ABSTRACT
A series of 4-piperidin-4-ylidenemethyl-benzamide δ-opioid receptor agonists is described with an emphasis on balancing the potency, subtype selectivity and in vitro ADME and safety properties. The three sites impacting SAR are substitutions on the aryl group (R(1)), the piperidine nitrogen (R(2)), and the amide (R(3)). Each region contributes to the balance of properties for δ opioid activity and a desirable CNS profile, and two clinical candidates (20 and 24) were advanced.
Subject(s)
Benzamides/pharmacology , Central Nervous System/drug effects , Piperidines/pharmacology , Receptors, Opioid, delta/agonists , Benzamides/chemistry , Central Nervous System/metabolism , Dose-Response Relationship, Drug , Ether-A-Go-Go Potassium Channels/antagonists & inhibitors , HEK293 Cells , Humans , Molecular Structure , Piperidines/chemistry , Receptors, Opioid, delta/metabolism , Stereoisomerism , Structure-Activity RelationshipABSTRACT
A novel series of piperazine derivatives exhibits sub-nanomolar binding and enhanced subtype selectivity as δ-opioid agonists. The synthesis and SAR are described as well as the application of computational models to improve in vitro ADME and safety properties suitable for CNS indications, specifically microsomal clearance, permeability, and hERG channel inhibition.
Subject(s)
Central Nervous System/drug effects , Piperazines/pharmacology , Receptors, Opioid, delta/agonists , Animals , Central Nervous System/metabolism , Computer Simulation , Dogs , Dose-Response Relationship, Drug , Ether-A-Go-Go Potassium Channels/antagonists & inhibitors , Humans , Molecular Structure , Piperazines/chemical synthesis , Piperazines/chemistry , Receptors, Opioid, delta/metabolism , Stereoisomerism , Structure-Activity RelationshipABSTRACT
Previously we reported on the synthesis and properties of a series of highly potent piperidinyl 2-subsituted-3-cyano-1-naphthamide NK1 antagonists that includes 3 and 4. Here we report our efforts to alleviate a troublesome atropisomeric property of those derivatives by introduction of a tethering bridge that, in addition, could be used to lock the resulting cyclic derivatives in a purported NK1 pharmacophore conformation. Using 3 as a starting point, the naphtho[2,1-b][1,5]oxazocine, 17, was found to contain the optimal ring tether size (8) for retaining NK1 activity, was more NK1 versus NK2 selective, and reduced the number of atropisomers from four to two. Cyclic derivatives 29 and 32, which exist as essentially single atropisomers in the purported pharmacophore conformation, were prepared in the closely related naphtho[1,2-f][1,4]oxazocine series as part of an effort to use mono methyl substitution of the tethering bridge as a conformation stabilizing factor. Both 29 and 32 were found to be less active as NK1 antagonists than the non-methylated parent 28 possibly due to methyl group destabilization of receptor interaction. We discuss the above findings in the context of a previously proposed NK1 pharmacophore model and present a further refinement of that model.
