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The identification of the first small-molecule ligand of the neuronal receptor sortilin and structure determination of the receptor–ligand complex are reported.

The discovery and structure-activity relationship of a series of hA(2A) receptor antagonists is described. Compound 28 was selected from the series as a potent and selective compound and was shown to be efficacious in an in vivo model of Parkinson's disease. It had acceptable ADME properties; however, the low intrinsic solubility of this compound was limiting for its developability, because the oral bioavailability from dosing in suspension was significantly lower than the oral bioavailability from solution dosage. As a consequence, prodrugs of 28 were prepared with dramatically increased aqueous solubility. The prodrugs efficiently delivered 28 into systemic circulation, with no detectable levels of prodrug in plasma samples. From this investigation, we selected 32 (Lu AA47070), a phosphonooxymethylene prodrug of 28, as a drug candidate.

By introducing distal substituents on a tetracyclic scaffold resembling the ergoline structure, two series of analogues were achieved exhibiting subnanomolar receptor binding affinities for the dopamine D2 and serotonin 5-HT6 receptor subtype, respectively. While the 5-HT6 ligands were antagonists, the D2 ligands displayed intrinsic activities ranging from full agonism to partial agonism with low intrinsic activity. These structures could potentially be interesting for treatment of neurological diseases such as schizophrenia, Parkinson's disease, and cognitive deficits.

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