標的抗原のIgGの固有の親和性と結合値を調節することにより、抗体媒介補体依存性細胞毒性の調節

補体依存性細胞毒性（CDC）は強力なエフェクターメカニズムであり、生来の免疫と適応免疫の両方を関与させます。抗体治療薬のCDC活性を改善するための戦略は、主に抗体結晶化可能なフラグメント（FC）とC1補体複合体（C1Q）の最初のサブコンポーネントとの相互作用の強化に焦点を当てていますが、標的抗原に対する抗体の固有の親和性と結合値の相対的な重要性は理解できません。ここでは、細胞表面標的抗原に対する抗体結合親和性が明らかに抗体媒介補体活性化の程度と有効性に影響を与えることを示します。さらに、C1Qを動員し、CDCを調節する能力における抗体結合値の基本的な役割を報告します。More specifically, an array of affinity-modulated variants and functionally monovalent bispecific derivatives of high-affinity anti-epidermal growth factor receptor (EGFR) and anti-human epidermal growth factor receptor 2 (HER2) therapeutic immunoglobulin Gs (IgGs), previously reported to be deficient in mediating complement activation, were tested for their ability to bind C1q by抗原充填バイオセンサーを使用した生体層干渉法と、さまざまな組織学的起源のEGFRおよびHER2腫瘍細胞のパネルに対してCDCを発揮します。重要なことに、アフィニティ還元バリアントまたは単独の誘導体は、高親和性の二価IgG対応物ではなく、以前は補体媒介攻撃に耐性があることが示されていた腫瘍細胞株のほぼ完全な細胞毒性を誘導しました。我々の発見は、単独のターゲットエンゲージメントが、C1Qを関与させて補体経路を展開するために、抗体FCの最適な幾何学的位置に寄与する可能性があることを示唆しています。

Complement-dependent cytotoxicity (CDC) is a potent effector mechanism, engaging both innate and adaptive immunity. Although strategies to improve the CDC activity of antibody therapeutics have primarily focused on enhancing the interaction between the antibody crystallizable fragment (Fc) and the first subcomponent of the C1 complement complex (C1q), the relative importance of intrinsic affinity and binding valency of an antibody to the target antigen is poorly understood. Here we show that antibody binding affinity to a cell surface target antigen evidently affects the extent and efficacy of antibody-mediated complement activation. We further report the fundamental role of antibody binding valency in the capacity to recruit C1q and regulate CDC. More specifically, an array of affinity-modulated variants and functionally monovalent bispecific derivatives of high-affinity anti-epidermal growth factor receptor (EGFR) and anti-human epidermal growth factor receptor 2 (HER2) therapeutic immunoglobulin Gs (IgGs), previously reported to be deficient in mediating complement activation, were tested for their ability to bind C1q by biolayer interferometry using antigen-loaded biosensors and to exert CDC against a panel of EGFR and HER2 tumor cells of various histological origins. Significantly, affinity-reduced variants or monovalent derivatives, but not their high-affinity bivalent IgG counterparts, induced near-complete cell cytotoxicity in tumor cell lines that had formerly been shown to be resistant to complement-mediated attack. Our findings suggest that monovalent target engagement may contribute to an optimal geometrical positioning of the antibody Fc to engage C1q and deploy the complement pathway.