Baskar Sivasubramanian, Peng Haiyong, Gaglione Erika M, Carstens Elizabeth J, Lindorfer Margaret A, Ahn Inhye E, Herman Sarah E M, Skarzynski Martin, Chang Jing, Keyvanfar Keyvan, Butera Vicent, Blackburn Amy, Vire Bérengère, Maric Irina, Stetler-Stevenson Maryalice, Yuan Constance M, Eckhaus Michael A, Soto Susan, Farooqui Mohammed Z H, Taylor Ronald P, Rader Christoph, Wiestner Adrian
Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD.
Department of Immunology and Microbiology, The Herbert Wertheim University of Florida Scripps Institute for Biomedical Innovation & Technology, Jupiter, FL.
Blood. 2025 Mar 20;145(12):1309-1320. doi: 10.1182/blood.2024024846.
Monoclonal antibodies (mAbs) improve survival of patients with mature B-cell malignancies. Fcγ receptor-dependent effector mechanisms kill tumor cells but can promote antigen loss through trogocytosis, contributing to treatment failures. Cell-bound mAbs trigger the complement cascade to deposit C3 activation fragments and lyse cells. Within 24 hours after ofatumumab administration to patients with chronic lymphocytic leukemia (CLL), circulating tumor cells had lost CD20 and were opsonized with C3d, the terminal covalently bound form of complement protein C3. We hypothesized that C3d provides a target to eliminate residual CD20- tumor cells. To test this hypothesis, we generated C8xi, a mouse/human chimeric immunoglobulin G1 (IgG1) that reacts with human but not mouse C3d. C8xi was effective in a patient-derived xenograft model against CD20-, C3d opsonized CLL cells from patients treated with ofatumumab. We also generated rabbit mAbs, 2 of which were chosen because they bound mouse and human C3d with low nanomolar affinity but were minimally cross-reactive with full-length C3. Anti-C3d rabbit/human chimeric IgG1 in combination with ofatumumab or rituximab prolonged survival of xenografted mice that model 3 different types of non-Hodgkin lymphoma (NHL). For example, in a diffuse large B-cell lymphoma model (SU-DHL-6), median survival with single-agent CD20 mAb was 114 days but was not reached for mAb combination treatment (P = .008). In another NHL model (SU-DHL-4), single-agent and combination mAb therapy eradicated lymphoma in most mice. In long-term survivors from both cohorts, there was no evidence of adverse effects. We propose that C3d mAbs combined with complement-fixing CD20 mAbs can overcome antigen-loss escape and increase efficacy of mAb-based therapy.
单克隆抗体（mAb）可提高成熟B细胞恶性肿瘤患者的生存率。Fcγ受体依赖性效应机制可杀死肿瘤细胞，但可通过胞啃作用促进抗原丢失，导致治疗失败。细胞结合型单克隆抗体触发补体级联反应，沉积C3激活片段并裂解细胞。在慢性淋巴细胞白血病（CLL）患者接受奥法木单抗治疗后24小时内，循环肿瘤细胞失去CD20，并被补体蛋白C3的末端共价结合形式C3d调理。我们假设C3d提供了一个消除残留CD20-肿瘤细胞的靶点。为了验证这一假设，我们制备了C8xi，一种小鼠/人嵌合免疫球蛋白G1（IgG1），它与人C3d反应，但不与小鼠C3d反应。C8xi在患者来源的异种移植模型中对接受奥法木单抗治疗患者的CD20-、C3d调理的CLL细胞有效。我们还制备了兔单克隆抗体，其中2种因其以低纳摩尔亲和力结合小鼠和人C3d，但与全长C3的交叉反应性最小而被选中。抗C3d兔/人嵌合IgG1与奥法木单抗或利妥昔单抗联合使用可延长模拟3种不同类型非霍奇金淋巴瘤（NHL）的异种移植小鼠的生存期。例如，在弥漫性大B细胞淋巴瘤模型（SU-DHL-6）中，单药CD20单克隆抗体治疗的中位生存期为114天，但联合单克隆抗体治疗未达到中位生存期（P = 0.008）。在另一个NHL模型（SU-DHL-4）中，单药和联合单克隆抗体治疗在大多数小鼠中根除了淋巴瘤。在这两个队列的长期存活者中，没有不良反应的证据。我们提出，C3d单克隆抗体与补体固定CD20单克隆抗体联合使用可以克服抗原丢失逃逸，提高基于单克隆抗体治疗的疗效。
