Humanization of hFcRn Mice for Physiological Evaluation of Therapeutic Antibodies

描述(申请人提供)：新生儿Fc受体(FcRN)有四个主要功能：分解代谢保护的免疫球蛋白和白蛋白，跨细胞的免疫球蛋白和抗原提呈。FcRN在许多组织中发挥作用，对于新生儿通过初乳和牛奶获得母体免疫球蛋白、肺部分泌免疫球蛋白以及通过成人肠道上皮双向传输免疫球蛋白和免疫复合体是至关重要的。它还参与T细胞抗原的提呈。免疫球蛋白在临床上的一个重大成功是作为一种“神奇子弹”，精准地瞄准和治疗一系列人类疾病，特别是癌症和炎症性疾病。这一成功的部分原因是，与其他血清蛋白相比，它们在体内的半衰期较长。带着我们的 了解FcRN在这一过程中的关键作用，一个解决血清蛋白质和小分子半衰期的新治疗领域已经出现。这一新领域的主要参与者是免疫球蛋白Fc结构域和白蛋白：临床上相关的分子通过融合与这些分子相连，延长了它们在体内的功能半衰期。延长化合物的功能半衰期有许多临床益处，包括：(1)减少有效剂量(减少不良反应)；(2)减少给药频率(延长药代动力学)；(3)提高生物利用度；(4)降低生产成本。 对免疫球蛋白和融合化合物的治疗发展至关重要的是临床前模型，它们准确地反映了人类生理。然而，FcRN在人类和啮齿动物之间表现出物种歧视结合的差异。为了克服这一问题，开发了缺乏小鼠FcRN并表达人FcRN(HPcRn)的小鼠。虽然这些模型很有用，但它们表达的是小鼠免疫球蛋白，而hFcRn和小鼠白蛋白不能有效地保护小鼠免疫球蛋白。这并不能反映正常的生理状况。对于白蛋白，目前还没有容易获得的模型。为了建立更好地反映人类生理过程的模型，我们建议用人Fc替换小鼠lgG2b的Fc结构域，并用人白蛋白替换小鼠白蛋白基因。为此，我们将使用TAL效应核酸酶在感兴趣区域两侧引入异种重组酶靶点，然后通过重组介导盒交换来直接对现有人源化FcRN小鼠模型的受精卵进行基因工程。通过对当前模型的顺序修改来创建这些新菌株，我们将建立在它们以前的使用和声誉(数据)的基础上，从而加快它们的实施。经过核实，这些新的毒株将通过JAX鼠标库分发。我们完全期望这些模型能够更准确地反映人类免疫球蛋白和人类白蛋白的生物学特性，从而迅速推动药物开发和FcRN生物学的发展。

DESCRIPTION (provided by applicant): The neonatal Fc receptor (FcRn) has four major functions: catabolic protection of IgG and albumin, transcytosis of IgG and antigen presentation. FcRn functions across many tissues and is critical for neonatal acquisition of maternal IgG via colostrum and milk, the pulmonary secretion of IgG and bidirectional transport of both IgG and immune complexes across the adult intestinal epithelium. It is also involved in T cell antigen presentation. A major clinical success of IgGs is as a "magic bullet" precisely targeting and treating a wide array of human disorders, especially cancer and inflammatory diseases. This success is due, in part, to their long half-life in vivo compared to other serum proteins. With our understanding of the critical role of FcRn in this process, a new therapeutic field addressing serum proteins and small molecules half-life has emerged. The major players of this new field are the IgG Fc domain and albumin: clinically relevant molecules are attached to these via fusion extending their functional in vivo half- life. Functional half-life extension of compounds has a number of clinical benefits including: (i) reduction of effective dosage (reducing adverse reactions); (ii) reduced frequency of administration (extended pharmacokinetics); (iii) improved bioavailability; and (iv) a reduction of production costs. Critical for therapeutic development of IgGs and fusion compounds are preclinical models, which accurately reflect human physiology. However, FcRn exhibits species-discrimination binding differences between human and rodents. To overcome this, mice lacking the mouse FcRn and expressing human FcRn (hPcRn) were developed. Although useful, these models express mouse IgGs, which are not effectively protected by hFcRn and mouse albumin. This does not reflect the normal physiological situation. For albumin there is currently no model easily available. To establish models that better reflect the human physiological processes, we propose to exchange the Fc domain of mouse lgG2b with human Fc and to replace the mouse albumin gene with human albumin. To do this, we will use TAL effector nucleases to introduce heterospecific recombinase target sites flanking the region of interest, followed by recombination mediated cassette exchange to directly genetically engineer the zygote of existing humanized FcRn mouse models. By creating these new strains via sequential modification of current models we will build upon their previous use and reputation (data), speeding their implementation. After verification, these novel strains will be distributed via the JAX Mouse Repository. We fully expect these models to more accurately reflect human IgG and human albumin biology and, therefore, rapidly advance drug development and FcRn biology.