Ever since the discovery of prostaglandin E₂ (PGE₂)_, this lipid mediator has been the focus of intense research. The diverse biological effects of PGE₂ are due, at least in part, to the existence of four distinct receptors (EP_1–4). This can complicate the analysis of the biological effects produced by PGE2. While there are currently selective pharmacological tools to explore the roles of the EP_1,3,4 receptors in cellular and tissue responses, analysis of EP₂ receptor‐induced responses has been hampered by the lack of a selective EP₂ receptor antagonist. The recent publication in this journal by af Forselles et al. suggests that such a tool compound is now available. In their manuscript, the authors describe a series of experiments that show PF‐04418948 to be a potent and selective EP₂ receptor antagonist. The discovery of this tool compound will interest many scientists and through collaborations with Pfizer they may have access to PF‐04418948 to facilitate further investigation of the biology of this fascinating lipid mediator.

LINKED ARTICLE This article is a commentary on af Forselles et al., pp. 1847–1856 of this issue. To view this paper visit http://dx.doi.org/10.1111/j.1476‐5381.2011.01495.x