Enerisant is a histamine H3 receptor antagonist. In H3 receptor binding assay using (R)​-​α-​methyl[3H]​histamine, enerisant showed IC50 of 4.9 nM. Enerisant may be useful for the treatment of Alzheimer's disease, schizophrenia, etc.

JNJ-39758979 is a histamine H4 receptor antagonist which clinical development for asthma and atopic dermatitis was halted during phase II because of the observation of idiosyncratic drug-induced agranulocytosis in two subjects.

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.

GSK-1004723 is a dual histamine H(1) and H(3) receptor antagonist with a long duration of action that has been investigated for the treatment of allergic rhinitis. GSK-1004723 was designed for intranasal administration as a suspension or solution. Clinical trials (phase 1 and 2) showed that GSK-1004723 is well tolerated and demonstrates clinically significant attenuation of symptoms (tested in an environmental allergen challenge chamber). However, attenuation of symptoms was less than seen for treatment with cetirizine (a commonly used over-the-counter antihistamine).

Tagorizine (also known as AL-3264) is a pyridylacrylamidoalkylpiperazine derivative patented by Dainippon Pharmaceutical Co., Ltd as an antiallergic agent. Tagorizine acts as 5-lipoxygenase inhibitor and blocks histamine H1-receptors in isolated guinea pig trachea, inhibits antigen-induced histamine release from isolated rat peritoneal mast cells, and suppress leukotriene production from activated human leukocytes. In preclinical models Tagorizine inhibited the antigen-induced leukotriene production in the abdominal cavity of passively sensitized rats and suppressed the arachidonic acid-induced ear edema in mice.

Efletirizine is histamine H1 receptor antagonist. Restricted to topical use. It was under investigation in Phase III (in Europe) clinical studies for the treatment of allergic rhinitis and chronic idiopathic urticarial. Research was discontinued in 2005 due to limited clinical efficacy and safety data. Efletirizine also reduced ocular itching.