Synthesis and Characterization of Novel 2-Amino-3-benzoylthiophene Derivatives as Biased Allosteric Agonists and Modulators of the Adenosine A₁ Receptor

Abstract

A series of novel 2-amino-3-benzoylthiophenes (2A3BTs) were screened using a functional assay of A(1)R mediated phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in intact CHO cells to identify potential agonistic effects as well as the ability to allosterically modulate the activity of the orthosteric agonist, R-PIA. Two derivatives, 8h and 8i, differing only in terms of the absence or presence of an electron-withdrawing group on the benzoyl moiety of the 2A3BT scaffold, were identified as biased allosteric agonists and positive allosteric modulators of agonist function at the adenosine A(1) receptor (A(1)R) in two different functional assays. Our findings indicate that subtle structural variations can promote functionally distinct receptor conformational states.

Advances in G Protein-Coupled Receptor Allostery: From Function to Structure

“…Although cinacalcet is clearly a PAM for intracellular calcium mobilization, it is a NAL at the ERK1/2 pathway (Davey et al, 2012;Leach et al, 2013). Similar pathwaydependent changes in that nature of the modulatory effect for a given pair of allosteric/orthosteric ligands have been observed at other GPCRs, including the NK2 (Maillet et al, 2007), A 1 (Valant et al, , 2012a, M 1 (Marlo et al, 2009), M 2 (Valant et al, 2012b), M 3 (Stewart et al, 2010), CRTH2 (Mathiesen et al, 2005), mGluR5 (Zhang et al, 2005;Bradley et al, 2011), PGF2a (Goupil et al, 2010), and CB 1 receptors. A particularly striking example of probe dependence that is indicative of biased modulation has been observed with LY2033298 at the M 2 mAChR (Valant et al, 2012b).…”

“…An advantage of the operational model as applied to SAR is that it can almost always be fitted to experimentally derived data to provide estimates of some, or all, of its parameters with regards both to allosteric modulators (Aurelio et al, 2009;Gregory et al, 2012;Valant et al, 2012a;Huynh et al, 2013;Mistry et al, 2013) and biased agonists (Tschammer et al, 2011b;Shonberg et al, 2013;Szabo et al, 2014). Table 1 illustrates an example of allosteric modulator SAR determined through analysis of the effects of various thienopyridine modulators on acetylcholine-mediated ERK1/2 phosphorylation at the M 4 mAChR.…”

Separation of on-target efficacy from adverse effects through rational design of a bitopic adenosine receptor agonist

“…The introduction of bulky substituents at the four and five positions of the thiophene ring of 2-amino-3-benzoylthiophene modulators can also preserve or enhance their allosteric properties (23,(33)(34)(35). We, thus, generated six hybrid ligands by attaching the N 6 of adenosine to the five position of the thiophene ring of VCP171 with a 4-benzamidoalkyl linker that ranged from 2 to 12 carbon atoms in length (Fig.…”

G Protein–coupled Receptor Biased Agonism

“…However, translation of adenosine A1 receptor agonists to clinical medicine has been limited because of the on target adverse effects such as bradycardia and hypotension [78, 79]. Therefore, it is important to better understand and characterize the mode of action of several of these allosteric modulators, and in fact, several groups have been working on better elucidating the activation of selective signaling by these ligands [80–83]. For example, preliminary work with VCP746, a hybrid molecule of adenosine linked to an allosteric modulator, showed that it led to cardioprotection with minimal effects on blood pressure and heart rate [84].…”