Torcitabine is the beta-L-enantiomer of the natural nucleoside D-cytidine. The drug was under development as an antiviral agent for the treatment of chronic hepatitis B virus infection. Torcitabine has poor oral bioavailability, but its 3’,5’-derivative ester (val-L-dC) and the 3’-monovaline ester, valtorcitabine dihydrochloride, have excellent oral bioavailability and consequently the torcitabine prodrug, valtorcitabine, has replaced torcitabine in clinical development. Torcitabine is active against hepadnaviruses, specifically human hepatitis B virus (HBV), duck hepatitis virus (DHBV) and woodchuck hepatitis virus (WHV). Torcitabine triphosphate is a selective inhibitor of the polymerase enzyme of HBV.

Fluprofylline, a central stimulant, was a very selective though not very potent alpha 1-adrenoceptor antagonist. However, information about the further development of this compound is not available.

Tipifarnib is an oral farnesyltransferase (FTase) inhibitor which was developed by Janssen (J&J). Upon administration, tipifarnib inhibits FTase and thus suppresses the activity of downstream effectors. The drug reached phase III of clinical trials for such diseases as pancreatic cancer (terminated), colorectal cancer (terminated) and acute myeloid leukemia (in elderly patients).

Lomeguatrib is a O6-methylguanine-DNA-methyl-transferase inhibitor which was developed by AstraZeneca for the treatment of cancer. It was tested in phase I and II of clinical trials for the treatment of colorectal cancer, melanoma and other solid tumors.

KETOTREXATE is an antifolate developed to overcome methotrexate (MTX) resistance. However, it demonstrated such potential only in MTX-resistant sensitive L1210/FR8 leukemia cells and its clinical development was discontinued. Unlike MTX, KETOTREXATE exhibited minimal inhibition of purified dihydrofolate reductase, which implies that it does not act as a classical antifolate.

Mureletecan is a water-soluble prodrug, consisting of camptothecin covalently linked to polymeric backbone methacryloylglycynamide, with potential antineoplastic activity. After entering tumor cells, the active moiety camptothecin is slowly released from mureletecan via hydrolysis of the ester linkage. Camptothecin, the active moiety, is an alkaloid isolatable from the Chinese tree Camptotheca acuminata. Camptothecin itself suffers from poor solubility, which is why it is often investigated with a solubilizing conjugate; such as in Mureletecan. Camptothecin binds to and stabilizes the topoisomerase I-DNA covalent complex producing potentially lethal double-stranded DNA breaks when encountered by DNA replication machinery. Camptothecin has also been shown to inhibit HIF1a. Camptothecin has been investigated with a number of solubilizing conjugates as a potential treatment in various forms of cancer.

Rebeccamycin analog (RA, Becatecarin/ BMS 181176, rebeccamycin derivative, NSC 655649) is an antitumor antibiotic with inhibitory activity against both topoisomerase I and II, and DNA-intercalating properties. The mechanism of action of becatecarin is not exactly known, but it is thought that by inhibiting (blocking) the function of topoisomerase enzymes, it will destroy cancer cells and slow down the growth of the tumour. On 25 July 2006, orphan designation (EU/3/06/388) was granted by the European Commission to Helsinn Birex Pharmaceuticals Ltd, Ireland, for becatecarin for the treatment of cancers of the biliary tree.

Perbufylline is a bronchodilator. It is N-methylated xanthine derivative. Perbufylline acts as a competitive antagonist at 5-HT2 and alpha1-adrenoceptors, with at least 100-fold less activity at alpha2-adrenoceptors.

Eniluracil (5-ethynyluracil, GW 776, 776C85) is a potent irreversible inhibitor of dihydropyrimidine dehydrogenase, the first enzyme in the catabolic pathway of 5-fluorouracil (5-FU), the most widely used drug in cancer chemotherapy. Eniluracil increases the oral bioavailability of 5-FU to 100%, facilitating uniform absorption and predictable toxicity. Eniluracil was being developed as a novel modulator of 5-FU for the treatment of cancer.