Baxalta Innovations GmbH, DC-Tower Vienna, Vienna, Austria.
J Thromb Haemost. 2015 Nov;13(11):2053-62. doi: 10.1111/jth.13137. Epub 2015 Oct 12.
Acquired thrombotic thrombocytopenic purpura (TTP) is caused by an autoantibody-mediated deficiency of the von Willebrand factor-cleaving protease ADAMTS-13. Acute episodes of the disease are treated with a combination of immunosuppression and repeated cycles of plasma exchange to remove anti-ADAMTS-13 autoantibodies and, at the same time, replenish functional ADAMTS-13. Although this is often effective, the mortality rate has remained between 10% and 20%, highlighting the need for safer treatment options.
We previously showed that, in vitro, human recombinant ADAMTS-13 (rADAMTS-13) is able to override neutralizing antibodies and restore ADAMTS-13 activity in plasma from patients with acquired TTP. In the present study, we assessed the in vivo feasibility of this strategy by using a rat model.
Wild-type rats were adjusted to an ADAMTS-13 inhibitor (inhibitor) titer of ~ 10 BU mL(-1) with goat anti-ADAMTS-13 IgG, and treated with increasing doses of rADAMTS-13. Blood samples were drawn and analyzed for ADAMTS-13-specific parameters, including FRETS-VWF73 activity, inhibitor, and ADAMTS-13-specific immune complexes (ICs). The pharmacokinetics of ADAMTS-13 activity and inhibitors were evaluated.
Administration of inhibitor titer-adjusted doses of rADAMTS-13 to inhibitor-treated rats predictably restored activity. Inhibitors were readily neutralized through formation of ADAMTS-13-specific ICs, which were cleared at a higher rate than the free inhibitor. Surplus protease was enzymatically active in plasma, and showed similar pharmacokinetics to ADAMTS-13 in not inhibitor-treated rats.
Defined doses of rADAMTS-13 neutralized circulating anti-ADAMTS-13 antibodies and enabled reconstitution of ADAMTS-13 activity in plasma in our model, indicating that the protease may be a promising candidate for further exploration in treating acute episodes of acquired TTP.
获得性血栓性血小板减少性紫癜（TTP）是由血管性血友病因子裂解蛋白酶 ADAMTS-13 的自身抗体介导的缺乏引起的。该疾病的急性发作采用免疫抑制联合反复血浆置换来治疗，以去除抗 ADAMTS-13 自身抗体，并同时补充有功能的 ADAMTS-13。尽管这通常是有效的，但死亡率仍保持在 10%至 20%之间，这突显了需要更安全的治疗选择。
我们之前的研究表明，在体外，人重组 ADAMTS-13（rADAMTS-13）能够克服中和抗体，并恢复来自获得性 TTP 患者血浆中的 ADAMTS-13 活性。在本研究中，我们使用大鼠模型评估了该策略的体内可行性。
用抗 ADAMTS-13 IgG 将野生型大鼠的 ADAMTS-13 抑制剂（抑制剂）滴度调整至约 10 BU mL(-1)，并用递增剂量的 rADAMTS-13 进行处理。采集血液样本并分析 ADAMTS-13 特异性参数，包括 FRETS-VWF73 活性、抑制剂和 ADAMTS-13 特异性免疫复合物（ICs）。评估 ADAMTS-13 活性和抑制剂的药代动力学。
向抑制剂处理的大鼠给予经抑制剂滴度调整的 rADAMTS-13 剂量可预期地恢复活性。抑制剂通过形成 ADAMTS-13 特异性 ICs 而被迅速中和，这些 ICs的清除速度高于游离抑制剂。多余的蛋白酶在血浆中具有酶活性，其药代动力学与未用抑制剂处理的大鼠中的 ADAMTS-13 相似。
在我们的模型中，rADAMTS-13 的确定剂量中和了循环中的抗 ADAMTS-13 抗体，并使 ADAMTS-13 活性在血浆中得以重建，这表明该蛋白酶可能是治疗获得性 TTP 急性发作的有前途的候选药物。
