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A compelling case for the potential utility of vasopressin (AVP) antagonists as a novel therapeutic class for the treatment of stress-related affective illness has emerged based on observations in depressed individuals, findings in animal models of anxiety and depression, and an understanding of changes in hypothalamic-pituitary-adrenal (HPA) axis regulation under chronic stress. The scientific bases for vasopressin antagonists as a pharmacotherapy for anxiety and depression include: 1) the neuroadaptation and dysregulation of HPA function that accompanies chronic stress in affected humans and in animal models of anxiety and depression, 2) recognition that AVP, not corticotrophin releasing factor (CRF), drives HPA function associated with chronic psychological stress, 3) the CNS localization of vasopressin V1a and V1b receptors in limbic system regions involved in HPA regulation and control of social behaviors, and 4) preclinical data showing efficacy in animal models employed as screens for anxiolytic and antidepressant activity. The public health need for new pharmaceutical treatments for stress-related affective illness is well documented. In the United States alone, anxiety and depression affect some 40 million people each year and carry a conservatively estimated annual total economic burden of at least $125 billion. Existing pharmacotherapies for both indications are not uniformly effective and frequently have undesirable side effects. These limitations demonstrate that a new treatment approach through vasopressin receptor antagonism in the CNS may offer significant opportunities for improved outcomes. In this review, the development of compounds in this class since 2005 is considered. The most advanced clinical candidates and newer compounds described in recent patents are presented.

The azetidinone LY307174 (1) was identified as a screening lead for the vasopressin V1a receptor (IC50 45 nM at the human V1a receptor) based on molecular similarity to ketoconazole (2), a known antagonist of the luteinizing hormone releasing hormone receptor. Structure–activity relationships for the series were explored to optimize receptor affinity and pharmacokinetic properties, resulting in compounds with Ki values

Studies in several species of rodents show that arginine vasopressin (AVP) acting through a V1Areceptor facilitates offensive aggression, i.e., the initiation of attacks and bites, whereas serotonin (5-HT) acting through a 5-HT1Breceptor inhibits aggressive responding. One area of the CNS that seems critical for the organization of aggressive behavior is the basolateral hypothalamus, particularly the anterior hypothalamic region. The present studies examine the neuroanatomical and neurochemical interaction between AVP and 5-HT at the level of the anterior hypothalamus (AH) in the control of offensive aggression in Syrian golden hamsters. First, specific V1Aand 5-HT1Bbinding sites in the AH are shown byin vitroreceptor autoradiography. The binding for each neurotransmitter colocalizes with a dense field of immunoreactive AVP and 5-HT fibers and putative terminals. Putative 5-HT synapses on AVP neurons in the area of the AH are identified by double-staining immunocytochemistry and laser scanning confocal microscopy. These morphological data predispose a functional interaction between AVP and 5-HT at the level of the AH. When tested for offensive aggression in a resident/intruder paradigm, resident hamsters treated with fluoxetine, a selective 5-HT reuptake inhibitor, have significantly longer latencies to bite and bite fewer times than vehicle-treated controls. Conversely, AVP microinjections into the AH significantly shorten the latency to bite and increase biting attacks. The action of microinjected AVP to increase offensive aggression is blocked by the pretreatment of hamsters with fluoxetine. These data suggest that 5-HT inhibits fighting, in part, by antagonizing the aggression-promoting action of the AVP system.

Background: Medicinal chemistry traditionally requires the identification of biologically active molecules by synthesizing and screening each purified substrate. Further progress in drug discovery then requires definition of the structure-activity, relationship of the lead compound. More recently, combinatorial chemistry has emerged as a way to examine structure-activity relationships by screening a large mixture of compounds synthesized in a predictably random manner, without the labor-intensive costs of molecular isolation and purification. We set out to use this approach to examine the structural requirements for peptide binding to serotonin and dopamine transporters.Results: We screened a tripeptide cassette library for serotonin and dopamine reuptake inhibition using cloned transporter assay systems. The method has afforded a number of tripeptide pharmacophores with inhibitory IC50 values ranging from 10 μM to < 1 μM in the dopamine and serotonin reuptake systems. The conformation of one of these tripeptides, N-acetyl-d-Trp-t-Phe-d-Lys-CONH2 (which inhibits serotonin uptake with an IC50 of 10 μM) was compared to that of the serotonin uptake inhibitor s-fluoxetine, and was shown to be more similar in conformation to fluoxetine than was an analogous tripeptide containing l-Lys (IC 50 > 50 μM).Conclusions: We have identified five tripeptides with inhibitory IC50 values of < 10 μM in the serotonin reuptake system. One tripeptide was predicted to have pharmacophore features similar to that of fluoxetine, a selective and potent non-peptide serotonin reuptake inhibitor. Our results suggest that tripeptides derived from combinatorial libraries will help to define the important structural elements of pharmacophores.

Arginine vasopressin functions as a neurochemical signal in the brain to affect social behavior. There is an expanding literature from animal and human studies showing that vasopressin, through the vasopressin 1A receptor (V1A), can stimulate aggressive behavior. Using a novel monocylic beta lactam platform, a series of orally active vasopressin V1a antagonists was developed with high affinity for the human receptor. SRX251 was chosen from this series of V1a antagonists to screen for effects on serenic activity in a resident-intruder model of offensive aggression. Resident, male Syrian golden hamsters were given oral doses of SRX251 or intraperitoneal Manning compound, a selective V1a receptor antagonist with reduced brain penetrance, at doses of 0.2 microg, 20 microg, 2 mg/kg or vehicle. When tested 90-120 min later, SRX251, but not Manning compound, caused a significant dose-dependent reduction in offensive aggression toward intruders as measured by latency to bite and number of bites. The reduction in aggression persisted for over 6 h and was no longer present 12 h post treatment. SRX251 did not alter the amount of time the resident investigated the intruder, olfactory communication, general motor activity, or sexual motivation. These data corroborate previous studies showing a role for vasopressin neurotransmission in aggression and suggest that V1a receptor antagonists may be used to treat interpersonal violence co-occurring with such illness as ADHD, autism, bipolar disorder, and substance abuse.

Anandamide (arachidonylethanolamide) is a novel lipid neurotransmitter first isolated from porcine brain which has been shown to be a functional agonist for the cannabinoid CB1 and CB2 receptors. Anandamide has never been isolated from human brain or peripheral tissues and its role in human physiology has not been examined. Anandamide was measured by LC/MS/MS and was found in human and rat hippocampus (and human parahippocampal cortex), striatum, and cerebellum, brain areas known to express high levels of CB1 cannabinoid receptors. Significant levels of anandamide were also found in the thalamus which expresses low levels of CB1 receptors. Anandamide was also found in human and rat spleen which expresses high levels of the CB2 cannabinoid receptor. Small amounts of anandamide were also detected in human heart and rat skin. Only trace quantities were detected in pooled human serum, plasma, and CSF. The distribution of anandamide in human brain and spleen supports its potential role as an endogenous agonist in central and peripheral tissues. The low levels found in serum, plasma, and CSF suggest that it is metabolized in tissues where it is synthesized, and that its action is probably not hormonal in nature.

Local delivery of serotonin (5-HT) produces a rapid edematous response in soft tissues via increased fluid extravasation which is prevented by 5-HT 2 antagonists such as ketanserin or mianserin. Here we report the effects of a new class of aminoguanidine 5-HT 2 antagonists, with relative selectivity for 5-HT 2A receptors which are potent inhibitors of 5-HT-induced paw edema in the rat. Radioligand binding studies with 125 I DOI on human 5-HT 2A and 5-HT 2C receptors and with 3 H-5-HT on human 5-HT 2B receptors demonstrated that, LY314228, and LY320954 displayed some selectivity for the 5-HT 2A receptor. When compared to binding at other 5-HT 2 receptor subtypes, LY314228 had an 18.6-fold greater affinity for the 5-HT 2A site over the 5-HT 2B site, and 2.6 fold greater at the5-HT 2C site. LY320954 displayed similar preference for 5-HT 2A sites. Both compounds also inhibited 5-HT-induced paw swelling in rats, with ED 50 's of 6.4 and 4.8 mg/kg (for LY314228 and LY320954, respectively). These studies offer evidence for a novel class of pharmacophores for the 5-HT 2 receptor family which show greater relative affinities for the 5-HT 2A receptor subclass.

A method was developed to induce contraction of immunologically sensitized mouse trachea by antigen (Schultz-Dale reaction). The response was mediated by immunoglobulin (Ig) E antibody directed against either the hapten DNP, the hapten carrier conjugate DNP-keyhole limpet hemocyanin (KLH), or the unmodified carrier KLH. Tracheal contractions were elicited by DNP-KLH, KLH, or DNP-bovine serum albumin (BSA) but not by DNP or BSA alone. This procedure represents a useful index of in vitro anaphylaxis in mouse airway smooth muscle.

Passive in vivo administration of antibody has been shown to enhance as well as dampen specific immune responses upon subsequent injection of antigen (1-3). In addition to modulating specific immune responses, immune complexes have been shown to nonspecifically activate human (4, 5), rabbit (6), and murine (2, 7) lymphocytes. Fc fragments derived from enzymatic cleavage of human immunoglobulin (Ig) (2, 8-11) and aggregated human gamma globulin (AHGG) t (2, 12) have also been shown to induce human and murine bone marrow-derived (B) lymphocytes to proliferate and secrete polyclonal antibody. Moreover, Fc fragments possess the same immunoregulatory potential described for immune complexes in that both humoral (13, 14) and thymus-derived (T) cell-mediated (15, 16) responses are augmented. The underlying feature of lymphocyte activation by immune complexes, Fc fragments, and AHGG is that they all require the carboxyl terminal portion of the Fc region of Ig (17). The active fragment of Fc can be derived by macrophage-dependent enzymatic cleavage of Fc into biologically active 14-19,000 tool wt Fc subfragments (9, 11). The studies in this report demonstrate that a synthetic 23-amino acid peptide homologous to 335-357 in Eu IgGa (18) has the ability to nonspecifically activate lymphocytes and regulate ongoing immune responses.