S-5751, an orally active prostanoid DP receptor antagonist, had potent anti-inflammatory effects in guinea pig and sheep asthma models. S-5751 had been in phase II clinical trials by Shionogi for the treatment of bronchial asthma. However, this study was discontinued in 2006.

SB-273005 is one in a series of orally active nonpeptide vitronectin αvβ3 inhibitors. SB-273005 had been in phase I clinical trials by GlaxoSmithKline for the treatment of postmenopausal osteoporosis and rheumatoid arthritis (RA). However, this research has been discontinued.

RU58841 is a topically active non-steroidal antiandrogen. It demonstrated efficacy in animal models of androgen-dependent skin disorders such as acne and androgenetic alopecia. Under name of PSK 3841 was being developed by ProStrakan. It underwent clinical evaluation for the treatment of androgen-dependent conditions, such as acne and alopecia. Following the conclusion of phase II trials, no further development was reported. Based on this and the fact the compound is not listed on the companies pipeline, development is presumed discontinued.

ABT-491 is highly potent, selective and orally active platelet-activating factor (PAF) receptor antagonist, developed by Abbott Laboratories for allergic rhinitis treatment. ABT-491 is a potent antagonist of responses linked to the PAF receptor at the cellular level, especially platelets and neutrophils. ABT-491 was also effective in blocking platelet activation in blood, indicating that the presence of high concentrations of protein and other serum factors slightly alters the ability of ABT-491 to interact with PAF receptor. ABT-491 effectively antagonizes PAF-induced platelet and neutrophil responses at submicromolar concentrations in vitro and exhibits in vivo efficacy in alleviating PAF-mediated inflammatory and pathological processes in various animals, including guinea pigs, mice, and rats, via either i.v., i.p. or p.o. routes.

Paraxanthine (1,7-dimethylxanthine), a metabolite of caffeine, is a central nervous stimulant and exerts anti-inflammatory effects. Paraxanthine functions as the antagonist of adenosine receptors A1 and A2a and has lower toxicity and lesser anxiogenic effects than caffeine. Also, paraxanthine acts as an inhibitor of nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1) and may have therapeutic potential in pulmonary inflammatory diseases such as COPD. In addition, paraxanthine, and some others metabolites of caffeine differed significantly between advanced-stage non-small cell lung cancer (NSCLC) patients with poor and good survival in both discovery and validation phases. That is why was made a conclusion, that the identified small metabolites, including paraxanthine, may be useful biomarker candidates to help identify patients who may benefit from platinum-based chemotherapy.

L-365,260 is an antagonist of gastrin and brain CCK-B receptor. In vivo, oral administration of L-365,260 antagonized gastrin-stimulated acid secretion. L-365,260 is used as a tool compound to investigate gastrin and brain CCK-B and their role in psysiology and disease. In a double-blind placebo-controlled study L-365,260 did not augment the analgesic effect of morphine in subjects with chronic neuropathic pain. Preclinical studies demonstrated modes activity of L-365,260 in models of anxiety and ulcers.

E-3174 is an active carboxylic acid metabolite of losartan and is an antagonist of the angiotensin II receptor, type 1 (AT1). Losartan was the first orally active AT1 receptor antagonist available on the market, and it is the antagonist with which the greatest clinical experience has been accumulated. EXP3174 is 10 to 20 times more potent than losartan and has a longer duration of action than losartan. However, the oral bioavailability of EXP 3174 is very low. Thus, the drug on the market is losartan, but most of the losartan’s antihypertensive effect is due to EXP 3174.

AMG-517, a potent and selective vanilloid receptor (VR1) antagonist, was in clinical trials with Amgen for the treatment of pain. AMG 517 inhibits CAP- (500 nM), acid- (pH 5.0), or heat-(45 °C) induced 45Ca2+ influx into human TRPV1-expressing CHO Cells with IC50 of 0.76 nM, 0.62 nM and 1.3 nM. AMG-517 blocks capsaicin-, proton-, and heat-induced inward currents in TRPV1-expressing cells similarly. AMG-517 inhibits native TRPV1 activation by capsaicin in rat dorsal root ganglion neurons with an IC50 value of 0.68 nM. Oral administration of AMG-517 produces a dose-dependent increase in plasma concentrations, it also produces a dose-dependent decrease in the number of flinches induced by capsaicin treatment. The minimally effective dose (MED), based on a statistically significant difference in number of flinches from the vehicle versus capsaicin-administered group, is 0.3 mg/kg for AMG 517. The corresponding plasma concentrations are 90 to 100 ng/mL for AMG-517. AMG-517 (3 mg/kg) exhibits significant reductions in capsaicin-induced flinch up to 24 h after dosing. AMG 517 blocks thermal hyperalgesia in CFA model of pain. Unfortunately, clinical studies of AMG-517 were discontinued due to the hyperthermia observed after exposure to single and multiple doses.

CE-178,253 benzenesulfonate is a CB1 antagonist discovered by Pfizer medicinal chemists. In vitro, CE-178,253 exhibits sub-nanomolar potency at human CB1 receptors in both binding (Ki = 0.33 nM) and functional assays (Ki = 0.07 nM). CE-178,253 has low affinity (Ki > 10,000 nM) for human CB2 receptors. In vivo, CE-178,253 exhibits concentration-dependent anorectic activity in both fast-induced re-feeding and spontaneous nocturnal feeding FI models. In two preclinical models of obesity, CE-178,253 dose-dependently promotes weight loss in diet-induced obese rats and mice.