Rapastinel (formerly known as GLYX-13) is an investigational intravenous formulation of a novel NMDA receptor partial agonist, which is being evaluated for adjunctive treatment of Major depressive disorder, and has shown a rapid onset of antidepressant efficacy 1 day after a single dose in a Phase 2 clinical trial of patients with Major depressive disorder who had an inadequate response to one or more antidepressants. No psychotomimetic or hallucinogenic side effects were observed with rapastinel. Few adverse events were reported by 5% or more of subjects and these were rated as mild or moderate. These included headache, somnolence, dizziness, dysgeusia, and fatigue. On January 29, 2016, Allergan (who acquired Naurex in July 2015) announced that rapastinel had received Breakthrough Therapy designation from the U.S. FDA for adjunctive treatment of major depressive disorder.

Canfosfamide is a modified glutathione analogue and nitrogen mustard prodrug, with potential antineoplastic activity. Canfosfamide is selectively activated by glutathione S-transferase P1-1 an enzyme that is over-expressed in many human cancers including ovarian cancer. GST P1-1-mediated cleavage leads to an active cytotoxic phosphorodiamidate alkylating metabolite that forms covalent linkages with nucleophilic centers in tumor cell DNA, which may induce a cellular stress response and cytotoxicity, and decrease tumor cell proliferation. Preclinical studies showed that canfosfamide inhibited the growth and was cytotoxic to a wide range of established cancer cell lines including those derived from ovarian cancer (OVCAR3, HEY, SK-OV-3). Canfosfamide treatment inhibited cancer cell proliferation and induced apoptosis through the activation of the cellular stress response kinase pathway. The cytotoxic activity of canfosfamide correlated with the expression of GST P1-1. Cancer cells in which GST expression levels were increased by transfection with the GST P1-1 gene, were more sensitive to the cytotoxic effects of canfosfamide than the parental cell lines Canfosfamide in combination with pegylated liposomal doxorubicin is well tolerated and active in platinum and paclitaxel refractory or resistant ovarian cancer.

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.

Folitixorin, a thymidylate synthase inhibitor is a substrate used by the enzyme methylenetetrahydrofolate reductase (MTHFR) to generate 5-methyltetrahydrofolate. Folitixorin was studied in clinical trials for the treatment of breast cancer, metastatic colorectal cancer and for the treatment of advanced pancreatic cancer. Folitixorin had been granted orphan drug status for the treatment of pancreatic cancer in both the U.S. and EU. However, further development of this drug was discontinued.

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.

Alitame [l-α-aspartyl-N-(2,2,4,4-tetramethyl-3-thioethanyl)-d-alaninamide] is an amino acid-based sweetener developed by Pfizer Central Research from l-aspartic acid, d-alanine, and 2,2,4,4-tetraethylthioethanyl amine. A terminal amide group instead of the methyl ester constituent of aspartame was used to improve the hydrolytic stability. The incorporation of d-alanine as a second amino acid in place of l-phenylalanine has resulted in optimum sweetness. The increased steric and lipophilic bulk on a small ring with a sulfur derivative has provided a very sweet product and good taste qualities. Alitame is noncariogenic. From an oral intake, 7–22% is unabsorbed and excreted in the feces. The remainder is hydrolyzed to aspartic acid and alanine amide. The aspartic acid is normally metabolized, and the alanine amide is excreted in the urine as a sulfoxide isomer, sulfone, or conjugated with glucuronic acid. U.S. Food and Drug Administration has approved alitame for use as per acceptable daily intake (ADI) value.

Evofosfamide, also formerly known as TH-302, is an investigational hypoxia-activated prodrug and is used to target cancerous cells under hypoxic conditions, which is a feature possessed by multiple solid tumors including glioblastoma and pancreatic cancer. Within regions of tumor hypoxia, evofosfamide releases bromo isophosphoramide mustard (Br-IPM), a potent DNA alkylating agent that kills tumor cells by forming DNA crosslinks. Once activated in hypoxic tissues, Br-IPM can also diffuse into surrounding oxygenated regions of the tumor and kill cells there via a “bystander effect”. Because of its preferential activation in the targeted hypoxic regions of solid tumors, evofosfamide may be less likely to produce broad systemic toxicity seen with untargeted cytotoxic chemotherapies.