Combined Factor VIII Replacement and Tolerance Therapy for Hemophilia A

描述(由申请人提供)：这一新的SBIR计划的目标是产生一种凝血因子VIII替代和免疫调节疗法的组合，将在治疗剂量为血友病A患者提供FVIII特异性耐受诱导。有1%功能性FVIII的血友病患者被归类为严重血友病患者，必须定期服用替代因子。成功的FVIII替代疗法治疗血友病A的一个主要问题是克服针对FVIII的中和抗体反应，这种中和抗体反应见于多达30%的血友病患者和50%的严重疾病患者。这些“抑制物”通过干扰FVIII与其配体的结合来延迟或抑制凝血。目前存在一些针对抑制剂的治疗方法，但这些方法要么不完全成功，要么仍处于实验阶段，对患者的健康构成了巨大的风险。迫切需要一种安全的、生物上合理的和成本效益高的方法来诱导对FVIII的长期免疫耐受。“三重表位”是免疫球蛋白衍生的自然调节性T细胞(NTreg)表位，它可以扩展循环中nTregs的一个子集，从而抑制炎症，当与靶抗原一起使用时，还能产生适应性耐受。自2008年发表这一发现以来，我们已经证明，在抗原提呈细胞(APC)表面向nTregs递呈Tregitope可以驱动APC和nTregs中的耐受通路，并诱导与相同APC相互作用的靶抗原特异性适应性Tregs。因此，作为一种天然免疫系统的“开关”，Tregitope具有巨大的治疗潜力，可以诱导对联合给药蛋白质的免疫耐受。因此，我们建议将Tregitope与FVIII偶联，以产生一种新的联合替代和耐受诱导疗法。在这一阶段的概念验证应用中，我们建议(I)证明FVIII-Tregitope调节人类T细胞反应，并建立可用于临床试验设计的耐受诱导的相关性，以及(Ii)在体内血友病模型中证明FVIII-Tregitope介导的耐受诱导，这使得能够评估Tregitope在关键结果--消除抑制剂上的有效性。在未来的第二阶段研究中，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是我们的第二阶段合作伙伴，是一家领先的公司，在生产重组人FVIII的核心活动方面拥有专业知识，包括细胞线工程、上游发酵、下游纯化、原料药的液体预配方和过程中分析，包括FVIII生物活性的滴度测定和显色测定。此外，我们还与一家在FVIII药物开发的监管和临床试验方面拥有经验的大型制药公司建立了强有力的合作关系，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--替代凝血因子VIII产生免疫耐受性。这项研究计划旨在证明，当因子VIII与免疫球蛋白的免疫抑制部分相关联时，在正常治疗剂量水平下是耐受的。

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.