ICI-118551 is a selective β2 adrenergic receptor antagonist, that was originally developed for the regulation of blood pressure. ICI-118551 crosses the blood-brain barrier and it was in phase I clinical trials for the treatment of chronic anxiety. Currently, ICI-118,551 has no known therapeutic use in humans although it has been used widely in research to understand the action of the β2 adrenergic receptor, as few other specific antagonists for this receptor are known.

CUDC-305, is a novel heat shock protein 90 (HSP90) inhibitor with strong affinity for HSP90 alpha/beta, high oral bioavailability and potent anti-proliferative activity against a broad range of cancer cell lines (with a mean IC50 of 220 nmol/L), including many non-small cell lung cancer (NSCLC) cell lines which are resistant to standard-of-care (SOC) agents. In both laboratory and animal testing, CUDC-305 demonstrated high potency in vitro and/or in vivo across a wide range of cancers. Most notably, Curis scientists observed complete tumor regression following oral administration of CUDC-305 in a mouse xenograft model of acute myelogenous leukemia (AML). Tumor regression has also been observed after treatment of CUDC-305 in mouse xenograft models of breast, non-small cell lung, gastric cancer and glioblastoma brain cancers. In this preclinical testing, the compound also demonstrated an ability to effectively cross the blood brain barrier, and demonstrated an ability to extend survival in an intracranial glioblastoma model. Early stage toxicity studies suggest that CUDC-305 appears to have a better therapeutic window than several leading Hsp90 inhibitors in clinical development.

TAK-960 is a novel, investigational, orally bioavailable, potent, and selective PLK1 inhibitor(IC50=1.5 nM) that has shown activity in several tumor cell lines, including those that express multidrug-resistant protein 1 (MDR1). In animal models, oral administration of TAK-960 increased pHH3 in a dose-dependent manner and significantly inhibited the growth of HT-29 colorectal cancer xenografts. Treatment with once daily TAK-960 exhibited significant efficacy against multiple tumor xenografts, including an adriamycin/paclitaxel-resistant xenograft model and a disseminated leukemia model. TAK-960 had been in phase I clinical trials by Takeda for the treatment of solid tumours. It had also been in preclinical trials for the treatment of acute myeloid leukaemia. However, these studies were discontinued.

SGX523 is a selective, ATP-competitive inhibitor of the MET receptor tyrosine kinase. SGX523 was able to inhibit HGF-induced cell migration and cell scatter. SGX523 inhibition of MET in vivo was associated with the dose-dependent inhibition of growth of tumor xenografts derived from human glioblastoma and lung and gastric cancers. The clinical development of SGX523, however, was discontinued at Phase I due to renal toxicity manifested by an early rise of serum blood urea nitrogen and creatinine.

EW-7197 is an orally bioavailable inhibitor of the serine/threonine kinase, transforming growth factor (TGF)-beta receptor type 1 (TGFBR1), also known as activin receptor-like kinase 5 (ALK5), with potential antineoplastic activity. EW-7197 is in phase I clinical trials for the treatment of solid tumors. Also, EW-7197 has a strong potential as an anti-fibrosis therapeutic agent.

MK-8033 is a dual c-Met/Ron inhibitor, which is under investigation by Merck for the treatment of cancer.

Pfizer was developing PF-03814735, an orally administered, reversible inhibitor of the Aurora A and Aurora B kinases. In intact cells, the inhibitory activity of PF-03814735 on the Aurora1 and Aurora2 kinases reduces levels of phospho-Aurora1 (Thr 232, a sensitive marker of Aurora1 activity, with IC50 ~ 20 nM), phosphohistone H3 (with IC50 50 nM), and phospho-Aurora2 (with IC50 150 nM). PF-03814735 produces a block in cytokinesis, resulting in inhibition of cell proliferation and the formation of polyploid multinucleated cells. A recent research indicates small cell lung cancer (SCLC) and, to a lesser extent, colon cancer lines are very sensitive to PF-03814735. The status of the Myc gene family and retinoblastoma pathway members significantly correlates with the efficacy of PF-03814735. PF-03814735 was under Phase I trials for patients with advanced solid tumors, but later this research was discontinued.

The sesquiterpene lactone thapsigargin is found in the plant Thapsia garganica L., and is one of the major constituents of the roots and fruits of this Mediterranean species. In 1978, the first pharmacological effects of thapsigargin were established and the full structure was elucidated in 1985. Thapsigargin is a potent inhibitor of Sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) and is widely used to study Ca2+-signaling. Thapsigargin is a non-cell-type specific toxin with documented ability to kill a broad spectrum of cancer cell lines as well as normal endothelial cells, fibroblasts and osteoblasts. It induces a rapid and pronounced increase in the concentration of cytosolic calcium, due to blockade of the Sarcoplasmic/Endoplasmic Reticulum Calcium ATPase (SERCA) pump to which it binds with high affinity. The increase in cytosolic calcium leads to induction of apoptosis and ensuing cell death. A prodrug, G-202 (mipsagargin) has been designed to target the blood vessels of cancer cells; the death of these blood vessels then leads to tumor necrosis. G-202 consists of a cytotoxic analog of thapsigargin coupled to a masking peptide which inhibits its biologic activity until proteolytic cleavage at the tumor site. The first clinical trials of this drug were initiated in 2008 for the treatment Advanced Solid Tumors.

The receptor tyrosine kinase c-Met is an attractive target for therapeutic blockade in cancer. MK-2461 is a novel ATP-competitive multitargeted inhibitor of activated c-Met, was synthesized by Merck and was investigated in phase I of clinical trial for the potential treatment of patients with advanced solid tumors.

Cinobufotalin, the bufadienolide isolated from toad venom, has displayed antitumor activities in many in vitro systems. It has been shown that cinobufotalin induced significant apoptosis in cultured human lymphoma U-937 cells. It induced DNA fragmentation, mitochondrial membrane potential decrease, and reactive oxygen species (ROS) production in U-937 cells. Cinobufotalin induces cytotoxic effect in cultured lung cancer cells. Cinobufotalin (1/5 mg/kg, i.p. twice daily, for 7 days) significantly inhibited A549 xenograft growth in mice. Further, same cinobufotalin administration improved mice survival at week five. Cinobufotalin administration didn’t significantly affect mice body weight, indicating the relative safety of this regimen. Thus, cinobufotalin inhibits A549 xenograft growth in vivo and improves mice survival.