Nifenalol is the beta-receptor antagonist. It has optical isomers. The racemic mixture and the levo-isomer are active in antagonizing beta-receptors, but the dextro-isomer is inactive. The levo-isomer seems to be about twice as active in blocking beta-receptors as the racemate. Nifenalol is virtually devoid of local anesthetic properties in contrast to procaine, propranolol, and butidrine. Nifenalol exacerbated the fighting behavior in male mice by foot-shock. Nifenalol has been studied in patients with coronary artery disease. It afforded the coronary patient good protection against angina and ischemic changes in the EKG. It was further noted that nifenalol had no antiarrhythmic action and that it was devoid of evident side effects. Nifenalol possessed weak action against tremorine and oxotremorine induced tremor.

Eplivanserin (SR 46349) is an antagonist of serotonin 2A receptor. Eplivanserin was previously in development by Sanofi-aventis in an effort to educate the public regarding this new mechanism of action for sleep aids. Eplivanserin was reviewed by the FDA as a potential treatment for patients with chronic insomnia, but the FDA requested additional information regarding benefit-risk and development of the drug has been discontinued.

Atrasentan (ABT-627, A-127722) is a selective endothelin A receptor antagonist. Atrasentan is being developed by AbbVie as an oral treatment for diabetic nephropathies.Abbott Laboratories was conducting clinical development of atrasentan for the treatment of certain cancers, including phase II trials for prostate cancer. However, no recent development has been reported for cancer indications and development is presumed to be discontinued.

S-(+)-niguldipine is a more active enantiomer and is a selective antagonist for the and α1A-adrenoceptor. In addition, it can be used for discriminating of alpha 1A- from alpha 1B-adrenoceptors. There were made attempts to investigate the antidepressant action of S-(+)-niguldipine on rats, but that studies were unsuccessful.

Piboserod (SB 207266) is a selective 5-HT(4) receptor, antagonist. The 5-HT4 receptor antagonists are thought to antagonize both the ability of serotonin to sensitize the peristaltic reflex and 5-HT-induced defecation, at least in animal studies. As 5-HT4 receptors are present in human atrial cells and when stimulated may cause atrial arrhythmias, piboserod was under investigation in clinical trials for atrial fibrillation. In addition, GlaxoSmithKline studied the drug for the management of irritable bowel syndrome. Nevertheless, development both indications had been discontinued. Piboserod has successfully passed phase II clinical trials for the treatment of patients with congestive heart failure.

Fispemifene acts via estrogen receptors and has tissue-selective estrogenic and/or antiestrogenic effects – it has antagonist activity in breast tissue and acts as an estrogen agonist in bone. Due to its low estrogenicity in male rats, it might also be applicable for men. Fispemifene exhibits both antiestrogenic and anti-inflammatory action in the prostate. It could be considered as a new therapeutic option in the treatment and prevention of prostatic inflammation. Fispemifene had been in phase II clinical trials for the oral treatment of hypogonadism.

XL-228 is a third generation inhibitor of Abl that shows efficacy in a variety of cell lines, including those exhibiting T315I mutations. XL-228, a tyrosine kinase inhibitor, is involved in binding to and inhibiting the activities of multiple tyrosine kinases, such as the insulin-like growth factor 1 receptor (IGF1R), Src tyrosine kinase, and Bcr-Abl tyrosine kinase. Blockade of these kinases may result in the inhibition of tumor angiogenesis, cell proliferation, and metastasis. XL-228 is a multitargeted protein kinase inhibitor targeting IGF1R, the aurora kinases, IGF-1R, cSrc, BCR/Abl and SRC kinases. XL-228 displays anticancer chemotherapeutic activity and it was in clinical trials as a potential treatment for chronic myelogenous leukemia (CML). On 22 Feb 2011 phase I clinical studies for chronic myeloid leukaemia and cancer in USA were discontinued.

Ridogrel is a dual action drug used for the prevention of systemic thrombo-embolism and as an adjunctive agent to thrombolytic therapy in acute myocardial infarction. Ridogrel, a combined thromboxane synthase inhibitor, and receptor antagonist is used with streptokinase as an adjunctive therapy to reduce the formation and size of blood clots. Blood clots can cause ischemic cardiac events (heart attacks). Ridogrel has the dual property of inhibiting the synthesis of thromboxane and blocking the receptors of thromboxane/prostaglandin/endoperoxides. It has been shown to accelerate the speed of recanalization and to delay or prevent reocclusion during systemic thrombolysis with tissue plasminogen activator (streptokinase). Ridogrel is a more potent antiplatelet agent than aspirin and might offer an advantage over aspirin as an adjunct to thrombolysis in patients suffering from acute myocardial infarction. While aspirin inhibits cyclooxygenase, the enzyme responsible for producing thromboxane, ridogrel inhibits thromboxane synthesis directly. Ridogrel has been studied primarily as an adjunctive agent to thrombolytic therapy in acute MI (AMI). Despite positive results from initial pilot studies, the largest clinical study, the Ridogrel versus Aspirin Patency Trial (RAPT) failed to demonstrate any advantage with this agent over aspirin. In the study of 907 patients with AMI, there was no difference in the primary endpoint of infarct vessel patency rate between those randomized to ridogrel (72.2%) or aspirin (75.5%). Various mechanisms are likely responsible for the results seen with ridogrel in clinical trials, including potentially ineffective thromboxane receptor inhibition with the concentrations of ridogrel used in human studies. As such, there currently are no clinical indications for preferential use of ridogrel over aspirin.

Elarofiban is a novel nonpeptide glycoprotein IIb/IIIa (GPIIb/IIIa) antagonist. It inhibits thrombin-induced platelet aggregation in human gel-filtered platelets and platelet aggregation in human platelet-rich plasma (PRP) in response to collagen, arachidonic acid, ADP, and SFLLRN-NH(2). Elarofiban had adequate oral pharmacokinetics in dogs and excellent oral pharmacodynamics. Elarofiban has been in phase II clinical trials for the treatment of myocardial infarction and thrombosis. However, this research has been discontinued.