CSN5i-3 is a novel, potent, highly selective, and orally bioavailable small molecule inhibitor that targets the CSN5/Jab1 (COPS5) protein—a key protein hydrolytic subunit of the COP9 signaling complex. CSN5i-3 exhibits extremely high inhibitory activity against this target, with an IC50 value of 5.8nM[1, 2]. The core function of CSN5 is to cleave the NEDD8 modification from the Cullin-RING E3 ubiquitin ligase. CSN5i-3 can potently inhibit this de-Neddase activity of CSN5, thereby interfering with the normal function of the CRL ubiquitin ligase[3].
In vitro, treatment of human breast cancer BT474 and SKBR3 cells with CSN5i-3 (2µM) for 24h significantly induced apoptosis and G1 phase cell cycle arrest, and increased the levels of the apoptosis marker cleaved PARP and the cell cycle-related protein p27[4]. Treatment of human umbilical vein endothelial cells (HUVECs) with CSN5i-3 (1, 4µM) for 5h induced a significant weakening of endothelial barrier function, induced the expression of RhoGTPase RhoB in endothelial cells, and formed actin stress fibers[5].
In vivo, subcutaneous injection of CSN5i-3 (10mg/kg) into MDA-MB-231 cell xenograft mice for 18 days inhibited tumor growth in mice, and combined treatment with Talazoparib significantly enhanced the antitumor efficacy[6].
References:
[1] Schlierf A, Altmann E, Quancard J, et al. Targeted inhibition of the COP9 signalosome for treatment of cancer[J]. Nature communications, 2016, 7(1): 13166.
[2] Yin L, Xue Y, Shang Q, et al. Pharmaceutical inhibition of neddylation as promising treatments for various cancers[J]. Current Topics in Medicinal Chemistry, 2019, 19(12): 1059-1069.
[3] Wu J T, Chan Y R, Chien C T. Protection of cullin–RING E3 ligases by CSN–UBP12[J]. Trends in cell biology, 2006, 16(7): 362-369.
[4] Xiao H, Claret F X, Shen Q. The novel Jab1 inhibitor CSN5i-3 suppresses cell proliferation and induces apoptosis in human breast cancer cells[J]. Neoplasma, 2019, 66(3).
[5] Majolée J, Pronk M C A, Jim K K, et al. CSN5 inhibition triggers inflammatory signaling and Rho/ROCK-dependent loss of endothelial integrity[J]. Scientific reports, 2019, 9(1): 8131.
[6] Peng X, Wang Y, Yu Z, et al. Jab1 regulates HRR mRNA stability to modulate PARP inhibitor sensitivity in triple-negative breast cancer[J]. Molecular Cancer, 2025, 24(1): 217.
CSN5i-3是一种新型、强效、高选择性且具有口服生物利用度的小分子抑制剂，其作用靶点为CSN5/Jab1（COPS5）蛋白——该蛋白是COP9信号体复合物的关键蛋白水解亚基。CSN5i-3对此靶点的抑制活性极高，IC50值为5.8nM[1, 2]。CSN5的核心功能是从Cullin-RING E3泛素连接酶上切除NEDD8修饰，CSN5i-3能够通过强效抑制CSN5的这一去Nedd化酶活过程，从而干扰CRL泛素连接酶的正常功能[3]。
在体外，CSN5i-3（2µM）处理人乳腺癌BT474和SKBR3细胞24h，均显著诱导了细胞凋亡和G1期细胞周期阻滞，提高了凋亡标志物cleaved PARP和细胞周期相关蛋白p27的水平[4]。CSN5i-3（1, 4µM）处理人脐静脉内皮细胞（HUVECs）5h，诱导了内皮屏障功能的显著减弱，诱导了内皮细胞中RhoGTP 酶RhoB的表达，并形成肌动蛋白应力纤维[5]。
在体内，CSN5i-3（10mg/kg）通过皮下注射治疗MDA-MB-231细胞异种移植小鼠18天，抑制了小鼠体内肿瘤生长，与Talazoparib联合治疗显著增强了抗肿瘤疗效[6]。