Kavli Affiliate:Allan Basbaum
| Authors: Isha Singh, Anubha Seth, Christian B. Billesbolle, Joao Braz, Ramona M. Rodriguiz, Kasturi Roy, Bethlehem Bekele, Veronica Craik, Xi-Ping Huang, Danila Boytsov, Parnian Lak, Henry R O’Donnell, Walter R Sandtner, Bryan L. Roth, Allan Basbaum, William C Wetsel, Aashish Manglik, Brian K. Shoichet and Gary Rudnick
| Summary:
The serotonin transporter (SERT) removes synaptic serotonin and is the target of anti-depressant drugs. SERT adopts three conformations: outward-open, occluded, and inward-open. All known inhibitors target the outward-open state except ibogaine, which has an unusual anti-depressant profile and stabilizes the inward-open conformation. Unfortunately, ibogaine is promiscuous and cardiotoxic, limiting understanding of inward-open state ligands. We computationally docked over 200 million small molecules against the ibogaine stabilized inward-open state of SERT. Thirty-six top-ranking compounds were synthesized and thirteen inhibited with potencies ranging from 29 to 5000 nM. Structure-based optimization led to two novel inhibitors with Ki values down to 3 nM. The new molecules stabilized an outward-closed state of the transporter and had little activity against off-targets. A cryo-EM structure of one of these bound to SERT confirmed the predicted geometry. In mouse behavioral assays, both had anxiolytic and anti- depressant activity, with potencies up to 200 better than fluoxetine.