The sigma-2 (σ-2) receptor: a review of recent patent applications: 2013-2018.

INTRODUCTION: The discovery of the sigma-2 receptor and the analogous sigma-1 receptor led to a decade-long quest to determine the true nature of this protein and novel ligands capable of modulating its activity. Despite this challenge, the sigma-2 receptor has been linked to several disease states, and multiple classes of sigma-2 ligands have been published in the 40+ years since its initial discovery. AREAS COVERED: This review covers newly published patent applications that describe sigma-2 receptor ligands capable of modulating disease states. The aforementioned documents entered the public domain as PCT patent applications between 2013 and 2018. EXPERT OPINION: In 2017, the sigma-2 receptor was positively identified as TMEM97 (transmembrane protein 97). The resolution of this 'identity crisis' will facilitate a greater understanding of the pharmacological role of sigma-2 receptor as well as support the identification of novel sigma-2 receptor ligands with potential utility as disease-modifying therapies.