Department of Radiology and Program in Pharmacology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA.
Immunology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA.
Eur J Nucl Med Mol Imaging. 2024 Nov;51(13):4001-4014. doi: 10.1007/s00259-024-06814-7. Epub 2024 Jul 11.
Immune cells are capable of eliminating leukemic cells, as evidenced by outcomes in hematopoietic cell transplantation (HCT). However, patients who fail induction therapy will not benefit from HCT due to their minimal residual disease (MRD) status. Thus, we aimed to develop an immunomodulatory agent to reduce MRD by activating immune effector cells in the presence of leukaemia cells via a novel fusion protein that chimerises two clinically tolerated biologics: a CD33 antibody and the IL15Ra/IL15 complex (CD33xIL15).
We generated a set of CD33xIL15 fusion protein constructs with varying configurations and identified those with the best in vitro AML-binding, T cell activation, and NK cell potentiation. Using Zr-immunoPET imaging we then evaluated the biodistribution and in vivo tumour retention of the most favourable CD33xIL15 constructs in an AML xenograft model. Ex vivo biodistribution studies were used to confirm the pharmacokinetics of the constructs.
Two of the generated fusion proteins, CD33xIL15 (N72D) and CD33xIL15wt, demonstrated optimal in vitro behaviour and were further evaluated in vivo. These studies revealed that the CD33xIL15wt candidate was capable of being retained in the tumour for as long as its parental CD33 antibody, Lintuzumab (13.9 ± 3.1%ID/g vs 18.6 ± 1.1%ID/g at 120 h).
This work demonstrates that CD33xIL15 fusion proteins are capable of targeting leukemic cells and stimulating local T cells in vitro and of concentrating in the tumour in AML xenografts. It also highlights the importance of Zr-immunoPET to guide the development and selection of tumour-targeted antibody-cytokine fusion proteins.
免疫细胞能够消除白血病细胞，造血细胞移植（HCT）的结果就是证明。然而，由于微小残留病（MRD）状态，未能接受诱导治疗的患者将无法从 HCT 中受益。因此，我们旨在开发一种免疫调节剂，通过在白血病细胞存在的情况下激活免疫效应细胞来减少 MRD，方法是使用一种新型融合蛋白，该融合蛋白将两种临床耐受的生物制剂：CD33 抗体和 IL15Ra/IL15 复合物（CD33xIL15）组合在一起。
我们生成了一组具有不同构型的 CD33xIL15 融合蛋白构建体，并确定了那些与 AML 结合、T 细胞激活和 NK 细胞增强作用最佳的构建体。然后，我们使用 Zr-免疫 PET 成像评估了最有利的 CD33xIL15 构建体在 AML 异种移植模型中的生物分布和体内肿瘤保留情况。进行了离体生物分布研究以确认构建体的药代动力学。
两种生成的融合蛋白，CD33xIL15（N72D）和 CD33xIL15wt，表现出最佳的体外行为，并在体内进一步进行了评估。这些研究表明，CD33xIL15wt 候选物能够像其亲本 CD33 抗体 Lintuzumab 一样在肿瘤中保留很长时间（120 小时时为 13.9±3.1%ID/g，而 18.6±1.1%ID/g）。
这项工作表明，CD33xIL15 融合蛋白能够靶向白血病细胞并在体外刺激局部 T 细胞，并且能够在 AML 异种移植瘤中集中在肿瘤中。它还强调了 Zr-免疫 PET 对于指导肿瘤靶向抗体-细胞因子融合蛋白的开发和选择的重要性。
