m-Chlorophenylpiperazine (meta-chlorophenylpiperazine or mCPP) is a psychoactive substance, which is illegal in many countries but can be found on the black market. It induces endocrine, neurological and psychiatric effects. mCPP is a partial agonist at the 5-HT2C receptor but antagonized the 5-HT2B and 5-HT3 receptors. mCPP is also an active metabolite of the drug trazodone, which is used as an effective antidepressant drug with a broad therapeutic spectrum, including anxiolytic efficacy. It is known, that mCPP induces migraine attacks and that the decrease of food intake induced by the mCPP depends on its ability to act as a serotonin agonist is a brain.

Toreforant (JNJ-38518168) is an orally active, selective histamine H4 receptor antagonist. Toreforant was investigated as an agent for the treatment of active rheumatoid arthritis. While some improvement in rheumatoid arthritis signs/symptoms through week 12 was observed in the phase IIa study, no efficacy was observed with toreforant at lower doses in a subsequent phase IIb study. Toreforant has been tested in clinical studies in patients with asthma and psoriasis. Toreforant failed to provide therapeutic benefit in population of patients with uncontrolled, eosinophilic, persistent asthma. Toreforant efficacy at 30 and 60 mg was greater than placebo but did not meet predefined success criterion in patients with moderate-to-severe psoriasis.

Eticlopride {2S(−)-3-chloro-5-ethyl-N-[(1-ethyl-2-pyrrolidinyl)methyl]-6-hydroxy-2-methoxybenzamide} is an antagonist at dopamine D2 and D3 receptors. It is widely used for in vivo, in vitro, and ex vivo examination of D2/D3 receptors densities and function. Eticlopride exerts antipsychotic activity in animals.

Setastine (Loderix) is a potent antagonist of histamine H1-receptor mediated responses. Setastine inhibits anaphylactic shock in guinea-pigs sensitized by horse serum. No antiserotonin, anticholinergic and antiadrenergic effect of the compound can be detected. Setastine has a long lasting (up to 16 h) antihistamine effect with a good oral effectiveness. It shows no cardiovascular effects in cats. Setastine shows a much weaker CNS depressant activity than clemestine fumarate. In displacement studies (3H-mepyramine) setastine had significantly weaker affinity for the central nervous system (CNS) H1-receptors than clemastine fumarate. It is concluded that setastine is a non-sedative highly active H1-antagonist.

Adoprazine (SVL-313) is a full 5-HT1A receptor agonist and full D2/3 receptor antagonist possessing characteristics of an atypical antipsychotic, representing a potential novel treatment for schizophrenia and bipolar disorder. This drug together with some others, e.g. Mazapertine succinate, PF-217830 was discontinued from clinical trials due to either non-optimal pharmacokinetic properties or insufficient therapeutical efficacy.

Olodanrigan (EMA-401) is an angiotensin II type 2 receptor antagonist. Olodanrigan may act on paracrine/autocrine mechanisms at peripheral nerve terminals, or intracrine mechanisms, to reduce neuropathic pain signalling in AngII/NGF/TRPV1-convergent pathways. Olodanrigan is being developed by Novartis for the treatment of neuropathic pain.

Indantadol (previously known as CHF-3381) is an oral and noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist and reversible monoamine oxidase-A (MAO-A) inhibitor that is being developed by Vernalis plc, under license from Chiesi Farmaceutici SpA, for the potential treatment of neuropathic pain. In preclinical studies, indantadol exhibited neuroprotective effects after kainate-induced seizures and displayed anticonvulsant and antihyperalgesic activity. Indantadol also caused a dose-dependent decrease in exploratory motility. In a human heat-capsaicin-induced pain model, indantadol at a dose of 500 mg effectively reduced the area of secondary hyperalgesia. The tolerability profile of the drug at single doses up to 600 mg and twice-daily doses up to 400 mg in clinical trials was significantly more favorable than for other NMDA antagonists. Most side effects have been observed to be mild, and include dizziness and asthenia. Indantadol was in phase II clinical trials for the treatment of chronic cough and neuropathic pain. However, these studies had been discontinued.

Ipenoxazone (NC 1200) is a muscle relaxant that is under investigation (phase II) for the treatment of Alzheimer's Dementia, Cognition Disorders. It acts as an Ionotropic glutamate receptor antagonist.