Immunotherapy and Cell Engineering Laboratory, Department of Engineering, Aarhus University, Aarhus, Denmark.
Department of Antibody Engineering, Leadartis SL, Madrid, Spain.
Front Immunol. 2019 Jul 31;10:1791. doi: 10.3389/fimmu.2019.01791. eCollection 2019.
4-1BB (CD137) is an inducible costimulatory receptor that promotes expansion and survival of activated T cells; and IgG-based 4-1BB-agonistic monoclonal antibodies exhibited potent antitumor activity in clinical trials. However, the clinical development of those antibodies is restricted by major off-tumor toxicities associated with FcγR interactions. We have recently generated an EGFR-targeted 4-1BB-agonistic trimerbody that demonstrated strong antitumor activity and did not induce systemic inflammatory cytokine secretion and hepatotoxicity associated with first-generation 4-1BB agonists. Here, we generate a bispecific 4-1BB-agonistic trimerbody targeting the carcinoembryonic antigen (CEA) that is highly expressed in cancers of diverse origins. The CEA-targeted anti-4-1BB-agonistic trimerbody consists of three 4-1BB-specific single-chain fragment variable antibodies and three anti-CEA single-domain antibodies positioned around a murine collagen XVIII-derived homotrimerization domain. The trimerbody was produced as a homogenous, non-aggregating, soluble protein purifiable by standard affinity chromatographic methods. The purified trimerbody was found to be trimeric in solution, very efficient at recognizing 4-1BB and CEA, and potently costimulating T cells in the presence of CEA. Therefore, trimerbody-based tumor-targeted 4-1BB costimulation is a broadly applicable and clinically feasible approach to enhance the costimulatory environment of disseminated tumor lesions.
4-1BB（CD137）是一种诱导共刺激受体，可促进激活的 T 细胞的扩增和存活；基于 IgG 的 4-1BB 激动型单克隆抗体在临床试验中显示出强大的抗肿瘤活性。然而，这些抗体的临床开发受到与 FcγR 相互作用相关的主要肿瘤外毒性的限制。我们最近生成了一种 EGFR 靶向的 4-1BB 激动型三聚体，该三聚体表现出强大的抗肿瘤活性，并且不会诱导与第一代 4-1BB 激动剂相关的全身性炎症细胞因子分泌和肝毒性。在这里，我们生成了一种针对癌胚抗原（CEA）的双特异性 4-1BB 激动型三聚体，该抗原在多种来源的癌症中高度表达。该 CEA 靶向的抗 4-1BB 激动型三聚体由三个 4-1BB 特异性单链片段可变抗体和三个位于鼠胶原 XVIII 同源三聚化结构域周围的抗 CEA 单结构域抗体组成。三聚体作为一种均质、无聚集、可通过标准亲和色谱方法纯化的可溶性蛋白产生。发现该三聚体在溶液中呈三聚体形式，非常有效地识别 4-1BB 和 CEA，并在 CEA 存在下有效地刺激 T 细胞。因此，基于三聚体的肿瘤靶向 4-1BB 共刺激是一种广泛适用且临床上可行的方法，可增强播散性肿瘤病变的共刺激环境。
