Therapeutic potential and challenges of targeting receptor tyrosine kinase ROR1 with monoclonal antibodies in B-cell malignancies.

Based on its selective cell surface expression in chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL), receptor tyrosine kinase ROR1 has recently emerged as a promising target for therapeutic monoclonal antibodies (mAbs). To further assess the suitability of ROR1 for targeted therapy of CLL and MCL, a panel of mAbs was generated and its therapeutic utility was investigated. A chimeric rabbit/human Fab library was generated from immunized rabbits and selected by phage display. Chimeric rabbit/human Fab and IgG1 were investigated for their capability to bind to human and mouse ROR1, to mediate antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and internalization, and to agonize or antagonize apoptosis using primary CLL cells from untreated patients as well as MCL cell lines. A panel of mAbs demonstrated high affinity and specificity for a diverse set of epitopes that involve all three extracellular domains of ROR1, are accessible on the cell surface, and mediate internalization. The mAb with the highest affinity and slowest rate of internalization was found to be the only mAb that mediated significant, albeit weak, ADCC. None of the mAbs mediated CDC. Alone, they did not enhance or inhibit apoptosis. Owing to its relatively low cell surface density, ROR1 may be a preferred target for armed rather than naked mAbs. Provided is a panel of fully sequenced and thoroughly characterized anti-ROR1 mAbs suitable for conversion to antibody-drug conjugates, immunotoxins, chimeric antigen receptors, and other armed mAb entities for preclinical and clinical studies.

基于其在慢性淋巴细胞白血病（CLL）和套细胞淋巴瘤（MCL）中选择性的细胞表面表达，受体酪氨酸激酶ROR1最近已成为治疗性单克隆抗体（mAbs）的一个有前景的靶点。为了进一步评估ROR1对CLL和MCL靶向治疗的适用性，制备了一组单克隆抗体并研究了其治疗效用。 从免疫后的兔子构建了一个兔/人嵌合Fab文库，并通过噬菌体展示进行筛选。研究了兔/人嵌合Fab和IgG1结合人和小鼠ROR1、介导抗体依赖性细胞毒性（ADCC）、补体依赖性细胞毒性（CDC）和内化以及使用来自未治疗患者的原发性CLL细胞以及MCL细胞系激活或拮抗细胞凋亡的能力。一组单克隆抗体对涉及ROR1所有三个细胞外结构域的多种表位表现出高亲和力和特异性，这些表位在细胞表面可及并介导内化。发现具有最高亲和力和最慢内化速率的单克隆抗体是唯一介导显著（尽管较弱）ADCC的单克隆抗体。没有一种单克隆抗体介导CDC。它们单独使用时不会增强或抑制细胞凋亡。 由于其相对较低的细胞表面密度，ROR1可能是武装单克隆抗体而非裸单克隆抗体的更优靶点。提供了一组完全测序且经过全面表征的抗ROR1单克隆抗体，适用于转化为抗体 - 药物偶联物、免疫毒素、嵌合抗原受体以及其他武装单克隆抗体实体，用于临床前和临床研究。