Sarizotan (also known as EMD-128,130), a chromane derivative that was developed as a selective 5-HT1A receptor agonist and D2 receptor antagonist. Experiments on animal models have shown that the drug effectively suppressed levodopa-induced dyskinesia in primate and rodent models of Parkinson's disease, and tardive dyskinesia in a rodent model. Sarizotan participated in phase II/III clinical trials in the treatment of dyskinesia associated with the dopaminergic treatment of Parkinson's disease. However, further development for this disease was discontinued by Merk, because phase III did not confirm earlier Phase II findings. On July 14, 2015, Newron Pharmaceuticals, research, and development company focused on the novel central nervous system (CNS) and pain therapies, announced that the U.S. Food and Drug Administration (FDA) has granted Orphan Drug Designation to sarizotan for treatment of Rett syndrome. Besides, the drug now is an ongoing clinical trial phase II/III to investigate its the tolerability and efficacy in reducing respiratory abnormalities in Rett Syndrome.

Mocetinostat is an rationally designed, orally available, Class 1-selective, small molecule, 2-aminobenzamide HDAC inhibitor with potential antineoplastic activity. Mocetinostat binds to and inhibits Class 1 isoforms of HDAC, specifically HDAC 1, 2 and 3, which may result in epigenetic changes in tumor cells and so tumor cell death; although the exact mechanism has yet to be defined, tumor cell death may occur through the induction of apoptosis, differentiation, cell cycle arrest, inhibition of DNA repair, upregulation of tumor suppressors, down regulation of growth factors, oxidative stress, and autophagy, among others. It is undergoing clinical trials for treatment of various cancers including bladder cancer, diffuse large B cell lymphoma, follicular lymphoma, myelodysplastic syndromes, non-small cell lung cancer. Fatigue, weight loss or anorexia were most common treatment-related adverse events.

Amicus Therapeutics was investigating afegostat (isofagomine; Plicera; HGT-3410; AT-2101), an orally available pharmacological chaperone molecule, which binds to glucocerebrosidase (Gba) and stimulates proper folding and trafficking of the enzyme, for the potential treatment of Parkinsons disease(PD) and Gaucher disease. Afegostat specifically and reversibly binds GCase in the ER with highaffinity; this stabilizes the active form of the enzyme in the ER and increases trafficking of GCase to lysosomes. In 2006, Orphan Drug designations were granted in the U.S. and E.U. in 2006 and 2007, respectively. However, this research has been discontinued.

Combretastatin A4 is a vascular disrupting agent (VDA) that targets tumor vasculature to inhibit angiogenesis. Combretastatin A4 is a tubulin-binding agent that binds at or near the colchicine binding site of β-tubulin and inhibits tubulin assembly. This tubulin-binding agent was originally isolated from an African shrub, Combretum caffrum. Combretastatin A4 is cytotoxic to umbilical-vein endothelial cells (HUVECs) and to a range of cells derived from primary tumors and these cytotoxicity profiles have been used to assess several novel analogs of the drug for future development. Combretastatin A4 has antitumor activity by inhibiting AKT function. The inhibited AKT activation causes decreased cell proliferation, cell cycle arrest, and reduced in vitro migration/invasiveness and in vivo metastatic ability. Several studies in mice have shown that a single administration of combretastatin A4 (100 mg/kg) does not significantly affect primary tumor growth. However, repeated administration (12.5 – 25.0mg/kg twice daily) for periods of 10 – 20 days resulted in approximately 50% retardation of growth of ectopic Lewis lung carcinoma and substantial growth delay of T138 spontaneous murine breast tumors. In clinical studies, Combretastatin A4 has been well tolerated in patients at doses up to 56 mg/m2, following a protocol of five daily 10-minute intravenous infusions every 21 days. The disodium combretastatin A4 phosphate prodrug is currently undergoing clinical trials in the UK and USA.

Ecopipam (SCH-39166) is a selective D1 dopamine receptor antagonist both in vitro and in vivo. Additionally, it exhibits saturable, high-affinity binding to D5 receptors. Ecopipam was studied clinically for a variety of indications, including schizophrenia, drug abuse, and obesity, but in each case undesirable effects were observed. Currently, ecopipam is in clinical trials for the treatment of Lesch-Nyhan and Gilles de la Tourette's syndromes.

Ezatiostat (TLK199) [γ-glutamyl-S-(benzyl)cysteinyl-R-phenyl glycine diethyl ester] is an inhibitor of Glutathione S-transferase P1–1 (GSTπ). The drug is a peptidomimetic of GSH (glutathione), esterified to enhance cellular uptake and designed to bind to the “G-site” of GSTP1–1. Independent of catalysis inhibition, TLK199 also disrupts the protein:protein interaction site(s) between GSTP1–1 and JNK1. Telik Inc was developing TLK-199 for the potential prevention of myelosuppression in blood diseases, namely myelodysplastic syndrome.

Oglufanide, an angiogenesis inhibitor, an immunomodulator, that originally was developed and registered in Russia under the brand name timogen. Oglufanide inhibits vascular endothelial growth factor (VEGF), which may inhibit angiogenesis. This agent has also been reported to stimulate the immune response to hepatitis C virus and intracellular bacterial infections. Oglufanide was studied in the USA for the treatment of cancer, and in September 2001, it was granted Orphan Drug designation for the treatment of ovarian cancer. In addition, in Australia this drug was involved in phase II clinical trial for the treatment of hepatitis C. Oglufanide is also participated in phase III trials for patients with Kaposi's sarcoma, however, this study was discontinued.

Clazosentan is an endothelin receptor antagonist, developed by the Swiss pharmaceutical company Actelion, and licensed to its spin-off, Idorsia. The drug was designed to inhibit endothelin-mediated cerebral vasospasm and associated delayed ischaemic neurological deficit. The drug has been investigated in a phase III clinical trials in patients with aneurysmal subarachnoid hemorrhage. Clazosentan at 5 mg/h had no significant effect on mortality and vasospasm-related morbidity or functional outcome. Clinical investigation of a higher dose of the drug is underway.

Gaboxadol (or THIP) is a direct GABA mimetic ligand at delta-containing receptors. Gaboxadol went into human clinical trials to test if the drug promoted sleep. It was generally well tolerated. Gaboxadol enhances delta power in NREM sleep in humans. Gaboxadol failed in Phase III for sleep studies. The side effects of Gaboxadol have been described as mild and similar in quality to those of other GABA-mimetics. Gaboxadol is in development with Ovid Therapeutics as a treatment for Angelman syndrome, fragile X syndrome and epilepsy.

Eprodisate (1,3-propanedisulfonate) is a negatively charged, sulfonated molecule of low molecular weight that has structural similarities to heparin sulfate; it is a glycosaminoglycan mimetic that binds to the glycosaminoglycan (GAG) binding site on serum A amyloid (AA) to prevent its interaction with glycosaminoglycan and arrest amyloidosis, or inhibit amyloid deposition. In nonclinical toxicity studies in two animal species (i.e., rat and dog), eprodisate was administered orally at doses of up to 2000 mg/kg/day for 39 weeks: eprodisate showed low toxicity potential at doses several fold higher than the anticipated clinical dose, was well tolerated upon chronic exposure and was found to be nonmutagenic and nonclastogenic. Furthermore, a series of safety pharmacology studies showed that eprodisate does not have any clinically significant effect on major organ function.