Combined Factor VIII Replacement and Tolerance Therapy for Hemophilia A

描述（由申请方提供）：该新SBIR项目的目标是生产凝血因子VIII替代和免疫调节联合治疗，为血友病A患者提供治疗剂量的FVIII特异性耐受诱导。功能性FVIII <1%的血友病患者被归类为重度，必须接受常规剂量的替代因子。血友病A的成功FVIII替代疗法的一个主要问题是克服在高达30%的血友病患者和50%的重度疾病患者中观察到的针对FVIII的中和抗体应答。这些“抑制剂”通过干扰FVIII与其配体的结合来延迟或抑制凝血。存在许多抑制剂的治疗方法，但这些方法要么不完全成功，要么仍处于实验阶段，并对患者造成很大的健康风险。迫切需要一种安全、生物学合理且具有成本效益的方法来诱导对FVIII的长期免疫耐受。“Tregitopes”是免疫球蛋白衍生的天然调节性T细胞（nTreg）表位，其扩增循环nTreg的子集，导致炎症的抑制，并且当与靶抗原一起施用时，导致适应性耐受。自2008年发表这一发现以来，我们已经表明，Tregitopes在抗原呈递细胞（APC）表面呈递给nTcl 3驱动APC和nTcl 3中的致耐受性途径，并诱导与相同APC相互作用的靶抗原特异性适应性Tcl 3。因此，作为天然免疫系统的“关闭开关”，Tregitopes具有作为治疗剂诱导对共同施用的蛋白质的免疫耐受性的巨大潜力。因此，我们提出将Tregitopes与FVIII偶联以产生新的组合替代和耐受诱导疗法。在该I期概念验证申请中，我们提出（i）证明FVIII-Tregitope调节人T细胞应答并建立可用于临床试验设计的耐受性诱导的相关性，和（ii）证明在体内血友病模型中FVIII-Tregitope介导的耐受性诱导，这使得能够评价Tregitope对关键结果-抑制剂消除的功效。在未来的II期研究中，我们将过渡到FVIII-Tregitope的重组生产，这一过程对于概念验证研究来说过于复杂和昂贵。ProBioGen是我们的II期合作者，是一家领先的公司，在重组人FVIII生产的核心活动方面拥有专业知识，包括细胞系工程、上游发酵、下游纯化、散装原料药的液体预配制和过程中分析，包括效价测定和FVIII生物活性的显色测定。此外，我们还与一家在FVIII药物开发的监管和临床试验方面具有丰富经验的大型制药公司建立了密切合作，并预计一旦我们实现SBIR计划的目标，FVIII-Tregitope将进入临床研究。 公共卫生相关性：血友病A患者不会对他们所需的治疗（凝血因子VIII替代品）产生免疫耐受。本研究计划旨在证明因子VIII与免疫球蛋白的免疫抑制片段连接时，在正常治疗剂量水平下具有致耐受性。

DESCRIPTION (provided by applicant): The goal of this new SBIR program is to produce a combined clotting Factor VIII replacement and immunomodulatory therapy that will provide FVIII-specific tolerance induction at therapeutic doses for Hemophilia A patients. Hemophiliacs with <1% functional FVIII are classified as severe and must receive regular doses of replacement factor. A major issue with successful FVIII replacement therapy for Hemophilia A is overcoming the neutralizing antibody response against FVIII that is seen in up to 30% of hemophiliacs and 50% of patients with severe disease. These "inhibitors" delay or inhibit clotting by interfering with FVIII binding to its ligands. A number of treatments for inhibitors exist but these approaches are either not fully successful or still experimental and present a large health risk for the patient. There is an urgent need for a safe, biologically rational and cost effective approach to induce long-term immune tolerance to FVIII. "Tregitopes" are immunoglobulin-derived natural regulatory T-cell (nTreg) epitopes that expand a subset of circulating nTregs, leading to suppression of inflammation and, when administered with a target antigen, adaptive tolerance. Since publication of this discovery in 2008, we have shown that presentation of Tregitopes at the surface of antigen presentation cells (APCs) to nTregs drives tolerogenic pathways in both APCs and nTregs, and induces target-antigen specific adaptive Tregs that interface with the same APC. Thus, as a natural immune system 'off switch,' Tregitopes have great potential as therapeutics to induce immunological tolerance to co-administered proteins. We therefore propose to couple Tregitopes to FVIII to produce a novel combined replacement and tolerance induction therapy. In this Phase I proof-of concept application, we propose to (i) demonstrate that FVIII-Tregitope modulates human T cell responses and establish correlates of tolerance induction that may be used in clinical trial design and (ii) demonstrate FVIII-Tregitope-mediated tolerance induction in an in vivo hemophilia model, which enables evaluation of Tregitope efficacy on the key outcome - elimination of inhibitors. In future Phase II studies, we will transition to recombinant production of FVIII-Tregitope, a process too complex and costly for proof-of-concept studies. ProBioGen, our Phase II collaborator, is a leading company with expertise in activities central to the manufacture of recombinant human FVIII, including cell line engineering, upstream fermentation, downstream purification, liquid pre-formulation of bulk drug substance and in-process analytics including titer determination and chromogenic determination of FVIII bioactivity. In addition, we have established a strong collaboration with a large Pharma that has experience in the regulatory and clinical trial aspects of FVIII drug development and anticipate that FVIII-Tregitope will move into clinical studies once we achieve the goals of the SBIR program. PUBLIC HEALTH RELEVANCE: Hemophilia A patients do not develop immune tolerance to the very treatment they require, replacement clotting Factor VIII. This research program aims to demonstrate that Factor VIII, when linked to immunosuppressive segments of immunoglobulin, is tolerogenic at normal therapeutic dosing levels.