Nolpitantium (SR-140333) is a highly selective nonpeptide antagonist of neurokinin-1 (NK1) receptor. Nolpitantium potently, selectively and competitively inhibited substance P binding to NK1 receptors from various animal species, including humans. In vitro, it was a potent antagonist in functional assays for NK1 receptors such as [Sar9, Met(O2)11]substance P-induced endothelium-dependent relaxation of rabbit pulmonary artery and contraction of guinea-pig ileum. Up to 1 mkM, Nolpitantium had no effect in bioassays for NK2 and NK3 receptors. The antagonism exerted by Nolpitantium toward NK1 receptors was apparently non-competitive, with pD2' values between 9.65 and 10.16 in the different assays. Nolpitantium also blocked in vitro [Sar9, Met(O2)11]substance P-induced release of acetylcholine from rat striatum. In vivo, Nolpitantium exerted highly potent antagonism toward [Sar9, Met(O2)11]substance P-induced hypotension in dogs, bronchoconstriction in guinea-pig) and plasma extravasation in rats. Nolpitantium was found to be effective in the modulation of the inflammatory response and airway remodeling in mice. Nolpitantium is reported to cause antagonism of the SP-induced relaxations of human isolated intralobar pulmonary arterial rings. Nolpitantium also blocked the activation of rat thalamic neurons after nociceptive stimulation. Nolpitantium has been shown to reduce the severity of inflammation in trinitrobenzene sulfonic acid-induced colitis in the rat colon. Nolpitantium inhibited mustard oil-induced plasma protein extravasations in the dorsal skin of the rat hind paw. Nolpitantium had been in some phase II clinical trials but further studies were 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.

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.

Dalvastatin is a synthetic HMG-CoA reductase inhibitor developed by Rhône-Poulenc Rorer. Dalvastatin is a prodrug and is itself an inactive lactone. After oral ingestion, the drug is hydrolyzed in vivo to the corresponding beta-hydroxy acid, which is the pharmacologically active form. HMG-CoA reductase is the rate-limiting enzyme in the cholesterol biosynthetic pathway. An active form of dalvastatin inhibits HMG-CoA reductase with IC50 of 3.4 nM. In ex vivo assay, orally administered dalvastatin inhibited cholesterol biosynthesis in rat liver slices with an ED50 value of 0.9. The efficacy of dalvastatin to lower cholesterol was investigated in the clinical trials in the 1990s, but no results were reported.

Elacytarabine (CP-4055 or araC-5'elaidic acid ester) is a lipid-conjugated derivative of the nucleoside analog cytarabine. Elacytarabine blocks cell division and may kill cancer cells. It is a type of antimetabolite. It was studied in clinical trials for the treatment of solid tumors. In preclinical and clinical studies, elacytarabine has demonstrated both safety and efficacy in acute myeloid leukemia (AML), with noteworthy activity among the cytarabine-refractory AML population. Elacytarabine was granted orphan drug designation status from the European Commission in 2007 and from the US FDA in 2008, with a fast-track approval designation from the FDA in 2010. Elacytarabine development has been discontinued.

Tozasertib, originally developed as VX-680 by Vertex (Cambridge, MA) and later renamed MK-0457 by Merck (Whitehouse Station, NY), was the first aurora kinase inhibitor to be tested in clinical trials. The drug, a pyrimidine derivative, has affinity for all aurora family members at nanomolar concentrations with inhibitory constant values (Ki(app)) of 0.6, 18, and 4.6 nM for aurora A, aurora B, and aurora C, respectively. Preclinical studies confirmed that tozasertib inhibited both aurora A and aurora B kinase activity, and activity has been reported against prostate, thyroid, ovarian, and oral squamous cancer cell lines. Upon treatment with tozasertib, cells accumulate with a 4N DNA content due to a failure of cytokinesis. This ultimately leads to apoptosis, preferentially in cells with a compromised p53 function. Tozasertib is an anticancer chemotherapeutic pan-aurora kinase (AurK) inhibitor that also inhibits FMS-like tyrosine kinase 3 (FLT3) and Abl. Tozasertib is currently in clinical trials as a potential treatment for acute lymphoblastic leukemia (ALL). In cellular models of cancer, tozasertib activates caspase-3 and PARP and decreases expression of HDAC, increasing apoptosis and inhibiting cell growth. In other cellular models, tozasertib inhibits cell proliferation and metastasis by blocking downstream ERK signaling and downregulating cdc25c and cyclin B. This compound also decreases tumor growth in an in vivo model of prostate cancer.

Tetronasin is a furanone derivative patented by Imperial Chemical Industries Ltd. as antibiotic and feed additive for ruminants. Tetronasin acts as divalent antiporter that binds preferentially with Ca2+ or Mg2+ and inhibits anaerobic fungi and Gram-negative bacteria in vitro.

AT-9283 was being developed by Astex Pharmaceuticals as a treatment for cancer and myelofibrosis. AT-9283 is an inhibitor of mitosis (cell division) and is the second most progressed drug candidate in the Astex portfolio of novel molecularly targeted cancer drugs. All of Astex’s current products have been discovered internally using its proprietary drug discovery approach. AT9283 is a potent inhibitor of the Aurora A and B kinases and has been shown to arrest tumour growth in a range of tumour models. Aurora kinases play a key role in mitotic checkpoint control in cell division. Both Aurora A and B are over-expressed in many human tumours and are believed to be excellent targets for anti-cancer therapy.

Cethexonium is a cyclohexanols derivative with antimicrobial activities.

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.