Large library docking of tangible molecules has revealed potent ligands across many targets. While make-on-demand libraries now exceed 75 billion enumerated molecules, their synthetic routes are dominated by a few reaction types, reducing diversity and inevitably leaving many interesting bioactive-like chemotypes unexplored. Here, we investigate the large-scale enumeration and targeted docking of isoquinuclidines. These “natural-product-like” molecules are rare in current libraries and are functionally congested, making them interesting as receptor probes. Using a modular, four-component reaction scheme, we built and docked a virtual library of over 14.6 million isoquinuclidines against both the μ- and κ-opioid receptors (MOR and KOR, respectively). Synthesis and experimental testing of 18 prioritized compounds found nine ligands with low μM affinities. Structure-based optimization revealed low- and sub-nM antagonists and inverse agonists targeting both receptors. Cryo-electron microscopy structures illuminate the origins of activity on each target. In mouse behavioral studies, a potent joint MOR-antagonist and KOR-inverse-agonist reversed morphine-induced analgesia, phenocopying the MOR-selective antioverdose agent naloxone. Encouragingly, the isoquinuclidine induced less severe opioid-withdrawal symptoms versus naloxone and did not induce conditioned-place aversion, reflecting reduced dysphoria, consistent with its KOR-inverse agonism. The strengths and weaknesses of bespoke library docking and of docking for opioid receptor polypharmacology will be considered.

The physical limit in determining the atomic structure of biological molecules is radiation damage. In electron cryomicroscopy, there have been num...

Large library docking of tangible molecules has revealed potent ligands across many targets. While make-on-demand libraries now exceed 75 billion enumerated molecules, their synthetic routes are domin...

Three proton-sensing G protein-coupled receptors (GPCRs)—GPR4, GPR65, and GPR68—respond to extracellular pH to regulate diverse physiology. How proton…

The big chill: Growth of in situ structural biology with cryo-electron tomography - Volume 5

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