Terbogrel, an agent having two pharmacodynamic actions, namely inhibition of thromboxane A2 synthase and antagonism of the thromboxane A2 receptor. The antithrombotic effect of terbogrel was dose-dependent and was associated with enhanced prostacyclin production. The drug was studied for the treatment of peripheral vascular disorders, pulmonary hypertension, and thrombosis. Terbogrel participated in phase II clinical trial to investigate its safety and efficacy in patients with primary pulmonary hypertension, however, this study was discontinued due to terbogrel’s induction of leg pain.

Ritanserin (INN, USAN, BAN) is a serotonin receptor antagonist which was never marketed for clinical use but has been used in scientific research. In humans, ritanserin increases deep slow-wave sleep, improved liveliness in a variety of psychiatric disorders and facilitated participation in behaviour therapy. During clinical trials, unexpected observations indicated that ritanserin may be of value in treating obsessive-compulsive disorder, acute mania, negative symptoms of schizophrenia, drug addicts, etc. Clinical observations confirmed the efficacy of ritanserin in the chronic withdrawal phase after detoxification from ethanol. Ritanserin had been in phase III clinical trials by Janssen L.P. for the treatment of anxiety disorder and major depressive disorder. However, the clinical development of ritanserin was discontinued.

Semaxanib is a potent and selective vascular endothelial growth factor (VEGF) receptor protein tyrosine kinase 1/2 inhibitor that also inhibits other tyrosine kinases KIT, MET, FLT3, and RET. Semaxanib inhibited cell migration of human vascular endothelial cells expressing both Flt-1 and KDR in response to VEGF and also inhibited the cell migration in response to placenta growth factor (PIGF), a specific ligand for Flt-1. Chemotaxis of monocytes expressing only Flt-1 was also inhibited by SU5416 in a dose-dependent manner. Semaxanib targets the VEGF pathway, and both in vivo and in vitro studies have demonstrated antiangiogenic potential. On February 2002, Pharmacia, the then-parent of Sugen, prematurely ended Phase III clinical trials of Semaxinib in the treatment of advanced colorectal cancer due to discouraging results.

Sephin1 is a guanabenz derivative that binds to and inhibits a regulatory subunit of the stress-induced protein phosphatase 1 (PPP1R15A), but not the constitutive PPP1R15B, and lacks beta2-adrenergic activity. Phosphorylation of eIF2α, α subunit of eukaryotic translation initiation factor 2, reduces protein synthesis and prevents the accumulation of misfolded protein in the endoplasmic reticulum (ER). PPP1R15A recruits the serine/threonine-protein phosphatase PP1 to dephosphorylate eIF2α, so inhibiting PPP1R15A activity prolongs the phosphorylation of eIF2α and aids in its prevention of the accumulation of misfolded protein. In vitro, Sephin1 protected cells from lethal protein misfolding and cytotoxic ER stress. In vivo Sephin1 prevented Charcot-Marie-Tooth 1B and ALS diseases in mice.