5-HT₆ Receptor ( pKi = 9.63 )

Intepirdine (SB742457) is a potent and selective 5-HT6 receptor antagonist that has been demonstrated to improve elderly rats' performance in a water maze task and to reverse a learning deficit caused by scopolamine in the novel object recognition test.[1]

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The present study aimed to examine the chronic effects of the selected APDs (haloperidol, risperidone, olanzapine), administered alone and in combination with a selective 5-HT6 agonist (WAY-181187) or antagonist (Intepirdine (SB742457)), on weight gain, food intake, serum lipid profile, glucose level, and a spectrum of hormones derived from adipose (leptin, adiponectin) and gastrointestinal (insulin, ghrelin) tissue in rats. SB-742457 inhibited increased weight gain and alleviated hyperglycemia induced by APDs more strongly than did WAY-181187, but also intensified dyslipidemia. WAY-181187 tended to improve the lipid profile, but increased the glucose level. The greatest benefits were obtained when WAY-181187 or Intepirdine (SB742457) were co-administered with haloperidol. It is difficult to assess whether the modification of the serum levels of insulin, leptin, ghrelin, and adiponectin depended on the treatment applied or other drug-independent factors; therefore, further research is needed. [2]

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The aim of the present study was to investigate and compare the effects of acute and chronic (21-day) administration of agonist (WAY-181187) and antagonist (Intepirdine (SB742457)) of the 5-hydroxytryptamine 6 receptor (5-HT6R) on MK-801-induced memory impairments in novel object recognition (NORT) and Y-maze continuous spontaneous alternation tests (Y-CAT). Further, the expression of the brain-derived neurotrophic factor (BDNF) in rat hippocampus was measured after 21-day administration to investigate BDNF participation in the pro-cognitive effects of 5-HT6R ligands. We found that acute administration of WAY-181187, as well as SB-742457, reversed the effects of MK-801 in NORT and Y-CAT, and that this influence persisted after prolonged application in NORT but not in Y-CAT. Both 5-HT6R ligands increased hippocampal BDNF protein expression, but WAY-181187 was much more potent than SB-742457 and alleviated the MK-801-induced inhibition of BDNF signaling pathways better, which seems to translate into a stronger WAY-181187 effect in behavioral tests. Collectively, both the 5-HT6R agonist and the antagonist, administered acutely and chronically, prevent memory impairments and alterations in BDNF signaling induced by MK-801 in rats. The present results confirm the pro-cognitive properties of both types of 5-HT6R ligands and suggest that BDNF pathways may be involved in their mechanism of action [3].

Group 2 (n = 6) was used for pharmacologic characterization of the regional binding of 11C-GSK215083. In addition to its affinity for 5HT6 receptors, the PET ligand 11C-GSK215083 also possesses an approximately 5-fold-lower affinity for the 5HT2A receptor (3). Therefore, we used ketanserin, a selective 5HT2A antagonist, to test for the existence of detectable binding to 5HT2A receptors and SIntepirdine (SB742457)to detect binding to 5HT6 receptors. Four subjects underwent a baseline 11C-GSK215083 scan followed by 2 further PET scans, after SB742457 (175 mg, orally, 5 h before 11C-GSK215083 administration) and after ketanserin (0.1 mg/kg, by slow intravenous injection, 2 h before 11C-GSK215083 administration), respectively, in a randomized fashion, 7 d apart. The remaining 2 subjects received a baseline scan, a second scan after SB742457 (175 mg), and a third scan, 7 d later (Fig. 1B).
Group 3 (n = 8) characterized the time and dose occupancy relationship of Intepirdine (SB742457) in the brain. Each subject underwent 3 PET scans. Scan 1 was a baseline scan with scans 2 and 3 following repeated once-daily dosing of SB742457 on 2 occasions between 7 and 28 d of dosing. Four subjects received a loading dose of SB742457 (175 mg) on day 1, followed by 35 mg daily for 21 or 28 d (2 subjects per group). Subjects were randomized to undergo 2 scans on days 7, 14, 21, and 28, such that 2 independent data points were collected for each time point (Fig. 1C). Similarly, 2 further subjects received SB742457 (70 mg) followed by 15 mg daily for 14 d, and the last 2 subjects received 15 mg followed by 3 mg daily for 14 d. All 4 subjects were scanned on days 7 and 14 (Fig. 1D). Scans were conducted approximately 5 h after SB742457 dosing.
Safety assessments included medical history, physical examination, adverse event reporting, clinical laboratory assessments and electrocardiogram, blood pressure, and pulse rate measurements (supplemental information). Blood samples were collected for pharmacokinetic analysis of SB742457 in plasma from subjects in groups 2 and 3 before and on completion of each scan for which Intepirdine (SB742457) was administered (supplemental information). https://pubmed.ncbi.nlm.nih.gov/26383152/

Western blot analysis [3]
Hippocampus samples were homogenized using T-PER mammalian protein extraction reagent with protease and phosphatase inhibitors. Protein concentrations was determined using the Bradford reaction. Aliquots (40 μg) were solubilise in Laemmli buffer with 2% 2-mercaptoethanol, and were subject to 10% SDS-polyacrylamide gel electrophoresis. The anti-brain derived neurotrophic factor (BDNF, 15 kDa) diluted 1:500 and anti-β-actin diluted 1:1000 were used. The secondary antibody was anti rabbit IgG (HRP) diluted 1:2000.

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Quantitative real-time PCR [3]
RNA was extracted from tissues using RNA Isolation kit. After quantity and quality evaluation, RNA concentration was normalized to 15 ng/µL. Reverse transcription was done with a High-Capacity Reverse Transcription Kit. qPCR 96-wells reaction plate was performed with TaqMan primers and probes for BDNF (Rn02531967_s1) according to the manufacturer’s protocol on The Applied Biosystems® 7500 Fast Real-Time PCR Instrument. Endogenous control genes Gapdh (Rn01775763_g1) and Tbp (Rn01455646_m1) were selected on the basis of the pilot experiment. Relative expression was calculated using ΔΔCq method.

A total of 140 rats were used in the study, and each treatment group consisted of 10 randomly selected animals. Due to the large number of animals and limited laboratory space, the experiment was carried out in three turns: the first included 4 treatment groups: vehicle (1% Tween 80), haloperidol, risperidone, and olanzapine; the second consisted of 5 treatment groups: vehicle (1% Tween 80), WAY-181187, haloperidol + WAY-181187, risperidone + WAY-181187, and olanzapine + WAY-181187; and the third consisted of 5 treatment groups: vehicle (1% Tween 80), Intepirdine (SB742457), haloperidol + SB-742457, risperidone + SB-742457, and olanzapine + SB-742457. One animal died during the administration of the compounds; therefore, one experimental group (i.e., risperidone + WAY-181187-treated group) eventually consisted of only 9 animals. 24 hours after the last drug administration, trained personnel sacrificed the rats by dislocating the cervical spinal cord.[2]

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Haloperidol risperidone, olanzapine, WAY-181187 (oxalate), and Intepirdine (SB742457) were used in the experiment. Doses of APDs (haloperidol 0.5 mg/kg, risperidone 0.5 mg/kg, and olanzapine 5 mg/kg) and 5-HT6 ligands (WAY-181187 3 mg/kg and SB-742457 3 mg/kg) were selected for the experiments, based on literature review and our previous studies which presented their separate and combined behavioral effects. The compounds were suspended in a 1% solution of Tween 80 (Sigma Aldrich, St. Louis, MO, USA) immediately before administration and injected intraperitoneally (ip) in a volume of 2 mL/kg. The compounds were dispensed to the rats once daily between 10:00 and 11:00 a.m. for 28 days. The last injection was given 24 h before sacrifice. The control rats received 1% Tween 80, on the same dosing regimen.[2]

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The following drugs were used: WAY-181187 (oxalate), Intepirdine (SB742457), (+)-MK-801 (hydrogen maleate). All the compounds, except for MK-801 which was dissolved in distilled water, were suspended in 1% solution of Tween 80 immediately before administration, and were injected i.p. in a volume of 2 ml/kg. In acute experiments 5-HT6R ligands were injected 60 min before testing, while in chronic tests once a day during consecutive 21 days, with the last injection 24 h before the test. MK-801 was administered only once, 30 min before the tests. Control rats received vehicle according to the same schedule. The doses of drugs refer to their salt forms. [3]

[1]. 5-HT6 receptor antagonists as novel cognitive enhancing agents for Alzheimer's disease. Neurotherapeutics. 2008 Jul;5(3):458-69.

[2]. Selective 5-HT6 Receptor Ligands (Agonist and Antagonist) Show Different Effects on Antipsychotic Drug-Induced Metabolic Dysfunctions in Rats. Pharmaceuticals (Basel). 2023 Jan 20;16(2):154.

[3]. 5-HT6 receptor agonist and antagonist improve memory impairments and hippocampal BDNF signaling alterations induced by MK-801. Brain Res. 2019 Nov 1:1722:146375.

Intepirdine has been used in trials studying the treatment of Alzheimer's Disease. INTEPIRDINE is a small molecule drug with a maximum clinical trial phase of III (across all indications) and has 2 investigational indications.

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In conclusion, the results obtained provide us with an unambiguous answer regarding whether the addition of a selective 5-HT6 agonist or antagonist will bring more benefits concerning post-APD metabolic disorders. The greatest benefits were obtained when the 5-HT6 ligand was co-administered with haloperidol, which, unlike risperidone (Ki = 420 nM) and olanzapine (Ki = 2.5 nM), has no affinity for the 5-HT6 receptor (Ki > 5000 nM). WAY-181187 normalized haloperidol-induced changes in the serum levels of peptides regulating appetite and metabolism activity and, to a lesser extent, decreased weight gain and food intake, while Intepirdine (SB742457) strongly reduced weight gain and food intake and was less likely to modify hormonal changes. Generally, SB-742457 more strongly inhibited increased weight gain and alleviated the hyperglycemia caused by APDs, but it should be noted that it also intensified dyslipidemia. On the other hand, WAY-181187 tended to improve the lipid profile, but increased the glucose level. It is also difficult to assess whether the modification of the serum levels of insulin, leptin, ghrelin, and adiponectin depended on the treatment applied or other drug-independent factors (for example: weight gain, daily locomotor activity, adipose tissue content); therefore, further research is needed.[2]

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MK-801 is a non-competitive antagonist of NMDA receptors (Wong et al., 1986) that induces cognitive disruptions similar to those associated with dementia (Ellison, 1995) and schizophrenia (Bubeníková-Valešová et al., 2008). MK-801-evoked memory deficit model is widely used in preclinical cognitive investigations (van der Staay et al., 2011). There are extensive number of animal tests sensitive to MK-801, including NORT and Y-CAT reflecting the rodent’s natural exploratory behaviors (Dix and Aggleton, 1999, Lalonde, 2002). In the present work, upon acute administration of MK-801, rats exhibited memory impairment when they were tested for their behavioral paradigms by NORT and Y-CAT, the tests reflecting episodic-like and spatial working memory processes, respectively. Then, the effects of acute and prolonged (21-day) i.p. administration of a selective 5-HT6R agonist, WAY-181187, and an antagonist, SB-745427, on these deficits induced by MK-801 were studied. In acute experiments, both, the 5-HT6R agonist (3 mg/kg) and the antagonist (1 and 3 mg/kg), prevented the cognitive impairments provoked by MK-801 in NORT. The memory enhancing effect of WAY-181187 was visibly stronger than that of Intepirdine (SB742457), but the difference of means did not reach the statistical significance (F(1, 13) = 1,9383, ns). Both 5-HT6R ligands, when given to animals once, also aided spatial memory task (Y-CAT), significantly improving the alternation performance of rats; WAY-181187 acted significantly at doses of 1 and 3 mg/kg while SB-742457 acted only at a dose of 3 mg/kg. Considering the efficacy of the two compounds given once at the same doses, slight differences can be observed in different memory function model. WAY-181187 showed a stronger effect in NORT at a higher dose than SB-742457 and a lack of activity when administered at a dose of 1 mg/kg. Moreover, DI value of WAY-181187, but not SB-742457, was clearly higher than that of control group, although statistically insignificant (one-way ANOVA followed by Bonferroni’s post hoc test revealed p = 0.08 vs vehicle-treated group). Such result suggests that some additional factors may be involved in the mechanism of pro-memory action of WAY-181187, but on this stage of studies the explanation of this phenomenon is difficult. In the Y-CAT model, the situation was reversed; pro-cognitive effects of both doses of WAY-181187 and a higher dose of SB-742457 were similar in efficacy and a lower dose of SB-742457 was inactive. In both tests, active doses of WAY-181187 and SB-742457 did not change exploratory activity of rats and so it can be assumed that the observed effects were specific.
After chronic treatment with both selective 5-HT6R ligands, a significant improvement in MK-801-disrupted cognitive processes persisted, with a slightly stronger effect of WAY-181187 in NORT. But the favorable action of WAY-181187 and SB-742457 in Y-CAT was not observed any longer. At this stage of research, it is difficult to explain this loss of activity in Y-CAT after chronic administration of the two 5-HT6R ligands, while their beneficial effects in NORT persisted. The beneficial effect of 5-HT6R ligands on memory functions has been repeatedly reported in literature. More consistent results were obtained for 5-HT6R antagonists that were investigated in animal models of cognitive disorders. 5-HT6R antagonists were shown to be effective in paradigms of episodic (NORT) and spatial working memory (mazes or spontaneous alternation tasks), social cognition, and executive functions (set-shifting or reversal learning tasks) and in preventing memory impairments induced by scopolamine, phencyclidine (PCP), MK-801, ketamine, streptozotocin, as well as age-associated impairments (reviewed in Bokare et al. (2018); de Bruin and Kruse (2015); de Jong and Mørk (2017); Fone (2008); Upton et al. (2008)). However, there are only a few reports on SB-742457 activity in animal models of cognition. de Bruin et al. (2011) showed that Intepirdine (SB742457) ameliorated scopolamine-induced deficits in object recognition when administered i.p. acutely at doses of 3 and 10 mg/kg and at a dose of 10 mg/kg given per os (p.o.) it reduced scopolamine-induced deficits in object location task. The same authors reported that SB-742457 (0.63 mg/kg), when administered sub-chronically (for 5 days), attenuated PCP-induced deficits in reversal learning in a two-lever operant chamber task in rats (de Bruin et al., 2013); however, in a similar test performed by Idris et al., SB-742457 was active after acute subcutaneous (s.c.) administration at doses of 2.5 and 5 mg/kg (Idris et al., 2010). Callaghan et al. showed that a 7-day p.o. administration of 3 mg/kg of the compound reversed age-related deficits in middle-aged (13 months) rats in a delayed non-matching-to-sample task (Callaghan et al., 2012). Thus, the findings on SB-742457 activity presented in the present study match the available preclinical data, further enriching the knowledge of its pro-memory potential in rats, especially in a model of episodic memory.[3]

C19H19N3O2S

353.44

353.119

C, 64.57; H, 5.42; N, 11.89; O, 9.05; S, 9.07

607742-69-8

11256720

Light yellow to yellow solid powder

1.3±0.1 g/cm3

608.3±45.0 °C at 760 mmHg

321.7±28.7 °C

0.0±1.7 mmHg at 25°C

1.649

2.1

1

5

3

25

535

0

S(C1C([H])=C([H])C([H])=C([H])C=1[H])(C1=C([H])N=C2C(C([H])=C([H])C([H])=C2N2C([H])([H])C([H])([H])N([H])C([H])([H])C2([H])[H])=C1[H])(=O)=O

JJZFWROHYSMCMU-UHFFFAOYSA-N

InChI=1S/C19H19N3O2S/c23-25(24,16-6-2-1-3-7-16)17-13-15-5-4-8-18(19(15)21-14-17)22-11-9-20-10-12-22/h1-8,13-14,20H,9-12H2

3-(benzenesulfonyl)-8-piperazin-1-ylquinoline

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)

Solubility in Formulation 1: ≥ 2.5 mg/mL (7.07 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (7.07 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: 2% DMSO , 48% PEG300, 2% Tween 80 and 48% water: 5mg/mL

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 (Please use freshly prepared in vivo formulations for optimal results.)