Department of Biochemistry, University of Lausanne, Epalinges, Switzerland.
Clinical Pharmacology, Quantitative Pharmacology, Global Early Development, Merck KGaA, Darmstadt, Germany.
Br J Pharmacol. 2019 Oct;176(20):4019-4033. doi: 10.1111/bph.14811. Epub 2019 Oct 15.
The TNF family ligands, B cell activating factor of the TNF family (BAFF, also known as B lymphocyte stimulator, BLyS) and a proliferation-inducing ligand (APRIL), share the transmembrane activator and calcium-modulator and cyclophilin ligand (CAML)-interactor (TACI) as one of their common receptors. Atacicept, a chimeric recombinant TACI/IgG1-Fc fusion protein, inhibits both ligands. TACI and APRIL also bind to proteoglycans and to heparin that is structurally related to proteoglycans. It is unknown whether the portion of TACI contained in atacicept can bind directly to proteoglycans, or indirectly via APRIL, and whether this could interfere with the anti-coagulant properties of heparin.
Binding of atacicept and APRIL to proteoglycan-positive cells was measured by FACS. Activities of heparin and atacicept were measured with activated factor Xa inhibition and cell-based assays. Effects of heparin on circulating atacicept was monitored in mice.
Atacicept did not bind to proteoglycan-positive cells, but when complexed to APRIL could do so indirectly via APRIL. Multimers of atacicept obtained after exposure to cysteine or BAFF 60-mer bound directly to proteoglycans. Atacicept alone, or in complex with APRIL, or in a multimeric form did not interfere with heparin activity in vitro. Conversely, heparin did not influence inhibition of BAFF and APRIL by atacicept and did not change circulating levels of atacicept.
Lack of detectable interference of APRIL-bound or free atacicept on heparin activity makes it unlikely that atacicept at therapeutic doses will interfere with the function of heparin in vivo.
TNF 家族配体，B 细胞激活因子（TNF 家族）（BAFF，也称为 B 淋巴细胞刺激因子，BLyS）和增殖诱导配体（APRIL），共享跨膜激活剂和钙调节剂以及环孢素配体（CAML）相互作用物（TACI）作为它们的共同受体之一。Atacicept 是一种嵌合重组 TACI/IgG1-Fc 融合蛋白，可抑制这两种配体。TACI 和 APRIL 也与蛋白聚糖和与蛋白聚糖结构相关的肝素结合。目前尚不清楚 atacicept 中包含的 TACI 部分是否可以直接与蛋白聚糖结合，或者是否通过 APRIL 间接结合，以及这是否会干扰肝素的抗凝特性。
通过流式细胞术测量 atacicept 和 APRIL 与蛋白聚糖阳性细胞的结合。使用活化因子 Xa 抑制和基于细胞的测定法测量肝素和 atacicept 的活性。在小鼠中监测肝素对循环中的 atacicept 的影响。
Atacicept 不与蛋白聚糖阳性细胞结合，但与 APRIL 形成复合物后，可以通过 APRIL 间接结合。暴露于半胱氨酸或 BAFF 60 -mer 后获得的 atacicept 多聚体直接与蛋白聚糖结合。Atacicept 本身、与 APRIL 形成复合物、或以多聚体形式均不会干扰肝素在体外的活性。相反，肝素不会影响 atacicept 对 BAFF 和 APRIL 的抑制作用，也不会改变循环中的 atacicept 水平。
缺乏可检测到的 APRIL 结合或游离 atacicept 对肝素活性的干扰，使得在治疗剂量下 atacicept 不太可能在体内干扰肝素的功能。
