Parafluorofentanyl is a selective mu-opioid agonist, an analog of fentanyl, developed by Janssen. The drug was not developed for human use but is produced and abused illegally.

MPEP (2-methyl-6-(phenylethynyl)pyridine) was one of the first compounds found to act a selective antagonist for the metabotropic glutamate receptor subtype mGluR5. It was under development by Novartis in the late 1990's. MPEP was found to produce neuroprotective effects following acute brain injury in animals. MPEP was also found to have positive effects on animal models of depression, anxiety and morphine withdrawl.

Avelestat, also known as AZD9668, is a novel, oral inhibitor of neutrophil elastase (NE), an enzyme implicated in the signs, symptoms, and disease progression in NE-driven respiratory diseases such as bronchiectasis, Cystic Fibrosis and chronic obstructive pulmonary disease via its role in the inflammatory process, mucus overproduction, and lung tissue damage. Its development was discontinued due to unknown reasons. Nevertheless, this drug in the phase II of clinical trial as adjunctive therapy in improving insulin sensitivity of insulin-resistant type 2 diabetic subjects. The drug's clinical profile suggests that it will be well tolerated with few, if any, side effects, and the existence of simple methods that can indirectly measure its activity in vivo.

Midesteine (previously known as MR 889), a thiolactic acid derivative was developed as an inhibitor of the chymotrypsin and elastolytic activity of leukocyte elastase. Midesteine participated in clinical trials for patients with chronic obstructive pulmonary disease. The drug is also studied to treat asthma, cystic fibrosis, and emphysema. However, all these studies were discontinued.

Arctigenin is a plant lignan extracted from Arctium lappa that has been shown to have estrogenic properties. In ER-positive MCF-7 cells, arctigenin efficiently inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced cell migration and invasion. Arctigenin confers anti-metastatic effects by inhibiting MMP-9 and uPA via the Akt, NF-κB and MAPK signaling pathways on breast cancer, regardless of ER expression. Intake of arctigenin could be an effective supplement for breast cancer patients. Arctigenin is a phenylpropanoid dibenzylbutyrolactone lignan compound possessing antitumor, anti-inflammatory, anti-influenza, antioxidant, antibacterial, and hypoglycaemic activities. Arctigenin exhibited significant antiproliferative activity against CCRF-CEM cells after 72 h treatment with IC50 values of 1.21 ± 0.15 um. It arrested CCRF-CEM cells in the S phase. It induced apoptosis in CCRF-CEM cells in a concentration- and time-dependent manner. Arctigenin is a good candidate for the development of novel agents against T-cell lymphoma. Arctigenin has been found to act as an agonist of adiponectin receptor 1 (AdipoR1). Arctigenin is an antagonist of MR and effectively decreases the Na/K-ATPase 1 gene expression, thus highlighting its potential as an anti-hypertensive drug lead compound.

AstraZeneca was developing AZD-8055, an orally active mTORC1/mTORC2 inhibitor, for the treatment of advanced solid tumours. AZD-8055 is an ATP-competitive mTORC1/2 inhibitor that exhibits immunosuppressive and anticancer chemotherapeutic activities. AZD-8055 promotes antibody class switching in B cells at low doses and decreases B cell proliferation and differentiation at high doses. In vivo, this compound suppresses CC4 and CD8 T cell proliferation, increasing survival among MHC-mismatched heart transplant recipients. In vitro, AZD-8055 decreases viability of brain tumor cells; in vivo, it inhibits tumor growth. AZD-8055 had been in phase I trials by AstraZeneca for the treatment of malignant gliomas and solid tumours. However, this research has been discontinued.

LY404039 [(-)-(1R,4S,5S,6S)-4-amino-2-sulfonylbicyclo[3.1.0]-hexane-4,6-dicarboxylic acid] is an agonist of orthosteric metabotropic glutamate receptor (mGluR)2/3. In addition, it acts as an agonist at dopamine D2 receptors. LY404039 demonstrated broad antipsychotic and anxiolytic efficacy across multiple animal models. LY-2140023 is a methionine amide prodrug of LY-404039 being developed by Eli Lilly & Co for the potential oral treatment of schizophrenia.

Rioprostil is a methylprostaglandin E1 analog. Rioprostil inhibits gastric acid secretion and enhances the gastric mucus-bicarbonate barrier. In peptic ulcer cases, it facilitates the healing process and the elimination of pain. Rioprostil can also be used to prevent recurrence of duodenal ulcers. However, its development has been discontinued in 2000.