Molecular mechanism of the wake-promoting agent TAK-925

Abstract The OX2 orexin receptor (OX2R) is a highly expressed G protein-coupled receptor (GPCR) in the brain that regulates wakefulness and circadian rhythms in humans. Antagonism of OX2R is a proven therapeutic strategy for insomnia drugs, and agonism of OX2R is a potentially powerful approach for narcolepsy type 1, which is characterized by the death of orexinergic neurons. Until recently, agonism of OX2R had been considered ‘undruggable.’ We harness cryo-electron microscopy of OX2R-G protein complexes to determine how the first clinically tested OX2R agonist TAK-925 can activate OX2R in a highly selective manner. Two structures of TAK-925-bound OX2R with either a Gq mimetic or Gi reveal that TAK-925 binds at the same site occupied by antagonists, yet interacts with the transmembrane helices to trigger activating microswitches. Our structural and mutagenesis data show that TAK-925’s selectivity is mediated by subtle differences between OX1 and OX2 receptor subtypes at the orthosteric pocket. Finally, differences in the polarity of interactions at the G protein binding interfaces help to rationalize OX2R’s coupling selectivity for Gq signaling. The mechanisms of TAK-925’s binding, activation, and selectivity presented herein will aid in understanding the efficacy of small molecule OX2R agonists for narcolepsy and other circadian disorders

Structure-Based Design and Synthesis of 3‑Amino-1,5-dihydro‑4<i>H</i>‑pyrazolopyridin-4-one Derivatives as Tyrosine Kinase 2 Inhibitors

We report herein the discovery and optimization of 3-amino-1,5-dihydro-4<i>H</i>-pyrazolopyridin-4-one TYK2 inhibitors. High-throughput screening against TYK2 and JAK1–3 provided aminoindazole derivative <b>1</b> as a hit compound. Scaffold hopping of the aminoindazole core led to the discovery of 3-amino-1,5-dihydro-4<i>H</i>-pyrazolopyridin-4-one derivative <b>3</b> as a novel chemotype of TYK2 inhibitors. Interestingly, initial SAR study suggested that this scaffold could have a vertically flipped binding mode, which prompted us to introduce a substituent at the 7-position as a moiety directed toward the solvent-exposed region. Introduction of a 1-methyl-3-pyrazolyl moiety at the 7-position resulted in a dramatic increase in TYK2 inhibitory activity, and further optimization led to the discovery of <b>20</b>. Compound <b>20</b> inhibited IL-23-induced IL-22 production in a rat PD assay, as well as inhibited IL-23 signaling in human PBMC. Furthermore, <b>20</b> showed selectivity for IL-23 signaling inhibition against GM-CSF, demonstrating the unique cytokine selectivity of the novel TYK2 inhibitor