MKC-1 is an orally available cell cycle inhibitor with downstream targets that include tubulin and the importin-β family. MKC-1 has shown broad antitumor activity in preclinical models. MKC-1 and its metabolites inhibit tubulin polymerization, blocking the formation of the mitotic spindle, which may result in cell cycle arrest at the G2/M phase and apoptosis. In addition, this agent has been shown to inhibit the activities of the oncogenic kinase Akt, the mTOR pathway, and importin-beta, a protein essential to the transport of other proteins from the cytosol into the nucleus. MKC-1 had been in phase II clinical trials for the treatment of ovarian cancer, endometrial cancer, pancreatic cancer and breast cancer. This compound was originally discovered by Roche, then licensed to EntreMed (now CASI Pharmaceuticals) the exclusive worldwide rights to develop and commercialize. However, no recent development has been reported.

Prinomastat is a synthetic hydroxamic acid derivative with potential antineoplastic activity. Prinomastat inhibits matrix metalloproteinases (MMPs) (specifically, MMP-2, 9, 13, and 14), thereby inducing extracellular matrix degradation, and inhibiting angiogenesis, tumor growth and invasion, and metastasis. As a lipophilic agent, prinomastat crosses the blood-brain barrier. Pfizer conducted multicenter, randomized, double-bind, placebo-controlled trials to evaluate the safety and efficacy of prinomastat in combination with standard chemotherapy in patients with advanced hormone refractory prostate cancer and non-small cell lung cancer. However, this study has been terminated for the reason that Prinomastat did not improve the outcome of chemotherapy in non-small cell Lung cancer patients.

Carboxyamidotriazole (L651582) is a carboxyamide-amino-imidazole compound originally developed as a coccidiostat, an antiprotozoal agent that acts upon Coccidia parasites. Carboxyamidotriazole (L651582) is an orally-active agent with potential antineoplastic activity. Carboxyamidotriazole binds to and inhibits non-voltage-operated Ca2 channels, blocking both Ca2 influx into cells and Ca2 release from intracellular stores and resulting in the disruption of calcium channel-mediated signal transduction and inhibition of vascular endothelial growth factor (VEGF) signaling, endothelial proliferation, and angiogenesis. This agent may also inhibit tumor cell growth, invasion, and metastasis.

A second generation of HDACs, synthetic benzamide-containing HDACs such as Tacedinaline (CI-994), have reached phase I and II clinical trials. It has been investigated for its applications to the treatment of cancers such as Breast cancer and Colorectal cancer. Tacedinaline has been in phase III clinical trials by Pfizer for the treatment of advanced non-small cell lung cancer and pancreatic cancer combined with gemcitabine. However, this research has been discontinued. Mechanism of Action: Angiogenesis inhibitors; Histone deacetylase inhibitors. Pharmacokinetics showed that CI-994 absorption and disposition were unaffected by carboplatin and paclitaxel coadministration.

Tariquidar, a non-competitive, specific P-glycoprotein (Pgp) inhibitor, is an anthranilamide derivative with multidrug resistance properties. Tariquidar binds to the ATP-binding cassette (ABC) transport protein Pgp, thereby inhibiting transmembrane transport of anticancer drugs resulting in their increased intracellular concentrations augmenting cytotoxicity of an anticancer drug. Tariquidar was discovered by Xenova Group and was developed for the treatment of multidrug resistance in cancer. In October 2002 the US Food and Drug Administration (FDA) has granted fast track review status to tariquidar for the treatment of multi-drug resistance in first-line treatment of non-small cell lung cancer (NSCLC) patients. Tariquidar is still undergoing research as an adjuvant against multidrug resistance in cancer.

Marizomib is a natural beta-lactone produced by the marine bacterium Salinispora tropica. Marizomib has a broad inhibition profile for the 20S proteasome and has been shown to inhibit the CT-L (beta5) CT-T-laspase-like (C-L, beta1) and trypsin-like (T-L, beta2) activities of the 20S proteasome. The drug is being tested in phase II clinical trials for the treatment of Multiple Myeloma and Malignant Glioma and in phase I in patients with Non-small Cell Lung Cancer, Pancreatic Cancer, Melanoma or Lymphoma

Rabusertib is a Chk1 kinase inhibitor which was developed by ICOS for the treatment of cancer. The drug was tested in phase II of clinical trials for pancreatic cancer and non small cell lung carcinoma, but its development was discontinued. Now the drug is undergoing phase I trial in Japanese patients with solid tumors.

Edelfosine is a synthetic alkyl-lysophospholipid, a potent immunomodulator and an effective inhibitor of tumor cell proliferation. The cytotoxic effect of edelfosine has been evaluated in a large variety of both tumor (leukemic and solid) and normal cell types, showing a high degree of selectivity towards tumor cells. Like all alkyl-lysophospholipids, Edelfosine incorporates into the cell membrane and does not target the DNA. In many tumor cells, Edelfosine causes selective apoptosis, sparing healthy cells. Edelfosine can activate the Fas/CD95cell death receptor, can inhibit the MAPK/ERK mitogenic pathway and the Akt/protein kinase B (PKB) survival pathway. Edelfosine apoptosis-inducing abilities were studied with several types of cancer, among them multiple myeloma and non-small and small cell lung carcinoma cell lines. In vivo activity against human solid tumors in mice was shown against malignant gynecological tumor cells, like ovarian cancer, and against breast cancer. In vivo biodistribution studies demonstrated a “considerably higher” accumulation of Edelfosine in tumor cells than in other analyzed organs. Several clinical trials were conducted. Among them, a phase I trials with solid tumors or leukemias and phase II with non-small-cell lung carcinomas (NSCLC). In Phase II clinical trial for use of Edelfosine in treating leukemia with bone marrow transplants, it was found to be safe and 'possibly effective'. A phase II trial for the treatment of brain cancers was also reported. It showed encouraging results in stopping the growth of the tumor and a considerable improvement in the “quality of life” of the patients. A phase II trial on the effect of Edelfosine on advanced non-small-cell bronchogenic carcinoma had a “remarkable” “high proportion of patients with stationary tumor status” as result, stable disease after initial progression in 50% of the patients.

AZD1775 selectively targets and inhibits WEE1, a tyrosine kinase that phosphorylates cyclin-dependent kinase 1 (CDK1, CDC2) to inactivate the CDC2/cyclin B complex. Inhibition of WEE1 activity prevents the phosphorylation of CDC2 and impairs the G2 DNA damage checkpoint. This may lead to apoptosis upon treatment with DNA damaging chemotherapeutic agents. Current ongoing trials of AZD1775 include monotherapy and combination therapy with certain DNA damaging agents in solid tumors, ovarian tumors, gynaecological cancer, non-small cell lung cancer. AZD1775 is genotoxic, which is considered to be a result of its mechanism of action. Common serious adverse events (with chemotherapy) include: febrile neutropenia, neutropenia, thrombocytopenia.

Rubitecan [Orathecin™] is a topoisomerase I inhibitor extracted from the bark and leaves of the Camptotheca acuminata tree, which is native to China. Rubitecan is an oral compound being developed for the treatment of pancreatic cancer and other solid tumours by SuperGen. Rubitecan binds to and inhibits the enzyme topoisomerase I and induces protein-linked DNA single-strand breaks, thereby blocking DNA and RNA synthesis in dividing cells; this agent also prevents repair of reversible single-strand DNA breaks.