Re-designing anti-CD20 monoclonal antibody therapy using novel insights into limitations of innate immune cytotoxicity

项目摘要 非结合的单抗是一种高效但无疗效的靶向治疗方法。 B细胞恶性肿瘤。Bruton酪氨酸激酶抑制剂(BTKi)伊布鲁替尼改善预后但不能治愈 慢性淋巴细胞性白血病(CLL)，美国最常见的淋巴系恶性肿瘤。伊布鲁替尼动员 CLL细胞进入循环，在那里它们对针对CD20的单抗(αCD20mAb)高度敏感。然而， 在临床试验中，向伊布鲁替尼添加标准剂量的αCD20mAb利妥昔单抗(RTX)没有任何益处。 我们等人的研究表明，先天性免疫细胞毒能力有限，CLL细胞CD20在 标准剂量αCD20单抗治疗及伊布鲁替尼非靶向效应对RTX细胞毒的抑制作用 对这一负面结果负有很大责任。我们认为，这些关于药物作用机制的数据 α、CD20mAb和BTKi可用于改善联合靶向治疗。 我们和其他人已经证明，通过固定激活抗体依赖的细胞吞噬作用(ADCP) 巨噬细胞是αCD20mAb的主要作用机制。然后我们展示了最初的快速 在ADCP(&lt；1h)期间，靶淋巴细胞被吞噬，随后是长达约24小时的停顿(吞噬功能低下) 这限制了先天免疫细胞毒能力。此外，标准剂量αCD20mAb治疗可诱导 B细胞膜CD20-α单抗免疫复合物从循环淋巴细胞中的有效非致死性清除 由免疫效应细胞(巨噬细胞增多症)引起耐药性。抗恶性B细胞单抗活性的研究 淋巴组织受限于这些大分子缓慢的组织渗透，有限的先天免疫细胞毒 容量和微环境支持。伊布鲁替尼可以动员淋巴组织驻留的CLL细胞进入 对αCD20mAb介导的细胞毒性敏感的循环。不幸的是，伊布鲁替尼也抑制了 MAb通过非靶点效应介导包括ADCP在内的细胞毒作用。相比之下，更具体的BTKi 阿卡拉布替尼在不抑制巨噬细胞介导的ADCP的情况下将CLL细胞动员到循环中。 利用这些数据，我们改变了RTX在一种新的高频低剂量方案中的用途 阿卡拉布替尼用于慢性淋巴细胞性白血病的初步治疗。该方案正在一名完全纳入的患者(n=38)中进行测试。 由Acerta/AstraZeneca(ClinicalTrials.gov NCT03788291)资助的临床试验。我们正在申请资金，以 执行所需的相关研究，以确定此设计是否实现了所述目标：1)确定 序贯小剂量RTX是否能最大限度地清除循环中的CLL细胞和2)确定 阿卡布替尼对CLL细胞对RTX细胞毒性敏感性的影响数据生成者 这些研究对于设计未来的临床试验至关重要，以测试优化治疗效果的策略， 以更低的成本获得宽容、便利和可及性。肝硬变αCD20mAb、BTK三联疗法的研究 而bcl2抑制剂可为CLL提供高效、短疗程甚至根治的治疗方法。

Project Summary Unconjugated monoclonal antibodies (mAbs) are highly effective but non-curative targeted therapies for B cell malignancies. The Bruton tyrosine kinase inhibitor (BTKi) ibrutinib improved outcomes but does not cure chronic lymphocytic leukemia (CLL), the most prevalent lymphoid malignancy in the USA. Ibrutinib mobilizes CLL cells into the circulation where they are highly sensitive to mAb targeting CD20 (αCD20 mAb). However, addition of standard doses of the αCD20 mAb rituximab (RTX) to ibrutinib showed no benefit in clinical trials. Studies by us and others suggest that limited innate immune cytotoxic capacity, decreased CLL cell CD20 after standard dose αCD20 mAb therapy, and inhibition of RTX induced cytotoxicity by off-target effects of ibrutinib are largely responsible for this negative outcome. We propose that these data on the mechanisms of action of αCD20 mAb and BTKi can be used to improve combination targeted therapy. We and others have shown that activating antibody dependent cellular phagocytosis (ADCP) by fixed macrophages is the primary mechanism of action of αCD20 mAb. We then showed that initially rapid engulfment of target lymphocytes during ADCP (< 1h) is followed by a prolonged pause of ~ 24h (hypophagia) which limits innate immune cytotoxic capacity. In addition, standard dose αCD20 mAb therapy induces sufficient non-lethal removal of B-cell membrane CD20-αCD20 mAb immune complexes from circulating CLL cells by immune effector cells (trogocytosis) to cause drug resistance. mAb activity against malignant B cells in lymphoid tissue is limited by slow tissue penetration by these large molecules, limited innate immune cytotoxic capacity, and microenvironment support. Ibrutinib can mobilize lymphoid tissue resident CLL cells into the circulation where they are sensitive to αCD20 mAb mediated cytotoxicity. Unfortunately, ibrutinib also inhibits mAb mediated cellular cytotoxicity including ADCP by off-target effects. In contrast the more specific BTKi acalabrutinib mobilizes CLL cells into the circulation without inhibiting macrophage mediated ADCP. Using these data, we have repurposed RTX in a novel high frequency low dose regimen with acalabrutinib for initial treatment of patients with CLL. The regimen is being tested in a fully enrolled (n=38) clinical trial funded by Acerta/AstraZeneca (ClinicalTrials.gov NCT03788291). We are requesting funding to perform the correlative studies required to determine if this design is achieving the stated goals: 1) Determine if sequential low dose RTX can achieve maximum clearance of circulating CLL cells and 2) Determine the effect of acalabrutinib on sensitivity of CLL cells to RTX induced cytotoxicity. Data generated by these studies are essential for designing future clinical trials to test strategies to optimize treatment efficacy, tolerance, convenience and accessibility at lower cost. A potential triplicate therapy of HFLD αCD20 mAb, BTK and BCL2 inhibitors could result in highly effective, limited duration and even curative therapy for CLL.