Synthesis and pharmacological evaluation of 11-(1,6-dimethyl-1,2,3,6-tetrahydropyridin-4-yl)-5H-dibenzo[b,e][1,4]diazepines with clozapine-like receptor occupancy at dopamine D1/D2 receptor.

Clozapine-like compound without agranulocytosis risk is need to cure the treatment resistant schizophrenia (TRS). We discovered (S)-3 as Clozapine-like dopamine D2/D1 receptor selectivity and improved reactive metabolites formation profile by the modification of piperazine moiety in Clozapine. The optimization of (S)-3 gave compound 5 to be best compound (approximately 10-fold stronger affinity for D2/D1 receptor and similar D2/D1 selectivity ratio with Clozapine). Clozapine-like D2/D1 receptor occupancy profile was proved by in vivo evaluation. In addition, the reactive metabolites derived agranulocytosis risk of compound 5 was considered to be lower than Clozapine. The pharmacology detail of compound 5 is being investigated to develop it for TRS treatment.

Translating the N-methyl-D-aspartate receptor antagonist model of schizophrenia to treatments for cognitive impairment in schizophrenia.

The N-methyl-D-aspartate receptor (NMDAR) antagonists, phencyclidine (PCP), dizocilpine (MK-801), or ketamine, given subchronically (sc) to rodents and primates, produce prolonged deficits in cognitive function, including novel object recognition (NOR), an analog of human declarative memory, one of the cognitive domains impaired in schizophrenia. Atypical antipsychotic drugs (AAPDs) have been reported to improve declarative memory in some patients with schizophrenia, as well as to ameliorate and prevent the NOR deficit in rodents following scNMDAR antagonist treatment. While the efficacy of AAPDs to improve cognitive impairment in schizophrenia (CIS) is limited, at best, and controversial, single doses of all currently available AAPDs so far tested transiently restore NOR in rodents following scNMDAR antagonist treatment. Typical antipsychotic drugs (APDs), e.g. haloperidol and perphenazine, are ineffective in this rodent model, and may be less effective as treatments of some domains of CIS. Serotonergic mechanisms, including, but not limited to serotonin (5-HT)2A and 5-HT7 antagonism, 5-HT(1A), and GABA(A) agonism, contribute to the efficacy of the AAPDs in the scNMDAR antagonist rodent models, which are relevant to the loss of GABA interneuron/hyperglutamate hypothesis of the etiology of CIS. The ability of sub-effective doses of the atypical APDs to ameliorate NOR in the scNMDAR-treated rodents can be restored by the addition of a sub-effective dose of the 5-HT(1A) partial agonist, tandospirone, or the 5-HT7 antagonist, SB269970. The mGluR2/3 agonist, LY379268, which itself is unable to restore NOR in the scNMDAR-treated rodents, can also restore NOR when given with lurasidone, an AAPD. Enhancing cortical and hippocampal dopamine and acetylcholine efflux, or both, may contribute to the restoration of NOR by the atypical APDs. Importantly, co-administration of lurasidone, tandospirone, or SB269970, with PCP, to rodents, at doses 5-10 fold greater than those acutely effective to restore NOR following scNMDAR treatment, prevents the effect of scPCP to produce an enduring deficit in NOR. This difference in dosage may be relevant to utilizing AAPDs to prevent the onset of CIS in individuals at high risk for developing schizophrenia. The scNMDAR paradigm may be useful for identifying possible means to treat and prevent CIS.

The novel antipsychotic drug lurasidone enhances N-methyl-D-aspartate receptor-mediated synaptic responses.

N-Methyl-D-aspartate (NMDA) receptor (NMDAR) hypofunction has been postulated to contribute to the cognitive deficit of schizophrenia. In this study, we examined the effect of lurasidone (Latuda; Dainippon Sumitomo Pharma Co. Ltd., Tokyo, Japan), a newly approved atypical antipsychotic drug (APD), on NMDAR synaptic function in rat frontal cortical pyramidal neurons. In vivo administration of lurasidone produced a significant and selective enhancement of NMDAR-mediated synaptic responses and surface expression of NR2A and NR2B subunits. Lurasidone has high affinity for serotonin 5-HT(1A), 5-HT(2A), and 5-HT(7) receptors and dopamine D(2) receptors. In vivo administration of the 5-HT(7) receptor antagonist (2R)-1-[(3-hydroxyphenyl)sulfonyl]-2 -(2-(4-methyl-1-piperidinyl)ethyl)pyrrolidine (SB-269970) mimicked the enhancing effect of lurasidone on NMDAR responses, whereas the D(2) receptor antagonist haloperidol failed to do so. Previous studies have found that short-term administration of lurasidone reverses the cognitive impairment induced by subchronic administration of phencyclidine (PCP), an NMDAR noncompetitive antagonist. In this study, we found that lurasidone, as well as the prototypical atypical APD clozapine, restored NMDAR-mediated synaptic responses to normal levels in the PCP model of schizophrenia. These results suggest that NMDAR is the potential key molecular target of lurasidone, possibility via antagonizing 5-HT(7) receptors, which is consistent with evidence that 5-HT(7) receptor antagonism contributes to cognitive enhancement by atypical APDs in patients with schizophrenia.

Discovery of 3H-imidazo[4,5-c]quinolin-4(5H)-ones as potent and selective dipeptidyl peptidase IV (DPP-4) inhibitors.

In recent years, dipeptidyl peptidase IV inhibitors have been noted as valuable agents for treatment of type 2 diabetes. Herein, we report the discovery of a novel potent DPP-4 inhibitor with 3H-imidazo[4,5-c]quinolin-4(5H)-one as skeleton. After efficient optimization of the lead compound 2a at the 7- and 8-positions using a docking study, we found 28 as a novel DPP-4 inhibitor with excellent selectivity against various DPP-4 homologues. Compound 28 showed strong DPP-4 inhibitory activity compared to marketed DPP-4 inhibitors. We also found that a carboxyl group at the 7-position could interact with the residue of Lys554 to form a salt bridge. Additionally, introduction of a carboxyl group to 7-position led to both activity enhancement and reduced risk for hERG channel inhibition and induced phospholipidosis. In our synthesis of compounds with 7-carboxyl group, we achieved efficient regioselective synthesis using bulky ester in the intramolecular palladium coupling reaction.

2-({6-[(3R)-3-amino-3-methylpiperidine-1-yl]-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydro-5H-pyrrolo[3,2-d]pyrimidine-5-yl}methyl)-4-fluorobenzonitrile (DSR-12727): a potent, orally active dipeptidyl peptidase IV inhibitor without mechanism-based inactivation of CYP3A.

We report on the identification of 2-({6-[(3R)-3-amino-3-methylpiperidine-1-yl]-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydro-5H-pyrrolo[3,2-d]pyrimidine-5-yl}methyl)-4-fluorobenzonitrile (DSR-12727) (7a) as a potent and orally active DPP-4 inhibitor without mechanism-based inactivation of CYP3A. Compound 7a showed good DPP-4 inhibitory activity (IC(50)=1.1 nM), excellent selectivity against related peptidases and other off-targets, good pharmacokinetic and pharmacodynamic profile, great in vivo efficacy in Zucker-fatty rat, and no safety concerns both in vitro and in vivo.

Discovery of new chemotype dipeptidyl peptidase IV inhibitors having (R)-3-amino-3-methyl piperidine as a pharmacophore.

Structures containing the (R)-3-amino-3-methyl piperidine unit as a new pharmacophore moiety have been shown to possess moderate inhibitory activity for DPP-4 with good pharmacokinetics profile. One of these compounds was found to have good oral bioavailability and PK/PD profile in ZF-rat.

Prolonged reversal of the phencyclidine-induced impairment in novel object recognition by a serotonin (5-HT)1A-dependent mechanism.

Many acute treatments transiently reverse the deficit in novel object recognition (NOR) produced by subchronic treatment with the N-methyl-d-aspartate receptor non-competitive antagonist, phencyclidine (PCP), in rodents. Treatments which restore NOR for prolonged periods after subchronic PCP treatment may have greater relevance for treating the cognitive impairment in schizophrenia than those which restore NOR transiently. We examined the ability of post-PCP subchronic lurasidone, an atypical APD with potent serotonin (5-HT)1A partial agonism and subchronic tandospirone, a selective 5-HT1A partial agonist, to enable prolonged reversal of the subchronic PCP-induced NOR deficit. Rats treated with subchronic PCP (2mg/kg, twice daily for 7 days) or vehicle, followed by a 7day washout period were subsequently administered lurasidone or tandospirone twice daily for 7 days (day 15-21), and tested for NOR weekly for up to two additional weeks. Subchronic lurasidone (1, but not 0.1mg/kg) or tandospirone (5, but not 0.6mg/kg) significantly reversed the PCP-induced NOR deficit at 24h and 7days after the last injection, respectively. The effect of lurasidone persisted for one more week (day 36, 14 days after the last lurasidone dose), while tandospirone-treated rats were able to perform NOR at 7, but not 14, days after the last tandospirone dose. Co-administration of WAY100635 (0.6mg/kg), a 5-HT1A antagonist, with lurasidone, blocked the ability of lurasidone to restore NOR, suggesting that 5-HT1A receptor stimulation is necessary for lurasidone to reverse the effects of PCP. The role of dopamine, GABA and the MAPK/ERK signalling pathway in the persistent, but not indefinite, restoration of NOR is discussed.

Combined serotonin (5-HT)1A agonism, 5-HT(2A) and dopamine D2 receptor antagonism reproduces atypical antipsychotic drug effects on phencyclidine-impaired novel object recognition in rats.

Subchronic administration of an N-methyl-D-aspartate receptor (NMDAR) antagonist, e.g. phencyclidine (PCP), produces prolonged impairment of novel object recognition (NOR), suggesting they constitute a hypoglutamate-based model of cognitive impairment in schizophrenia (CIS). Acute administration of atypical, e.g. lurasidone, but not typical antipsychotic drugs (APDs), e.g. haloperidol, are able to restore NOR following PCP (acute reversal model). Furthermore, atypical APDs, when co-administered with PCP, have been shown to prevent development of NOR deficits (prevention model). Most atypical, but not typical APDs, are more potent 5-HT(2A) receptor inverse agonists than dopamine (DA) D2 antagonists, and have been shown to enhance cortical and hippocampal efflux and to be direct or indirect 5-HT(1A) agonists in vivo. To further clarify the importance of these actions to the restoration of NOR by atypical APDs, sub-effective or non-effective doses of combinations of the 5-HT(1A) partial agonist (tandospirone), the 5-HT(2A) inverse agonist (pimavanserin), or the D2 antagonist (haloperidol), as well as the combination of all three agents, were studied in the acute reversal and prevention PCP models of CIS. Only the combination of all three agents restored NOR and prevented the development of PCP-induced deficit. Thus, this triple combination of 5-HT(1A) agonism, 5-HT(2A) antagonism/inverse agonism, and D2 antagonism is able to mimic the ability of atypical APDs to prevent or ameliorate the PCP-induced NOR deficit, possibly by stimulating signaling cascades from D1 and 5-HT(1A) receptor stimulation, modulated by D2 and 5-HT(2A) receptor antagonism.

D(1) receptor agonists reverse the subchronic phencyclidine (PCP)-induced novel object recognition (NOR) deficit in female rats.

Development of dopamine (DA) D(1) receptor agonists is a priority to improve cognitive impairment in schizophrenia (CIS). This study examined the dose-response relationship of the selective D(1) agonist, SKF38393 (0.5-40 mg/kg), to reverse the deficit in novel object recognition (NOR), an analog of declarative memory in man, produced by subchronic phencyclidine (PCP), an N-methyl-D-aspartate (NMDA) receptor non-competitive antagonist, and the ability of the D(1) antagonists, SCH23390 (0.05 mg/kg) and SKF83566 (0.15 mg/kg), to impair NOR in normal Long-Evans female rats. We also examined the ability of tandospirone, a serotonin (5-HT)(1A) receptor partial agonist, and LY341495, a mGluR2/3 receptor antagonist, to potentiate or block the effects of SKF38393 on NOR, respectively. SKF38393 reversed the persistent NOR deficit produced by subchronic PCP; the dose-response curve for SKF38393 was an inverted U-shape, with the peak effect at 6 mg/kg. SKF83566 and SCH23390 impaired NOR in normal rats. Co-administration of sub-effective doses of SKF38393 (0.25 mg/kg) and tandospirone (0.2 mg/kg) improved the PCP-induced NOR deficit, while LY341495 (1 mg/kg) blocked the ameliorating effect of SKF38393 (6 mg/kg), respectively. These data provide the first evidence that the reversal of the PCP-induced NOR deficit by D(1) agonism has an inverted U-shaped dose-response curve and that 5-HT(1A) and mGluR2/3 receptor signalling facilitates the efficacy of D(1) agonism to improve these deficits. These data suggest that although D(1) agonists may be useful to improve CIS, these agents, particularly higher doses, may also worsen cognitive function in some patients, because of an inverted U-shaped dose response curve.

The role of 5-HT7 receptor antagonism in the amelioration of MK-801-induced learning and memory deficits by the novel atypical antipsychotic drug lurasidone.

Lurasidone is a novel atypical antipsychotic with high affinity for dopamine D2, serotonin 5-HT7 and 5-HT2A receptors. We previously reported that lurasidone and the selective 5-HT7 receptor antagonist, SB-656104-A improved learning and memory deficits induced by MK-801, an N-methyl-d-aspartate (NMDA) receptor antagonist, in the rat passive avoidance test. In this study, we first examined the role of the 5-HT7 receptor antagonistic activity of lurasidone in its pro-cognitive effect to ameliorate MK-801-induced deficits in the rat passive avoidance test. The 5-HT7 receptor agonist, AS19, (2S)-(+)-5-(1,3,5-trimethylpyrazol-4-yl)-2-(dimethylamino) tetralin, (3 mg/kg, s.c.) completely blocked the attenuating effects of lurasidone (3 mg/kg, p.o.), highlighting the importance of 5-HT7 receptor antagonism in the pro-cognitive effect of lurasidone. AS19 (3 mg/kg, s.c.) also blocked the ameliorating effect of SB-656104-A (10 mg/kg, i.p.) in the same experimental paradigm. To further extend our observation, we next tested whether 5-HT7 receptor antagonism still led to the amelioration of MK-801-induced deficits when combined with D2 and 5-HT2A receptor antagonists, and found that SB-656104-A (10 mg/kg, i.p.) significantly ameliorated MK-801-induced deficits even in the presence of the D2 receptor antagonist raclopride (0.1 mg/kg, s.c.) and 5-HT2A receptor antagonist ketanserin (1 mg/kg, s.c.). Taken together, these results suggest that the 5-HT7 receptor antagonistic activity of lurasidone plays an important role in its effectiveness against MK-801-induced deficits, and may contribute to its pharmacological actions in patients with schizophrenia.

5-HT1A and 5-HT7 receptors contribute to lurasidone-induced dopamine efflux.

Lurasidone is a novel, atypical antipsychotic drug with serotonin [5-hydroxytryptamine (5-HT)]2A, 5-HT7, dopamine (DA) D2 antagonist, and 5-HT1A receptor partial agonist properties. The ability of lurasidone to reverse the effects of subchronic administration phencyclidine, to impair novel object recognition in rats, an animal model of cognitive impairment in schizophrenia, is dependent, in part, on its 5-HT1A agonist and 5-HT7 receptor antagonist properties. We tested whether 5-HT1A partial agonism or 5-HT7 antagonism, or both, contributed to the ability of lurasidone to enhance cortical and hippocampal DA efflux, which may be related to its ability to improve cognition. Here, we report that lurasidone, 0.25 and 0.5, but not 0.1 mg/kg, subcutaneously, significantly increased DA efflux in the prefrontal cortex and hippocampus in a dose-dependent manner. Lurasidone, 0.5 mg/kg, also produced a smaller increase in DA efflux in the nucleus accumbens. Pretreatment with the 5-HT1A receptor antagonist, WAY100635 (0.2 mg/kg, subcutaneously), partially blocked the lurasidone-induced cortical and hippocampal DA efflux. Further, subeffective doses of the 5-HT1A receptor agonist, tandospirone (0.2 mg/kg), or the 5-HT7 antagonist, SB269970 (0.3 mg/kg), potentiated the ability of a subeffective dose of lurasidone (0.1 mg/kg) to increase DA efflux in the prefrontal cortex. These findings suggest that the effects of lurasidone on the prefrontal cortex and hippocampus, DA efflux are dependent, at least partially, on its 5-HT1A agonist and 5-HT7 antagonist properties and may contribute to its efficacy to reverse the effects of subchronic phencyclidine treatment and improve schizophrenia.

Prevention of the phencyclidine-induced impairment in novel object recognition in female rats by co-administration of lurasidone or tandospirone, a 5-HT(1A) partial agonist.

Hypoglutamatergic function may contribute to cognitive impairment in schizophrenia (CIS). Subchronic treatment with the N-methyl-D-aspartate receptor antagonist, phencyclidine (PCP), induces enduring deficits in novel object recognition (NOR) in rodents. Acute treatment with atypical antipsychotic drugs (APDs), which are serotonin (5-HT)(2A)/dopamine D(2) antagonists, but not typical APDs, eg, haloperidol, reverses the PCP-induced NOR deficit in rats. We have tested the ability of lurasidone, an atypical APD with potent 5-HT(1A) partial agonist properties, tandospirone, a selective 5-HT(1A) partial agonist, haloperidol, a D(2) antagonist, and pimavanserin, a 5-HT(2A) inverse agonist, to prevent the development of the PCP-induced NOR deficit. Rats were administered lurasidone (0.1 or 1 mg/kg), tandospirone (5 mg/kg), pimavanserin (3 mg/kg), or haloperidol (1 mg/kg) b.i.d. 30 min before PCP (2 mg/kg, b.i.d.) for 7 days (day1-7), followed by a 7-day washout (day 8-14). Subchronic treatment with PCP induced an enduring NOR deficit. Lurasidone (1 mg/kg) but not 0.1 mg/kg, which is effective to acutely reverse the deficit due to subchronic PCP, or tandospirone, but not pimavanserin or haloperidol, significantly prevented the PCP-induced NOR deficit on day 15. The ability of lurasidone co-treatment to prevent the PCP-induced NOR deficit was enduring and still present at day 22. The preventive effect of lurasidone was blocked by WAY100635, a selective 5-HT(1A) antagonists, further evidence for the importance of 5-HT(1A) receptor stimulation in the NOR deficit produced by subchronic PCP. Further study is needed to determine whether these results concerning mechanism and dosage can be the basis for prevention of the development of CIS in at risk populations.

Interaction of mGlu2/3 agonism with clozapine and lurasidone to restore novel object recognition in subchronic phencyclidine-treated rats.

RATIONALE: Subchronic administration to rodents of the N-methyl-D-aspartate non-competitive antagonist, phencyclidine (PCP), impairs novel object recognition (NOR). Atypical antipsychotic drugs (APDs) reverse the effects of subchronic PCP on NOR. The effect of metabotropic glutamate2/3 receptor (mGlu2/3) agonists upon NOR is unknown. OBJECTIVES AND METHODS: We tested the hypotheses that the mGlu2/3 agonist, LY379268, by itself, or in combination with APDs or pimavanserin, a 5-HT(2A) inverse agonist, would reverse the deficit in NOR induced by subchronic treatment with PCP (2 mg/kg, b.i.d., for 7 days). RESULTS: The mGlu2/3 agonist LY379268 (1 or 3 mg/kg) did not attenuate the PCP-induced NOR deficit. However, together with sub-effective dose of the atypical APDs, clozapine (0.1 mg/kg) or lurasidone (0.03 mg/kg), but not the typical APD, haloperidol (0.1 mg/kg), or pimavanserin (3 mg/kg), LY379268, 1 mg/kg, significantly reversed the PCP-induced NOR deficit. Moreover, the effect of clozapine was blocked by the mGlu2/3 antagonist, LY341495 (1 mg/kg). CONCLUSIONS: These results indicate that mGlu2/3 agonism can potentiate the ability of atypical, but not typical APDs, to ameliorate the effect of subchronic PCP on NOR, that mGlu2/3 agonism may contribute to the ability of atypical APDs to acutely reverse the effect of subchronic PCP on NOR, but that by itself, mGlu2/3 agonism, is ineffective in this model of cognitive impairment in schizophrenia. These results suggest that mGlu2/3 receptor agonism should be investigated as an adjunctive treatment of cognitive impairment in schizophrenia rather than as monotherapy, which may be effective for control of psychosis, but not for cognitive impairment.

The role of serotonin in the NMDA receptor antagonist models of psychosis and cognitive impairment.

OBJECTIVE: To review the evidence that agents which preferentially affect serotonin (5-HT) attenuate the ability of N-methyl-D-aspartate (NMDA) receptor non-competitive antagonists (NMDA-RA), e.g., phencyclidine (PCP), dizocilpine (MK-801), and ketamine, to stimulate locomotor activity (LA), and to impair novel object recognition (NOR). RATIONALE: NMDA-RA-induced increased LA and impairment of NOR are widely used models of the pathophysiology of schizophrenia, the mechanism of action of antipsychotic drugs (APDs), and the identification of novel treatments. Serotonin (5-HT) plays an important role in attenuating these effects of NMDA-RA. RESULTS: Selective 5-HT(2A) inverse agonists, e.g., M100907 and ACP-103, and atypical APDs, which are more potent 5-HT(2A) than D(2) antagonists, e.g., clozapine and lurasidone, are more effective than selective D(2) receptor antagonists to attenuate NMDA-RA-induced increased LA. 5-HT(2A) inverse agonists alone are not effective to improve NMDA-RA-impaired NOR, but augment the effects of atypical, but not typical APDs, to improve NOR. The 5-HT(1A) receptor partial agonist tandospirone alone and the 5-HT(1A) agonist effects of atypical APDs may substitute for, or contribute to, the effects of D(2) and 5-HT(2A) receptor antagonism to reverse the NMDA-RA impairment in NOR. 5-HT(6) and 5-HT(7) receptor antagonists may also attenuate these NMDA-RA-induced behaviors. 5-HT(2C) receptor inverse agonist, but not neutral antagonists, block NOR in naïve rats and the effects of atypical APDs to restore NOR in PCP-treated rats, suggesting the importance of the constitutive activity of 5-HT(2C) receptors in NOR. CONCLUSIONS: Multiple 5-HT receptors contribute to effective treatments to reverse adverse effects of NMDA-RA which model psychosis and cognitive impairment.

pH-dependent translocation of alpha-tocopherol transfer protein (alpha-TTP) between hepatic cytosol and late endosomes.

BACKGROUND: alpha-Tocopherol transfer protein (alpha-TTP), a member of the Sec14 protein family, plays an important role in transporting alpha-tocopherol, a major lipid-soluble anti-oxidant, in the cytosolic compartment of hepatocytes and is known as a product of the causative gene for familial isolated vitamin E deficiency. It has been shown that the secretion of hepatocyte alpha-tocopherol taken up with plasma lipoproteins is facilitated by alpha-TTP. To explore the mechanism of alpha-TTP mediated alpha-tocopherol secretion, we investigated drugs which may affect this secretion. RESULTS: We found that, in a hepatocyte cell culture system, intracellular alpha-tocopherol transport is impaired by chloroquine, an agent known for its function of elevating the pH in acidic compartments. Under chloroquine treatment, the diffuse cytosolic distribution of alpha-TTP changes to a punctate pattern. Double-staining experiments with endocytosis markers revealed that alpha-TTP accumulates transiently on the cytoplasmic surface of late endosomal membranes. This phenomenon is specific for hepatoma cell lines or primarily cultured hepatocytes. Other members of the Sec14 family, such as cellular retinaldehyde-binding protein (CRALBP) and supernatant protein factor (SPF), do not show this accumulation. Furthermore, we elucidate that the obligatory amino acid sequence for this function is located between amino acids 21 and 50, upstream of the N-terminal end of the lipid-binding domain. CONCLUSION: We hypothesize that a liver-specific target molecule for alpha-TTP exists on the late endosomal membrane surface. This transient binding may explain the mechanism of how alpha-tocopherol is transferred from late endosomes to cytosolic alpha-TTP.