ABSTRACT

Conditionally active COBRA™ (COnditional Bispecific Redirected Activation) T cell engagers are engineered to overcome the limitations of inherently active first-generation T cell engagers, which are unable to discern between tumor and healthy tissues. Designed to be administered as prodrugs, COBRAs target cell surface antigens upon administration, but engage T cells only after they are activated within the tumor microenvironment (TME). This allows COBRAs to be preferentially turned on in tumors while safely remaining inactive in healthy tissue. Here, we describe the development of the COBRA design and the characterization of these conditionally active T cell engagers. Upon administration COBRAs are engineered to bind to tumor-associated antigens (TAAs) and serum albumin (to extend their half-life in circulation), but are inhibited from interacting with the T cell receptor complex signaling molecule CD3. In the TME, a matrix metalloproteinase (MMP)-mediated linker cleavage event occurs within the COBRA construct, which rearranges the molecule, allowing it to co-engage TAAs and CD3, thereby activating T cells against the tumor. COBRAs are conditionally activated through cleavage with MMP9, and once active are highly potent, displaying sub-pM EC₅₀s in T cell killing assays. Studies in tumor-bearing mice demonstrate COBRA administration completely regresses established solid tumor xenografts. These results strongly support the further characterization of the novel COBRA design in preclinical development studies.

摘要

有条件激活的COBRA™（标准双特异性重定向激活）T细胞接合体经过工程设计，可克服固有的第一代T细胞接合体固有的局限性，后者无法区分肿瘤组织和健康组织。设计为以前药形式给药，COBRAs在给药时靶向细胞表面抗原，但仅在肿瘤微环境（TME）中被激活的T细胞参与。这样可以使COBRAs在肿瘤中优先打开，同时安全地在健康组织中保持无效。在这里，我们描述了COBRA设计的发展以及这些条件激活T细胞接合子的表征。给药后，将COBRA设计为与肿瘤相关抗原（TAA）和血清白蛋白结合（以延长其在循环中的半衰期），但被抑制与T细胞受体复合物信号分子CD3相互作用。在TME中，基质金属蛋白酶（MMP）介导的接头切割事件发生在COBRA构建物中，该事件重新排列了分子，使其与TAA和CD3共接合，从而激活T细胞抵抗肿瘤。COBRAs通过MMP9的裂解而被有条件地激活，一旦激活，便具有很高的效力，显示出亚pM EC在T细胞杀伤试验中₅₀ s。在荷瘤小鼠中的研究表明，COBRA给药可以完全消退已建立的实体瘤异种移植物。这些结果有力地支持了临床前研究中新型COBRA设计的进一步表征。