The BET-bromodomain inhibitor OTX015 (MK-8628) was initially developed by Mitsubishi Tanabe Pharma Corporation, but then was licensed by OncoEthix, privately held biotechnology company. OTX015 is a selective bromodomains: BRD2, BRD3, and BRD4 inhibitor and inhibits their binding to AcH4. Bromodomains have an important role in the targeting of chromatin-modifying enzymes to specific sites, including methyltransferases, HATs and transcription factors and regulate diverse biological processes from cell proliferation and differentiation to energy homeostasis and neurological processes. OTX015 has potent antiproliferative activity accompanied by c-MYC down-regulation in several tumor types, and has demonstrated synergism with the mTOR inhibitor everolimus in different models. Oral administration of OTX-015 markedly inhibited tumor growth and reduced tumor volume. OTX015 is currently in Phase 1b studies for the treatment of hematological malignancies and advanced solid tumors such as Triple Negative Breast Cancer, Non-small Cell Lung Cancer, Castrate-resistant Prostate Cancer (CRPC) and Pancreatic Ductal Adenocarcinoma. In addition, OTX015 was in phase II for the treatment of Glioblastoma Multiforme, but there were not detected clinical activity of the drug in the treatment populations and trial was closed.

Motesanib (AMG 706), a novel nicotinamide, was identified as a potent, orally bioavailable inhibitor of the VEGFR1/Flt1, VEGFR2/kinase domain receptor/Flk-1, VEGFR3/Flt4 and Kit receptors. Motesanib was expected to reduce vascular permeability and blood flow in human tumours. A phase III trial of motesanib in combination with paclitaxel and carboplatin in non-squamous NSCLC has been terminated by Takeda and subsequently the development was discontinued. Motesanib has also been investigated up to phase II in breast, thyroid, colorectal and gastrointestinal stromal tumours. However, development has been discontinued in these indications.

Otenabant (CP-945,598) is Pfizer developed as a potent and selective cannabinoid receptor CB1 antagonist with Ki of 0.7 nM, which exhibits 10,000-fold greater selectivity against human CB2 receptor, for treatment of obesity. In clinical trial III Pfizer decided to discontinue the development program based on changing regulatory perspectives on the risk/benefit profile of the CB1 class and likely new regulatory requirements for approval.

Tozasertib, originally developed as VX-680 by Vertex (Cambridge, MA) and later renamed MK-0457 by Merck (Whitehouse Station, NY), was the first aurora kinase inhibitor to be tested in clinical trials. The drug, a pyrimidine derivative, has affinity for all aurora family members at nanomolar concentrations with inhibitory constant values (Ki(app)) of 0.6, 18, and 4.6 nM for aurora A, aurora B, and aurora C, respectively. Preclinical studies confirmed that tozasertib inhibited both aurora A and aurora B kinase activity, and activity has been reported against prostate, thyroid, ovarian, and oral squamous cancer cell lines. Upon treatment with tozasertib, cells accumulate with a 4N DNA content due to a failure of cytokinesis. This ultimately leads to apoptosis, preferentially in cells with a compromised p53 function. Tozasertib is an anticancer chemotherapeutic pan-aurora kinase (AurK) inhibitor that also inhibits FMS-like tyrosine kinase 3 (FLT3) and Abl. Tozasertib is currently in clinical trials as a potential treatment for acute lymphoblastic leukemia (ALL). In cellular models of cancer, tozasertib activates caspase-3 and PARP and decreases expression of HDAC, increasing apoptosis and inhibiting cell growth. In other cellular models, tozasertib inhibits cell proliferation and metastasis by blocking downstream ERK signaling and downregulating cdc25c and cyclin B. This compound also decreases tumor growth in an in vivo model of prostate cancer.

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.

Omtriptolide (previously known as PG490-88 or F60008), an immunosuppressant that has been shown to be the safe and potent antitumor agent and it has been approved entry into Phase I clinical trial for the treatment of prostate cancer in the USA. In addition, the drug is participating in phase I clinical trial for the treatment of myeloid leukemia. Experiments on animals have shown omtriptolide was highly effective in the prevention of murine graft-versus-host disease (GVHD). The immunosuppressive effect of the drug was mediated by inhibition of alloreactive T cell expansion through interleukin-2 production. However, this study was discontinued. Recently published article has shown omtriptolide possesses the potential as a prophylactic agent to prevent ischemia/reperfusion (I/R)-induced lung injury.

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.

Dovitinib is an orally active small molecule that exhibits potent inhibitory activity against multiple receptor tyrosine kinases (RTK) involved in tumor growth and angiogenesis. Dovitinib strongly binds to fibroblast growth factor receptor 3 (FGFR3) and inhibits its phosphorylation, which may result in the inhibition of tumor cell proliferation and the induction of tumor cell death. In addition, this agent may inhibit other members of the RTK superfamily, including the vascular endothelial growth factor receptor; fibroblast growth factor receptor 1; platelet-derived growth factor receptor type 3; FMS-like tyrosine kinase 3; stem cell factor receptor (c-KIT); and colony-stimulating factor receptor 1; this may result in an additional reduction in cellular proliferation and angiogenesis, and the induction of tumor cell apoptosis. There are several ongoing Phase I/III clinical trials for dovitinib.

Omtriptolide (previously known as PG490-88 or F60008), an immunosuppressant that has been shown to be the safe and potent antitumor agent and it has been approved entry into Phase I clinical trial for the treatment of prostate cancer in the USA. In addition, the drug is participating in phase I clinical trial for the treatment of myeloid leukemia. Experiments on animals have shown omtriptolide was highly effective in the prevention of murine graft-versus-host disease (GVHD). The immunosuppressive effect of the drug was mediated by inhibition of alloreactive T cell expansion through interleukin-2 production. However, this study was discontinued. Recently published article has shown omtriptolide possesses the potential as a prophylactic agent to prevent ischemia/reperfusion (I/R)-induced lung injury.

Amuvatinib (formerly known as MP470) is an oral multi-targeted tyrosine kinase inhibitor, which play critical roles in transducing growth signals to cancer cells. It suppresses c-MET, c-RET and the mutant forms of cKIT, PDGFR and FLT3. It also disrupts DNA repair likely through suppression of homologous recombination protein Rad51, an important survival pathway in many human cancers. In vitro and in vivo data have demonstrated amuvatinib synergy with DNA damaging agents including etoposide and doxorubicin. Overall, in the amuvatinib clinical development program, over 200 subjects were exposed to at least one dose of amuvatinib. In the Phase 1b clinical study in combination with carboplatin and etoposide, responses in small cell lung cancer (SCLC), neuroendocrine as well as other tumor types were observed. Human pharmacokinetic data suggest that co-administration of amuvatinib did not alter exposures of standard of care agents including carboplatin, etoposide, doxorubicin, paclitaxel, topotecan or erlotinib as measured by overall exposure. In the first-in-human study, durable clinical benefit was observed in the gastrointestinal stromal tumors (GIST) with modulation of Rad51 observed in skin punch biopsies. In clinical trials, amuvatinib has demonstrated a wide therapeutic window and shows minimal toxicity in the expected therapeutic dose range, despite suppressing several signaling pathways within cells. However, in spite of this, this drug was discontinued, because it was not pre-specified primary endpoints in the clinical proof of concept (cPOC) stage. But the combination of MP470 and Erlotinib, which target the HER family/PI3K/Akt pathway may represent a novel therapeutic strategy for prostate cancer.