Limits...
Discovery of the first small-molecule opioid pan antagonist with nanomolar affinity at mu, delta, kappa, and nociceptin opioid receptors.

Zaveri NT, Journigan VB, Polgar WE - ACS Chem Neurosci (2015)

Bottom Line: When rational chemical modifications of JDTic were carried out, based on our previously established NOP pharmacophoric structure-activity relationship (SAR) model, most modifications led to a significant decrease in NOP and opioid binding affinity compared to JDTic.AT-076 is the first opioid pan antagonist with high affinity at all four opioid receptor subtypes.Our SAR studies show that the 3,4-dimethyl groups of the well-known trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine opioid antagonist scaffold may be removed without significant loss in binding affinity or antagonist potency to obtain an opioid pan antagonist such as AT-076.

View Article: PubMed Central - PubMed

Affiliation: †Astraea Therapeutics, 320 Logue Avenue, Suite 142, Mountain View, California 94043, United States.

ABSTRACT
The trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine scaffold is a known pharmacophore for mu opioid (MOP), kappa opioid (KOP), and delta opioid (DOP) receptor antagonists; however, it has not been explored in nociceptin opioid (NOP/ORL-1) receptor ligands. We recently found that the selective KOP antagonist JDTic, (3R)-7-hydroxy-N-((1S)-1-{[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide, containing this opioid antagonist pharmacophore, has significant binding affinity at the NOP receptor (Ki 16.67 ± 0.76 nM), with no intrinsic activity in the [(35)S]GTPγS functional assay. Since this is the first ligand containing the trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine opioid antagonist pharmacophore to have affinity for the NOP receptor, we explored the structural determinants of its NOP binding affinity. When rational chemical modifications of JDTic were carried out, based on our previously established NOP pharmacophoric structure-activity relationship (SAR) model, most modifications led to a significant decrease in NOP and opioid binding affinity compared to JDTic. Interestingly, however, removal of the 3,4-dimethyl groups of the trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine antagonist scaffold of JDTic increased the binding affinity at NOP by 10-fold (Ki 1.75 ± 0.74 nM) while maintaining comparable affinity for KOP, MOP, and DOP receptors (Ki 1.14 ± 0.63, 1.67 ± 0.6, and 19.6 ± 1.3 nM, respectively). In vitro functional efficacy studies using the [(35)S]GTPγS assay showed that this compound AT-076 functions as an antagonist at all four opioid receptors. Detailed characterization of the antagonist activity of AT-076 shows that it has a noncompetitive antagonist profile at the NOP and KOP receptors (insurmountable antagonism), but is a potent competitive antagonist at the MOP and DOP receptors, with Ke values 3-6-fold more potent than those of JDTic. AT-076 is the first opioid pan antagonist with high affinity at all four opioid receptor subtypes. Our SAR studies show that the 3,4-dimethyl groups of the well-known trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine opioid antagonist scaffold may be removed without significant loss in binding affinity or antagonist potency to obtain an opioid pan antagonist such as AT-076.

Show MeSH
(A) Bindingmodel of JDTic in the NOP receptor crystal structure 4EA3. The TM helicesare color-coded and annotated. The NOP antagonist C-24 bound in theNOP crystal structure is shown in cyan, whereas JDTic is in magenta.Key interacting amino acids are as indicated. (B) Binding orientationof opioid pan antagonist AT-076 in the NOP crystal structure. AT-076(green) is superimposed on JDTic (magenta) in the NOP binding pocket.Both ligands bind in an extended conformation in the NOP receptor.(C) Binding model of AT-076 in the KOP receptor crystal structure 4DJH. AT-076 (green)is superimposed on the bound orientation of JDTic (magenta) in theKOP crystal structure. Note that AT-076 binds KOP in a similar V-shapedorientation as JDTic, but with the phenylpiperidine and isoquinolinemoieties oriented exactly opposite to those of JDTic.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4401318&req=5

fig3: (A) Bindingmodel of JDTic in the NOP receptor crystal structure 4EA3. The TM helicesare color-coded and annotated. The NOP antagonist C-24 bound in theNOP crystal structure is shown in cyan, whereas JDTic is in magenta.Key interacting amino acids are as indicated. (B) Binding orientationof opioid pan antagonist AT-076 in the NOP crystal structure. AT-076(green) is superimposed on JDTic (magenta) in the NOP binding pocket.Both ligands bind in an extended conformation in the NOP receptor.(C) Binding model of AT-076 in the KOP receptor crystal structure 4DJH. AT-076 (green)is superimposed on the bound orientation of JDTic (magenta) in theKOP crystal structure. Note that AT-076 binds KOP in a similar V-shapedorientation as JDTic, but with the phenylpiperidine and isoquinolinemoieties oriented exactly opposite to those of JDTic.

Mentions: We carried out molecular docking of JDTic and AT-076 into the NOPcrystal structure 4EA3 (bound to the NOP antagonist ligand C-2423) using Surflex Dock (Tripos SYBYL X1.2) andcompared it to the docked pose of JDTic in the KOP crystal structure4DJH (Figure 3). Unlike its V-shaped boundorientation in the KOP crystal structure, JDTic binds to NOP in anextended conformation, similar to the binding orientation of the NOPantagonist C-24 (Figure 3A). The 3-OH-containingphenylpiperidine moiety is buried deep inside the binding pocket ofNOP, where the piperidine nitrogen makes the classic ionic interactionwith the conserved Asp130 of TM3. Another distinctive difference betweenJDTic’s binding to NOP versus its interaction with KOP is that,in the NOP receptor, only the piperidine nitrogen of JDTic (but notthe isoquinoline nitrogen) makes an ionic interaction with the conservedAsp1303.32 (superscript denotes Ballesteros-Weinstein numbering)(Figure 3A), whereas in KOP both the piperidinenitrogen as well as the isoquinoline Tic-nitrogen interact in a bidentateionic interaction with the conserved Asp1383.32 (Figure 3C). This lack of an additional ionic interactionin NOP may contribute to JDTic’s 10-fold lower binding affinitycompared to that at KOP. The 3,4-desmethyl JDTic analogue 6 (AT-076) was also docked into NOP (Figure 3B) and found to bind in an extended orientation similar to and superimposablewith JDTic. On the other hand, at the KOP receptor, the top-scoringAT-076 docking pose showed that while it binds in a V-shaped orientationsimilar to JDTic’s bound conformation in KOP, the phenylpiperidineand isoquinoline rings of AT-076 are oriented opposite to those ofJDTic (Figure 3C). The protonated nitrogensof the phenylpiperidine and isoquinoline groups of AT-076 still appearto interact with the Asp138 in KOP, as seen with JDTic.


Discovery of the first small-molecule opioid pan antagonist with nanomolar affinity at mu, delta, kappa, and nociceptin opioid receptors.

Zaveri NT, Journigan VB, Polgar WE - ACS Chem Neurosci (2015)

(A) Bindingmodel of JDTic in the NOP receptor crystal structure 4EA3. The TM helicesare color-coded and annotated. The NOP antagonist C-24 bound in theNOP crystal structure is shown in cyan, whereas JDTic is in magenta.Key interacting amino acids are as indicated. (B) Binding orientationof opioid pan antagonist AT-076 in the NOP crystal structure. AT-076(green) is superimposed on JDTic (magenta) in the NOP binding pocket.Both ligands bind in an extended conformation in the NOP receptor.(C) Binding model of AT-076 in the KOP receptor crystal structure 4DJH. AT-076 (green)is superimposed on the bound orientation of JDTic (magenta) in theKOP crystal structure. Note that AT-076 binds KOP in a similar V-shapedorientation as JDTic, but with the phenylpiperidine and isoquinolinemoieties oriented exactly opposite to those of JDTic.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401318&req=5

fig3: (A) Bindingmodel of JDTic in the NOP receptor crystal structure 4EA3. The TM helicesare color-coded and annotated. The NOP antagonist C-24 bound in theNOP crystal structure is shown in cyan, whereas JDTic is in magenta.Key interacting amino acids are as indicated. (B) Binding orientationof opioid pan antagonist AT-076 in the NOP crystal structure. AT-076(green) is superimposed on JDTic (magenta) in the NOP binding pocket.Both ligands bind in an extended conformation in the NOP receptor.(C) Binding model of AT-076 in the KOP receptor crystal structure 4DJH. AT-076 (green)is superimposed on the bound orientation of JDTic (magenta) in theKOP crystal structure. Note that AT-076 binds KOP in a similar V-shapedorientation as JDTic, but with the phenylpiperidine and isoquinolinemoieties oriented exactly opposite to those of JDTic.
Mentions: We carried out molecular docking of JDTic and AT-076 into the NOPcrystal structure 4EA3 (bound to the NOP antagonist ligand C-2423) using Surflex Dock (Tripos SYBYL X1.2) andcompared it to the docked pose of JDTic in the KOP crystal structure4DJH (Figure 3). Unlike its V-shaped boundorientation in the KOP crystal structure, JDTic binds to NOP in anextended conformation, similar to the binding orientation of the NOPantagonist C-24 (Figure 3A). The 3-OH-containingphenylpiperidine moiety is buried deep inside the binding pocket ofNOP, where the piperidine nitrogen makes the classic ionic interactionwith the conserved Asp130 of TM3. Another distinctive difference betweenJDTic’s binding to NOP versus its interaction with KOP is that,in the NOP receptor, only the piperidine nitrogen of JDTic (but notthe isoquinoline nitrogen) makes an ionic interaction with the conservedAsp1303.32 (superscript denotes Ballesteros-Weinstein numbering)(Figure 3A), whereas in KOP both the piperidinenitrogen as well as the isoquinoline Tic-nitrogen interact in a bidentateionic interaction with the conserved Asp1383.32 (Figure 3C). This lack of an additional ionic interactionin NOP may contribute to JDTic’s 10-fold lower binding affinitycompared to that at KOP. The 3,4-desmethyl JDTic analogue 6 (AT-076) was also docked into NOP (Figure 3B) and found to bind in an extended orientation similar to and superimposablewith JDTic. On the other hand, at the KOP receptor, the top-scoringAT-076 docking pose showed that while it binds in a V-shaped orientationsimilar to JDTic’s bound conformation in KOP, the phenylpiperidineand isoquinoline rings of AT-076 are oriented opposite to those ofJDTic (Figure 3C). The protonated nitrogensof the phenylpiperidine and isoquinoline groups of AT-076 still appearto interact with the Asp138 in KOP, as seen with JDTic.

Bottom Line: When rational chemical modifications of JDTic were carried out, based on our previously established NOP pharmacophoric structure-activity relationship (SAR) model, most modifications led to a significant decrease in NOP and opioid binding affinity compared to JDTic.AT-076 is the first opioid pan antagonist with high affinity at all four opioid receptor subtypes.Our SAR studies show that the 3,4-dimethyl groups of the well-known trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine opioid antagonist scaffold may be removed without significant loss in binding affinity or antagonist potency to obtain an opioid pan antagonist such as AT-076.

View Article: PubMed Central - PubMed

Affiliation: †Astraea Therapeutics, 320 Logue Avenue, Suite 142, Mountain View, California 94043, United States.

ABSTRACT
The trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine scaffold is a known pharmacophore for mu opioid (MOP), kappa opioid (KOP), and delta opioid (DOP) receptor antagonists; however, it has not been explored in nociceptin opioid (NOP/ORL-1) receptor ligands. We recently found that the selective KOP antagonist JDTic, (3R)-7-hydroxy-N-((1S)-1-{[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide, containing this opioid antagonist pharmacophore, has significant binding affinity at the NOP receptor (Ki 16.67 ± 0.76 nM), with no intrinsic activity in the [(35)S]GTPγS functional assay. Since this is the first ligand containing the trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine opioid antagonist pharmacophore to have affinity for the NOP receptor, we explored the structural determinants of its NOP binding affinity. When rational chemical modifications of JDTic were carried out, based on our previously established NOP pharmacophoric structure-activity relationship (SAR) model, most modifications led to a significant decrease in NOP and opioid binding affinity compared to JDTic. Interestingly, however, removal of the 3,4-dimethyl groups of the trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine antagonist scaffold of JDTic increased the binding affinity at NOP by 10-fold (Ki 1.75 ± 0.74 nM) while maintaining comparable affinity for KOP, MOP, and DOP receptors (Ki 1.14 ± 0.63, 1.67 ± 0.6, and 19.6 ± 1.3 nM, respectively). In vitro functional efficacy studies using the [(35)S]GTPγS assay showed that this compound AT-076 functions as an antagonist at all four opioid receptors. Detailed characterization of the antagonist activity of AT-076 shows that it has a noncompetitive antagonist profile at the NOP and KOP receptors (insurmountable antagonism), but is a potent competitive antagonist at the MOP and DOP receptors, with Ke values 3-6-fold more potent than those of JDTic. AT-076 is the first opioid pan antagonist with high affinity at all four opioid receptor subtypes. Our SAR studies show that the 3,4-dimethyl groups of the well-known trans-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine opioid antagonist scaffold may be removed without significant loss in binding affinity or antagonist potency to obtain an opioid pan antagonist such as AT-076.

Show MeSH