Barasertib (AZD1152) is a dihydrogen phosphate prodrug of a pyrazoloquinazoline Aurora kinase inhibitor [AZD1152–hydroxyquinazoline pyrazol anilide (HQPA)] and is converted rapidly to the active AZD1152-HQPA in plasma. AstraZeneca was developing the aurora kinase inhibitor, barasertib (AZD 1152) as a therapeutic for cancer. AZD1152-HQPA is a highly potent and selective inhibitor of Aurora B (Ki, 0.36nmol/L) compared with Aurora A (Ki, 1,369nmol/L) and has a high specificity versus a panel of 50 other kinases. Consistent with inhibition of Aurora B kinase, addition of AZD1152-HQPA to tumour cells in vitro induces chromosome misalignment, prevents cell division, and consequently reduces cell viability and induces apoptosis. Barasertib (AZD1152) potently inhibited the growth of human colon, lung, and haematologic tumour xenografts (mean tumour growth inhibition range, 55% to ≥100%; P < 0.05) in immunodeficient mice. Detailed pharmacodynamic analysis in colorectal SW620 tumour-bearing athymic rats treated i.v. with Barasertib (AZD1152) revealed a temporal sequence of phenotypic events in tumours: transient suppression of histone H3 phosphorylation followed by accumulation of 4N DNA in cells (2.4-fold higher compared with controls) and then an increased proportion of polyploid cells (>4N DNA, 2.3-fold higher compared with controls). Histologic analysis showed aberrant cell division that was concurrent with an increase in apoptosis in AZD1152-treated tumours. Bone marrow analyses revealed transient myelosuppression with the drug that was fully reversible following cessation of Barasertib (AZD1152) treatment. Barasertib (AZD1152) was in phase III for the treatment of Acute myeloid leukaemia, but later these studies were discontinued.

CPI-0610 is a small molecule inhibitor of the Bromodomain and Extra-Terminal (BET) family of proteins, with potential antineoplastic activity. Upon administration, the BET inhibitor CPI-0610 binds to the acetylated lysine recognition motifs on the bromodomain of BET proteins, thereby preventing the interaction between the BET proteins and acetylated histone peptides. This disrupts chromatin remodeling and gene expression. Prevention of the expression of certain growth-promoting genes may lead to an inhibition of tumor cell growth. CPI-0610 is currently being evaluated in three Phase 1 clinical trials in the U.S.

Amgen is developing AMG-900, an orally active, small molecule aurora kinase A, B and C inhibitor for the treatment of solid tumours and haematological malignancies. In tumor cells, AMG-900 inhibited autophosphorylation of aurora-A and -B as well as phosphorylation of histone H3 on Ser(10), a proximal substrate of aurora-B. The predominant cellular response of tumor cells to AMG-900 treatment was aborted cell division without a prolonged mitotic arrest, which ultimately resulted in cell death. AMG-900 inhibited the proliferation of 26 tumor cell lines, including cell lines resistant to the antimitotic drug paclitaxel and to other aurora kinase inhibitors (AZD1152, MK-0457, and PHA-739358), at low nanomolar concentrations. Furthermore, AMG-900 was active in an AZD1152-resistant HCT116 variant cell line that harbors an aurora-B mutation (W221L). Oral administration of AMG-900 blocked the phosphorylation of histone H3 in a dose-dependent manner and significantly inhibited the growth of HCT116 tumor xenografts. Importantly, AMG-900 was broadly active in multiple xenograft models, including 3 multidrug-resistant xenograft models, representing 5 tumor types. AMG-900 has entered clinical evaluation in adult patients with advanced cancers and has the potential to treat tumors refractory to anticancer drugs such as the taxanes.

BVD-523 potently and selectively inhibits ERK1 and ERK2 kinases in a reversible, ATP-competitive fashion. Consistent with its mechanism of action, BVD-523 inhibits signal transduction, cell proliferation, and cell survival, most potently in cell lines bearing mutations that activate MAPK pathway signaling. Similarly, single-agent BVD-523 inhibits tumor growth in vivo in BRAF-mutant melanoma and colorectal xenografts as well as in KRAS-mutant colorectal and pancreatic models. BioMed Valley Discoveries is developing ulixertinib, a potent and selective small molecule inhibitor of ERK 1 and 2 kinases, as an oral treatment for cancers harbouring mutations in the MAPK signaling pathway. Phase I/II development of the drug for advanced cancers including, acute myeloid leukaemia and myelodysplastic syndromes is underway in the US. A phase I trial is underway in the US for pancreatic cancer.

BI-2536, an inhibitor of Polo-like kinase 1 (Plk-1) was being investigated by Boehringer Ingelheim as a possible treatment for cancer. BI-2536 inhibits Plk1 enzyme activity at low nanomolar concentrations. The compound potently causes a mitotic arrest and induces apoptosis in human cancer cell lines of diverse tissue origin and oncogenome signature. BI-2536 inhibits growth of human tumor xenografts in nude mice and induces regression of large tumors with well-tolerated intravenous dose regimens. In treated tumors, cells arrest in prometaphase, accumulate phosphohistone H3, and contain aberrant mitotic spindles. This mitotic arrest is followed by a surge in apoptosis, detectable by immunohistochemistry and noninvasive optical and magnetic resonance imaging. For addressing the therapeutic potential of Plk1 inhibition, BI-2536 has progressed into clinical studies in patients with locally advanced or metastatic cancers. It underwent phase II clinical studies for the treatment of breast cancer; non-small cell lung cancer; pancreatic cancer; prostate cancer; small cell lung cancer, but these studies were discontinued later.

Tosedostat is a proprietary orally bioavailable inhibitor of the M1 family of aminopeptidases with potential antineoplastic activity. Tosedostat is converted intracellularly into a poorly membrane-permeable active metabolite (CHR-79888) which inhibits the M1 family of aminopeptidases, particularly puromycin-sensitive aminopeptidase (PuSA), and leukotriene A4 (LTA4) hydrolase; inhibition of these aminopeptidases in tumor cells may result in amino acid deprivation, inhibition of protein synthesis due to a decrease in the intracellular free amino acid pool, an increase in the level of the proapoptotic protein Noxa, and cell death. There are several ongoing Phase 2 cooperative group-sponsored trials and investigator-sponsored trials evaluating the clinical activity of Tosedostat in combination with standard agents in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS).

AZD-1208 is an orally available, potent and highly selective Pim inhibitor that effectively inhibits all three isoforms. AZD-1208 inhibits the growth of several AML cell lines and sensitivity correlates with the level of Pim-1 expression, STAT5 activation and presence of protein tyrosine kinase mutation. AZD-1208 causes cell cycle arrest and apoptosis in MOLM-16 cells in culture. This is accompanied by a dose-dependent reduction in phosphorylation of BAD, 4EBP1 and p70S6K. In addition, AZD-1208 leads to potent inhibition of colony growth of primary AML cells from bone marrow aspirates and downregulates phosphorylation of Pim targets. AZD-1208 was in Phase 1 trials to evaluate the safety and tolerability profile and to determine the maximum tolerated dose (MTD). There were two trials where AZD-1208 had been administered orally in AML and solid tumour (of all types) patients. The studies had being discontinued due to safety reasons.

Pevonedistat (MLN4924), discovered by Millennium, is a small molecule inhibitor of the NEDD8-Activating Enzyme (NAE), a key component of the protein homeostasis pathway. MLN4924 is a mechanism-based inhibitor of NAE and creates a covalent NEDD8-MLN4924 adduct catalyzed by the enzyme. The NEDD8-MLN4924 adduct resembles NEDD8 adenylate, the first intermediate in the NAE reaction cycle, but cannot be further utilized in subsequent intraenzyme reactions. The stability of the NEDD8-MLN4924 adduct within the NAE active site blocks enzyme activity, thereby accounting for the potent inhibition of the NEDD8 pathway by MLN4924. This drug is in phase II clinical trial for the treatment acute myeloid leukemia, chronic myelomonocytic leukemia and myelodysplastic syndromes. In addition in phase I for treatment acute lymphoblastic leukemia. The ability of MLN4924 to cross the blood-brain barrier, its low toxicity, and clinical efficacy in other cancers suggests that this drug is an attractive treatment against glioblastomas.

Troxacitabine is a synthetic nucleoside analogue. It is a poor substrate for nucleoside transporters and gains entry into cells by passive diffusion. Intracellular conversion to its active triphosphate form is via deoxycytidine kinase. Incorporation of this metabolite into DNA results in immediate chain termination and apoptosis induction. It is the first nucleoside analog with anticancer activity that has an unnatural stereochemical configuration. The dose-limiting adverse reactions were stomatitis and hand–foot syndrome.

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.