Mapinastine (E 4716) is a selective antagonist of histamine H1 receptors. In animal models, mapinastine exerts antiallergic and anti-asthmatic properties. It demonstrated a lack of central effects. Mapinastine development has been discontinued.

Meglitinide (HB 699) is an antidiabetic compound. Meglitinide is a short-acting insulin secretagogue that targets one of the main defects that characterizes type 2 diabetes: the progressive loss of early phase prandial insulin secretion. It acts in a glucose-dependent manner to close adenosine triphosphate (ATP)-dependent potassium channels on the β-cell membrane, depolarize the β-cell, resulting in the opening of calcium channels, increased calcium influx and insulin secretion.

Napamezole [WIN 51181] is a potent alpha-2 adrenergic receptor antagonist and a selective inhibitor of 5-hydroxytryptamine re-uptake in vitro. Napamezole was at the phase I stage of development with Sanofi Winthrop (formerly known as Sterling Drug before it was purchased by Sanofi) in the USA as a treatment for depression. The alpha adrenergic antagonist activity of napamezole was determined in vitro in rat brain receptor binding assay using [3H]clonidine and [3H]prazosin for alpha-2 and alpha-1 receptors, respectively. The Ki values for napamezole were 28 nM (alpha-2) and 93 nM (alpha-1).

Cinanserin is a 5-hydroxytryptamine receptor antagonist; it shows a low affinity to 5-HT2b binding sites and a 4-to 10-fold lower affinity to 5-HT2c receptor binding sites than for 5-HT2a sites. Nevertheless, at concentrations normally used 5-HT2c receptor blocking effects are still likely. Experiments on animal have shown that intravenous administration of cinanserin significantly reduces systemic burn edema and leukocyte-endothelial interactions.

Butamoxane is aminomethyl-benzodioxane derivative with sympatholytic activity. Butamoxane showes a central action as well as the adrenaline-antagonizing action.

Emicerfont (GW876008) is a nonpeptide vcorticotropin-releasing factor type 1 (CRF1) receptor antagonist. It was in clinical trials for the treatment of anxiety disorders, irritable bowel syndrome and major depressive disorder however development of emicerfont has been discontinued.

Setoperone is and antagonist of the brain serotonin 5-HT2 receptor and particular the 5-HT2A isoform. Setoperone is radiolabeled with the radioisotope fluorine-18 and is used in positron emission tomography (PET) in neuroimaging for the study neuropsychiatric disorders, such as schizophrenia and depression.

Enprofylline is a xanthine derivative that shares theophylline's bronchodilator properties. It can be considered a relatively selective, though not potent adenosine A2B receptors antagonist. Enprofylline is used in asthma, chronic obstructive pulmonary disease, and in the management of cerebrovascular insufficiency, sickle cell disease, and diabetic neuropathy. Long-term enprofylline administration may be associated with the elevation in liver enzyme levels and unpredictable blood levels.

Spiroxatrine is a drug which acts as a selective antagonist at both the 5-HT1A receptor and the α2 adrenergic receptor. Spiroxatrine was identified as a moderately potent but non-selective agonist at the human nociceptin/orphanin FQ receptor, ORL1

Fenobam is a selective and potent metabotropic glutamate (mGlu)5 receptor antagonist with inverse agonist activity. Fenobam was previously investigated as an anxiolytic in a number of phase II studies in the early 1980s. These studies revealed a mixed picture of anxiolytic efficacy, with double blind, placebo controlled trials variously reporting the compound as active or inactive. This discrepancy was not easily reconciled based on patient numbers, dose level, duration of treatment, or outcome measures. The positive effects seen in animal models of fragile X syndrome (FXS) treated with fenobam or other mGluR5 antagonists, the apparent lack of clinically significant adverse effects, and the potential beneficial clinical effects seen in this pilot trial support further study of the compound in adults with FXS.