Description
Na
v1.8 is a tetrodotoxin-
resistant (TTX-
R) sodium channel with high activation threshold and slow inactivating kinetics that is highly expressed in small-
diameter sensory neurons and has been implicated in signaling various types of pain. A-
803467 is a sodium channel blocker with high-
affinity and selectivity for inhibiting human Na
v1.8 sodium channels (IC
50 = 8 nM when stimulated at half-
maximal inactivation and IC
50 = 79 nM at a resting state).
1 This compound is unusual in that it blocks hNav1.8 at negative resting membrane potentials (many small molecule sodium channel blockers show a reduced affinity for the resting state) and does not demonstrate significant frequency-
dependent block during a 10 Hz pulse train.
2 A-
803467 dose-
dependently reduces behavioral responses in a variety of neuropathic and inflammatory pain models.
1
Chemical Properties
White Solid
Uses
A selective NaV1.8 sodium channel blocker, reduces behavioral measures of chronic pain.
General Description
The small molecule A-803467 is a potent and selective Nav1.8 sodium channel blocker. Nav1.8 is a tetrodotoxin-resistant (TTX-R) sodium channel that contributes to pain sensation by transmitting pain stimuli in peripheral sensory neurons; blockage of this channel by A-803467 reduces pain with varying effectiveness in a number of different models. A-803467 has been used to further understand the role of Nav1.8 in transmitting pain stimuli and also can be used as an analgesic.
Biological Activity
Selective blocker of Na V 1.8 channels (IC 50 values are 8, 2450, 6740, 7340 and 7380 nM for hNa V 1.8, hNa V 1.3, hNa V 1.7, hNa V 1.5 and hNa V 1.2 channels respectively). Shows no significant activity against TRPV1, P2X 2/3 , Ca V 2.2 and KCNQ2/3 channels. Antinociceptive; potently attenuates mechanical allodynia in two models of neuropathic pain following i.p. administration.
Biochem/physiol Actions
A-803467 blocks Nav1.8 in both half-maximal inactive and resting states with an IC50 of 8 nM and IC50 of 79 nM, respectively. A-803467 is over 100-fold more selective vs. human Nav1.2, 1.3, 1.5 and 1.7.
Enzyme inhibitor
This potent sodium channel blocker (FW = 357.79 g/mol; CAS 944261-79-
4; Solubility: 72 mg/mL DMSO; <1 mg/mL H2O), also named 5- (4-
chlorophenyl) -N- (3,5-dimethoxyphenyl) furan-2-carboxamide, selectively
targets NaV1.8 channels (IC50 = 8 nM), blocking tetrodotoxin-resistant
currents and exhibiting >100x selectivity against human NaV1.2, NaV1.3,
NaV1.5, and NaV1.7. A-803467 potently blocks tetrodotoxin-resistant
currents (IC50 = 140 nM), generating spontaneous and electrically evoked
action potentials in vitro in rat dorsal root ganglion neurons. Later
studies reported the additive antinociceptive effects of the selective Nav1.8
blocker A-803467 and selective TRPV1 antagonists in rat inflammatory
and neuropathic pain models. Inhibition of Drug Efflux: ATP-binding
cassette (ABC) multidrug transporters (such as ABCB1, or MDR1/P-
glycoprotein); ABCC1 (MRP1) and ABCG2 (BCRP/MXR) ) mediate drug
efflux in human cancers. ABCG2 is a 72-kDa half transporter that is
specifically localized at the apical surface of enterocytes, the luminal
surface of liver canaliculi, the luminal surface of the proximal convoluted
tubule of the kidneys, the blood–brain barrier (BBB), blood–testis barrier
(BTB), blood–placental and blood–retinal barriers. Because of its
localization on the secretory surface of the major organs involved in drug
transport, ABCG2 alters absorption, distribution, metabolism and
elimination of its substrate drugs. A-803467 significantly increases the
cellular sensitivity to ABCG2 substrates in drug-resistant cells
overexpressing either wild-type or mutant ABCG2. At 7.5 μM, A-803467
3
significantly increases the intracellular accumulation of [H]-mitoxantrone
by inhibiting the transport activity of ABCG2, without altering its
expression levels. In addition, A-803467 stimulates the ATPase activity in
membranes overexpressed with ABCG2. In a murine model system,
combination treatment of A-803467 (35 mg/kg) and topotecan (3 mg/kg)
significantly inhibits the tumor growth in mice xenografted with ABCG2-
overexpressing cancer cells. Such findings indicate that a combination of
A-803467 and ABCG2 substrates may potentially be a novel therapeutic
treatment in ABCG2-positive drug resistant cancers.
References
1) Jarvis et al. (2007), A-803467, a potent and selective Nav1.8 sodium channel blocker, attenuates neuropathic and inflammatory pain in the rat; Proc. Natl. Acad. Sci. USA, 104 8520
2) McGaraughty et al. (2008), A selective Nav1.8 sodium channel blocker, A-803467 [5-(4-chlorophenyl-N-(3,5-dimethoxyphenyl)furan-2-carboxamide], attenuates spinal neuronal activity in neuropathic rats; J. Pharmacol. Exp. Ther., 324 1204