AF‐353, a novel, potent and orally bioavailable P2X3/P2X2/3 receptor antagonist

Abstract

Background and purpose: Purinoceptors containing the P2X3 subunit (P2X3 homotrimeric and P2X2/3 heterotrimeric) are members of the P2X family of ion channels gated by ATP and may participate in primary afferent sensitization in a variety of pain-related diseases. The current work describes the in vitro pharmacological characteristics of AF-353, a novel, orally bioavailable, highly potent and selective P2X3/P2X2/3 receptor antagonist. Experimental approach: The antagonistic potencies (pIC50) of AF-353 for rat and human P2X3 and human P2X2/3 receptors were determined using methods of radioligand binding, intracellular calcium flux and whole cell voltage-clamp electrophysiology. Key results: The pIC50 estimates for these receptors ranged from 7.3 to 8.5, while concentrations 300-fold higher had little or no effect on other P2X channels or on an assortment of receptors, enzymes and transporter proteins. In contrast to A-317491 and TNP-ATP, competition binding and intracellular calcium flux experiments suggested that AF-353 inhibits activation by ATP in a non-competitive fashion. Favourable pharmacokinetic parameters were observed in rat, with good oral bioavailability (%F = 32.9), reasonable half-life (t1/2 = 1.63 h) and plasma-free fraction (98.2% protein bound). Conclusions and implications:The combination of a favourable pharmacokinetic profile with the antagonist potency and selectivity for P2X3 and P2X2/3 receptors suggests that AF-353 is an excellent in vivo tool compound for study of these channels in animal models and demonstrates the feasibility of identifying and optimizing molecules into potential clinical candidates, and, ultimately, into a novel class of therapeutics for the treatment of pain-related disorders.

2′,3′-O-Substituted ATP derivatives as potent antagonists of purinergic P2X3 receptors and potential analgesic agents

“…The potent non-competitive P2X3 antagonist AF-353 [68] was also tested for comparison. These antagonists were tested at concentrations close to their IC 50 values (0.05 μM for compounds 4 and 10; 0.01 μM for AF-353) and applied for 5 min.…”

P2X receptor antagonists for pain management: examination of binding and physicochemical properties

“…A-317491(compound 7) was the first selective small molecule compound for P2X3 and P2X2/3. Subsequently, other potent P2X3 antagonists were reported including RO-3 (compound 9), and RO-4 (compound 10) that are at least 100-fold less active across a wide range of kinases, receptors, and ion channels [35,36,39]. These compounds have improved drug-like properties relative to earlier P2X3 antagonists (e.g., compounds 1-6) (Fig.…”

“…MK-3901 has an MPO score of 3.8 and has good (%F=60) oral bioavailabilty [37]. Another potent P2X3 antagonist, AF-219 (structure undisclosed), is reported to have advanced into clinical studies [39].…”

P2X Receptors as New Therapeutic Targets

“…AF-353, which is synthesized by Roche Palo Alto are novel, selective and highly potent P2X 3 and P2X 2/3 receptor antagonist. It has been proved that AF-353 is orally bioavailable (%F = 32.9) and stable in vivo for the treatment of pain which is in clinical trial (Gever et al 2010). The antagonistic potencies (pIC(50)) for rat and human P2X 3 and human P2X 2/3 receptors ranged from 7.3 to 8.5 which had little or no effect on other P2X receptors (Gever et al 2010).…”

“…It has been proved that AF-353 is orally bioavailable (%F = 32.9) and stable in vivo for the treatment of pain which is in clinical trial (Gever et al 2010). The antagonistic potencies (pIC(50)) for rat and human P2X 3 and human P2X 2/3 receptors ranged from 7.3 to 8.5 which had little or no effect on other P2X receptors (Gever et al 2010). Comparing with A-317491 and TNP-ATP, AF-353 inhibits activation by ATP in noncompetitive fashion.…”