Monoclonal antibodies targeting novel sites of vulnerability in marburg virus glycoprotein

丝状病毒由两个主要病毒家族组成，包括埃博拉病毒和马尔堡病毒（MARV和 RAVV）引起严重病毒性出血热的周期性爆发，死亡率高达90%。因为它 很难预测将主导未来疫情的物种，发展广泛的保护性 预防和管理未来丝状病毒爆发的治疗剂具有高度优先性。与最近的 我们和其他人报告说，在隔离和发展一些有效和广泛的 尽管针对埃博拉病毒的中和mAb（bNAbs）中，仅针对马尔堡病毒GP的单一类别的mAb已被发现， 描述了靶向MARV和RAVV GP的受体结合位点（RBS）内的相同表位。Mr191 是唯一的MARV/RAVV GP RBS特异性单克隆抗体（mAb），已被证明可以保护免受 然而，非人灵长类动物（NHP）中的MARV感染在非常高的剂量下（2次给药，每次50 mg/kg）。因此 重要的是要确定MARV/RAVV GP中新的脆弱性位点，并开发更有效的 免疫疗法来对抗这些致命的病毒具有多种bNAb将允许设计治疗性药物。 含有针对不同表位的多个单克隆抗体的鸡尾酒，这种策略已被证明是非常有效的。 有效对抗埃博拉病毒以对抗可能的病毒逃逸变体。 Integrated BioTherapeutics（IBT）与 马里兰州大学（UMD）的研究人员最近已经产生了具有显著的 在包括EBOV、SUDV和BDBV的非人灵长类动物（NHP）和雪貂模型的动物模型中的功效 感染（Zhao等人，Cell 169，891-904 e815（2017））。最近，在NHP中使用初免/加强免疫策略， 结合用工程化GP突变体进行的新的记忆B细胞反筛选，我们能够分离， 这是第一次，一组高效的MARV/RAVV bNAb靶向一类新的表位， RBS结合MR系列。在这个STTR应用中，我们的目标是解决MARV的主要挑战 通过开发来自这些新的马尔堡病毒的领先候选马尔堡病毒治疗抗体， MARV/RAVV bNAb。我们将i）在目前的bNAb候选物中选择3-4种领先的治疗性mAb; ii）优化 前导mAb，并通过最先进的计算机辅助选择最终的人源化/优化候选物 在严格的MARV感染豚鼠模型中的优化和功效研究;以及iii）鉴定最终先导化合物 通过测试候选物在MARV感染的NHP模型中的功效来评价mAb（或混合物）的活性。完成后 我们设想了一个具有以下目标的第二阶段项目：i）扩大疗效 研究RAVV和NHP中的剂量优化; ii）在CHO细胞中开发生产细胞系，iii）开发 产品放行和PK的生物分析方法，以及iv）使用 GLP级临床候选人如果成功，我们预计将在国防部或 巴尔达根据FDA动物法规获得资助和批准。

Filoviruses, consisting of two major virus families including the ebolaviruses and marburgviruses (MARV and RAVV), cause periodic outbreaks of severe viral hemorrhagic fever with mortality rates as high as 90%. Since it is difficult to predict the species that would dominate future outbreaks, development of broadly protective therapeutics to prevent and manage future filovirus outbreaks is of high priority. In sharp contrast to the recent major breakthrough reported by us and others on isolation and development of a number of effective and broadly neutralizing mAbs (bNAbs) for ebolaviruses, only a single class of mAbs against marburgvirus GP has been described that target the same epitope within the receptor binding site (RBS) of MARV and RAVV GP. MR191 is the only MARV/RAVV GP RBS-specific monoclonal antibody (mAb) that has been shown to protect against MARV infection in nonhuman primates (NHPs) however at very high doses (2 doses of 50 mg/kg each). Thus, it is important to identify novel sites of vulnerability in MARV/RAVV GP and develop more potent immunotherapeutics against these deadly viruses. Having a variety of bNAbs will allow the design of therapeutic cocktails containing multiple mAbs targeting distinct epitopes, a strategy that has been shown tobe extremely effective against ebolaviruses to combat possible virus escape variants. There has been a long-standing and productive collaboration between Integrated BioTherapeutics (IBT) and University of Maryland (UMD) that has recently resulted in highly potent ebolavirus bNAbs with remarkable efficacy in animal models including nonhuman primate (NHP) and ferret models of EBOV, SUDV, and BDBV infection (Zhao et al., Cell 169, 891-904 e815 (2017)). Lately, using a prime/boost immunization strategy in NHPs combined with a novel memory B cell counter-screening with engineered GP mutants, we were able to isolate, for the first time, a group of highly potent MARV/RAVV bNAbs that target a new class of epitopes distinct from the RBS-binding MR series. In this STTR application, we aim to address the major challenge of MARV immunotherapy by developing top lead candidate marburgvirus therapeutic antibodies derived from these novel MARV/RAVV bNAbs. We will i) select 3-4 lead therapeutic mAbs among the current bNAb candidates; ii) optimize the lead mAbs and select for the final humanized/optimized candidate by state-of-the-art computer-aided optimization and efficacy study in a stringent guinea pig model of MARV infection; and iii) identify the final lead mAb (or cocktail) by testing the efficacy of candidates in NHP model of MARV infection. Upon completion of the proposed Phase I project we envision a Phase II project with the following objectives: i) expand the efficacy studies to RAVV and dose optimization in NHPs; ii) develop manufacturing cell lines in CHO cells, iii) develop bioanalytical methods for product release and PK, and iv) conduct safety and tissue cross reactivity studies using the GLP-grade clinical candidate. If successful, we anticipate further development of the product under DoD or BARDA funding and approval under FDA Animal Rule.