Antibody Neutralization of CXCL10 in Vivo Is Dependent on Binding to Free and Not Endothelial-bound Chemokine IMPLICATIONS FOR THE DESIGN OF A NEW GENERATION OF ANTI-CHEMOKINE THERAPEUTIC ANTIBODIES

To improve our understanding of properties that confer successful inhibition of chemokines in vivo, we analyzed antimurine CXCL10 monoclonal antibodies (mAb) having different characteristics. 1B6 displayed potent inhibition of cell recruitment in vitro with an IC50 of 0.5 nM but demonstrated little efficacy in various animal models of human disease. On the contrary, 1P11 showed efficacy in several models of inflammation yet was less potent at inhibiting chemotaxis in vitro with an IC50 of 21 nM. Furthermore, we observed that 1B6 displayed a rapid dosedependent clearance (t1/ 2 1060 h) in contrast to 1F11, which presented a dose-proportional pharmacokinetic profile and a half-life of 12 days. Moreover, 1B6 recognized glycosaminoglycan (GAG)bound CXCL10, resulting in target-mediated clearance, which was corroborated using CXCL10-deficient mice. In contrast to 1B6, 1F11 inhibited the interaction of CXCL10 with GAGs, did not recognize GAG-bound CXCL10, and did not display target-mediated drug disposition. Confirming previous animal studies, 1B6 was poor at reversing glycemia in a model of type 1 diabetes, whereas 1F11 induced early and prolonged control of diabetes. Furthermore, when using 1A4, a subsequently generated anti-mCXCL10 mAb that shares the property with 1F11 of being unable to recognize CXCL10 immobilized on GAG, we observed a similar superior control of diabetes as compared with 1B6. We therefore concluded that targeting chemokines with antibodies such as 1B6 that recognize the more abundant GAG-bound form of the chemokine may not be the optimal strategy to achieve disease control.