Incomplete inhibition by eculizumab: mechanistic evidence for residual C5 activity during strong complement activation
Incomplete inhibition by eculizumab: mechanistic evidence for residual C5 activity during strong complement activation
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DOI：
10.1182/blood-2016-08-732800
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发表时间：
2017-02-23
期刊：
影响因子：
20.3
通讯作者：
Schmidt, Christoph Q.
中科院分区：
文献类型：
--
作者：
Harder, Markus J.;Kuhn, Nadine;Schmidt, Christoph Q.
依库珠单抗通过阻断补体蛋白C5的活化来抑制补体的末端裂解途径，并且在某些补体介导的疾病中显示出显著的临床益处。然而，一些报告表明，即使在超过C5的依库珠单抗过量的情况下，C5的活化在患者中也不总是被完全抑制，这表明残留的C5活性可能在某些条件下减损药物的治疗益处。通过使用依库珠单抗和蜱衍生的C5抑制剂coversin，我们确定了C5抑制不完全的离体条件。这种残余溶解活性的程度取决于补体激活剂的强度和所产生的补体激活产物C3b的表面密度，其通过旁路途径（AP）扩增环进行自扩增。我们表明，在高C3b密度所需的结合和激活C5，这两种抑制剂减少，但不取消这种相互作用。在C5抑制剂存在下C5与C3b簇结合的减少与残留溶血水平相关。然而，通过同时使用不同的C5抑制剂，可以消除残留的溶血活性。在依库珠单抗存在下AP产生的C3b簇对于C5活化的重要性通过以下发现得到证实：经典途径的强力活化后的残留溶血可以通过阻断AP来减少。通过提供对C5激活和抑制的见解，我们的研究提供了依库珠单抗治疗下临床观察到的残留末端途径活性现象的基本原理，这对一般的抗C5治疗具有重要意义。
Eculizumab inhibits the terminal, lytic pathway of complement by blocking the activation of the complement protein C5 and shows remarkable clinical benefits in certain complement-mediated diseases. However, several reports suggest that activation of C5 is not always completely suppressed in patients even under excess of eculizumab over C5, indicating that residual C5 activity may derogate the drug's therapeutic benefit under certain conditions. By using eculizumab and the tick-derived C5 inhibitor coversin, we determined conditions ex vivo in which C5 inhibition is incomplete. The degree of such residual lytic activity depended on the strength of the complement activator and the resulting surface density of the complement activation product C3b, which autoamplifies via the alternative pathway (AP) amplification loop. We show that at high C3b densities required for binding and activation of C5, both inhibitors reduce but do not abolish this interaction. The decrease of C5 binding to C3b clusters in the presence of C5 inhibitors correlated with the levels of residual hemolysis. However, by employing different C5 inhibitors simultaneously, residual hemolytic activity could be abolished. The importance of AP-produced C3b clusters for C5 activation in the presence of eculizumab was corroborated by the finding that residual hemolysis after forceful activation of the classical pathway could be reduced by blocking the AP. By providing insights into C5 activation and inhibition, our study delivers the rationale for the clinically observed phenomenon of residual terminal pathway activity under eculizumab treatment with important implications for anti-C5 therapy in general.