5-HT₆ Receptor ( pKi = 8.92-9.09 )

In vitro activity :SB 271046 competitively inhibited 5-HT-induced stimulation of adenylyl cyclase activity in functional studies on human 5-HT6 receptors, with a pA2 of 8.71[1].

SB-271046 results in a minimum effective dose of approximately 0.1 mg/kg p.o. and maximum effect at 4 hours post-dose in the rat maximal electroshock seizure threshold (MEST) test. This rises the seizure threshold over a broad dose range. The blood and brain concentrations of SB 271046 (EC50 of 0.16 μM) and C_max (0.01-0.04 μM) showed a strong correlation with the achieved level of anticonvulsant activity[1].

SB271046 Hcl is an effective, pKi of 8.9, selective, and oral 5-HT6 receptor antagonist. IC50 Value: 8.9(pKi). A sulfonamidal benzothiophene derivative, SB 271046 hydrochloride has been demonstrated to function as a selective 5-HT6 antagonist, with pKi values of 9.02-8.92, 6.55, 6.35, 6.27, 6.05, 5.95, 5.76, 5.73, 5.62, 5.55, 5.41, 5.39, 5.27, and < 4.99 for 5-HT6, 5-HT1D, 5-HT1A, D3, 5-HT1B, 5-HT1F, α1B, 5-HT2C, 5-HT2A, D2, 5-HT2B, 5-HT7, 5-HT4 and 5-HT1E, respectively. It is also > 200-fold selective over 55 other receptors, enzymes, and ion channels.

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Radioligand binding [1]
Radioligand binding was carried out as described (Hirst et al., 2000). In brief, radioligand binding was performed on membranes from HeLa cells stably transfected with the human 5-HT6 receptor (see above) and striatal tissue from adult rats (Sprague-Dawley, 200–250 g), adult pigs (from a local abattoir) and human caudate putamen tissues (from non-identifiable patients aged 64–76 years, whose cause of death was non-neurological). Membranes were incubated with 1 nM [125I]-SB-258585 (Hirst et al., 2000) or 2 nM [3H]-LSD for 45 min at 37°C. Non-specific binding was defined by the inclusion of 10 μM methiothepin and the assay was terminated by rapid filtration through Whatman GF/B filters. For receptor selectivity studies on other 5-HT receptors, details of the radioligands used and assay conditions are given in Hirst et al. (2000). SB-271046 was also tested in a further 55 binding assays by CEREP.

Male Sprague Dawley rats; Dissolved in 1% methyl cellulose in water; 30 mg/kg; Oral gavage

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Maximal electroshock seizure threshold (MEST) test [1]
Male Sprague Dawley rats (100–150 g), supplied by Charles River, U.K. were housed in groups of 10 at a room temperature of 20–22°C. Animals were maintained on a 12 h light/dark cycle with lights on between 0600 and 1800 h Food nd water were available ad libitum. Drug treatments were evaluated between 1400 and 1800 h alongside time-matched vehicle-treated controls.
The threshold current for electroshock-induced tonic hindlimb extensor seizure was determined using a Hugo Sachs Electronik stimulator, which delivered an adjustable constant current (1–300 mA) of 0.3 s duration, 50 Hz, sinewave form, via corneal electrodes. The stimulus intensity was varied, from a typical baseline of 25 mA, by an ‘up and down' method of shock titration (see Upton et al., 1997, for details). Data generated from treatment groups of n=11–14 were used to calculate the seizure threshold (current producing tonic hindlimb extensor seizure in 50% of animals)±s.e. values according to the method of Kimball et al. (1957). Elevation of seizure threshold is indicative of an anticonvulsant effect whereas a reduction in seizure threshold is indicative of proconvulsant activity. The effects of the selective 5-HT6 receptor antagonists, SB-271046 (0.1–30 mg kg−1 p.o., 4 h pre-test), SB-258510 (10 mg kg−1 p.o., 2–6 h pre-test) (Bromidge et al., 1999) and Ro 04-6790 (0.3–30 mg kg−1 i.p., 1 h pre-test) (Sleight et al., 1998), on seizure threshold were determined. The doses of Ro 04-6790 selected for this study cover the range previously reported to evoke a number of behavioural effects in rats (Sleight et al., 1998; Bentley et al., 1999). SB-271046 and SB-258510 were suspended in 1% methyl cellulose in water and Ro 04-6790 was dispersed in saline. A 1 ml kg−1 dose volume was used for all treatments and doses are expressed as free base.
In order to evaluate the relationship between the level of anticonvulsant activity achieved and blood concentration, the duration of action of a high submaximal dose (10 mg kg−1 p.o.) of SB-271046 in the rat MEST test was evaluated in detail over a 24 h period. Following the conclusion of this study, whole brain and blood samples were taken from randomly selected animals (n=5) at 13 different timepoints. Samples were assayed for SB-271046 using a method based on protein precipitation with acetonitrile, followed by LC/MS/MS analysis employing positive-ion electrospray ionization, with a lowest limit of quantification (LLQ) of 0.01 μM.

[1]. Characterization of SB-271046: a potent, selective and orally active 5-HT(6) receptor antagonist. Br J Pharmacol. 2000 Aug;130(7):1606-12.

SB-271046 effectively replaced the [3H]-LSD and [125I]-SB-258585 recombinantly expressed human 5-HT6 receptor in HeLa cells in vitro (pKi values of 8.92 and 9.09, respectively). SB-271046 also replaced [125I]-SB-258585 on the human caudate nucleus and the striatal membrane of rats and pigs (pKi values of 8.81, 9.02, and 8.55, respectively). Compared with 55 other receptors, binding sites, and ion channels, SB-271046 showed more than 200-fold higher selectivity for the 5-HT6 receptor. In functional studies of the human 5-HT6 receptor, SB-271046 competitively antagonized 5-HT-induced adenylate cyclase activity with a pA2 value of 8.71. In the rat maximum electroconvulsive seizure threshold (MEST) assay, SB-271046 increased the seizure threshold over a wide dose range, with a minimum effective dose ≤0.1 mg kg⁻¹ (oral), and the maximum effect occurring 4 hours after administration. The achieved anticonvulsant activity levels correlated well with SB-271046 plasma concentrations (EC50 = 0.16 μM) and brain tissue concentrations (Cmax = 0.01–0.04 μM). These data, combined with the anticonvulsant activity observed in rat MEST tests of other selective 5-HT6 receptor antagonists SB-258510 (10 mg kg⁻¹, pre-test 2–6 h) and Ro 04-6790 (1–30 mg kg⁻¹, pre-test 1 h), suggest that the anticonvulsant properties of SB-271046 are likely mediated by 5-HT6 receptors. In summary, these studies demonstrate that SB-271046 is a potent and selective 5-HT6 receptor antagonist with oral activity in rat MEST tests. SB-271046 is an effective tool for assessing the central function of 5-HT6 receptors in vivo. [1] This study demonstrates that SB-271046 has potent and sustained anticonvulsant activity in rat MEST tests. The MEST test is a previously reported model used to study the role of the serotonergic pathway in the regulation of epileptic seizures (e.g., Upton et al., 1998). Since SB-271046 is a highly selective 5-HT6 receptor antagonist (Bromidge et al., 1999; Routledge et al., 1999), its anticonvulsant properties are likely mediated by blocking the 5-HT6 receptor. Furthermore, the pharmacokinetic and pharmacodynamic characteristics of this compound are closely correlated with the anticonvulsant activity observed in other selective 5-HT6 receptor antagonists, such as SB-258510 (Bromidge et al., 1999; human 5-HT6 receptor pKi value 9.2) and the chemically distinct compound Ro 04-6790 (Sleight et al., 1998), further supporting these conclusions. In summary, these data suggest that the MEST trial may provide a reliable in vivo model of 5-HT6 receptor function, and also indicate that SB-271046 is a potent and orally effective 5-HT6 receptor antagonist. However, the strength of these antiepileptic effects is limited compared to known antiepileptic drugs. For example, under the same test conditions, drugs such as carbamazepine can raise the seizure threshold by more than 1200% (Upton et al., 1997), while SB-258510 and SB-271046 only raised the threshold by a maximum of 132% and 166%, respectively. This low level of anticonvulsant efficacy associated with 5-HT6 receptor blockade may explain why SB-271046, SB-258510, and Ro 04-6790 did not show a significant dose-dependent effect in the MEST test, as the anticonvulsant activity of SB-271046 is clearly related to its blood exposure level. Therefore, it remains unclear how this observation relates to the potential clinical value of SB-271046 in the treatment of epilepsy. In summary, these data indicate that SB-271046 is a potent, selective, and orally effective 5-HT6 receptor antagonist. This compound provides a useful tool for further elucidating the physiological function of the 5-HT6 receptor in vivo. [1]

C20H22CLN3O3S2

451.99

487.056

209481-20-9

SB 271046 Hydrochloride; 209481-24-3

5312149

Typically exists as solid at room temperature

1.400

664.3ºC at 760 mmHg

240-241℃ (DEC.)

355.5ºC

6.431

2

7

5

29

656

0

CC1=C(SC2=C1C=C(C=C2)Cl)S(=O)(=O)NC3=CC(=C(C=C3)OC)N4CCNCC4

LOCQRDBFWSXQQI-UHFFFAOYSA-N

InChI=1S/C20H22ClN3O3S2/c1-13-16-11-14(21)3-6-19(16)28-20(13)29(25,26)23-15-4-5-18(27-2)17(12-15)24-9-7-22-8-10-24/h3-6,11-12,22-23H,7-10H2,1-2H3

5-chloro-N-(4-methoxy-3-piperazin-1-ylphenyl)-3-methyl-1-benzothiophene-2-sulfonamide

SB-271046; SB 271046; SB271046; 209481-20-9; Sb 271046; SB-271046; SB271046; 5-chloro-N-(4-methoxy-3-(piperazin-1-yl)phenyl)-3-methylbenzo[b]thiophene-2-sulfonamide; 5-chloro-N-(4-methoxy-3-piperazin-1-ylphenyl)-3-methyl-1-benzothiophene-2-sulfonamide; L3SK5KX24S; Benzo[b]thiophene-2-sulfonamide, 5-chloro-N-[4-methoxy-3-(1-piperazinyl)phenyl]-3-methyl-; SB-271046 HCl; SB-271046 hydrochloride

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO: ~40 mg/mL (~81.9 mM)
Water: <1 mg/mL
Ethanol: <1 mg/mL

1% methylcellulose: ~30 mg/mL (Please use freshly prepared in vivo formulations for optimal results.)