D3 Receptor 10.7-11.2 nM (Ki) D2 Receptor 5-HT1D Receptor 5-HT1B Receptor

SB-277011A dihydrochloride has pKis of 8.0, 6.0, <5.2, and 5.9 for D3, D2, 5-HT1B, and 5-HT1D receptors, respectively. It is a strong, selective, brain-penetrant, and orally bioavailable dopamine D3 receptor antagonist that restores ≥100-fold selectivity against these receptors[1].

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Replacement of the 1-naphthyl group of 23 by a 4-quinolinyl group, as in SB-277011/24, maintained D3 receptor affinity and restored ≥100-fold selectivity against the D2, 5-HT1B, and 5-HT1D receptors. Subsequent cross-screening showed 24 to be ≥100-fold selective against a package of 63 other receptors and ion channels. An in vitro functional assay using microphysiometry in CHO cells expressing human cloned dopamine D3 and D2 receptors demonstrated that SB-277011/24 was devoid of agonist-like activity and was a potent and selective antagonist (D3, pKb 8.4; D2, pKb 6.5) [1].

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In vitro radioligand binding properties of YQA14 and NGB2904 on DA receptors [2]
Figure 1 shows the chemical structures of YQA14, NGB-2904 and SB-277011. Table 1 shows the Ki values of YQA14 on D1–D5 receptors expressed on CHO or HEK293 cells, demonstrating that YQA14 has the highest binding affinity for the D3 receptor over other DA receptors, and has two specific binding sites on D3 receptors with Ki-High (0.68 × 10−4 nM) and Ki-Low (2.11 nM). In contrast, NGB2904 has only one high-affinity binding site on D3 receptors with Ki value of 4.36 nM. Given that the Ki values of YQA14 (335.3 nM) and NGB2904 (502.3 nM) on D2 receptors are significantly higher than those on D3 receptors, this suggests that YQA14 may have ~5 000 000-fold and 150-fold higher selectivity, respectively, for D3 over D2 receptors at each binding site. Table 2 shows the Ki values of SB-277011/SB-277011A, NGB2904 and YQA14, demonstrating that YQA14 has similar or higher potency and selectivity than SB-277011A or NGB2904 for D3 over D2 receptors.

The rat SB-277011 hydrochloride has a clean P450 profile, a brain:blood ratio of 3.6:1, an oral bioavailability of 43%, a half-life of 2.0 hours, and a plasma clearance of 19 milliliters per minute/kg. It also has an outstanding pharmacokinetic profile[1]. In rats, quinelorane at 93 mg/kg in the striatum is not reversed by SB-277011 hydrochloride (SB 277011; 3 mg/kg, po), but it is entirely reversed in the nucleus accumbens[1]. In rats, intravenous cocaine self-administration is considerably and dose-dependently reduced by SB-277011 (intraperitoneal injection; 12.5–25 mg/kg) in both low fixed-ratio and progressive-ratio reinforcement scenarios. SB-277011 can considerably reduce both basal and cocaine-enhanced rat locomotion when administered at a dose of 50 mg/kg[2]. SB-277011A (SB 277011; 3 mg/kg, p.o.) totally undoes the effects of quinelorane in the nucleus accumbens in rats, but does not undo the effects of the drug at 93 mg/kg in the striatum[1].

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Using in vivo microdialysis in the rat, the dopamine agonist quinelorane has been shown to reduce dopamine levels in the nucleus accumbens and the striatum. Compound 24/SB-277011 dose dependently reversed the effects of quinelorane in the nucleus accumbens, with complete reversal at a dose of 3 mg/kg po. In contrast, the effects of quinelorane in the striatum were not reversed by 24/SB-277011 at a high dose of 93 mg/kg. The regional selectivity of the effect of 24 on the reversal of the quinelorane-induced reduction in dopamine efflux is in good agreement with the regional distribution of D3 receptors in rat forebrain.
The low level of dopamine D3 receptors in the dorsal striatum and the pituitary gland has led to the hypothesis that selective D3 receptor antagonists would have reduced liability to induce extrapyramidal movement disorders and would not induce hyperprolactinaemia. In agreement with this hypothesis, 24/SB-277011 dosed up to 80 mg/kg po displayed no cataleptic activity in the rat and did not elevate prolactin levels. In contrast, the typical antipsychotic agent haloperidol produced a complete cataleptic response and significantly elevated serum prolactin levels at a dose of 3 mg/kg po.[1]

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Systemic administration of YQA14 (6.25-25 mg/kg) or SB-277011/SB-277011A (12.5-25 mg/kg) significantly and dose-dependently reduced intravenous cocaine self-administration under both low fixed-ratio and progressive-ratio reinforcement conditions in rats, while failing to alter oral sucrose self-administration and locomotor activity, suggesting a selective inhibition of drug reward. However, when the drug dose was increased to 50 mg/kg, YQA14 and SB-277011A/SB-277011 significantly inhibited basal and cocaine-enhanced locomotion in rats. Finally, both D3 antagonists dose-dependently inhibited intravenous cocaine self-administration in wild-type mice, but not in D3 receptor-knockout mice, suggesting that their action is mediated by D3 receptor blockade. These findings suggest that YQA14 has a similar anti-addiction profile as SB-277011/SB-277011A, and deserves further study and development [2].

Radiolig and Binding Assays. [1]
Radioligand binding assays at hD2 and hD3 receptors were carried out using membranes from CHO cells. Membranes (5−15 μg of protein) were incubated with [125I]iodosulpride (0.1 nM) in buffer containing 50 mM Tris-HCl, 120 mM NaCl, 5 mM KCl, 2 mM CaCl2, and 1 mM MgCl2 (pH 7.4) for 30 min at 37 °C in the presence or absence of competing ligands. Nonspecific binding was defined with 0.1 mM iodosulpride. Binding to a wide variety of monoamine receptors was performed as described in ref 20. Radioligand binding assays were also performed on 55 receptors, ion channels, and enzymes.

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In vitro radioligand binding assays [2]
The methods for DA receptor binding were slightly modified from those described in a previous report (Shahid et al. 2009). Stored membranes were thawed and suspended in reaction buffer as described above. The receptor binding assay was carried out in reaction buffer (200 μl) containing 25 μg membrane protein and various concentrations of [3H]spiperone (0.075–4.8 nM) were used to construct saturation binding curves to determine receptor binding activity on transfected cells and an optimal concentration of [3H]spiperone to be used in subsequent YQA14 receptor binding assays. The effects of YQA14 or NGB2904 on [3H]spiperone or [3H]SCH23390 binding to cell membrane were determined in the presence of 0.5 nM [3H]spiperone or 1.0 nM [3H]SCH23390 and varying concentrations of YQA14 (10−16–10−5 M) or NGB2904 (10−10–10−5 M). After 1 hour incubation (at 25°C), the reaction was terminated by filtration through Whatman GF/C filters pre-soaked in 0.3% polyethyleneimine for 30 minutes. The filter was then washed five times with 3 ml of cold 50 mM Tris-HCl. Radioactivity on each filter was measured with a liquid scintillation spectrometer. Nonspecific binding was determined in the presence of 0.5 nM [3H]spiperone and 10 μM haloperidol or 1 nM [3H]SCH23390 and 10 μM (+)-butaclamol. Specific receptor binding was calculated by subtracting nonspecific binding from total ligand binding. The receptor binding data were analyzed using a non-linear regression model (GraphPad Software, San Diego, CA) (Castelli et al. 2001). IC50 values of YQA14 or NGB2904 were determined using the method described by Cheng & Prusoff (1973). Ki value was calculated using the equation Ki = IC50/(1 + [S]/Kd) ([S] – radioligand substrate concentration) (Cheng & Prusoff 1973). All data are presented as mean values of two to three dependent experimental assays.

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[35S]GTPγS-binding assay [2]
Procedures for the [35S]GTPγS binding assay were slightly modified from the methods of Vanhauwe et al. (1999). Briefly, stored membranes were thawed and diluted in reaction buffer (20 mM HEPES, 100 mM NaCl, 3 mM MgCl2, 1 mM EGTA, 0.1 mM dithiothreitol, 1 mM guanosine diphosphate, pH 7.4). Membrane proteins (35 μg) were pre-incubated with unlabeled quinpirole (10−12–10−5 M) in reaction buffer (400 μl, 30°C) containing 3 μM GTP but no [35S]GTPγS for 30 minutes, following which 100 μl 1.0 nM [35S]GTPγS was added. The mixture was incubated for another 30 minutes. Basal [35S]GTPγS binding was measured in the absence of quinpirole. Nonspecific binding was measured in the presence of 0.2 nM [35S]GTPγS and 40 μM unlabeled GTPγS. The intrinsic activity (agonist or antagonist) of YQA14 alone on [35S]GTPγS binding was measured in the absence of quinpirole. The effects of YQA14 on quinpirole-stimulated [35S]GTPγS binding were measured in the presence of varying concentrations of YQA14(10−14–10−5 M), 10 μM quinpirole and 0.2 nM [35S]GTPγS. Reactions were terminated by rapid filtration with Whatman GF/B filters as described above. The filters were then washed with 3 ml of washing buffer (50 mM Tris-HCl, 50 mM NaCl, 5 mM MgCl2-6H2O, pH 7.4, 4°C). The radioactivity on each filter was measured with a scintillation spectrometer. GraphPad Prism software was used to calculate EC50 values of quinpirole-stimulated [35S]GTPγS binding and IC50 values of YQA14 on quinpirole-stimulated [35S]GTPγS binding. To obtain a stable maximal [35S]GTPγS binding to CHO-hD3R cell membranes, we used a high concentration of quinpirole (10 μM) as an agonist. However, such concentrations of quinpirole may also affect YQA14 binding to CHO-hD3R cells. Thus, the original IC50 values of YQA14 measured from the functional response curve with the GraphPad Prism software were corrected or normalized to the corrected IC50 (cIC50) according to the following equation: cI.

Cell Culture. [1]
CHO cells expressing hD2 receptors were grown in 50:50 Dulbecco's modified Eagles Medium (DMEM; without sodium pyruvate, with glucose):Ham's F-12 containing 10% (v/v) foetal bovine serum (FBS). For hD3 CHO, clones the growth medium was DMEM (without sodium pyruvate, with glucose) containing 10% FBS, 100 nM methotrexate, 2 mM glutamine, 500 nM (−)-sulpiride, and 1% (v/v) essential amino acids. Cells were removed from confluent plates by scraping and were harvested by centrifugation (200g, 5 min, room temperature). Following resuspension in 10 mL of fresh culture medium, an aliquot was counted and the cells passaged at 12 500 or 25 000 cells cm2. Cultures between passages 5 and 30 were used for functional studies.

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Determination of Extracellular Acidification Rates in Microphysiometer. [1]
Cells were seeded into 12 mm transwell inserts at 300 000 cells/cup in FBS-containing growth medium. The cells were incubated for 6 h at 37 °C in 95%O2/5%CO2, before changing to FBS and sulpiride-free medium. After a further 16−18h, cups were loaded into the sensor chambers of the Cytosensor microphysiometer. The chambers were perfused with running medium (bicarbonate-free Dulbecco's modified Eagles medium containing 2 mM glutamine and 44 mM NaCl) at a flow rate of 100 μL/min and temperature of 37 °C. Each pump cycle lasted 90 s. The pump was on for the first 60 s and the acidification rate determined between 68 and 88 s. Cells were exposed (4.5 min for hD2, 7.5 min for hD3) to increasing concentrations (at half log unit intervals) of quinpirole at half hourly intervals. For antagonist studies, a control concentration−response curve to quinpirole was conducted, and the cells were then exposed to antagonist for at least 42 min prior to construction of a further quinpirole concentration-effect curve in the presence of antagonist. Each chamber therefore acted as its own control. Drug additions were performed using the Cytosensor autosampler from deep well blocks.

In Vivo Microdialysis. [1]
Male Sprague Dawley rats (250−350 g) were anaesthetized with medetomidine HCl (0.4 mg/kg, sc) and fentanyl (0.45 mg/kg, ip), and a guide cannula (BAS, Congleton, UK) was implanted in either the nucleus accumbens (AP + 2.7 mm from bregma, L + 1.6 mm from midline, V − 5.6 mm from dura), striatum (A/P + 0.0 mm, L + 2.8 mm, V − 3.5 mm), or frontal cortex (A/P + 3.2 mm, L + 2.0 mm, V − 1.2 mm) according to the atlas of Paxinos & Watson. Anaesthesia was reversed with atipamezole HCl (2.5 mg/kg, sc) and nalbuphine HCl (2 mg/kg, sc). Rats were housed singly, and at least 2 weeks were allowed for postoperative recovery. The rats were allowed food and water ad libitum up to approximately 400 g in weight, when their diet was restricted to 20 g/day. On the day of an experiment, rats were anaesthetized with isoflurane to facilitate insertion of the microdialysis probe (BAS Congleton, UK; 4 mm membrane for striatum, 2 mm membrane for nucleus accumbens and cortex) into the guide cannula and allowed to recover for 1 h. Probes were perfused with artificial cerebrospinal fluid (NaCl, 125 mM; KCl, 2.5 mM; MgCl2, 1.18 mM; CaCl2, 1.26 mM; pH 7.4) at a flow rate of 1 μL/min. Perfusate from the first 2 h was discarded and subsequent samples were collected at 1 h intervals for 6 h. Each sample was collected into 10 μL acetic acid (0.3% w/v) to prevent degradation of dopamine.
After the first hourly fraction had been collected, either SB-277011 (0.28−2.8 mg/kg, po; nucleus accumbens) or SB-277011 (93 mg/kg, po for striatum) or vehicle (1% methylcellulose, 2 mL/kg) was administered. Two hours later either quinelorane (30 μg/kg, sc) or vehicle (saline, 1 mL/kg, sc) was administered. Samples were collected for a further 3 h.
Samples were analyzed for dopamine using HPLC-ECD. A Jasco (PU-980) HPLC pump (flow rate 0.3 mL/min) pumped mobile phase (0.07 M KH2PO4, 1 mM octane sulfonic acid, 0.1 mM EDTA, 10% methanol, pH 2.5) through a Symmetry C18 analytical column (3.5 μm, 2.1 × 150 mm plus guard column). Eluates were detected using an ANTAC Decade detector set at a voltage of 0.8 V. The amount of dopamine in the first 1 h collection sample was used as the baseline, and all subsequent values were calculated as a percentage of this for each individual rat. A standard sample was included every six samples to enable quantification and check for reproducibility.

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Catalepsy. [1]
Catalepsy was assessed by positioning rats with their hindpaws on the bench and their forelimbs rested on a 1 cm diameter horizontal bar, 10 cm above the bench. The length of time in this position was recorded to a maximum of 120 s. Vehicle (1% methylcellulose, 2 mL/kg po) or SB-277011 (2.5, 7.9, 25.2 or 78.8 mg/kg po) or haloperidol (2.8 mg/kg po) was injected (2 mL/kg). Catalepsy was assessed 180 and 210 min (for habituation purposes) and 240 min after drug administration. Rats were judged cataleptic and assigned a score of 1 if they maintained an immobile attitude for 30 s or more at the 240 min time point; otherwise, they were given a score of 0. A logistic regression analysis (SAS-RA, version 6.11; SAS Institute Inc.) was used to analyze the data at the 240 min time point. In a separate experiment, vehicle (1% methylcellulose, 2 mL/kg po) or SB-277011 (2.5, 7.9, 25.2 or 78.8 mg/kg po) was injected in a volume of 2 mL/kg, followed 150 min later by saline or haloperidol (1.13 mg/kg ip) in a volume of 1 mL/kg. Catalepsy was assessed 180, 210, and 240 min after SB-277011 administration.

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PlasmaProlactinLevels. [1]
Animals were pretreated with either, haloperidol (3 mg/kg po), SB-277011 (93 mg/kg po) or vehicle (1% methylcellulose, 2 mL/kg po). After 2 h the animals were decapitated and the blood collected into glass vials. Samples were kept at 4 °C overnight, and then the serum was separated and stored at −70 °C until subsequent assay. Serum prolactin was assayed by radioimmunoassay. Serum prolactin measures were transformed (log) prior to analysis by analysis of variance and Dunnett's t-test.

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Multiple-dose cocaine self-administration [2]
To determine whether the behavioral effects of YQA14 or SB-277011A/SB-277011 on cocaine self-administration were dependent on drug (YQA14 or SB-277011/SB-277011A) and cocaine doses, we examined the effects of YQA14 or SB-277011A on cocaine self-administration maintained by a full dose range of cocaine (0.031, 0.0625, 0.125, 0.25, 0.5 and 1.0 mg/kg per infusion) in a single session. The session consisted of five sequential 20-minute components, each preceded by a 20-minute timeout period for changing the cocaine dose. The infusion volumes and durations of each component were identical except that cocaine concentrations for corresponding unit cocaine doses differed. There was a 30-minute extinction period (0 mg/kg cocaine) before each daily cocaine self-administration session. Testing continued until stable cocaine-maintained responding was achieved (i.e. a minimum of 10 mg/kg cocaine infusions per session, with less than 10% variation in total number of cocaine injections for 3 consecutive days, and at least fivefold higher maximal response rates compared with those maintained during extinction). Then, each rat randomly received one of three doses of YQA14 (6.25, 12.5 or 25 mg/kg, i.p.) or vehicle (25% 2-hydroxypropyl-β-cyclodextrin) 20 minutes prior to the test session. Additional rats were used to observe the effects of SB-277011A (12.5 or 25 mg/kg i.p.) on cocaine self-administration using the same procedure as described above. Animals then received an additional 5–7 days of self-administration of cocaine alone until baseline response was re-established prior to testing the next dose of YQA14 or SB-277011A. The order of testing for the various doses of drug or vehicle was counterbalanced.

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Cocaine self-administration under PR reinforcement [2]
After stable cocaine self-administration under FR2 reinforcement was established, subjects were switched to cocaine self-administration (0.5 mg/kg per injection) under PR reinforcement, during which the work requirement (lever presses) needed to receive a single i.v. cocaine infusion was progressively raised within each test session (see details in Richardson & Roberts 1996) according to the following PR series: 1, 2, 4, 6, 9, 12, 15, 20, 25, 32, 40, 50, 62, 77, 95, 118, 145, 178, 219, 268, 328, 402, 492 and 603 until the break-point was reached. The break-point was defined as the maximal workload (i.e. number of lever presses) completed for the last cocaine infusion prior to a 1-hour period during which no infusions were obtained by the animal. Animals were allowed to continue daily sessions of cocaine self-administration under PR reinforcement conditions until day-to-day variability in break-point fell within 1–2 ratio increments for 3 consecutive days. Once a stable break-point was established, subjects were assigned to seven subgroups. Then, each group randomly received vehicle (25% 2-hydroxypropyl-β-cyclodextrin), one of three doses YQA14 (1.00, 6.25 or 12.5 mg/kg, i.p.), or one of three doses of SB-277011/SB-277011A (6, 12 or 25 mg/kg, i.p.) 20 minutes prior to the test session.

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Experiment 3. Oral sucrose self-administration in rats [2]
The procedures for oral sucrose self-administration testing were identical to the procedures used for cocaine self-administration, except for the following minor differences: (1) no surgery was carried out in this experiment; and (2) active lever presses led to delivery of 0.1 ml of 5% sucrose solution into a liquid food tray on the operant chamber wall. The effects of the same doses of YQA14 or SB-277011/SB-277011A on oral sucrose self-administration were evaluated in this group of rats.

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Experiment 4. Locomotion behavior in rats [2]
Before receiving any drug, rats were placed in a locomotor detection chamber for habituation for 1 hour per day for 3 days. Rats were then divided into four groups. Two groups of rats were used to determine whether YAQ14 or SB-277011A alone altered locomotion, whereas two other groups of rats were used to determine whether pre-treatment with YQA14 or SB-277011/SB-277011A altered cocaine-enhanced locomotion. On test days, each rat randomly received vehicle or one of two doses of YQA14 (12.5 or 25 mg/kg, i.p.) or SB-277011/SB-277011A (12.5 or 25 mg/kg, i.p.). Twenty minutes later, the first two groups of rats were placed in the locomotor detection chambers for 2 hours, whereas the other two pre-treatment groups of rats received 10 mg/kg cocaine immediately before they were placed into the locomotion detection chambers. After each test, animals received 2–3 additional days of habituation training (1 hour per day) in the same test chambers before the next dose was tested. The order of testing for various doses of YQA14, SB-277011A or vehicle was counterbalanced. Total distance counts were used to evaluate the effect of YQA14 and SB-277011A on basal and cocaine-enhanced locomotion.

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Cocaine self-administration under FR1 reinforcement [2]
After recovery from surgery, each mouse was placed into a test chamber and allowed to lever-press for i.v. cocaine (1 mg/kg per infusion) delivered in 0.015 ml over 4.2 seconds on an FR1 reinforcement schedule. For the first 3–5 days, all animals received five free cocaine infusions within a 2- to 5-minute time interval at the beginning of each self-administration session to prime the animal for drug-seeking and drug-taking behavior. These five free drug infusions were subtracted from the total number of drug infusions in data analysis. During the 4.2-second injection period, additional responses on the active lever were recorded but did not lead to additional infusions. Each session lasted 3 hours. After 1 week of cocaine self-administration, the cocaine dose was switched from 1 to 0.5 mg/kg per infusion for an additional 1–2 weeks of cocaine self-administration until stable day-to-day self-administration was established, which was defined as ≥ 20 cocaine infusions per session with a steady self-administration pattern for at least 3 consecutive days. Then, each mouse randomly received vehicle (25% 2-hydroxypropyl-β-cyclodextrin solution) or one of two doses of YQA14 (25 or 50 mg/kg, i.p.) or SB-277011/SB-277011A (50 or 100 mg/kg, i.p.) at 20 minutes prior to testing. We chose two to four times higher drug doses in mice than those used in rats based on our pilot preliminary data about the minimal effective doses and the fact that drug metabolism is in general faster in smaller animals (such as mice) than in larger ones (such as rats) (Zhao & Ishizaki 1997; Bun et al. 1999). Thus, higher drug doses are required to produce effective pharmacological effects in mice than in rats. Animals then received an additional 5–7 days of cocaine self-administration until baseline response was re-established prior to testing the next dose of the drug.

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Cocaine self-administration under PR reinforcement [2]
The procedure for PR cocaine self-administration was identical to that used in rats (described above). In brief, mice were initially trained under FR1 reinforcement as outlined above. After stable cocaine self-administration was established, animals were switched from FR1 to PR reinforcement, under which the work requirement (lever presses) to receive a cocaine infusion was progressively raised within each test session (Roberts 1989; Roberts, Loh & Vickers 1989; Rodefer & Carroll 1996). Once a stable break-point was established, subjects randomly received vehicle (25% 2-hydroxypropyl-β-cyclodextrin) or one of two doses of YQA14 (50 or 75 mg/kg, i.p.) or SB-277011/SB-277011A (50 or 100 mg/kg, i.p.) 20 minutes prior to PR cocaine self-administration testing.

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Drugs [2]
SB-277011A/SB-277011 (Trans-N-[4-[2-(6-cyano 1, 2, 3, 4-tetrahydroisoquinolin-2-yl) ethyl] cyclohexyl]-4-quinolinecarboxamide) was dissolved in vehicle, i.e. 25% 2-hydroxypropyl-β-cyclodextrin.

Compound 24 (SB-277011) was shown to have an excellent pharmacokinetic profile in the rat (oral bioavailability 43%, half-life 2.0 h, plasma clearance 19 mL/min/kg) and to be highly brain-penetrant (brain:blood ratio of 3.6:1), with a clean P450 profile. [1]

[1]. Design and synthesis of trans-N-[4-[2-(6-cyano-1,2,3, 4-tetrahydroisoquinolin-2-yl)ethyl]cyclohexyl]-4-quinolinecarboxamide (SB-277011): A potent and selective dopamine D(3) receptor antagonist with high oral bioavailability and CNS penetration in the rat. J Med Chem. 2000 May 4;43(9):1878-85.

[2]. YQA14: a novel dopamine D3 receptor antagonist that inhibits cocaine self-administration in rats and mice, but not in D3 receptor-knockout mice. Addict Biol. 2012 Mar;17(2):259-73.

A selective dopamine D(3) receptor antagonist offers the potential for an effective antipsychotic therapy, free of the serious side effects of currently available drugs. Using clearance and brain penetration studies as a screen, a series of 1,2,3, 4-tetrahydroisoquinolines, exemplified by 13, was identified with high D(3) affinity and selectivity against the D(2) receptor. Following examination of molecular models, the flexible butyl linker present in 13 was replaced by a more conformationally constrained cyclohexylethyl linker, leading to compounds with improved oral bioavailability and selectivity over other receptors. Subsequent optimization of this new series to improve the cytochrome P450 inhibitory profile and CNS penetration gave trans-N-[4-[2-(6-cyano-1, 2,3, 4-tetrahydroisoquinolin-2-yl)ethyl]cyclohexyl]-4-quinolinecarbo xamide (24, SB-277011). This compound is a potent and selective dopamine D(3) receptor antagonist with high oral bioavailability and brain penetration in the rat and represents an excellent new chemical tool for the investigation of the role of the dopamine D(3) receptor in the CNS. [1]

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The dopamine (DA) D3 receptor is posited to be importantly involved in drug reward and addiction, and D3 receptor antagonists have shown extraordinary promise as potential anti-addiction pharmacotherapeutic agents in animal models of drug addiction. SB-277011/SB-277011A is the best characterized D3 receptor antagonist in such models. However, the potential use of SB-277011A in humans is precluded by pharmacokinetic and toxicity problems. We here report a novel D3 receptor antagonist YQA14 that shows similar pharmacological properties as SB-277011A. In vitro receptor binding assays suggest that YQA14 has two binding sites on human cloned D3 receptors with K(i-High) (0.68 × 10(-4) nM) and K(i-Low) (2.11 nM), and displays > 150-fold selectivity for D3 over D2 receptors and > 1000-fold selectivity for D3 over other DA receptors. Systemic administration of YQA14 (6.25-25 mg/kg) or SB-277011A (12.5-25 mg/kg) significantly and dose-dependently reduced intravenous cocaine self-administration under both low fixed-ratio and progressive-ratio reinforcement conditions in rats, while failing to alter oral sucrose self-administration and locomotor activity, suggesting a selective inhibition of drug reward. However, when the drug dose was increased to 50 mg/kg, YQA14 and SB-277011A significantly inhibited basal and cocaine-enhanced locomotion in rats. Finally, both D3 antagonists dose-dependently inhibited intravenous cocaine self-administration in wild-type mice, but not in D3 receptor-knockout mice, suggesting that their action is mediated by D3 receptor blockade. These findings suggest that YQA14 has a similar anti-addiction profile as SB-277011A, and deserves further study and development. [2]

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In conclusion, the present study demonstrates that YQA14 is a novel selective D3 receptor antagonist. It displays similar or higher potency and selectivity than SB-277011/SB-277011A for D3 over D2 and other DA receptors in receptor binding and intracellular signal-coupling assays in vitro, and similar or more potent pharmacological action than SB-277011A in antagonizing cocaine’s action in vivo. Given that YQA14, at doses that inhibit cocaine self-administration, fails to inhibit locomotion and sucrose self-administration, it is suggested that YQA14 may produce fewer unwanted side effects (such as sedation and natural reward suppression) if used for treating cocaine addiction at the human level. Taken together, the present experiments support the conclusion that YQA14 deserves further research as a potential medication for the treatment of cocaine or psychostimulant addiction.[2]

C28H30N4O

438.564

474.218

215804-67-4

SB-277011;215803-78-4;SB-277011 dihydrochloride;1226917-67-4

24845776

Off-white to light yellow solid powder

2

4

5

34

708

0

C1CC(CCC1CCN2CCC3=C(C2)C=CC(=C3)C#N)NC(=O)C4=CC=NC5=CC=CC=C45.Cl

DKPTUMKZXQOJCX-UHFFFAOYSA-N

InChI=1S/C28H30N4O.ClH/c29-18-21-5-8-23-19-32(16-13-22(23)17-21)15-12-20-6-9-24(10-7-20)31-28(33)26-11-14-30-27-4-2-1-3-25(26)27;/h1-5,8,11,14,17,20,24H,6-7,9-10,12-13,15-16,19H2,(H,31,33);1H

N-[4-[2-(6-cyano-3,4-dihydro-1H-isoquinolin-2-yl)ethyl]cyclohexyl]quinoline-4-carboxamide;hydrochloride

SB 277011 Hydrochloride; 215804-67-4; SB-277011 (hydrochloride); SB-277011 hydrochloride; N-[4-[2-(6-cyano-3,4-dihydro-1H-isoquinolin-2-yl)ethyl]cyclohexyl]quinoline-4-carboxamide;hydrochloride;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

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

DMSO: 50 mg/mL (105.26 mM)
H2O: 16.67 mg/mL (35.09 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (4.38 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 20.8 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: ≥ 2.08 mg/mL (4.38 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 20.8 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: ≥ 2.08 mg/mL (4.38 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (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 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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