Recent Developments in Sigma-2 Receptor Compounds for Pain

After years of enigmatic pharmacology, non-selective ligands, and uncertain clinical application, sigma receptors have emerged as interesting therapeutic drug discovery-development targets. Two subtypes of sigma receptors have now been cloned, sigma-1 receptor (S1R) and sigma-2 receptor (S2R), and there has been much complementary and converging information from advances in molecular biology, computer modeling, virtual screening, and in vitro and in vivo testing. One of several evolving areas of therapeutic potential is for the treatment of pain. In particular, there is accumulating recent evidence from preclinical models that the demonstrated positive effects of S2R compounds in these models suggest possible positive implications for clinical effectiveness against pains that have a neuropathic component. Such pain conditions have imperfect therapeutic options currently. The addition of new drugs to the now available armamentarium would represent a very significant advance for the large number of patients who suffer from these types of intractable pain. Further research is needed to identify and characterize compounds that have not only good in vitro activity but also the characteristics needed to enter clinical trials. Here, we summarize some of the recent reports of the analgesic activity of S2R compounds.