5-Methoxytryptamine (aka 5-MT, mexamine) is a tryptamine derivative closely related to the neurotransmitters serotonin and melatonin. 5-MT is produced endogenously at low levels; it is biosynthesized by deacetylation of melatonin in the pineal gland. 5-MT acts as a full agonist at the 5-HT1, 5-HT2, 5-HT4, 5-HT6, and 5-HT7 receptors. It is often used as a chemical probe in the study of serotonin receptors, but it has also been used in a clinical trial to mitigate the anemic effects of cisplatin chemotherapy.

Latrunculin A is a naturally occurring toxin that can be purified from the red sea sponge Latrunculia magnifica. It disrupts actin polymerization and prevents mitotic spindle formation; therefore preventing proper cellular replication. It was discovered that latrunculin A has strong anticancer effects, and it was investigated as a treatment candidate for peritoneal dissemination of gastric cancer.

Gosogliptin (PF-734200) is a compound developed for treatment of type II diabetes and has been approved for use in Russia. It is a selective dipeptidyl peptidase 4 (DPP-4) inhibitor, with hypoglycemic activity. The drug is safe and well tolerated at all doses tested when added to metformin (a diabetes drug), and safely and effectively lowered HbA (1c) in subjects receiving metformin. A phase 3 study to study the safety and efficacy of gosogliptin has been completed. Gosogliptin has also been studied as potential drug for the treatment of renal insufficiency.

Sipoglitazar (TAK 654) was a novel, azolealkanoic acid derivative that possesses selective activity for the peroxisome proliferator-activated receptors (PPAR) PPARγ, PPARα, and PPARδ. Sipoglitazar was developed to improve peripheral insulin sensitivity, normalize circulating lipid profiles, and reduce body weight in patients with metabolic syndrome and type 2 diabetes mellitus (T2DM). Sipoglitazar was being developed by Takeda for the treatment of diabetes mellitus, however in September 2006, development was discontinued.

Irosustat is a first-generation, orally active, irreversible steroid sulfatase inhibitor. It did not stimulate the growth of estrogen-sensitive MCF-7 breast cells in vitro. Irosustat was in phase II clinical trials for the treatment of breast cancer and endometrial cancer and phase I clinical trial for the treatment of prostate cancer. However, this research has been discontinued.

Bisphenol A is a small estrogenic monomer that is polymerized to produce polycarbonate plastic and resins used to line metal cans. It is also used to make some dental sealants. Bisphenol A had been considered to be a very weak environmental estrogen. It is able to interact with human estrogen receptors. In addition, it binds strongly to the estrogen-related receptor gamma. Bisphenol A inhibited androgen-induced androgen receptor transcriptional activity. Prenatal exposure to maternal Bisphenol A concentrations were related to higher levels of anxiety, depression, aggression, and hyperactivity in children. Bisphenol A exposure in childhood was associated with higher levels of anxiety, depression, hyperactivity, inattention, and conduct problems. It never found use as a drug.

FLOVAGATRAN is a potent, reversible, low-molecular-weight, highly selective synthetic direct thrombin inhibitor that has demonstrated promising pharmacokinetic properties and biological activity in preclinical studies. However, its development for thrombosis was discontinued in Phase II.

Alisertib (MLN8237) is an orally available selective aurora A kinase inhibitor developed by Takeda. Alisertib inhibited AAK over ABK with a selectivity of more than 200-fold in cells and produced a dose-dependent decrease in bipolar and aligned chromosomes in the HCT-116 xenograft model, a phenotype consistent with AAK inhibition. Alisertib inhibited proliferation of human tumor cell lines in vitro and produced tumor growth inhibition in solid tumor xenograft models and regressions in in vivo lymphoma models. It is currently in phase II clinical trials for acute myeloid leukaemia; B cell lymphoma; brain cancer; mesothelioma; prostate cancer; small cell lung cancer.

Fenclonine, also known as p-chlorophenylalanine, is an inhibitor of tryptophan hydroxylase, the enzyme that plays a rate-limiting role in the biosynthesis of serotonin. Fenclonine was studied for the treatment of carcinoid syndrome, but the psychological side effects, prevented for the further development for this use.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mutagenic and carcinogenic heterocyclic amine formed during ordinary cooking, and is subsequently metabolically activated by cytochrome P4501A2 (CYP1A2) and N-acetyltransferase 2 (NAT2). PhIP has been used in trials studying the basic science of Pancreas Cancer.