5-HT1A targeting PARCEST agent DO3AM-MPP with potential for receptor imaging: Synthesis, physico-chemical and MR studies.

Contrast enhancement in MRI using magnetization or saturation transfer techniques promises better sensitivity, and faster acquisition compared to T1 or T2 contrast. This work reports the synthesis and evaluation of 5-HT1A targeted PARACEST MRI contrast agent using 1,4,7,10-tetraazacycloDOdecane-4,7,10-triacetAMide (DO3AM) as the bifunctional chelator, and 5-HT1A-antagonist methoxyphenyl piperazine (MPP) as a targeting unit. The multi-step synthesis led to the MPP conjugated DO3AM with 60% yield. CEST-related physicochemical parameters were evaluated after loading DO3AM-MPP with paramagnetic MRI active lanthanides: Gadolinium (Gd-DO3AM-MPP) and Europium (Eu-DO3AM-MPP). Luminescence lifetime measurements with Eu-DO3AM-MPP and computational DFT studies using Gd-DO3AM-MPP revealed the coordination of one water molecule (q = 1.43) with metal-water distance (rM-H2O) of 2.7 Å and water residence time (τm) of 0.23 ms. The dissociation constant of Kd 62 ± 0.02 pM as evaluated from fluorescence quenching of 5-HT1A (protein) and docking score of -4.81 in theoretical evaluation reflect the binding potential of the complex Gd-DO3AM-MPP with the receptor 5-HT1A. Insights of the docked pose reflect the importance of NH2 (amide) and aromatic ring in Gd-DO3AM-MPP while interacting with Ser 374 and Phe 370 in the antagonist binding pocket of 5-HT1A. Gd-DO3AM-MPP shows longitudinal relaxivity 5.85 mM-1s-1 with a water residence lifetime of 0.93 ms in hippocampal homogenate containing 5-HT1A. The potentiometric titration of DO3AM-MPP showed strong selectivity for Gd3+ over physiological metal ions such as Zn2+ and Cu2+. The in vitro and in vivo studies confirmed the minimal cytotoxicity and presential binding of Gd-DO3AM-MPP with 5-HT1A receptor in the hippocampus region of the mice. Summarizing, the complex Gd-DO3AM-MPP can have a potential for CEST imaging of 5-HT1A receptors.

6-Acetyl-5-hydroxy-4,7-dimethylcoumarin derivatives: Design, synthesis, modeling studies, 5-HT1A, 5-HT2A and D2 receptors affinity.

Molecular docking studies using appropriate 5-HT1A, 5-HT2A and D2 receptors models were used to design sixteen new 5-hydroxycoumarin derivatives with piperazine moiety (3-18). The microwave radiation have been used to synthesize them and their structures have been confirmed using mass spectrometry, 1H and 13C NMR. All newly prepared derivatives were evaluated for their 5-HT1A, 5-HT2A and D2 receptor affinity. Seven of the synthesized derivatives showed very high affinities to 5-HT1A receptor (3-4.0 nM, 6-4.0 nM, 7-1.0 nM, 9-6.0 nM, 15-4.3 nM, 16-1.0 nM, 18-3.0 nM) and one of them showed high affinities to 5-HT2A receptor (16-8.0 nM). In the case of the D2 receptor none of the tested derivatives showed high affinity. Compounds 7 and 16 were identified as potent antagonists of the 5-HT1A receptor as shown by the [35S]GTPcS binding assay but they didn't show any antidepressant effect at the single dose tested (10 mg/kg) in the tail suspension tests.

Effect of the rigidification of propranolol, a mixed ß-adrenoceptor and 5-HT1AR antagonist.

Propranolol is a popular ß adrenergic antagonists that, together with pindolol, binds also to serotoninergic receptors, namely 5-HT1A/B. In this work the rigidification of the propranolol structure by locking its hydroxyl group within a 1,3-dioxolane ring was investigated. Constrained derivatives of propranolol were synthesized, fully characterized and tested for their affinity at ß-adrenoreceptors and 5-HT1A/B/C receptors using radioligand binding assay. The constrained derivatives were inactive, as expected, at ß1/2/3 adrenergic receptors. Although less expected, these derivatives failed to bind also to 5-HT1A/B/C receptors. The rigidification of propranolol is detrimental for 5-HT1AR activity.

Synthesis and biological evaluation of a series of novel pyridinecarboxamides as potential multi-receptor antipsychotic drugs.

In previous study, a series of benzamides was identified as potent antipsychotic agents. As a continuation of the program to discover novel antipsychotics, herein we reported the evaluation of a series of pyridinecarboxamide derivatives. The most promising compound 7h not only held good activities on dopamine D2, serotonin 5-HT1A and 5-HT2A receptors, but also exhibited low potency for α1A, H1 and 5-HT2C receptors, indicating a low propensity of side effects like orthostatic hypotension and weight gain. Furthermore, 7h exhibited more potent antipsychotic-like effect than aripiprazole in behavioral studies. The preliminary results were promising enough for further research around this scaffold.

5-HT1A and 5-HT2A receptors affinity, docking studies and pharmacological evaluation of a series of 8-acetyl-7-hydroxy-4-methylcoumarin derivatives.

In this work we describe the synthesis, docking studies and biological evaluation of a focused library of novel arylpiperazinyl derivatives of 8-acetyl-7-hydroxy-4-methylcoumarin. The new compounds were screened for their 5-HT1A and 5-HT2A receptor affinity. Among the evaluated compounds, six displayed high affinities to 5-HT1A receptors (4a-0.9 nM, 6a-0.5 nM, 10a-0.6 nM, 3b-0.9 nM, 6b-1.5 nM, 10b-1 nM). Compound 6a and 10a bearing a bromo- or methoxy- substituent in ortho position of the piperazine phenyl ring, were identified as potent antagonists of the 5-HT1A receptors. In the tail suspension test, mice injected with 6a showed a dose-dependent increase in depressive-like behavior that was related to a decrease in locomotor activity. Compound 10a did not decrease or prolong immobility time nor did it affect home cage activity. Molecular docking studies using 5-HT1A and 5-HT2A homology models revealed structural basis of the high affinity of ortho-substituted derivatives and subtle changes in amino acid interactions patterns depending on the length of the alkyl linker.

Structure-5-HT receptor affinity relationship in a new group of 7-arylpiperazynylalkyl and 7-tetrahydroisoquinolinylalkyl derivatives of 8-amino-1,3-dimethyl-1H-purine-2,6(3H,7H)-dione.

In our previous paper, we have reported that some 8-alkoxy-1,3-dimethyl-1H-purine-2,6(3H,7H)-dione derivatives possessed high affinity and displayed agonistic activity for the serotonin 5-HT1A receptor. In order to examine the influence of the substituent in the position 8 of the purine moiety on the affinity for the serotonin 5-HT1A , 5-HT2A , and 5-HT7 receptors, a series of 7-arylpiperazynylalkyl and 7-tetrahydroisoquinolinylalkyl (THIQ) derivatives of 8-amino-1,3-dimethyl-1H-purine-2,6(3H,7H)-dione were synthesized. All the final compounds were investigated in in vitro competition binding experiments for serotonin 5-HT1A , 5-HT2A , and 5-HT7 receptors. The structure-affinity relationships for this group of compounds were discussed. For selected compounds, functional assays for the 5-HT1A receptor were carried out. The results of the assays indicated that these groups of derivatives possessed antagonistic activity for this receptor.

New arylpiperazinylalkyl derivatives of 8-alkoxy-purine-2,6-dione and dihydro[1,3]oxazolo[2,3-f]purinedione targeting the serotonin 5-HT1A /5-HT2A /5-HT7 and dopamine D2 receptors.

To obtain potential antidepressants and/or antipsychotics, a series of new long-chain arylpiperazine derivatives of 8-alkoxy-purine-2,6-dione (10-24) and dihydro[1,3]oxazolo[2,3-f]purinedione (30-34) were synthesized and their serotonin (5-HT1A , 5-HT2A , 5-HT6 , 5-HT7 ) and dopamine (D2 ) receptor affinities were determined. The study allowed the identification of some potent 5-HT1A /5-HT7 /D2 ligands with moderate affinity for 5-HT2A sites. The binding mode of representative compounds from both chemical classes (11 and 31) in the site of 5-HT1A receptor was analyzed in computational studies. In functional in vitro studies, the selected compounds 15 and 16 showed antagonistic properties for the evaluated receptors. 8-Methoxy-7-{4-[4-(2-methoxyphenyl)-piperazin-1-yl]-butyl}-1,3-dimethyl-purine-2,6-dione (15) showed a lack of activity in terms and under the conditions of the forced swim, four plate and amphetamine-induced hyperactivity tests in mice, probably as a result of its high first pass effect in the liver.

Fragment informatics and computational fragment-based drug design: an overview and update.

Fragment-based drug design (FBDD) is a promising approach for the discovery and optimization of lead compounds. Despite its successes, FBDD also faces some internal limitations and challenges. FBDD requires a high quality of target protein and good solubility of fragments. Biophysical techniques for fragment screening necessitate expensive detection equipment and the strategies for evolving fragment hits to leads remain to be improved. Regardless, FBDD is necessary for investigating larger chemical space and can be applied to challenging biological targets. In this scenario, cheminformatics and computational chemistry can be used as alternative approaches that can significantly improve the efficiency and success rate of lead discovery and optimization. Cheminformatics and computational tools assist FBDD in a very flexible manner. Computational FBDD can be used independently or in parallel with experimental FBDD for efficiently generating and optimizing leads. Computational FBDD can also be integrated into each step of experimental FBDD and help to play a synergistic role by maximizing its performance. This review will provide critical analysis of the complementarity between computational and experimental FBDD and highlight recent advances in new algorithms and successful examples of their applications. In particular, fragment-based cheminformatics tools, high-throughput fragment docking, and fragment-based de novo drug design will provide the focus of this review. We will also discuss the advantages and limitations of different methods and the trends in new developments that should inspire future research.

Synthesis and pharmacological evaluation of novel tricyclic[2,1-f]theophylline derivatives.

The multireceptor strategy was implemented to obtain potential antipsychotics and/or antidepressants in a series of long-chain arylpiperazines bearing a tricyclic theophylline fragment. Their binding profile toward monoaminergic receptors (α1, 5-HT(1A), 5-HT(2A), 5-HT6, 5-HT7, D2, D3) was determined as well. The selected compounds 7 and 9 were tested in functional in vivo models and showed, like atypical antipsychotic drugs, presynaptic 5-HT(1A) receptor agonistic and postsynaptic 5-HT(1A), 5-HT(2A), and D2 receptor antagonistic activity.

A new class of 5-HT1A receptor antagonists with procognitive and antidepressant properties.

Aims: 5-HT1A receptor antagonists constitute a potential group of drugs in the treatment of CNS diseases. The aim of this study was to search for new procognitive and antidepressant drugs among amide derivatives of aminoalkanoic acids with 5-HT1A receptor antagonistic properties. Materials & methods: Thirty-three amides were designed and evaluated in silico for their drug-likeness. The synthesized compounds were tested in vitro for their 5-HT1A receptor affinity and functional profile. Moreover, their selectivity over 5-HT7, 5-HT2A and D2 receptors and ability to inhibit phosphodiesterases were evaluated. Results: A selected 5-HT1A receptor antagonist 20 (Ki = 35 nM, Kb = 4.9 nM) showed procognitive and antidepressant activity in vivo. Conclusion: Novel 5-HT1A receptor antagonists were discovered and shown as potential psychotropic drugs.

Novel anilide and benzylamide derivatives of arylpiperazinylalkanoic acids as 5-HT1A/5-HT7 receptor antagonists and phosphodiesterase 4/7 inhibitors with procognitive and antidepressant activity.

A library of novel anilide and benzylamide derivatives of ω-(4-(2-methoxyphenyl)piperazin-1-yl)alkanoic acids as combined 5-HT1A/5-HT7 receptor ligands and phosphodiesterase PDE4B/PDE7A inhibitors was designed using a structure-based drug design approach. The in vitro studies of 33 newly synthesized compounds (7-39) allowed us to identify 22 as the most promising multifunctional 5-HT1A/5-HT7 receptor antagonist (5-HT1AKi = 8 nM, Kb = 0.04 nM; 5-HT7Ki = 451 nM, Kb = 460 nM) with PDE4B/PDE7A inhibitory activity (PDE4B IC50 = 80.4 µM; PDE7A IC50 = 151.3 µM). Compound 22 exerted a very good ability to passively penetrate through biological membranes and a high metabolic stability in vitro. Moreover, the pharmacological evaluation of 22 showed its procognitive and antidepressant properties in rat behavioral tests. Compound 22 at a dose of 3 mg/kg (i.p.) significantly reversed MK-801-induced episodic memory deficits in the novel object recognition test, while at a dose of 10 mg/kg (i.p.) reduced the immobility time of animals (by about 34%) in the forced swimming test. The antidepressant-like effect produced by compound 22 was stronger than that of escitalopram used as a reference drug. This study opens a new perspective in the search for efficacious drugs for the treatment of cognitive and depressive disorders.

4-Phenyl quinoline derivatives as potential serotonin receptor ligands with antiproliferative activity.

Antagonists of signaling receptors are often effective non-toxic therapeutic agents. Over the years, there have been evidences describing the role of serotonin or 5-hydroxytryptamine (5-HT) in development of cancer. Although there are reports on the antiproliferative effects of some serotonin receptor antagonists, there are very few investigations related to understanding their structure-activity relationships. In this study, we report the screening of a library of 4-phenyl quinoline derivatives for their antiproliferative activities. Preliminary docking studies indicated that these ligands had the ability to bind to two of the serotonin receptors, 5-HT1B and 5-HT2B. The results of the in silico experiments were validated by performing in vitro studies on MCF-7 breast cancer cell line. The ethylpiperazine derivatives showed maximum toxicity against this cancer cell line. The compounds inhibited Calcium ion efflux (induced by serotonin) and ERK activation. One of the most active 4-phenyl quinoline derivatives (H3a) also induced apoptosis, thereby, suggesting the use of this scaffold as a potential anticancer drug.

The Versatile 2-Substituted Imidazoline Nucleus as a Structural Motif of Ligands Directed to the Serotonin 5-HT1A Receptor.

The involvement of the serotonin 5-HT1A receptor (5-HT1A -R) in the antidepressant effect of allyphenyline and its analogues indicates that ligands bearing the 2-substituted imidazoline nucleus as a structural motif interact with 5-HT1A -R. Therefore, we examined the 5-HT1A -R profile of several imidazoline molecules endowed with a common scaffold consisting of an aromatic moiety linked to the 2-position of an imidazoline nucleus by a biatomic bridge. Our aim was to discover other ligands targeting 5-HT1A -R and to identify the structural features favoring 5-HT1A -R interaction. Structure-activity relationships, supported by modeling studies, suggested that some structural cliché such as a polar function and a methyl group in the bridge, as well as proper steric hindrance in the aromatic area of the above scaffold, favored 5-HT1A -R recognition and activation. We also highlighted the potent antidepressant-like effect (mouse forced swimming test) of (S)-(+)-19 [(S)-(+)-naphtyline] at very low dose (0.01 mg kg-1 ). This effect was clearly mediated by 5-HT1A , as it was significantly reduced by pretreatment with the 5-HT1A antagonist WAY100635.

Synthesis and evaluation of a series of 3,4,5-trimethoxycinnamic acid derivatives as potential antinarcotic agents.

A series of 3,4,5-trimethoxycinnamic acid derivatives was prepared and evaluated for antinarcotic effects on morphine dependence in mice and binding affinities on serotonergic receptors. The key synthetic strategies involve generation of ketones 6-7, esters 9-12 through condensation reaction, and amides 13-19 via coupling reaction using 1-hydroxybenzotriazole/ethyl(dimethylaminopropryl)carbodiimide system in high yield. We found that the naloxone-induced morphine withdrawal syndrome was significantly suppressed by new synthetic 3,4,5-trimethoxycinnamic acid derivatives (20 mg/kg/day). Most of 3,4,5-trimethoxycinnamic acid derivatives were found to have high affinity to 5-HT(1A) receptor. The naloxone-induced morphine withdrawal syndrome was attenuated by (+)8-OH-DPAT (0.1 mg/kg/day, i.p.), a 5-HT(1A) receptor agonist. In cortical neuronal cells, (+)8-OH-DPAT (1 µM) produced an elevation of the pERK 1/2 expression, and the elevated pERK levels were inhibited by WAY 100635, a 5-HT(1A) receptor-specific antagonist. Interestingly, the pERK levels were increased by the 3,4,5-trimethoxycinnamic acid derivatives and the derivatives-mediated changes in pERK levels were blocked by the WAY 100635. These results suggested that new synthetic 3,4,5-trimethoxycinnamic acid derivatives have a potential antinarcotic effect through acting as a 5-HT(1A) receptor agonist in mice.

Synthesis, biological evaluation, and docking studies of tetrahydrofuran- cyclopentanone- and cyclopentanol-based ligands acting at adrenergic α1- and serotonine 5-HT1A receptors.

A series of aralkylphenoxyethylamine and aralkylmethoxyphenylpiperazine compounds was synthesized and their in vitro pharmacological profile at both 5-HT(1A) receptors and α(1)-adrenoceptor subtypes was measured by binding assay and functional studies. The results showed that the replacement of the 1,3-dioxolane ring by a tetrahydrofuran, cyclopentanone, or cyclopentanol moiety leads to an overall reduction of in vitro affinity at the α(1)-adrenoceptor while both potency and efficacy were increased at the 5-HT(1A) receptor. A significant improvement of 5-HT(1A)/α(1) selectivity was observed in some of the cyclopentanol derivatives synthesized (4acis, 4ccis and trans). Compounds 2a and 4ccis emerged as novel and interesting 5-HT(1A) receptor antagonist (pK(i) = 8.70) and a 5-HT(1A) receptor partial agonist (pK(i) = 9.25, pD(2) = 9.03, E(max) = 47%, 5-HT(1A)/α(1a) = 69), respectively. Docking studies were performed at support of the biological data and to elucidate the molecular basis for 5-HT(1A) agonism/antagonism activity.

New pyridobenzoxazepine derivatives derived from 5-(4-methylpiperazin-1-yl)-8-chloro-pyrido[2,3-b][1,5]benzoxazepine (JL13): chemical synthesis and pharmacological evaluation.

A series of new pyridobenzoxazepine derivatives with various heterocyclic amine side chains were synthesized to explore two main parameters related to the distal basic nitrogen. These compounds were tested for their affinity for dopamine D(2L) and D(4), serotonin 5-HT(1A) and 5-HT(2A), and adrenergic α(2A) receptors in comparison with 5-(4-methylpiperazin-1-yl)-8-chloro-pyrido[2,3-b][1,5]benzoxazepine, JL13 (1), and other diarylazepine derivatives. In terms of multireceptor target strategy, 2 and 5 present the most promising in vitro binding profile. Bulky, polar, and more flexible side chains are not favorable in this context. Compounds 2 and 5 were tested in adult rats to evaluate their long-term effects on dopamine and serotonin receptors density in different brain areas. Similar to 1 and other second-generation antipsychotic drugs, repeated treatment with 2 significantly increased D(1) and D(4) receptors in nucleus accumbens and caudate putamen and D(2) receptors in medial prefrontal cortex and hippocampus, while 5 significantly increased D(2) and D(4) receptors in nucleus accumbens. In addition, 2 increased 5-HT(1A) and decreased 5-HT(2A) receptors in cerebral cortex. In contrast, 5 did not alter levels of any 5-HT receptor subtype in any brain region examined. These results encourage further development of 2 as a novel second-generation antipsychotic agent.

Novel 4-aryl-pyrido[1,2-c]pyrimidines with dual SSRI and 5-HT(1A) activity. part 3.

A number of 4-aryl-5,6,7,8-tetrahydropyrido[1,2-c]pyrimidine with 3-(1,2,3,6-tetrahydro-pyridin-4-yl)-1H-indole or 2-methyl-3-(1,2,3,6-tetrahydro-pyridin-4-yl)-1H-indole residues were synthesized for further investigation of SAR in a group of pyrido[1,2-c]pyrimidine derivatives with dual 5-HT(1A)/SERT activity. Compounds 8a-8p were found to be potent ligands for both 5-HT(1A) and SERT with K(i) ranging from 28,3 to 642 nM and 42,4 nM-1,8 µM, respectively. Moreover compounds 8a, 8b, 8c, 8d, 8e and 8g were found to be selective agonists, while 8i as an antagonist of 5-HT(1A) presynaptic receptors in the inducible hypothermia test in mice.

1,3-Dioxolane-based ligands incorporating a lactam or imide moiety: structure-affinity/activity relationship at alpha1-adrenoceptor subtypes and at 5-HT1A receptors.

A series of 1,3-dioxolane-based compounds incorporating a lactam (2-4) or imide (5-7) moiety was synthesized and the pharmacological profile at alpha(1)-adrenoceptor subtypes and 5-HT(1A) receptor was assessed through binding and functional experiments. Starting from the 2,2-diphenyl-1,3-dioxolane derivative 1, previously shown to be a selective alpha(1a(A))/alpha(1d(D))-adrenoceptor subtype antagonist, over alpha(1b(B)) subtype and 5-HT(1A) receptor, and replacing one phenyl ring with lactam or imide moiety a reduction of alpha(1)/5-HT(1A) selectivity is observed, mainly due to the increase in 5-HT(1A) affinity. In functional experiments lactam derivatives seems to favour 5-HT(1A) receptor antagonism (pKb = 7.20-7.80) and alpha(1B)-adrenoceptor antagonist selectivity (alpha(1B)/alpha(1A) and alpha(1B)/alpha(1D) of about 10-fold). The most interesting of the various imide derivatives is compound 7t, which is a selective alpha(1D)-adrenoceptor antagonist (pKb = 8.1 and alpha(1D)/alpha(1A) and alpha(1D)/alpha(1B) selectivity ratios of 16 and 11 respectively) whereas at 5-HT(1A) receptor it is a potent partial agonist (pD2 = 7.98, E(max) = 60%).]. Given that cis and trans diastereomer pairs for 2-7 are possible, a computational strategy based on molecular docking studies was used to elucidate the atomic details of the 5HT(1A)/agonist and 5HT(1A)/antagonist interaction.