BB-Cl-Amidine is a modified version of Cl-amidine that retains the functional components but possesses a C-terminal benzimidazole group designed to limit proteolysis of the C-terminal amide.1 BB-Cl-Amidine irreversibly inactivates all four PAD subtypes (kinact/KI = 16,100, 4,100, 6,800, and 13,300 M-1min-1 for PAD1-4, respectively) by covalently modifying an active site cysteine that is important for its catalytic activity.2,3 The cellular potency of BB-Cl-amidine against PAD4 is increased 20-fold over the parent compound (EC50 = 8.8 ?M versus >200 ?M for Cl-amidine). BB-Cl-Amidine also has a significantly longer in vivo half-life than Cl-amidine (1.75 h versus ~15 min, respectively). Both compounds inhibit the formation of neutrophil extracellular traps without altering H2O2 production by neutrophils.1 BB-Cl-Amidine is effective in vivo, improving endothelial function while downregulating the expression of type I interferon-regulated genes in MRL/lpr mice.
1.Knight, J.S., Subramanian, V., O'Dell, A.A., et al.Peptidylarginine deiminase inhibition disrupts NET formation and protects against kidney, skin and vascular disease in lupus-prone MRL/lpr miceAnn. Rheum. Dis.74(12)2199-2206(2015) 2.Luo, Y., Arita, K., Bhatia, M., et al.Inhibitors and inactivators of protein arginine deiminase 4: Functional and structural characterizationBiochemistry45(39)11727-11736(2006) 3.Muth, A., Subramanian, V., Beaumont, E., et al.Development of a selective inhibitor of protein arginine deiminase 2.J. Med. Chem.60(7)3198-3211(2017)