From receptor binding kinetics to signal transduction; a missing link in predicting in vivo drug-action

Abstract

An important question in drug discovery is how to overcome the significant challenge of high drug attrition rates due to lack of efficacy and safety. A missing link in the understanding of determinants for drug efficacy is the relation between drug-target binding kinetics and signal transduction, particularly in the physiological context of (multiple) endogenous ligands. We hypothesized that the kinetic binding parameters of both drug and endogenous ligand play a crucial role in determining cellular responses, using the NK1 receptor as a model system. We demonstrated that the binding kinetics of both antagonists (DFA and aprepitant) and endogenous agonists (NKA and SP) have significantly different effects on signal transduction profiles, i.e. potency values, in vitro efficacy values and onset rate of signal transduction. The antagonistic effects were most efficacious with slowly dissociating aprepitant and slowly associating NKA while the combination of rapidly dissociating DFA and rapidly associating SP had less significant effects on the signal transduction profiles. These results were consistent throughout different kinetic assays and cellular backgrounds. We conclude that knowledge of the relationship between in vitro drug-target binding kinetics and cellular responses is important to ultimately improve the understanding of drug efficacy in vivo.

Perspective: Implications of Ligand–Receptor Binding Kinetics for Therapeutic Targeting of G Protein-Coupled Receptors

“…For NK 1 R, the kinetic characterization of the endogenous ligands led to an excellent correlation between the ligand’s RT and in vitro efficacy, as well as between the ligand’s k on and the in vitro potency, as determined via a label-free assay . Moreover, a follow-up study showed that antagonists display different inhibitory potencies depending on the binding kinetics of the endogenous agonist …”

“…87 Moreover, a follow-up study showed that antagonists display different inhibitory potencies depending on the binding kinetics of the endogenous agonist. 23 In case of the GnRHR, synthetic GnRH analogs displayed RTs ranging from 6 to 111 min in radioligand binding assays, whereas the RT measured by time-resolved fluorescence resonance energy transfer (FRET) varied from 2 to 61 min. 30 Interestingly, the RT of GnRH itself was around 6 min, indicating that most of these synthetic analogs had a longer RT.…”

“…Depending on the disease type, short or long RT ligands are preferred. Examples of antagonists with long RT drugs are (1) the neurokinin-1 receptor (NK 1 R) antagonist aprepitant, which shows superior antagonism over the NK 1 R antagonists ZD6021 and CP-99994 in treatment of chemotherapy-induced emesis; ,, (2) maraviroc, a selective CC chemokine receptor 5 (CCR5) antagonist with antihuman immunodeficiency virus type 1 (HIV-1) activity; (3) olmesartan, an angiotensin II type 1 receptor (AT 1 R) antagonist targeting hypertension; (4) rupatadine, a histamine H 1 receptor (H 1 R) antagonist against allergic disorders; and (5) muscarinic 3 receptor (M 3 R) antagonist tiotropium for the treatment of chronic obstructive pulmonary disease (COPD) and asthma . Tiotropium also binds to muscarinic 2 receptor (M 2 R), but here its RT is around 10-fold lower than that for M 3 R. Moreover, ipratropium, a short RT ligand for the same receptor (with >11-fold lower RT than tiotropium and with 6.5-fold lower affinity), is less effective in vivo than tiotropium. , In the case of marketed agonists , deslorelin has a longer RT than goserelin for the gonadotropin-releasing hormone receptor (GnRHR) .…”

The Neurokinin-1 Receptor: Structure Dynamics and Signaling

“…Aside from fine structural studies revealing activated and inactivated conformations of the receptors induced by movements of receptor domains, determining the binding kinetics of both agonist and antagonist ligands deserves attention to ascertain signal transduction outcomes and determine new drugs' specificity, efficacy, modulation, and potency [117].…”

Bioluminescence Resonance Energy Transfer Based G Protein-Activation Assay to Probe Duration of Antagonism at the Histamine H3 Receptor

“…In contrast to binding assays that are routinely performed with cell homogenates or isolated membranes, functional assays are performed on intact living cells and, consequently also account for dynamic cellular processes such as effector pre-coupling, receptor reserve and receptor regulation. Fast and/or real time cellular responses such as Ca 2+ influx, cyclic adenosine-monophosphate (cAMP) production and cellular impedance-based assays, have recently been used to measure the recovery of receptor responsiveness as measure of pre-bound antagonist dissociation upon washout of unbound antagonist [3,7,9,10,11,12]. Indeed, recovery time of Gα q -coupled histamine H 1 receptor (H 1 R) responsiveness in a Ca 2+ mobilization and label free dynamic mass redistribution (DMR) assay after antagonist washout highly correlated to residence times of these antihistamines, as determined in competitive radioligand binding assays [7].…”