Denosumab

Denosumab is a fully human IgG2 monovlonal antibody that binds human RANKL with a high affinity, exhibiting a dissociation equilibrium binding constant (K_d) of 3 pM as determined by immunoaffinity exclusion chromatography. Denosumab binds both soluble and membrane-bound primate RANKL but fails to recognize mouse or rat RANKL- a finding that is supported by sequence analysis of RANKL from diverse mammalian species. ^[2]

Initial screening of RANKL antibodies for in vivo bioactivity leveraged the crossreactivity of Denosumab with cynomolgus RANKL. Single-dose testing in cynomolgus monkeys revealed that infrequent dosing regimens in humans may be possible. The primary in vivo testing in primates accelerated the developmental timeframe of this molecule, which normally would have been preceded by extensive testing in animal models of bone loss in which recombinant OPG was active. ^[2]

Denosumab does not bind to other TNF family members, such as TRAIL, CD40 ligand (CD40L), TNFα and THFβ. Denosumab binds to the DE loop region of human RANKL, which is one of the surface loop structures that forms contacts with RANK on responding cells. Owing to the different terminology used for the loop regions, the human DE loop region corresponds to the CD loop regions of the murine RANKL structure. Both Denosumab and OPG-Fc bind to soluble or membrane-bound human RANKL and block it from binding to and oligomerizing its receptor, RANK. Denosumab, however, is more specific than human OPG-Fc because Denosumab recognizes only human and non-human primate RANKL, in contrast to OPG, which also binds to mouse and rat RANKL as well as TRAIL. ^[1,2]

References:
[1]. Feng, Qi et al. Denosumab inhibits MCF-7 cell line-induced spontaneous osteoclastogenesis via the RANKL/MALAT1/miR-124 axis.” Translational cancer research vol. 9,4 (2020): 2482-2491.
[2]. Lacey, David L et al. Bench to bedside: elucidation of the OPG-RANK-RANKL pathway and the development of Denosumab. Nature reviews. Drug discovery vol. 11,5 (2012): 401-19.

Denosumab 是一种全人 IgG2 单克隆抗体，它以高亲和力结合人 RANKL，通过免疫亲和排阻色谱法测定其解离平衡结合常数 (K_d) 为 3 pM。 Denosumab 结合可溶性和膜结合的灵长类动物 RANKL，但无法识别小鼠或大鼠 RANKL - 这一发现得到了来自不同哺乳动物物种的 RANKL 序列分析的支持。 ^[2]

RANKL 抗体的体内生物活性初步筛选利用了地诺单抗与食蟹猴 RANKL 的交叉反应性。在食蟹猴中进行的单剂量试验表明，人类可能采用不频繁的给药方案。在灵长类动物中进行的主要体内测试加速了该分子的发育时间框架，通常在重组 OPG 活跃的骨质流失动物模型中进行广泛测试之前。 ^[2]

Denosumab 不与其他 TNF 家族成员结合，例如 TRAIL、CD40 配体 (CD40L)、TNFα 和 THFβ。 Denosumab 结合人 RANKL 的 DE 环区域，它是与反应细胞上的 RANK 形成接触的表面环结构之一。由于用于环区域的不同术语，人 DE 环区域对应于鼠 RANKL 结构的 CD 环区域。 Denosumab 和 OPG-Fc 均与可溶性或膜结合的人 RANKL 结合，并阻止其与其受体 RANK 结合并寡聚化。然而，Denosumab 比人 OPG-Fc 更具特异性，因为 Denosumab 仅识别人和非人灵长类动物 RANKL，与 OPG 相比，OPG 还结合小鼠和大鼠 RANKL 以及 TRAIL。 ^[1,2]