近正常抗体结构。我们优选的抗体源自利用不同FLT3抗体和CD3抗体的初步筛选过程，包含FLT3抗体4G8和CD3抗体UCHT1。发现4G8×UCHT1 Fabsc抗体在以下方面优于具有相同特异性的bssc抗体：（i）对靶抗原FLT3的亲和力，（ii）转染细胞的产量，以及（iii）聚集体形成减少。在有和没有培养的白血病细胞存在的情况下，T细胞激活以及对这些细胞的杀伤作用在这两种分子中相当。此外，发现4G8×UCHT1 Fabsc抗体可在急性髓系白血病（AML）患者的原代外周血单个核细胞（PBMC）培养物中诱导T细胞激活并有效杀伤白血病母细胞。在这些实验中，双特异性分子明显优于先前描述的Fc优化的单特异性FLT3抗体，这表明在AML患者的PBMC中，T细胞的募集比自然杀伤细胞更有效。
FLT3 is a receptor-tyrosine-kinase that is expressed on leukemic cells of the myeloid and lymphoid lineage rather specifically. We here report on the construction and selection of bispecific FLT3 X CD3 antibodies in a new recombinant format, termed Fabsc, that resembles the normal antibody structure more closely than the well-established bispecific single chain (bssc)-format. Our preferred antibody, which emerged from an initial selection procedure utilizing different FLT3- and CD3-antibodies, contains the FLT3-antibody 4G8 and the CD3-antibody UCHT1. The 4G8 X UCHT1 Fabsc-antibody was found to be superior to a bssc-antibody with identical specificities with respect to (i) affinity to the target antigen FLT3, (ii) production yield by transfected cells, and (iii) the diminished formation of aggregates. T-cell activation in the presence and absence of cultured leukemic cells and killing of these cells was comparable for both molecules. In addition, the 4G8 X UCHT1 Fabsc-antibody was found to induce T-cell activation and efficient killing of leukemic blasts in primary peripheral blood mono-nuclear cell (PBMC) cultures of acute myeloid leukemia (AML) patients. In these experiments, the bispecific molecule was clearly superior to an Fc-optimized monospecific FLT3-antibody described previously, indicating that within PBMC of AML patients the recruitment of T cells is more effective than that of natural killer cells.