Discovery and Biological Evaluation of Novel Cyanoguanidine P2X7 Antagonists with Analgesic Activity in a Rat Model of Neuropathic Pain

We disclose the design of a novel series of cyanoguanidines that are potent (IC50 similar or equal to 10-100 nM) and selective (>= 100-fold) P2X(7) receptor antagonists against the other P2 receptor subtypes such as the P2Y(2), P2X(4), and P2X(3). We also found that these P2X(7) antagonists effectively reduced nociception in a rat model of neuropathic pain (Chung model). Particularly, analogue 53 proved to be effective in the Chung model, with an ED50 of 38 mu mol/kg after intraperitoneal administration. In addition compound 53 exhibited antiallodynic effects following oral administration and maintained its efficacy following repeated administration in the Chung model. These results suggest an important role of P2X(7) receptors in neuropathic pain and therefore a potential use of P2X(7) antagonists as novel therapeutic tools for the treatment of this type of pain.