Biased ligands at G-protein-coupled receptors: promise and progress

doi:10.1016/j.tips.2014.04.007

Trends in Pharmacological Sciences

Volume 35, Issue 7, July 2014, Pages 308-316

https://doi.org/10.1016/j.tips.2014.04.007 Get rights and content

Highlights

•
Biased ligands stabilize subsets of receptor conformations to engage unique pharmacology.
•
Biased ligands may reduce on-target adverse effects or engender novel pharmacology.
•
TRV027, in clinical trials for the treatment of acute heart failure, illustrates differentiation of a β-arrestin-biased ligand at the angiotensin II type 1 receptor.
•
TRV130, in clinical development for the management of pain, illustrates differentiation of a G-protein-biased ligand at the μ opioid receptor.

Drug discovery targeting G protein-coupled receptors (GPCRs) is no longer limited to seeking agonists or antagonists to stimulate or block cellular responses associated with a particular receptor. GPCRs are now known to support a diversity of pharmacological profiles, a concept broadly referred to as functional selectivity. In particular, the concept of ligand bias, whereby a ligand stabilizes subsets of receptor conformations to engender novel pharmacological profiles, has recently gained increasing prominence. This review discusses how biased ligands may deliver safer, better tolerated, and more efficacious drugs, and highlights several biased ligands that are in clinical development. Biased ligands targeting the angiotensin II type 1 receptor and the μ opioid receptor illustrate the translation of the biased ligand concept from basic biology to clinical drug development.

Section snippets

New frontiers for G protein-coupled receptors

G protein-coupled receptors (GPCRs) have long occupied a central role in pharmacology. They are the targets of many of the most widely prescribed drugs in central nervous system (CNS), cardiovascular, pulmonary, gastrointestinal, and many other disease areas. Originally conceived as theoretical entities to explain the drug-specific responses of tissues, GPCRs are now known to be a superfamily of membrane proteins that bind hormones, neurotransmitters, and other extracellular cues to transmit

Pleuripotency of signaling: pathway validation

Classically, agonist-occupied GPCRs mediate cellular responses by binding heterotrimeric G proteins, which initiate cascades of second-messenger responses to alter metabolism, cytoskeletal structure, transcription and translation, and tissue-specific responses such as myocyte contractility and neuron polarization among many others. Almost every GPCR couples to one or more G protein classes, which dictates different cellular responses. Almost every receptor also engages a parallel set of

Concept of ligand bias

Classically, agonists were thought to entrain the entire signal repertoire of a receptor, and thus pharmacological selectivity was specified as selectivity of a drug, hormone, or neurotransmitter for a particular receptor type. Receptors were either ‘on’ or ‘off’ as envisioned in the classic two-state model of receptor function [8]. The discovery of partial agonists and inverse agonists revealed new levels of pharmacological properties, often differentiating these agonists from full agonists

Definition of ligand bias versus functional selectivity: not just semantics

The notion of selective signaling in pharmacology has a long history predating the isolation of receptors, beginning with classification of drugs according to differential pharmacology in different tissues. As molecular biology and genetics have uncovered the many mechanisms by which compounds can exert distinct pharmacology, pharmacological nomenclature has evolved, so that drugs are now described by their efficacy (agonist, antagonist, partial agonist, or inverse agonist) and target (receptor

Measurement

In some cases, ligand bias is evident from qualitative comparisons of data from different assays systems, as when the relative potencies or efficacies of two compounds are reversed in different systems [25]. However, in many cases the varying sensitivities of assay formats necessitate quantitative measures of ligand bias to discriminate intrinsic bias from functional selectivity arising from differential amplification of signals downstream of a partial agonist. Several methods have been

Translation of mechanistic insights to novel pharmacology: compounds in the clinic

Since the recognition of ligand bias, numerous groups have speculated that biased ligands could deliver novel pharmacology distinct from classical agonists or antagonists 25, 30, 31, 32. Broadly, ligand bias may differentiate in several ways. Biased ligands may eliminate on-target adverse events by avoiding undesirable signaling pathways, increase the efficacy of agonists and antagonists by avoiding or stimulating specific positive or negative feedback loops in signaling pathways, and reveal

Evidence of differential pharmacology at other GPCRs: paths to future drug discovery?

Evidence has accumulated for a number of GPCRs that biased ligands may offer safer, better-tolerated, or more efficacious drugs, in some cases suggesting a path to successful drug development for targets that have been abandoned because of on-target adverse pharmacology. Some of these hypotheses relate to selective engagement of G protein and β-arrestin signals as discussed above, but others relate to additional receptor signaling and regulatory mechanisms. Several receptors discussed below

Translation of concept to new medicines

The identification of a biased ligand suitable for clinical development from a medicinal chemistry perspective can be challenging. Optimization for bias in addition to potency at the receptor, selectivity, and pharmaceutical properties adds a degree of complexity to such an effort. High-throughput screens utilizing assays of G protein coupling, β-arrestin recruitment, and other receptor functions have identified hits with varying degrees of bias, but bias can also be engendered by iterative

Concluding remarks

In summary, the concept of biased ligands targeting GPCRs has gained significant traction in recent years. The number of biased ligands reported in the literature continues to grow. With several biased ligands in clinical proof-of-concept studies, and a growing number of receptor targets that may offer improved therapeutic profiles with biased ligands, GPCRs may deliver a new generation of important medicines.

References (84)

R.J. Lefkowitz
Historical review: a brief history and personal retrospective of seven-transmembrane receptors
Trends Pharmacol. Sci.
(2004)
A.K. Shukla
Emerging paradigms of β-arrestin-dependent seven transmembrane receptor signaling
Trends Biochem. Sci.
(2011)
C.L. Schmid et al.
Physiological and pharmacological implications of β-arrestin regulation
Pharmacol. Ther.
(2009)
P. Samama
A mutation-induced activated state of the beta 2-adrenergic receptor. Extending the ternary complex model
J. Biol. Chem.
(1993)
T.A. Kohout
Differential desensitization, receptor phosphorylation, beta-arrestin recruitment, and ERK1/2 activation by the two endogenous ligands for the CC chemokine receptor 7
J. Biol. Chem.
(2004)
G. Swaminath
Probing the β2 adrenoceptor binding site with catechol reveals differences in binding and activation by agonists and partial agonists
J. Biol. Chem.
(2005)
G. Swaminath
Sequential binding of agonists to the β2 adrenoceptor. Kinetic evidence for intermediate conformational states
J. Biol. Chem.
(2004)
G.L. Christensen
Quantitative phosphoproteomics dissection of seven-transmembrane receptor signaling using full and biased agonists
Mol. Cell. Proteomics
(2010)
J.D. Violin et al.
β-Arrestin-biased ligands at seven-transmembrane receptors
Trends Pharmacol. Sci.
(2007)
S. Galandrin
The evasive nature of drug efficacy: implications for drug discovery
Trends Pharmacol. Sci.
(2007)

S. Ahn

β-Arrestin-2 mediates anti-apoptotic signaling through regulation of BAD phosphorylation

J. Biol. Chem.

(2009)

S.A. Hunt

Focused update incorporated into the ACC/AHA 2005 Guidelines for the Diagnosis and Management of Heart Failure in Adults. A report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines developed in collaboration with the International Society for Heart and Lung Transplantation

J. Am. Coll. Cardiol.

(2009)

D.E. Forman

Incidence, predictors at admission, and impact of worsening renal function among patients hospitalized with heart failure

J. Am. Coll. Cardiol.

(2004)

J.D. Violin

GPCR biased ligands as novel heart failure therapeutics

Trends Cardiovasc. Med.

(2013)

D. Soergel

TRV027, a β-arrestin biased ligand at the angiotensin 2 type 1 receptor, produces rapid, reversible changes in hemodynamics in patients with stable systolic heart failure

J. Am. Coll. Cardiol.

(2013)

B.L. Kieffer

Opioids: first lessons from knockout mice

Trends Pharmacol. Sci.

(1999)

W. Schroder

Differential contribution of opioid and noradrenergic mechanisms of tapentadol in rat models of nociceptive and neuropathic pain

Eur. J. Pain

(2010)

C.H. Yang

Antinociceptive potentiation and attenuation of tolerance by intrathecal β-arrestin 2 small interfering RNA in rats

Br. J. Anaesth.

(2011)

K.M. Raehal et al.

The role of β-arrestin2 in the severity of antinociceptive tolerance and physical dependence induced by different opioid pain therapeutics

Neuropharmacology

(2011)

K. Ikeda

Molecular mechanisms of analgesia induced by opioids and ethanol: is the GIRK channel one of the keys?

Neurosci. Res.

(2002)

T. Asgeirsson

Postoperative ileus: it costs more than you expect

J. Am. Coll. Surg.

(2010)

D. Verzijl

Sphingosine-1-phosphate receptors: zooming in on ligand-induced intracellular trafficking and its functional implications

Mol. Cells

(2010)

J.M. Beaulieu

The Akt–GSK-3 signaling cascade in the actions of dopamine

Trends Pharmacol. Sci.

(2007)

D.Y. Oh

GPR120 is an omega-3 fatty acid receptor mediating potent anti-inflammatory and insulin-sensitizing effects

Cell

(2010)

M. Lukasova

Nicotinic acid (niacin): new lipid-independent mechanisms of action and therapeutic potentials

Trends Pharmacol. Sci.

(2011)

J.A. Pitcher

G protein-coupled receptor kinases

Annu. Rev. Biochem.

(1998)

S.M. DeWire

β-Arrestins and cell signaling

Annu. Rev. Physiol.

(2007)

L. Hunyady et al.

Pleiotropic AT1 receptor signaling pathways mediating physiological and pathogenic actions of angiotensin II

Mol. Endocrinol.

(2006)

S.M. DeWire et al.

Biased ligands for better cardiovascular drugs: dissecting G-protein-coupled receptor pharmacology

Circ Res.

(2011)

D. Spengler

Differential signal transduction by five splice variants of the PACAP receptor

Nature

(1993)

C. Watson

The use of stimulus-biased assay systems to detect agonist-specific receptor active states: implications for the trafficking of receptor stimulus by agonists

Mol. Pharmacol.

(2000)

D.A. Zidar

Selective engagement of G protein coupled receptor kinases (GRKs) encodes distinct functions of biased ligands

Proc. Natl. Acad. Sci. U.S.A.

(2009)

D.M. Mottola

Functional selectivity of dopamine receptor agonists. I. Selective activation of postsynaptic dopamine D2 receptors linked to adenylate cyclase

J. Pharmacol. Exp. Ther.

(2002)

B.F. Roettger

Antagonist-stimulated internalization of the G protein-coupled cholecystokinin receptor

Mol. Pharmacol.

(1997)

D. Wacker

Structural features for functional selectivity at serotonin receptors

Science

(2013)

G. Fenalti

Molecular control of δ-opioid receptor signalling

Nature

(2014)

T.P. Kenakin

Pharmacological onomastics: what's in a name?

Br. J. Pharmacol.

(2008)

K. Xiao

Global phosphorylation analysis of β-arrestin-mediated signaling downstream of a seven transmembrane receptor (7TMR)

Proc. Natl. Acad. Sci. U.S.A.

(2010)

J.D. Violin

Selectively engaging β-arrestins at the angiotensin II type 1 receptor reduces blood pressure and increases cardiac performance

J. Pharmacol. Exp. Ther.

(2010)

T.P. Kenakin

Cellular assays as portals to seven-transmembrane receptor-based drug discovery

Nat. Rev. Drug. Discov.

(2009)

L. Chen

An update of novel screening methods for GPCR in drug discovery

Expert Opin. Drug Discov.

(2012)

T. Kenakin

Functional selectivity through protean and biased agonism: who steers the ship?

Mol. Pharmacol.

(2007)

Cited by (299)

Functional profiling of the G protein-coupled receptor C3aR1 reveals ligand-mediated biased agonism
2024, Journal of Biological Chemistry
G protein-coupled receptors (GPCRs) are leading druggable targets for several medicines, but many GPCRs are still untapped for their therapeutic potential due to poor understanding of specific signaling properties. The complement C3a receptor 1 (C3aR1) has been extensively studied for its physiological role in C3a-mediated anaphylaxis/inflammation, and in TLQP-21-mediated lipolysis, but direct evidence for the functional relevance of the C3a and TLQP-21 ligands and signal transduction mechanisms are still limited. In addition, C3aR1 G protein coupling specificity is still unclear, and whether endogenous ligands, or drug-like compounds, show ligand-mediated biased agonism is unknown. Here, we demonstrate that C3aR1 couples preferentially to Gi/o/z proteins and can recruit β-arrestins to cause internalization. Furthermore, we showed that in comparison to C3a_63-77, TLQP-21 exhibits a preference toward Gi/o-mediated signaling compared to β-arrestin recruitment and internalization. We also show that the purported antagonist SB290157 is a very potent C3aR1 agonist, where antagonism of ligand-stimulated C3aR1 calcium flux is caused by potent β-arrestin-mediated internalization. Finally, ligand-mediated signaling bias impacted cell function as demonstrated by the regulation of calcium influx, lipolysis in adipocytes, phagocytosis in microglia, and degranulation in mast cells. Overall, we characterize C3aR1 as a Gi/o/z-coupled receptor and demonstrate the functional relevance of ligand-mediated signaling bias in key cellular models. Due to C3aR1 and its endogenous ligands being implicated in inflammatory and metabolic diseases, these results are of relevance toward future C3aR1 drug discovery.
Quantitative assessment of ligand bias from bias plots: The bias coefficient “kappa”
2023, Biochimica et Biophysica Acta - General Subjects
The current methods for quantifying ligand bias involve the construction of bias plots and the calculations of bias coefficients that can be compared using statistical methods. However, widely used bias coefficients can diverge in their abilities to identify ligand bias and can give false positives. As the empirical bias plots are considered the most reliable tools in bias identification, here we develop an analytical description of bias plot trajectories and introduce a bias coefficient, kappa, which is calculated from these trajectories. The new bias coefficient complements the tool-set in ligand bias identification in cell signaling research.
Built-in functional selectivity in neurons is mediated by the neuronal protein, GINIP
2023, Molecular Cell
Signaling snapshots of a serotonin receptor activated by the prototypical psychedelic LSD
2022, Neuron
Serotonin (5-hydroxytryptamine [5-HT]) 5-HT2-family receptors represent essential targets for lysergic acid diethylamide (LSD) and all other psychedelic drugs. Although the primary psychedelic drug effects are mediated by the 5-HT_2A serotonin receptor (HTR2A), the 5-HT_2B serotonin receptor (HTR2B) has been used as a model receptor to study the activation mechanisms of psychedelic drugs due to its high expression and similarity to HTR2A. In this study, we determined the cryo-EM structures of LSD-bound HTR2B in the transducer-free, Gq-protein-coupled, and β-arrestin-1-coupled states. These structures provide distinct signaling snapshots of LSD’s action, ranging from the transducer-free, partially active state to the transducer-coupled, fully active states. Insights from this study will both provide comprehensive molecular insights into the signaling mechanisms of the prototypical psychedelic LSD and accelerate the discovery of novel psychedelic drugs.
Danavorexton, a selective orexin 2 receptor agonist, provides a symptomatic improvement in a narcolepsy mouse model
2022, Pharmacology Biochemistry and Behavior
Citation Excerpt :
Thus, profile of danavorexton would have a significant impact on our understanding for the possibility of OX2R as a drug target. There are several types of GPCR activators, such as partial agonists, biased agonists, and allosteric modulators, that can affect the pharmacological profiles of each drug (Clark et al., 1999; Sako et al., 2019; Violin et al., 2014). Therefore, detailed preclinical characterization of danavorexton was conducted.
Narcolepsy type 1 (NT1), caused by loss of orexin neurons, is a neurological disorder characterized by excessive daytime sleepiness, cataplexy, disrupted nighttime sleep, hypnagogic/hypnopompic hallucinations and sleep paralysis, as well as a high risk of obesity. Danavorexton (TAK-925) is a novel brain-penetrant orexin 2 receptor (OX2R)-selective agonist currently being evaluated in clinical trials for the treatment of hypersomnia disorders including NT1. Thus, detailed characterization of danavorexton is critical for validating therapeutic potential of OX2R-selective agonists. Here, we report preclinical characteristics of danavorexton as a therapeutic drug for NT1. Danavorexton showed rapid association/dissociation kinetics to OX2R. The activation mode of endogenous OX2R by danavorexton and orexin peptide was very similar in an electrophysiological analysis. In orexin/ataxin-3 mice, a mouse model of NT1, danavorexton promoted wakefulness, and ameliorated fragmentation of wakefulness during the active phase after both acute and repeated administration, suggesting a low risk of receptor desensitization. Electroencephalogram (EEG) power spectral analysis revealed that danavorexton, but not modafinil, normalized dysregulated EEG power spectrum in orexin/ataxin-3 mice during the active phase. Finally, repeated administration of danavorexton significantly suppressed the body weight gain in orexin/ataxin-3 mice. Danavorexton may have the potential to treat multiple symptoms of NT1. These preclinical findings, together with upcoming clinical observations of danavorexton, could improve our understanding of the pathophysiology of NT1 and therapeutic potential of OX2R agonists.
G protein–coupled receptor interactions with arrestins and GPCR kinases: The unresolved issue of signal bias
2022, Journal of Biological Chemistry
G protein–coupled receptor (GPCR) kinases (GRKs) and arrestins interact with agonist-bound GPCRs to promote receptor desensitization and downregulation. They also trigger signaling cascades distinct from those of heterotrimeric G proteins. Biased agonists for GPCRs that favor either heterotrimeric G protein or GRK/arrestin signaling are of profound pharmacological interest because they could usher in a new generation of drugs with greatly reduced side effects. One mechanism by which biased agonism might occur is by stabilizing receptor conformations that preferentially bind to GRKs and/or arrestins. In this review, we explore this idea by comparing structures of GPCRs bound to heterotrimeric G proteins with those of the same GPCRs in complex with arrestins and GRKs. The arrestin and GRK complexes all exhibit high conformational heterogeneity, which is likely a consequence of their unusual ability to adapt and bind to hundreds of different GPCRs. This dynamic behavior, along with the experimental tactics required to stabilize GPCR complexes for biophysical analysis, confounds these comparisons, but some possible molecular mechanisms of bias are beginning to emerge. We also examine if and how the recent structures advance our understanding of how arrestins parse the “phosphorylation barcodes” installed in the intracellular loops and tails of GPCRs by GRKs. In the future, structural analyses of arrestins in complex with intact receptors that have well-defined native phosphorylation barcodes, such as those installed by the two nonvisual subfamilies of GRKs, will be particularly illuminating.

View all citing articles on Scopus

View full text

Trends in Pharmacological Sciences

ReviewBiased ligands at G-protein-coupled receptors: promise and progress

Highlights

Section snippets

New frontiers for G protein-coupled receptors

Pleuripotency of signaling: pathway validation

Concept of ligand bias

Definition of ligand bias versus functional selectivity: not just semantics

Measurement

Translation of mechanistic insights to novel pharmacology: compounds in the clinic

Evidence of differential pharmacology at other GPCRs: paths to future drug discovery?

Translation of concept to new medicines

Concluding remarks

Trends Pharmacol. Sci.

Trends Biochem. Sci.

Pharmacol. Ther.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

Mol. Cell. Proteomics

Trends Pharmacol. Sci.

Trends Pharmacol. Sci.

J. Biol. Chem.

J. Am. Coll. Cardiol.

J. Am. Coll. Cardiol.

Trends Cardiovasc. Med.

J. Am. Coll. Cardiol.

Trends Pharmacol. Sci.

Eur. J. Pain

Br. J. Anaesth.

Neuropharmacology

Neurosci. Res.

J. Am. Coll. Surg.

Mol. Cells

Trends Pharmacol. Sci.

Cell

Trends Pharmacol. Sci.

G protein-coupled receptor kinases

Annu. Rev. Biochem.

β-Arrestins and cell signaling

Annu. Rev. Physiol.

Pleiotropic AT1 receptor signaling pathways mediating physiological and pathogenic actions of angiotensin II

Mol. Endocrinol.

Biased ligands for better cardiovascular drugs: dissecting G-protein-coupled receptor pharmacology

Circ Res.

Differential signal transduction by five splice variants of the PACAP receptor

Nature

The use of stimulus-biased assay systems to detect agonist-specific receptor active states: implications for the trafficking of receptor stimulus by agonists

Mol. Pharmacol.

Selective engagement of G protein coupled receptor kinases (GRKs) encodes distinct functions of biased ligands

Proc. Natl. Acad. Sci. U.S.A.

Functional selectivity of dopamine receptor agonists. I. Selective activation of postsynaptic dopamine D2 receptors linked to adenylate cyclase

J. Pharmacol. Exp. Ther.

Antagonist-stimulated internalization of the G protein-coupled cholecystokinin receptor

Mol. Pharmacol.

Structural features for functional selectivity at serotonin receptors

Science

Molecular control of δ-opioid receptor signalling

Nature

Pharmacological onomastics: what's in a name?

Br. J. Pharmacol.

Global phosphorylation analysis of β-arrestin-mediated signaling downstream of a seven transmembrane receptor (7TMR)

Proc. Natl. Acad. Sci. U.S.A.

Selectively engaging β-arrestins at the angiotensin II type 1 receptor reduces blood pressure and increases cardiac performance

J. Pharmacol. Exp. Ther.

Cellular assays as portals to seven-transmembrane receptor-based drug discovery

Nat. Rev. Drug. Discov.

An update of novel screening methods for GPCR in drug discovery

Expert Opin. Drug Discov.

Functional selectivity through protean and biased agonism: who steers the ship?

Mol. Pharmacol.

Review
Biased ligands at G-protein-coupled receptors: promise and progress