A 331440 dihydrochloride

A-331440 is described here instead of A-331440 dihydrochloride. A-331440 is an antagonist of non-imidazole histamine H3 receptor with an IC50 value of 22.7 nM for human cortex histamine H3 [1].

Histamine, as a neurotransmitter, is important in homeostasis and physiology. In the CNS, histamine released has the potential to interact with H1, H2, H3 and possibly H4 receptors. All the receptors are G-protein coupled receptors [2].

In HEK 293 cells stably transfected with rat or human histamine H3 receptors, A-331440 was tested for its ability to antagonize increasing calcium mobilization in response to (R)-α-methylhistamine and showed pKb ± S.E.M. values of 7.38 ± 0.10 and 7.37 ± 0.29 for rat histamine H3 and human histamine H3, respectively [1].

In mice, treatment with A-331440 at a dose of 100 mg/kg resulted in piloerection and hypoactivity in the first 2 h, but diminished thereafter. In naive male CD-1 mice, administration with comparable doses of A-331440 i.p. also produced similar data. By day 28, mice treated with A-331440 at the intermediate dose weighed 35.7 ± 0.93 g with an average weight loss of 5.3 ± 0.99 g. The high dose of A-331440 (15 mg/kg, p.o., b.i.d.) produced a marked and sustained weight loss [1].

References:
[1].  Hancock AA, Bennani YL, Bush EN, et al. Antiobesity effects of A-331440, a novel non-imidazole histamine H3 receptor antagonist. European journal of pharmacology, 2004, 487(1): 183-197.
[2].  Hancock AA, Diehl MS, Faghih R, et al. In vitro Optimization of Structure Activity Relationships of Analogues of A-331440 Combining Radioligand Receptor Binding Assays and Micronucleus Assays of Potential Antiobesity Histamine H3 Receptor Antagonists. Basic & clinical pharmacology & toxicology, 2004, 95(3): 144-152.

Antiobesity effects of A-331440, a novel non-imidazole histamine H3 receptor antagonist.[Pubmed:15033391]

Eur J Pharmacol. 2004 Mar 8;487(1-3):183-97.

Histamine affects homeostatic mechanisms, including food and water consumption, by acting on central nervous system (CNS) receptors. Presynaptic histamine H(3) receptors regulate release of histamine and other neurotransmitters, and histamine H(3) receptor antagonists enhance neurotransmitter release. A-331440 [4'-[3-(3(R)-(dimethylamino)-pyrrolidin-1-yl)-propoxy]-biphenyl-4-carbonitrile] is a histamine H(3) receptor antagonist which binds potently and selectively to both human and rat histamine H(3) receptors (K(i)<==25 nM). Mice were stabilized on a high-fat diet (45 kcal % lard) prior to 28-day oral b.i.d. dosing for measurement of obesity-related parameters. A-331440 administered at 0.5 mg/kg had no significant effect on weight, whereas 5 mg/kg decreased weight comparably to dexfenfluramine (10 mg/kg). A-331440 administered at 15 mg/kg reduced weight to a level comparable to mice on the low-fat diet. The two higher doses reduced body fat and the highest dose also normalized an insulin tolerance test. These data show that the histamine H(3) receptor antagonist, A-331440, has potential as an antiobesity agent.

In vitro optimization of structure activity relationships of analogues of A-331440 combining radioligand receptor binding assays and micronucleus assays of potential antiobesity histamine H3 receptor antagonists.[Pubmed:15447739]

Basic Clin Pharmacol Toxicol. 2004 Sep;95(3):144-52.

A-331440 [4'-[3-(3(R)-(dimethylamino)-pyrrolidin-1-yl)-propoxy]-biphenyl-4-carbonitrile], a potent and selective antagonist of histamine H3 receptors, yielded positive results in an in vitro micronucleus assay, predictive of genotoxicity in vivo. Because this compound has highly favourable properties and potential as an antiobesity agent, new compounds of this general chemical class were sought that would retain or improve upon the high potency and selectivity of A-331440 for H3 receptors, but would lack the potential for genotoxicity obtained with that compound. Our working hypothesis was that the biphenyl rings in A-331440 might contribute to interactions with DNA and thereby predispose toward genotoxicity. Toward this end, several analogues were prepared, with substituents introduced onto the biaryl ring to alter the orientation, electronegativity, and polarity of this moiety, and were tested for their radioligand binding potency and selectivity and their propensity to induce genotoxicity in the in vitro micronucleus assay. Using this strategy, novel compounds were discovered that retained or improved upon the potency and selectivity of A-331440 for H3 receptors and were devoid of genotoxicity in vitro. Of these, the simple mono- and di-fluorinated analogues (A-417022 [4'-[3-[(3R)-3-(dimethylamino)-1-pyrrolidinyl]propoxy]-3'-fluoro-1,1'-biphenyl-4- carbonitrile] and A-423579 [4'-[3-[(3R)-3-(dimethylamino)-1-pyrrolidinyl]-propoxy]-3',5'-difluoro-1,1'-biphe nyl-4-carbonitrile], respectively) were found to bind to H3 receptors at least as potently as A-331440, while lacking genotoxicity in the micronucleus assay. The reason of the lack of genotoxicity of the fluorinated analogues is unclear, but is especially noteworthy in light of the general principle that fluorine and hydrogen are very similar in size. Therefore, these fluorinated analogues of A-331440 represented the most potent and potentially safest compounds for further evaluation as antiobesity leads. Preliminary findings with one of these examples, A-417022, in a mouse model of obesity are presented.