Perzinfotel (EAA-090) is a novel squaric acid amide derivative that has been identified as a potential treatment for ischemic brain damage resulting from stroke. EAA-090 is a competitive inhibitor at the NMDA-selective subtype of the glutamate receptor. The compound demonstrates potent inhibitory activity in both in vitro and in vivo models of NMDA-induced excitotoxicity and provides neuroprotective efficacy in several animal models of stroke. EAA-090 is unique among competitive NMDA antagonists in displaying a clear separation between predicted efficacious dose and doses that induce PCP-like psychotomimetic side effects in both animals and humans. This unique profile makes EAA-090 an exciting candidate for assessing the neuroprotective potential of the competitive NMDA mechanism.

Sitamaquine (WR-6026) is an orally active 8-aminoquinoline analog in development by the Walter Reed Army Institute, in collaboration with GlaxoSmithKline (formerly SmithKline Beecham), for the potential treatment of visceral leishmaniasis. Phase III trials for the treatment of visceral leishmaniasis had been initiated by March 2002, at which time GlaxoSmithKline hoped to file an MAA in 2003. By 1999, the compound had also undergone phase I trials in HIV-infected individuals for the treatment of Pneumocystis carinii infection. Preclinical studies have been conducted in primates and rodents for the potential treatment of Babesia microti infection.

AstraZeneca was developing AZD-7762 for the treatment of solid tumours. AZD-7762 is a potent inhibitor of Chk1 that binds in the ATP binding pocket (IC50 of 5nM; Ki of 3.6nM). AZD-7762 has activity on a range of other kinases {examples with a < 5 fold selectivity included Rous sarcoma oncogene cellular homolog (SRC) family members (e.g., Fgr, Fyn, lymphocyte-specific protein-tyrosine kinase [Lck], and Lyn, but not SRC), Flt1/3, colony stimulating factor receptor (CSF1R), RET, Abelson tyrosine kinase (Abl), and checkpoint kinase 2 (Chk2)}. It is not known if these in vitro kinase inhibitions translate into an effect in vivo. In combination with DNA-damaging agents (gemcitabine, topotecan, doxorubicin, and cisplatin), AZD-7762 inhibits tumour cell growth in vitro with a mode of action that correlates with Chk1 inhibition and abrogation of the Gap 2 (G2) and S phase checkpoints. Rightward shifts in 50% growth inhibition (GI50) values over DNA-damaging agents alone ranged from 5- to 20-fold with gemcitabine demonstrating the largest shifts followed by topotecan. In combination with radiation, AZD-7762 enhances tumour cell growth inhibition and death with survival enhancement ratios ranging from 1.7 to 1.9. Triple combinations with AZD-7762, gemcitabine, and radiation yield the largest survival enhancement ratios. AZD-7762 had been in phase I clinical trials by AstraZeneca for the treatment of solid tumors. However, this study was terminated for the safety reason in 2011.

Zosuquidar (LY-335979) is an experimental antineoplastic drug. It is is a potent modulator of P-glycoprotein-mediated multi-drug resistance with Ki of 60 nM. Zosuqidar was initially characterized by Syntex Corporation, which was acquired by Roche in 1990. Roche licensed the drug to Eli Lilly in 1997. It was granted orphan drug status by the FDA in 2006 for AML. Zosuquidar Trihydrochloride had been in phase III clinical trials by Kanisa Pharmaceuticals for the treatment of acute myeloid leukaemia. However, this research has been discontinued.

Tecalcet (also known as KRN-568; NPS-R-568; R-568), is an oral calcium channel agonist potentially for the treatment of hyperparathyroidism. Calcimimetics, such as Tecalcet, are agonists and activate the calcium channel in a non-competitive fashion. Tecalcet does not compete directly with calcium that activates the receptor through binding in the extracellular domain of these receptors, but rather, calcimimetics such as Tecalcet, bind allosterically in the seven transmembranes to ‘sensitize’ the receptor to extracellular calcium. Tecalcet acts as an agonist of the calcium receptors of the parathyroid cells, causing a decrease in PTH release. Tecalcet also acts on the parafollicular cells (C-cells) of the thyroid gland, resulting in an increase in calcitonin release. These effects ultimately lead to a decrease in plasma calcium concentrations. Studies in rats have shown that oral administration of R-568 at doses ranging from 3 to 100 mg/kg caused a rapid (<30 minutes) decrease in plasma PTH concentrations and an increase in calcitonin concentrations, accompanied by a dose-dependent decrease in calcium concentrations. Tecalcet had been in phase II clinical trials by for the treatment of hyperparathyroidism, postmenopausal osteoporosis and rheumatic disorders in Japan and US. Development of Tecalcet has been discontinued.

Betulinic acid (BA) is a plant-derived pentacyclic triterpenoid that exerts potent anti-cancer effects in vitro and in vivo. It`s anticancer property is linked to its ability to induce apoptotic cell death in cancer cells by triggering the mitochondrial pathway of apoptosis. In contrast to the cytotoxicity of betulinic acid against a variety of cancer types, normal cells and tissue are relatively resistant to betulinic acid, pointing to a therapeutic window. Compounds that exert a direct action on mitochondria present promising experimental cancer therapeutics, since they may trigger cell death under circumstances in which standard chemotherapeutics fail. Thus, mitochondrion-targeted agents such as betulinic acid hold great promise as a novel therapeutic strategy in the treatment of human cancers. Betulinic acid has antiretroviral, antimalarial, and anti-inflammatory properties. Betulinic acid exerts its inhibitory effect by preventing topoisomerase I-DNA interaction as a result of which the 'cleavable complex' is not formed. In consequence, it also acts as an antagonist to camptothecin-mediated cleavage. The antitumor pharmacological effects of BA consist of triggering apoptosis via the mitochondrial pathway, regulating the cell cycle and the angiogenic pathway via factors, including specificity protein transcription factors, cyclin D1 and epidermal growth factor receptor, inhibiting the signal transducer and activator of transcription 3 and nuclear factor‑κB signaling pathways, preventing the invasion and metastasis of tumor cells, and affecting the expression of topoisomerase I, p53 and lamin B1. Betulinic Acid has also been used in trials studying the treatment of Dysplastic Nevus Syndrome. Betulinic acid acts as anti-melanoma agent through inhibiting aminopeptidase N activity with IC50 of 7.3 uM. Betulinic acid is an inhibitor of HIV-1 with EC50 of 1.4 uM.

Apricitabine (ATC) is an investigational drug that was being studied for the treatment of HIV infection. Apricitabine belongs to a class (group) of HIV drugs called nucleoside reverse transcriptase inhibitors (NRTIs). NRTIs block an HIV reverse transcriptase. By blocking reverse transcriptase, NRTIs prevent HIV from multiplying and can reduce the amount of HIV in the body. In vitro studies have shown that apricitabine appears to work on certain HIV strains against which other FDA-approved NRTIs, such as lamivudine (brand name: Epivir), may no longer work. Apricitabine shows antiviral activity in vitro against HIV-1 strains and clinical isolates with mutations in the reverse transcriptase that confer resistance to other NRTIs, including M184V, thymidine analogue mutations (TAMs), nucleoside-associated mutations such as L74V and certain mutations at codon 69. Apricitabine has shown activity in treatment-experienced HIV-1-infected patients with NRTI resistance (with M184V and up to five TAMs) as well as in treatment-naive patients. The study of apricitabine as an HIV medicine was discontinued in 2016. The company developing the drug decided to stop their clinical trials due to a lack of funding and a lack of interest in apricitabine’s early access program.

Enzastaurin is a serine/threonine kinase inhibitor that showed antiangiogenic, antiproliferative, and proapoptotic properties in vitro and antitumor activity in vivo in a xenograft Waldenström macroglobulinemia (WM) model. Enzastaurin (LY317615) is a potent PKCβ selective inhibitor. Enzastaurin suppresses angiogenesis and was advanced for clinical development based upon this antiangiogenic activity. Enzastaurin suppresses tumor growth through multiple mechanisms: direct suppression of tumor cell proliferation and the induction of tumor cell death coupled to the indirect effect of suppressing tumor-induced angiogenesis. Enzastaurin is an orally administered drug that was intended for the treatment of solid and haematological cancers. Enzastaurin had shown encouraging preclinical results for the prevention of angiogenesis, inhibition of proliferation and induction of apoptosis as well as showing limited cytotoxicity within phase I clinical trials. However, during its assessment in phase II and III clinical trials the efficacy of enzastaurin was poor both in combination with other drugs and as a single agent. Eli Lilly discontinued development of enzastaurin after top-line data from the double-blind, international Phase III PRELUDE trial in 758 DLBCL patients showed that enzastaurin missed the primary endpoint of improving DFS vs. placebo.

Falnidamol is an epidermal growth factor receptor inhibitor, developed by Boehringer Ingelheim. Falnidamol demonstrated anticancer activity in vitro. The phase I trial was discontinued due to a dose-limiting increase of liver enzymes, low bioavailability of the drug and the detection of a pharmacologically inactive metabolite.

Hydroxytamoxifen (Afimoxifene) is an active metabolite of tamoxifen exerting estrogen receptor modulatory function. In addition, hydroxytamoxifen binds to regulates transcriptional activity of the estrogen-related receptor gamma. ASCEND Therapeutics, Inc. was developing TamoGel (4-hydroxytamoxifen gel) for a variety of estrogen-dependent conditions, including breast cancer, cyclic breast pain and gynecomastia.