Most current therapies that target plasma membrane receptors function by antagonizing ligand binding or enzymatic activities. However, typical mammalian proteins comprise multiple domains that execute discrete but coordinated activities. Thus, inhibition of one domain often incompletely suppresses the function of a protein. Indeed, targeted protein degradation technologies, including proteolysis-targeting chimeras¹ (PROTACs), have highlighted clinically important advantages of target degradation over inhibition². However, the generation of heterobifunctional compounds binding to two targets with high affinity is complex, particularly when oral bioavailability is required³. Here we describe the development of proteolysis-targeting antibodies (PROTABs) that tether cell-surface E3 ubiquitin ligases to transmembrane proteins, resulting in target degradation both in vitro and in vivo. Focusing on zinc- and ring finger 3 (ZNRF3), a Wnt-responsive ligase, we show that this approach can enable colorectal cancer-specific degradation. Notably, by examining a matrix of additional cell-surface E3 ubiquitin ligases and transmembrane receptors, we demonstrate that this technology is amendable for ‘on-demand’ degradation. Furthermore, we offer insights on the ground rules governing target degradation by engineering optimized antibody formats. In summary, this work describes a strategy for the rapid development of potent, bioavailable and tissue-selective degraders of cell-surface proteins.

目前大多数靶向质膜受体的疗法通过拮抗配体结合或酶活性发挥作用。然而，典型的哺乳动物蛋白质包含执行离散但协调活动的多个域。因此，抑制一个结构域通常不能完全抑制蛋白质的功能。事实上，靶向蛋白质降解技术，包括蛋白水解靶向嵌合体¹ (PROTAC)，已经突出了靶标降解相对于抑制的临床重要优势²。然而，以高亲和力结合两个靶标的异双功能化合物的生成很复杂，尤其是在需要口服生物利用度时³. 在这里，我们描述了蛋白水解靶向抗体 (PROTAB) 的开发，该抗体将细胞表面 E3 泛素连接酶连接到跨膜蛋白，从而导致体外和体内的靶标降解。我们专注于锌和无名指 3 (ZNRF3)，一种 Wnt 反应性连接酶，表明这种方法可以实现结直肠癌特异性降解。值得注意的是，通过检查额外的细胞表面 E3 泛素连接酶和跨膜受体矩阵，我们证明该技术适用于“按需”降解。此外，我们通过工程优化的抗体形式提供了关于控制目标降解的基本规则的见解。总之，这项工作描述了一种快速开发有效的、生物可利用的和组织选择性细胞表面蛋白降解剂的策略。