Targeting the minor pocket of C5aR for the rational design of an oral allosteric inhibitor for inflammatory and neuropathic pain relief

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 111; no. 47; pp. 16937 - 16942
• Main Authors: Moriconi, Alessio, Cunha, Thiago M., Souza, Guilherme R., Lopes, Alexandre H., Cunha, Fernando Q., Carneiro, Victor L., Pinto, Larissa G., Brandolini, Laura, Aramini, Andrea, Bizzarri, Cinzia, Bianchini, Gianluca, Beccari, Andrea R., Fanton, Marco, Bruno, Agostino, Costantino, Gabriele, Bertini, Riccardo, Galliera, Emanuela, Locati, Massimo, Ferreira, Sérgio H., Teixeira, Mauro M., Allegretti, Marcello
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 25.11.2014; National Acad Sciences
• Subjects: Administration, Oral; Allosteric Regulation; Analgesics - chemistry; Analgesics - therapeutic use; Animals; Biological Sciences; Disease Models, Animal; Drug Design; Drug interactions; Humans; Hyperalgesia; Hypersensitivity; Inflammation - drug therapy; Ligands; Medical treatment; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Neuralgia - drug therapy; Pain; Peptides; Pharmacology; Rats; Receptor, Anaphylatoxin C5a - drug effects; Receptors; Rodents; Side effects; Vehicles; GPCR; inflammatory pain; allosteric antagonism; neuropathic pain; C5a
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1417365111

Significance Persistent pain in inflammatory and neuropathic conditions is often refractory to conventional analgesic therapy, with most patients suffering with unrelieved pain and serious treatment-related side effects. There is still a tremendous need to identify novel therapeutics for pain control with innovative biological mechanisms and minimal side effects. In this paper we challenge the hypothesis that a conserved structural motif across the G protein-coupled receptor family plays a regulatory role in the negative modulation of receptor activation and use a multidisciplinary approach to the rational drug design and characterization of a novel potent allosteric inhibitor of the C5a anaphylatoxin receptor (C5aR), thus providing a new promising avenue for the improvement of pharmacotherapy of chronic pain. Chronic pain resulting from inflammatory and neuropathic disorders causes considerable economic and social burden. Pharmacological therapies currently available for certain types of pain are only partially effective and may cause severe adverse side effects. The C5a anaphylatoxin acting on its cognate G protein-coupled receptor (GPCR), C5aR, is a potent pronociceptive mediator in several models of inflammatory and neuropathic pain. Although there has long been interest in the identification of C5aR inhibitors, their development has been complicated, as for many peptidomimetic drugs, mostly by poor drug-like properties. Herein, we report the de novo design of a potent and selective C5aR noncompetitive allosteric inhibitor, DF2593A, guided by the hypothesis that an allosteric site, the “minor pocket,” previously characterized in CXC chemokine receptors-1 and -2, is functionally conserved in the GPCR class. In vitro, DF2593A potently inhibited C5a-induced migration of human and rodent neutrophils. In vivo, oral administration of DF2593A effectively reduced mechanical hyperalgesia in several models of acute and chronic inflammatory and neuropathic pain, without any apparent side effects. Mechanical hyperalgesia after spared nerve injury was also reduced in C5aR ⁻/⁻ mice compared with WT mice. Furthermore, treatment of C5aR ⁻/⁻ mice with DF2593A did not produce any further antinociceptive effect compared with C5aR ⁻/⁻ mice treated with vehicle. The successful medicinal chemistry strategy confirms that a conserved minor pocket is amenable for the rational design of selective inhibitors and the pharmacological results support that the allosteric blockade of the C5aR represents a highly promising therapeutic approach to control chronic inflammatory and neuropathic pain.