Computationally informed discovery of scavenging-sparing inhibitors of CC chemokine receptor 2

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The G protein-coupled CC chemokine receptor 2 (CCR2) is expressed on circulating monocytes and drives their recruitment to infected and damaged tissues, where the monocytes differentiate into infiltrating macrophages and promote the formation of an inflammatory pro-fibrotic environment. Because this process is key to the pathogenesis of many inflammatory diseases (rheumatoid arthritis, multiple sclerosis, neuropathic pain, and fibrosis, among others), CCR2 has been pursued for decades as a therapeutic target. However, no anti-CCR2 therapeutics have so far made it to the clinic, with most failing for lack of efficacy. Paradoxically, all known CCR2 antagonists cause a profound elevation in plasma levels of CCR2 agonist chemokine CCL2, which they were designed to inhibit in the first place. The therapeutic consequences of this are not clear: the elevation may be a desired (via blunting of chemokine gradients and migratory responses) or an unwanted (via “inhibition of an inhibitor”) phenomenon. Additional complexity arises from non-migratory functions of CCL2 in e.g. regulating leukocyte differentiation. Concerningly, antagonist-induced CCL2 elevation reaches its peak when the plasma concentration of the antagonist itself wanes. Therefore, this side effect may compromise the safety and efficacy of anti-CCR2 clinical candidates. Unfortunately, systematic investigation of this phenomenon in vivo is currently impossible, for the lack of proper pharmacological tools. The applicants’ long-term goal is to decipher the intricacies of CCR2 signaling and to develop clinically successful CCR2-targeting agents. The applicants have recently discovered the basis for antagonist-induced CCL2 elevation, and demonstrated that it occurs via inhibition of an important but underappreciated regulatory function of CCR2 where it scavenges CCL2 constitutively produced by tissues, and clears it from plasma. Scavenging is inhibited because all known antagonists prevent chemokine binding to CCR2. These findings outline the conceptual possibility of an antagonist of CCR2-mediated migration that does not cause CCL2 elevation, by sparing chemokine binding to CCR2 and hence its scavenging. The goal of the present proposal is to discover such antagonists via a computationally guided approach, by pursuing two Specific Aims: (1) Via in silico compound library screening against an ensemble of CCR2:CCL2 complex models, identify chemicals that bind CCR2 concurrently with CCL2, and characterize their pharmacology in vitro. (2) Computationally elucidate the dynamics of CCR2 in complex with CCL2, and identify G-protein- incompatible states with the potential to enrich for scavenging-sparing inhibitors in VLS. The outcome of the proposed work will be the discovery of the first chemical probes with novel pharmacology in relation to CCR2: the inhibitors of CCR2-mediated cell migration that spare CCL2 scavenging. These molecules will assist investigations of antagonist-induced CCL2 elevation in vivo by the applicant’s group and others. The findings will also inform future efforts of therapeutic targeting of CCR2 for inflammation and cancer.