Elacridar is an oral bioenhancer that targets multiple drug resistance in tumors. Elacridar is a strong and relatively specific inhibitor of P-gp and BCRP, two main efflux transporters. Development of elacridar is assumed to have been discontinued.

XL-228 is a third generation inhibitor of Abl that shows efficacy in a variety of cell lines, including those exhibiting T315I mutations. XL-228, a tyrosine kinase inhibitor, is involved in binding to and inhibiting the activities of multiple tyrosine kinases, such as the insulin-like growth factor 1 receptor (IGF1R), Src tyrosine kinase, and Bcr-Abl tyrosine kinase. Blockade of these kinases may result in the inhibition of tumor angiogenesis, cell proliferation, and metastasis. XL-228 is a multitargeted protein kinase inhibitor targeting IGF1R, the aurora kinases, IGF-1R, cSrc, BCR/Abl and SRC kinases. XL-228 displays anticancer chemotherapeutic activity and it was in clinical trials as a potential treatment for chronic myelogenous leukemia (CML). On 22 Feb 2011 phase I clinical studies for chronic myeloid leukaemia and cancer in USA were discontinued.

Kynurenic acid is a product of the normal metabolism of amino acid L-tryptophan which has been shown to have a neuroactive profile. It exhibits activity against NMDA receptors and Neuronal acetylcholine receptor subunit alpha-7. It has been investigated as a potential therapeutic compound and as a biomarker in a number of neurological disorders. Although Kenyruic acid exhibits a poor penetration of the blood-brain barrier, it remains to be of particular interest to those researching Schizophrenia.

Indole-3-carbinol (I3C), a common phytochemical in cruciferous vegetables, and its condensation product, 3,3'-diindolylmethane (DIM) exert several biological activities on cellular and molecular levels, which contribute to their well-recognized chemoprevention potential. ndole-3-carbinol is used for prevention of breast cancer, colon cancer, and other types of cancer. The National Institutes of Health (NIH) has reviewed indole-3-carbinol as a possible cancer preventive agent and is now sponsoring clinical research for breast cancer prevention. Indole-3-carbinol is also used for fibromyalgia, tumors inside the voice box (laryngeal papillomatosis) caused by a virus, tumors inside the respiratory tract (respiratory papillomatosis) caused by a virus, abnormal cell growth in the cervix (cervical dysplasia), and systemic lupus erythematosus (SLE). Indole-3-carbinol scavenges free radicals and induces various hepatic cytochrome P450 monooxygenases. Specifically, this agent induces the hepatic monooxygenase cytochrome P4501A1 (CYP1A1), resulting in increased 2-hydroxylation of estrogens and increased production of the chemoprotective estrogen 2-hydroxyestrone. Accumulating evidence indicates that the antitumor activity of indole-3- carbinol is attributable to its ability to interfere with multiple oncogenic signaling pathways governing cell cycle progression, survival, invasion, and other aggressive phenotypes of cancer cells. Reported signaling targets of indole-3- carbinol in various cancer cell lines include EGFR/Src, Akt/NF-B, stress responses, elastase, and Rho kinase. Moreover, indole-3-carbinol functions as a negative regulator of estrogen action in hormonesensitive cancer cells through the inhibition of estrogen receptor (ER)-alpha signaling and/or induction of cytochrome P-450-mediated estrogen metabolism, suggesting its clinical use in hormone-sensitive cancers.

Ormaplatin (NSC 363812, tetraplatin) is a stable platinum (IV) analog. Ormaplatin alkylates DNA, forming both inter- and intra-strand platinum-DNA crosslinks, which result in inhibition of DNA replication and transcription and cell-cycle nonspecific cytotoxicity. Ormaplatin showed marked antitumor activity both in vitro and vivo. The severe, cumulative and irreversible peripheral neurotoxicity observed in phase I studies resulted in termination of further clinical development of ormaplatin.

Pyrazofurin (PF) (3,β-D-ribofuranosyl, 4-hydroxyprazole-5-carboxamide) is a C-nucleoside antibiotic, one in which the ribose joins the base-ring carbon instead of a base-ring nitrogen. Pyrazofurin potently inhibits orotidine 5'-monophosphate (OMP) decarboxylase, thereby interfering with de novo synthesis of uridine nucleotides and resulting in cytotoxicity. This agent also causes a rapid depletion of the pyrimidine deoxynucleotide pool, thereby inhibiting DNA synthesis and cell replication. PF was isolated from fermentation filtrate of Strepomyces candidus. This compound was initially found to have inhibitory activity against the vaccinia, herpes simplex, rhino and measles viruses in vitro and the vaccinia virus in vivo. More recently the antiviral spectrum has been extended to include the polio, Coxsackie, Sindbis and vesicular stomatitis viruses.

Harmine (aka telepathine) is a fluorescent harmala alkaloid belonging to the beta-carboline family of compounds. It is a naturally occurring metabolite in a number of plants, notably the Middle Eastern plant harmal or Syrian rue (Peganum harmala) and the South American vine Banisteriopsis caapi. Harmine is a reversible inhibitor of monoamine oxidase A (MAO-A), but not MAO-B. Harmine has been found to have potential anti-cancer and neuroprotective properties, and also promotes differentiation of osteoblasts and chondrocytes while inhibiting osteoclastogenesis. Harmine has also been used as a C-11 labeled probe in positron emission tomography.

Streptonigrin is an antibiotic produced by Streptomyces flocculus. Streptonigrin exhibits activity as a broad spectrum antibiotic against both Gram-positive and Gram-negative bacteria. Streptonigrin shows antitumor activity against sarcomas, carcinomas, leukemias and lymphomas in vivo and in vitro. Due to its high toxicity, streptonigrin has not recieved widespread clinical use.

Clorgiline is a monoamine oxidase (MAO) inhibitor. Specifically, it is an irreversible and selective inhibitor of MAO-A. Clorgiline was under investigation for antidepressant and anxiolytic potential but has never been marketed, likely due to efficacy concerns. It continues to see routine use as a molecular probe in biomedical research examining a number of neurological disease and cancer models. In addition to inhibiting the MAO-A receptor, it has also been found to bind to the sigma1 receptor, and with high affinity to the I2 imidazoline receptor.

Fusaric acid (J-butylpicolinic acid) is a fungal toxin with low to moderate toxicity synthesized by some Fusurium species which cause infections in cereal grains and other agricultural commodities. It may potentiate the effects of other Fusurium toxins. Fusaric acid is a potent inhibitor of DNA synthesis. Fusaric acid has potent anti-proliferative activity in vitro on various normal and cancer cell lines and suggest that it exhibits some cytotoxic specificity for growing and confluent colorectal adenocarcinoma and mammary adenocarcinoma cell lines. Fusaric acid is known as a potent dopamine-beta-hydroxylase inhibitor of high specificity. Fusaric acid calcium salt elicited the hypotensive response primarily through the reduction of total peripheral vascular resistance index.