5-HT1A Agonist Activity Research Articles

Emerging trends in antipsychotic and antidepressant drug development: Targeting nonmonoamine receptors and innovative mechanisms.

The domain of psychiatric drug development is currently witnessing a notable transformation, with a paramount emphasis on targeting nonmonoamine receptors and exploring inventive mechanisms of action. This paper presents an overview of the ongoing advancements in antipsychotic and antidepressant drug development. Historically, antipsychotics predominantly targeted dopamine receptors, but there is now an escalating interest in drugs that act on alternative receptors, exemplified by the TAAR1 receptor. One noteworthy candidate is Ulotaront (SEP-363856), an agent acting as a TAAR1 agonist with 5-HT1A agonist activity, demonstrating promising outcomes in the treatment of schizophrenia, devoid of extrapyramidal symptoms or metabolic side-effects. Similarly, MIN-101 (Roluperidone) and KarXT are currently in development, with its focus on addressing the symptoms in schizophrenia. In the domain of antidepressants, novel therapeutic approaches have surfaced, such as Auvelity, a Food and Drug Administration (FDA)-approved NMDA receptor antagonist synergistically combined with Bupropion to enhance its effects. Another notable candidate is Zuranolone, operating as a GABA A receptor-positive allosteric modulator, showcasing efficacy in treating major depressive disorder (MDD) and postpartum depression. Additionally, TAK-653 (NBI-1065845) and MJI821 (Onfasprodil) have emerged as potential antidepressants targeting AMPA receptors and NMDA receptor 2B (NR2B) negative allosteric modulation, respectively. This paper underscores the transformative potential of these novel drug candidates in psychiatric treatment and their ability to address cases that were previously treatment-resistant. By focusing on nonmonoamine receptors and introducing innovative mechanisms, these drugs offer a promising prospect of improved outcomes for individuals suffering from schizophrenia and MDD. Thus, sustained attention and dedication to the development of such drugs are essential to augmenting the therapeutic options available for psychiatric patients.

Review of the Trace Amine-Associated Receptor 1 (TAAR1) Agonist Ulotaront: Part II—Summary of Initial Clinical Efficacy/Safety Results

AbstractIntroductionUlotaront is a trace amine-associated receptor 1 (TAAR1) agonist with serotonin 5-HT1A agonist activity that has received FDA Breakthrough Therapy Designation for the treatment of schizophrenia. Here we summarize ongoing clinical research characterizing the efficacy and safety of ulotaront as a member of the novel trace amine-associated receptor 1 (TAAR1) agonist class.MethodsSummarized are results from a double-blind, placebo-controlled study to evaluate the efficacy and safety of ulotaront (50 mg or 75 mg) in an acute exacerbation of schizophrenia, and a 6-month, open-label follow-up study. Also summarized are post-hoc analyses evaluating negative symptom efficacy, and key safety and adverse event (AE) outcomes.ResultsIn the short-term study, treatment with ulotaront was associated with significant (p<0.001) endpoint improvement in the PANSS total score (effect size [ES]: 0.45), the CGI-Severity score (ES: 0.52) and the Brief Negative Symptom Scale total score (ES: 0.48). The incidence of any AE was lower on ulotaront versus placebo (45.8% vs. 50.4%), and the number needed to harm (NNH) for individual AEs on ulotaront were all >40. Ulotaront was associated with lower risk for antipsychotic class-related AEs (extrapyramidal symptoms, akathisia, somnolence, nausea/vomiting, increased weight/metabolic labs, prolactinemia). The 6-month study demonstrated further improvement, with a completion rate (67%) that was higher than reported for current dopamine D2 antipsychotics.ConclusionsThe emerging profile of ulotaront is characterized by significant improvement in positive and negative symptoms of schizophrenia. The safety and tolerability profile of ulotaront is markedly different with respect to antipsychotic class-related AEs. The benefit-risk profile of ulotaront, as a member of a novel TAAR1 agonist class, is distinguished from antipsychotics by lack of AEs related to D2 and serotonin 5-HT2A receptor blockade.FundingSunovion Pharmaceuticals, Inc., and Otsuka Pharmaceutical Development & Commercialization, Inc.

Review of the TAAR1 Agonist Ulotaront: Part I—From Discovery to Clinic

AbstractIntroductionTrace amine-associated receptors (TAARs) are a family of G-protein-coupled receptors (GPCRs) first identified in 2001. TAAR1 has emerged as a promising therapeutic target due to its ability to modulate monoaminergic and glutamatergic neurotransmission. Ulotaront is a trace amine-associated receptor 1 (TAAR1) agonist with serotonin 5-HT1A agonist activity that has received FDA Breakthrough Therapy Designation for the treatment of schizophrenia. Here we provide a brief review of the discovery of ulotaront and preclinical research suggesting efficacy in schizophrenia, leading to the first clinical trial of ulotaront resulting in FDA Breakthrough Therapy Designation.MethodsUlotaront was discovered through a target-agnostic approach optimized to identify drug candidates that demonstrate an antipsychotic-like profile in vivo but lack D2 and 5-HT2A receptor antagonism. Ulotaront was further characterized by in vitro pharmacology, electrophysiology, behavioral, and imaging studies.ResultsUlotaront demonstrated an antipsychotic-like profile in a high-throughput, phenotypic behavior screening platform, as well as efficacy in preclinical models of schizophrenia, including phencyclidine (PCP)-induced hyperactivity, prepulse inhibition of acoustic startle, and subchronic PCP-induced deficits in social interaction. Although not fully elucidated, ulotaront’s mechanism of action appears to be mediated by agonism at trace amine-associated 1 (TAAR1) and 5-HT1A receptors. This was further corroborated with whole cell patch clamp recordings, demonstrating inhibition of dorsal raphe nucleus (DRN) and ventral tegmental area (VTA) neuronal firing via 5-HT1A and TAAR1 receptors. Furthermore, ulotaront attenuated the ketamine-induced increase in striatal dopamine synthesis capacity, suggesting that it may modulate presynaptic dopamine dysfunction which is hypothesized to contribute to the pathophysiology of schizophrenia.ConclusionsPreclinical studies have identified ulotaront as a TAAR1 agonist with antipsychotic-like activity. Ulotaront’s unique receptor profile led to its designation as a member of the new “-taront” class of TAAR1 agonists, distinct in pharmacology from the D2/5-HT2A class of antipsychotics. A companion poster will summarize the efficacy and safety of ulotaront based on initial clinical trials in schizophrenia.FundingSunovion Pharmaceuticals, Inc., and Otsuka Pharmaceutical Development & Commercialization, Inc.

In Vitro ADME and Preclinical Pharmacokinetics of Ulotaront, a TAAR1/5-HT1A Receptor Agonist for the Treatment of Schizophrenia

PurposeUlotaront (SEP-363856) is a TAAR1 agonist with 5-HT1A agonist activity currently in clinical development for the treatment of schizophrenia. The objectives of the current study were to characterize the in vitro ADME properties, preclinical PK, and to evaluate the DDI potential of ulotaront and its major metabolite SEP-383103.MethodsSolubility, permeability, plasma protein binding, CYP inhibition and induction, transporter inhibition and uptake studies were conducted in vitro. Phenotyping studies were conducted using recombinant human CYPs and FMOs, human liver microsomes and human liver homogenates. Preclinical plasma and brain pharmacokinetics were determined after a single intraperitoneal, intravenous, and oral administration of ulotaront.ResultsUlotaront is a compound of high solubility, high permeability, and low binding to plasma proteins. Ulotaront metabolism is mediated via both NADPH-dependent and NADPH-independent pathways, with CYP2D6 as the major metabolizing enzyme. Ulotaront is an inducer of CYP2B6, and an inhibitor of CYP2D6, OCT1 and OCT2, while SEP-383103 is neither a CYP inducer nor a potent inhibitor of CYPs and human transporters. Ulotaront exhibits rapid absorption, greater than 70% bioavailability, approximately 3.5 L/kg volume of distribution, 1.5-4 h half-life, 12-43 ml/min/kg clearance, and good penetration across the blood–brain barrier in preclinical species.ConclusionsUlotaront has been designated as a BCS1 compound by US FDA. The ability of ulotaront to penetrate the blood–brain barrier for CNS targeting has been demonstrated in mice and rats. The potential for ulotaront and SEP-383103 to act as perpetrators of CYP and transporter-mediated DDIs is predicted to be remote.

Ulotaront, a novel TAAR1 agonist with 5-HT1A agonist activity, lacks abuse liability and attenuates cocaine cue-induced relapse in rats

BackgroundUlotaront (SEP-363856) is a trace amine-associated receptor 1 (TAAR1) agonist with 5-hydroxytryptamine type 1A (5-HT1A) agonist activity that is currently in Phase 3 clinical development for the treatment of schizophrenia. Unlike available antipsychotics, the efficacy of ulotaront is not mediated by blockade of dopamine D2 or serotonin 5-HT2A receptors. In a short-term randomized clinical trial, ulotaront has demonstrated significant efficacy in the treatment of adults with an acute exacerbation of schizophrenia. Given ulotaront’s novel mechanism of action a series of preclinical studies were performed to evaluate its potential abuse liability. MethodsA battery of studies were conducted in male and female rats to evaluate whether ulotaront produces behavioral changes suggestive of human abuse potential. In addition, studies were undertaken to probe the potential for ulotaront to block reinstatement of cocaine-seeking behavior in male rats. ResultsUlotaront was not self-administered by rats trained to self-administer amphetamine, cocaine, or heroin. The subjective qualities of ulotaront were distinct from those produced by amphetamine in a drug discrimination procedure. Ulotaront, and buspirone, a non-scheduled anxiolytic with 5-HT1A agonism, partially generalized to the interoceptive cue elicited by 3, 4-methylenedioxymethamphetamine (MDMA). In addition, ulotaront demonstrated a trend to reduce cocaine-primed induced reinstatement, and dose-dependently reduced cue-reinstated responding. ConclusionThe current results suggest that the TAAR1/5-HT1A agonist ulotaront is not likely to pose a risk for recreational abuse in humans and may have potential therapeutic utility as a treatment of substance use disorders.

Population pharmacokinetic analysis of ulotaront in subjects with schizophrenia.

Ulotaront (SEP‐363856) is a trace amine–associated receptor 1 agonist with 5‐HT1A agonist activity in phase III development for the treatment of schizophrenia. The efficacy of ulotaront is not mediated by blockade of D2 or 5‐HT2A receptors. The aim of this study was to evaluate the population pharmacokinetics (PopPKs) of ulotaront in adult subjects using pooled data from seven phase I studies, one phase II acute study, and one 6‐month extension study. Single and multiple (up to 7 days) oral doses (5–150 mg/day) were studied in both healthy adult subjects (with intensive serial plasma sampling) and adult patients with schizophrenia (some with intensive and some with sparse plasma sampling). Ulotaront was well‐absorbed and exhibited dose‐proportionality in doses ranging from 10 to 100 mg, in mean maximum concentration, area under the concentration‐time curve, and minimum concentration. Moderate interindividual variability was observed in concentration‐time profiles. The estimated median time to maximal concentration was 2.8 h and the median effective half‐life was 7 h, corresponding to an exposure accumulation ratio of 1.10 at steady‐state with daily dosing. There was no indication of time‐dependent changes in PKs after up to 12 weeks of daily dose administration. No clinically meaningful effects on ulotaront PK parameters were observed based on race, age, sex, formulation (capsule or tablet), or clinical status (healthy volunteer vs. patient with schizophrenia); body weight was the only meaningful covariate.

Design, synthesis and evaluation of vilazodone-tacrine hybrids as multitarget-directed ligands against depression with cognitive impairment

Depression, a severe mental disease, is greatly difficult to treat and easy to induce other neuropsychiatric symptoms, the most frequent one is cognitive impairment. In this study, a series of novel vilazodone-tacrine hybrids were designed, synthesized and evaluated as multitarget agents against depression with cognitive impairment. Most compounds exhibited good multitarget activities and appropriate blood-brain barrier permeability. Specifically, compounds 1d and 2a exhibited excellent 5-HT1A agonist activities (1d, EC50 = 0.36 ± 0.08 nM; 2a, EC50 = 0.58 ± 0.14 nM) and 5-HT reuptake inhibitory activities (1d, IC50 = 20.42 ± 6.60 nM; 2a, IC50 = 22.10 ± 5.80 nM). In addition, they showed moderate ChE inhibitory activities (1d, AChE IC50 = 1.72 ± 0.217 μM, BuChE IC50 = 0.34 ± 0.03 μM; 2a, AChE IC50 = 2.36 ± 0.34 μM, BuChE IC50 = 0.10 ± 0.01 μM). Good multitarget activities with goodt blood-brain barrier permeability of 1d and 2a make them good lead compounds for the further study of depression with cognitive impairment.

Antidepressant effect of atypical antipsychotic ziprasidone in albino rats

Background: Depression is a common psychiatric illness but conventional antidepressants are often shows unpredictable response. Pharmacological profiles of many atypical antipsychotics have potential antidepressant effect. Ziprasidone is an atypical antidepressant with 5HT1A agonistic activity and 5HT1D, 5HT2A and D2 receptors antagonistic activity. It’s a potential candidate for evaluating possible antidepressant activity.Methods: Behavioural despair test are widely used for evaluation of potential antidepressant molecule. Tail suspension test is a variant of behavioural despair test. Healthy male Wistar albino rat 18 in number and weighing between of 150-200 grams were divided in 3 groups with 6 rats in each group. Group A was treated with 0.9% Normal Saline, Group B with Fluoxetine and Group C with Ziprasidone for 28 days. Tail suspension test was done on day 0, 7, 14, 21 and 28 days.Results: In comparison to Normal saline both the drugs shows significant antidepressant activity after 28 days of treatment. While antidepressant activity of fluoxetine started to appear from day 7; that of ziprasidone started to appear from 14th day.Conclusions: Ziprasidone can be suitable candidate for clinical trials of Major Depressive Disorders not responding to conventional antidepressant.

Antidepressant effect of Ziprasidone in wistar albino rat by forced swimming test model

Background: Major depressive disorder is a common psychiatric condition and response conventional antidepressant drugs are sometimes unpredictable. Atypical antipsychotics by virtue of their pharmacodynamic profile show potential antidepressant effect. Newer antidepressants as monotherapy or as augmenting agent for current therapy are need of the day. Ziprasidone is an atypical antidepressant drug possesses potential antidepressant activity by virtue of its 5HT1A agonistic activity and 5HT1D, 5HT2A and D2 receptors antagonistic activity. Method : Since its introduction in 1977 the forced swimming test model is still being used for evaluation of potential antidepressant molecule. 30 healthy male Wistar albino rat of 150-200 grams weight were divided in 3 groups with 10 rats in each. Group A was treated with 0.9% Normal Saline, Group B with Fluoxetine and Group C with Ziprasidone for 42 days. Forced Swimming test was done on day 0, 7, 14, 21, 28, 35 and 42 days. Result: After 42 days of treatment both fluoxetine and ziprasidone shows significant antidepressant activity. In comparison to Normal saline both the drugs shows significant antidepressant activity. There is significant deference in antidepressant activity between Fluoxetine and Ziprasidone. Antidepressant activity of Fluoxetine started to appear from day 7 with p vale of 0.000 and of Ziprasidone started to appear from 14 days with p value of 0.000. Conclusion: Ziprasidone as virtue of its diverse pharmacodynamic effect can be suitable candidate for clinical trials of MDD as monotherapy or as an augmenting agent of standard antidepressant therapy.

(6aR)-11-Amino-N-propyl-noraporphine, a new dopamine D2 and serotonin 5-HT1A dual agonist, elicits potent antiparkinsonian action and attenuates levodopa-induced dyskinesia in a 6-OHDA-lesioned rat model of Parkinson's disease

Parkinson's disease (PD) drug therapy remains a challenge. Dual modulation of dopamine and 5-HT receptors has emerged as a promising approach in anti-PD drug development. Taking advantage of the newly discovered aporphine analogue(s), (6aR)-11-amino-N-propyl-noraporphine (SOMCL-171), which exhibited dual D2/5-HT1A receptor agonistic activity, we studied the effects of the compound on levodopa-induced dyskinesia (LID) in a PD animal model. The results demonstrated that SOMCL-171 elicited a potent anti-PD effect in a 6-OHDA-lesioned rat model. Chronic use of SOMCL-171 reduced LID without compromising the antiparkinsonian efficacy. Furthermore, we found that the antidyskinesia effect of SOMCL-171 is associated with its 5-HT1A agonistic activity and the up-regulation of the striatal 5-HT1A receptor. The present data indicated that chronic SOMCL-171 alone produced potent antiparkinsonian effects with weak dyskinesia, compared with that of levodopa. In addition, chronic SOMCL-171 application attenuated the development of levodopa-induced LID at no expense to the antiparkinsonian efficacy. Taken together, our data suggested that dual modulation of D2/5-HT1A receptors may provide a novel approach for drug development in PD and LID.

Two cases of mild serotonin toxicity via 5-hydroxytryptamine 1A receptor stimulation

We propose the possibility of 5-hydroxytryptamine (5-HT)1A receptor involvement in mild serotonin toxicity. A 64-year-old woman who experienced hallucinations was treated with perospirone (8 mg/day). She also complained of depressed mood and was prescribed paroxetine (10 mg/day). She exhibited finger tremors, sweating, coarse shivering, hyperactive knee jerks, vomiting, diarrhea, tachycardia, and psychomotor agitation. After the discontinuation of paroxetine and perospirone, the symptoms disappeared. Another 81-year-old woman, who experienced delusions, was treated with perospirone (8 mg/day). Depressive symptoms appeared and paroxetine (10 mg/day) was added. She exhibited tachycardia, finger tremors, anxiety, agitation, and hyperactive knee jerks. The symptoms disappeared after the cessation of paroxetine and perospirone. Recently, the effectiveness of coadministrating 5-HT1A agonistic psychotropics with selective serotonin reuptake inhibitors (SSRIs) has been reported, and SSRIs with 5-HT1A agonistic activity have been newly approved in the treatment of depression. Perospirone is a serotonin–dopamine antagonist and agonistic on the 5-HT1A receptors. Animal studies have indicated that mild serotonin excess induces low body temperature through 5-HT1A, whereas severe serotonin excess induces high body temperature through 5-HT2A activation. Therefore, it could be hypothesized that mild serotonin excess induces side effects through 5-HT1A, and severe serotonin excess induces lethal side effects with hyperthermia through 5-HT2A. Serotonin toxicity via a low dose of paroxetine that is coadministered with perospirone, which acts agonistically on the 5-HT1A receptor and antagonistically on the 5-HT2A receptor, clearly indicated 5-HT1A receptor involvement in mild serotonin toxicity. Careful measures should be adopted to avoid serotonin toxicity following the combined use of SSRIs and 5-HT1A agonists.

Mechanism of action of the bimodal antidepressant vilazodone: evidence for serotonin1A-receptor-mediated auto-augmentation of extracellular serotonin output

The recently approved antidepressant vilazodone, a serotonin (5-HT)1A receptor partial agonist/selective 5-HT reuptake inhibitor offers new possibilities to study the underlying mechanisms of depression pharmacotherapy and of 5-HT augmenting antidepressants. The role of the 5-HT1A receptor with respect to the regulation of 5-HT output in the mechanism of action of vilazodone. We measured 5-HT levels in two subregions of the rat prefrontal cortex by microdialysis, and 5-hydroxytryptophan (5-HTP) accumulation and tissue 5-HT concentrations ex vivo. Vilazodone-induced maximal 5-HT levels were similar in the medial and the lateral cortex and were up to sixfold higher than those induced by paroxetine, citalopram, or fluoxetine tested in parallel. Depolarization/autoreceptor-insensitive 5-HT release by vilazodone could be excluded. The citalopram (1μM, locally infused)-induced increase of 5-HT was further increased by vilazodone (1mg/kgi.p.), but not by citalopram (10mg/kgi.p.). Unlike fluoxetine, vilazodone-induced extracellular 5-HT output was not potentiated by cotreatment with the 5-HT1A receptor blocker N-[2-(4-{2-methoxyphenyl}-1-piperazinyl)-ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY 100635). In contrast to fluoxetine, vilazodone exhibited intrinsic 5-HT1A agonist activity: it reduced, similar to (±)-8-hydroxy-2-(dipropylamino)-tetralin (8-OH-DPAT), 5-HTP accumulation in striatum and n. raphe of reserpinized rats. Hence, vilazodone's agonistic actions must be 5-HT1A receptor-related since endogenous 5-HT is lacking in the reserpine-depleted animal. In spite of high intrinsic 5-HT1A activity in reserpinized rats, the net effect of vilazodone at release-regulating 5-HT1A autoreceptors must be inhibitory, leading to markedly increased 5-HT output. Another possibility is that vilazodone rapidly desensitizes autoinhibitory 5-HT1A receptors by an unknown mechanism.

Quetiapine and Buspirone Both Elevate Cortical Levels of Noradrenaline and Dopamine In vivo, but Do Not have Synergistic Effects

Decreased cognitive ability is a significant problem in schizophrenia, and it has been proposed that augmentation of antipsychotics with 5HT1A receptor agonists may improve cognitive performance. Clinical studies have been mixed but there have been no studies specifically examining the effects of combining the atypical antipsychotic quetiapine with the 5HT1A receptor partial agonist, buspirone on monoamine release. This is of interest given previous evidence that monoamine release can alter cognition in schizophrenia. In the present study we measured in vivo levels of monoamines in the frontal cortex of Sprague Dawley rats and examined if buspirone (2.5 mg/kg i.p.), altered monoamine release both when given alone and when combined with quetiapine (10 mg/kg i.p.). We found that serotonin levels were not altered by either drug, either alone or in combination. In contrast, both buspirone and quetiapine monotherapy significantly increased release of noradrenaline (112 and 160% respectively) and dopamine (169 and 191% respectively) compared to controls. However, there were no additional increases in in vivo monoamine release when the combination of these drugs were given. One possible explanation for these negative findings could be that the intrinsic 5HT1A agonist activity of quetiapine on its own is of such significance that it is not further enhanced by buspirone. These findings do not support clinical studies combining buspirone and quetiapine, if these were to be used on the basis of enhanced monoamine neurotransmission. These findings may also have implications for the atypical antipsychotic drugs in development which combine dopamine D2 antagonism with 5HT1A partial agonism.

An in vivo pharmacological evaluation of pardoprunox (SLV308) — A novel combined dopamine D2/D3 receptor partial agonist and 5-HT1A receptor agonist with efficacy in experimental models of Parkinson's disease

Partial D(2/3) dopamine (DA) receptor agonists provide a novel approach to the treatment of the motor symptoms of Parkinson's disease (PD) that may avoid common dopaminergic side-effects, including dyskinesia and psychosis. The present study focussed on the in vivo pharmacological and therapeutic characterisation of the novel D(2/3) receptor partial agonist and full 5-HT(1A) receptor agonist pardoprunox (SLV308; 7-[4-methyl-1-piperazinyl]-2(3H)-benzoxazolone monochloride). Pardoprunox induced contralateral turning behaviour in rats with unilateral 6-hydroxydopamine-induced lesions of the substantia nigra pars compacta (SNpc) (MED=0.03mg/kg; po). In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated common marmosets, pardoprunox dose-dependently increased locomotor activity (MED=0.03mg/kg; po) and decreased motor disability (MED=0.03mg/kg; po). The effects of pardoprunox were reversed by the D(2) antagonist sulpiride. In contrast pardoprunox attenuated novelty-induced locomotor activity (MED=0.01mg/kg; po), (+)-amphetamine-induced hyperlocomotion (MED=0.3mg/kg; po) and apomorphine-induced climbing (MED=0.6mg/kg; po) in rodents. Pardoprunox also induced 5-HT(1A) receptor-mediated behaviours, including flat body posture and lower lip retraction (MED=0.3mg/kg; po) and these were reversed by the 5-HT(1A) receptor antagonist WAY100635. Collectively, these findings demonstrate that pardoprunox possesses dopamine D2/3 partial agonist effects, 5-HT1A agonist effects and reduces parkinsonism in animal models. functional DA D(2) receptor partial agonist activity and is effective in experimental models predictive of efficacy in PD. The presence of functional 5-HT(1A) agonist activity might confer anti-dyskinetic activity and have effects that control neuropsychiatric components of PD.

P01-67 - 5HT1A agonist activity and the antidepressant efficacy of Lu AA21004

ObjectivesTo discuss a case study that suggests advantages for the combination of 5HT transporter inhibition plus 5HT1A receptor agonism over transporter inhibition alone.MethodsNaturalistic clinical case study.ResultsThe patient had a documented 10 year history of poor response to SSRI's including s-citalopram. There was no suggestion of placebo response in the past. He responded well to Lu AA21004 and sustained this remission over a period of 9 months. He relapsed after Lu AA21004 was ceased. He recovered and again achieved a sustained remission after being prescribed a combination of s-citalopram plus pindolol.ConclusionsThe addition of pindolol (a 5HT1A receptor partial agonist) to s-citalopram adds 5HT1A receptor agonism to the 5HT transporter inhibition of s-citalopram. This is a similar profile to Lu AA21004. It is noted that Lu AA21004 also has 5HT3 receptor antagonism which is postulated to impact more on side effect profile than antidepressant efficacy. The current case strongly suggests that (in some instances at least) the addition of 5HT1A agonism to 5HT transporter inhibition might convert non-responders to responders and thus offer clinical advantage over transporter inhibition alone.

Parishin C Attenuates Phencyclidine-Induced Schizophrenia-Like Psychosis in Mice: Involvements of 5-HT1A Receptor

Parishin C, a major component of Gastrodia elata BLUME (GE), was purified from GE. Because GE modulates the serotonergic system and the 5-HT1A receptor is an important therapeutic target of schizophrenia, we examined whether parishin C affects phencyclidine-induced abnormal behaviors in mice. Phencyclidine-induced abnormal behaviors were significantly ameliorated by parishin C. These effects were reversed by WAY 100635, a 5-HT1A–receptor antagonist. Consistently, parishin C showed high affinity at 5-HT1A receptor as well as a 5-HT1A–agonist activity in a 8-OH-DPAT–stimulated [ 35S]GTP-γS binding assay. Our results suggest that the antipsychotic effects of parishin C require activation of 5-HT1A receptors.

Design and Synthesis of Piperazinylpyridine Derivatives as Novel 5-HT1A Agonists/5-HT3 Antagonists for the Treatment of Irritable Bowel Syndrome (IBS)

We have prepared a series of piperazinylpyridine derivatives for the treatment of irritable bowel syndrome (IBS). These compounds, which were designed by pharmacophore analysis, bind to both serotonin subtype 1A (5-HT1A) and subtype 3 (5-HT3) receptors. The nitrogen atom of the isoquinoline, a methoxy group and piperazine were essential to the pharmacophore for binding to these receptors. We also synthesized furo- and thienopyridine derivatives according to structure-activity relationship analyses. Compound 17c (TZB-20810) had high affinities to these receptors and exhibited 5-HT1A agonistic activity and 5-HT3 antagonistic activity concurrently, and is a promising drug for further development in the treatment of IBS.

Aripiprazole augmentation in treatment-refractory obsessive–compulsive disorder

Obsessive–compulsive disorder (OCD) responds preferentially to cognitive behavioural therapy (CBT) and to pharmacological treatment such as antidepressant drugs like serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants with a predominantly serotonergic mechanism (Math and Janardhan Reddy 2007). Approximately half of OCD patients treated with an adequate trial of SSRIs fail to fully respond and continue to exhibit significant symptoms (Bloch et al 2006). Aripiprazole is a quinolinone derivative with a high affinity for dopamine D2 and D3 receptors as well as serotonin 5HT1A, 5-HT2A and 5-HT2B receptors. Aripiprazole is an atypical antipsychotic medication that works via partial dopaminergic, 5-HT1A, 5-HT2A and 5-HT2B receptor agonist activity (Rugino and Janvier 2005). We report a case of an OCD patient in whom a treatment regimen with escitalopram was successfully augmented with aripiprazole.

Behavioral effects of dipropyltryptamine in rats: evidence for 5-HT1A and 5-HT2A agonist activity

These studies investigated the role of serotonin-1A (5-HT1A) and 5-HT2A receptors in the behavioral effects of dipropyltryptamine (DPT). Eight rats discriminated 0.56 mg/kg 2,5-dimethoxy-4-methylamphetamine (DOM) from saline and responded under a fixed ratio 5 schedule of food presentation; 12 other rats were used for observational studies. DOM and DPT increased responding on the DOM lever with 3.2 mg/kg DPT producing greater than 95% responding on the DOM lever; this effect of DPT was antagonized by the 5-HT2A receptor antagonist MDL100907. In another study, the 5-HT1A and 5-HT7 receptor agonist 8-OH-DPAT produced lower-lip retraction and, at larger doses, flat body posture; DPT alone produced flat body posture and not lower-lip retraction; MDL100907 alone did not produce either effect. Pretreatment with DPT blocked 8-OH-DPAT-elicited lower-lip retraction, suggesting antagonist activity of DPT at 5-HT1A receptors; however, in the presence of MDL100907 DPT produced not only flat body posture but also lower-lip retraction, suggesting that agonist activity of DPT at 5-HT2A receptors masked agonist activity at 5-HT1A receptors. Lower-lip retraction and flat body posture by DPT in the presence of MDL100907 were attenuated by the 5-HT1A receptor antagonist WAY100635. These findings suggest that DPT has agonist activity at 5-HT1A and 5-HT2A receptors and that effects at 5-HT2A receptors mask effects at 5-HT1A receptors.

Putative antipsychotics with pronounced agonism at serotonin 5-HT1A and partial agonist activity at dopamine D2 receptors disrupt basal PPI of the startle reflex in rats

Prepulse inhibition (PPI) of the startle reflex has been extensively studied because it is disrupted in several psychiatric diseases, most notably schizophrenia. In rats, and to a lesser extent, in humans, PPI can be diminished by dopamine (DA) D(2)/D(3) and serotonin 5-HT(1A) receptor agonists. A novel class of potential antipsychotics (SSR181507, bifeprunox, and SLV313) possess partial agonist/antagonist properties at D(2) receptors and various levels of 5-HT(1A) activation. It thus appeared warranted to assess, in Sprague-Dawley rats, the effects of these antipsychotics on basal PPI. SSR181507, sarizotan, and bifeprunox decreased PPI, with a near-complete abolition at 2.5-10 mg/kg; SLV313 had a significant effect at 0.16 mg/kg only. Co-treatment with the 5-HT(1A) receptor antagonist WAY100,635 (0.63 mg/kg) showed that the 5-HT(1A) agonist activity of SSR181507 was responsible for its effect. By contrast, antipsychotics with low affinity and/or efficacy at 5-HT(1A) receptors, such as aripiprazole (another DA D(2)/D(3) and 5-HT(1A) ligand), and established typical and atypical antipsychotics (haloperidol, clozapine, risperidone, olanzapine, quetiapine, and ziprasidone) had no effect on basal PPI (0.01-2.5 to 2.5-40 mg/kg). The present data demonstrate that some putative antipsychotics with pronounced 5-HT(1A) agonist activity, coupled with partial agonist activity at DA D(2) receptors, markedly diminish PPI of the startle reflex in rats. These data raise the issue of the influence of such compounds on sensorimotor gating in humans.