新型HER2抗体TPC对HER2阳性Trastuzumab耐受型乳腺癌的杀伤作用及分子机理研究

Approximately 20% to 25% of invasive breast cancers have overexpression of the human epidermal growth factor receptor (HER)2 tyrosine kinase receptor. Vast number of studies have demonstrated that elevation of HER2 expression levels are associated with reduced disease-free and overall survival in metastatic breast cancer (MBC), and therapeutic strategies are being developed to target this oncoprotein. Trastuzumab, a recombinant humanized monoclonal antibody (mAb) directed against an extracellular region of HER2, was the first HER2-targeted therapy approved for the treatment of HER2-overexpressing MBC. It has revolutionized the approach to treat patients with HER2-positive breast cancer (BC) and the prognosis of the disease. Nevertheless, not all patients benefit from trastuzumab. Around 15% of women relapse after trastuzumab-based therapy, indicating the presence of trastuzumab resistance. The pursuit of improved reagents to replace trastuzumab is intense, with several candidates currently under clinical evaluation. Pertuzumab is another ErbB2-specific humanized antibody that binds to a distinct epitope from trastuzumab. Its mechanism of action is complementary to trastuzumab, inhibiting ligand-dependent HER2-HER3 dimerization and reducing signaling via intracellular pathways such as phosphatidylinositol 3-kinase (PI3K/Akt). A phase II trial of Pertuzumab and Trastuzumab combination therapy in Patients With HER2-overexpressing MBC indicated that the combination of pertuzumab and trastuzumab is active and well tolerated in patients with HER2-positive MBC who had experienced progression during prior trastuzumab therapy. All of these experimental and clinical data revealed that HER2 still can be considered as a valid therapeutic target even after BC have progressed on multiple HER2-directed therapies and that simultaneous blockade of HER2 protein by trastuzumab and pertuzumab may overcome trastuzumab resistance..  The classical IgG architecture as it was selected during evolution has many advantages for the therapeutic application of bispecific antibodies.The Fc part is identical to that of a conventional IgG antibody, resulting in IgG-like pharmacokinetic properties and retained effector functions such as the mediation of ADCC through FcγRIIIa binding. IgG-like size and molecular weight are expected to result in IgG-like diffusion, tumor penetration, and accumulation in comparison with bispecific tetravalent antibodies of higher molecular weight. Considering these benefits, we will convert the HER2 antibody trastuzumab and pertuzumab into an IgG-like bispecific antibody (Tras-Per CrossMab) by using CrossMab technology and evaluate its anti-tumor activities against Trastuzumab-sensitive and -resistant MBC. These studies will provide the theoretical evidence for development of novel therapeutic agents for combating trastuzumab resistance in MBC.

虽然HER2抗体trastuzumab广泛应用于治疗乳腺癌，但是绝大多数患者治疗后产生耐受。目前，迫切需要设计抗瘤活性更好的新型HER2抗体用于克服Trastuzumab治疗耐受。最新临床数据表明能够结合HER2不同结构域的Trastuzumab与Pertuzumab的联合用药能够治疗Trastuzumab治疗复发的乳腺癌患者，提示同时靶向HER2这两个结构域也许能够克服Trastuzumab耐受。经过长期进化而来的全抗体结构在临床治疗中有很多优势。本研究以Trastuzumab和Pertuzumab作用的结构域为靶点，借助最新的CrossMab技术和计算机辅助设计优化抗体结构，设计新型具有全抗体结构的双靶向HER2抗体Tras-Per CrossMab（TPC），评价其对Trastuzumab耐受乳腺癌的杀伤并阐明其作用机理，为后续设计更有效的新型HER2抗体药物提供指导和理论依据。

虽然HER2抗体Trastuzumab已广泛应用于乳腺癌的临床治疗，但是绝大多数患者治疗后产生耐受。迫切需要设计具有更好抗肿瘤活性的新型HER2抗体用于乳腺癌的临床治疗。众所周知，由于肿瘤发生、发展的复杂性和多因素决定了临床上广泛使用的单一靶标的靶向抗体很难取得更好的疗效。因此，多靶向抗体是目前肿瘤靶向抗体研究的热点和难点。多靶向抗体的关键技术是如何将两个不同抗体重链能够特异性的组装，最终形成多靶向抗体。目前主流的抗体两重链特异性组装技术为罗氏公司专利所属的"Knob-into-Holes"技术，然而其组装特异性依然有待提高。借助最新的NVIDIA CUDA技术，我们打造了运算能力达到近100万亿次/秒的蛋白质模拟工作站。在此基础上，基于抗体晶体结构设计并优化了具有更好组装特异性的"Lock-and-Key"技术。该项技术的发明打破了国外多靶向抗体专利技术的封锁，获得了具有自主知识产权的具有更好组装特异性的多靶向抗体关键技术。在此基础上，我们构建、表达了HER2双靶向抗体，通过体内外试验系统评价了其抗肿瘤效果。该项目不仅提供了具有自主知识产权、具有更好组装特异性的多靶向抗体关键技术，而且为后续乳腺癌的临床治疗提供了潜在候选双靶向抗体药物。