PD-0325901 is an orally bioavailable inhibitor of mitogen-activated protein kinase kinases (MAPK/ERK kinases or MEK) with potential antineoplastic activity. MEK inhibitor PD325901, a derivative of MEK inhibitor CI-1040, selectively binds to and inhibits MEK, which may result in the inhibition of the phosphorylation and activation of MAPK/ERK and the inhibition of tumor cell proliferation. PD-0325901 is tested in clinical trials against non-small cell lung cancer, neurofibromatosis, melanoma and breast cancer.

Selumetinib (AZD6244 or ARRY-142886) is a potent, selective, and ATP-uncompetitive inhibitor of Ras-Raf-mitogen-activated protein kinase kinase (MEK1/2). This inhibition can prevent ERK activation, disrupt downstream signal transduction, and inhibit cancer cell proliferation and survival. Selumetinib has shown tumour suppressive activity in multiple rodent models of human cancer including melanoma, pancreatic, colon, lung, and breast cancers. AstraZeneca is responsible for development and commercialization of selumetinib.

Binimetinib (MEK162) is an oral small-molecule with potential antineoplastic activity. It is a selective mitogen-activated protein kinase 1 and 2 (MEK1/2) inhibitor, a key protein kinase in the RAS/RAF/MEK/ERK pathway, which regulates several key cellular activities including proliferation, differentiation, migration, survival and angiogenesis. Inappropriate activation of this pathway has been shown to occur in many cancers, in particular through mutations in BRAF, KRAS and NRAS. MEK162 at 6 mg/kg, BID combined with BEZ235 (dual PI3K/mTOR inhibitor) resulted in a significant reduction of tumor growth in immunodeficient mice injected with MCF7 cells. There are three ongoing Phase 3 trials with binimetinib in advanced cancer patients: NEMO (NRAS-mutant melanoma), COLUMBUS (encorafenib in combination with binimetinib in BRAF-mutant melanoma) and BEACON CRC (encorafenib, binimetinib and cetuximab in BRAF-mutant colorectal cancer).

Trametinib is a reversible and specific inhibitor of mitogen-activated protein kinase kinases MEK1 and MEK2 which are involved in a RAS/RAF/MEK/ERK signaling pathway and control cell growth, survival, and differentiation. By inhibiting MEK1 and MEK2 trametinib blocks dual phosphorylation of ERK1/2 and stops cell cycling. In addition, trametinib blocks BRAF pathway in the cells with BRAF V600E mutations. Trametinib (as a single agent and in combination with dabrafenib) is approved for the treatment of unresectable or metastatic melanoma with BRAF V600E or V600K mutations.

Refametinib (RDEA-119, BAY- 869766) is a highly potent and selective inhibitor of mitogen-activated ERK kinase (MEK1/2) activity, Refametinib binds to an allosteric pocket adjacent to the ATP binding site, locking the enzyme in a catalytically inactive conformation. This compound is highly efficacious at inhibiting cell proliferation in several tumor cell lines in vitro. In vivo, Refametinib exhibits potent activity in xenograft models of cancers. Ardea Biosciences (a subsidiary of AstraZeneca) and Bayer HealthCare are developing refametinib for the treatment of cancer. The sulfonamide agent was originally developed by Valeant Pharmaceuticals International. Refametinib is in phase II development for hepatocellular carcinoma, and phase I/II development for pancreatic cancer and other solid tumours.

CI 1040 is an inhibitor of the mitogen-activated protein (MAP) kinase signal transduction pathway and has been shown to specifically inhibit MAP kinase kinase (MEK). CI 1040 was being developed by Parke-Davis (formerly a division of WarnerLambert, Now Pfizer) as an anticancer agent. It was the initial MEK inhibitor to undergo clinical evaluation based on promising preclinical activity. However, its development has been discontinued.

U0126 is a highly selective inhibitor of both MEK1 and MEK2, a type of MAPK/ERK kinase. The inhibitory effects of U0126 on MEK and ERK activation have been confirmed repeatedly, and treatments with U0126 have been shown to inhibit proliferation and migration of cancer cells in vivo and in vitro. U0126 has been widely used as an inhibitor for the Ras/Raf/MEK/ERK signaling pathway. U0126 treatments lead to cancer cell death, which agrees with the well-known role of the Ras/Raf/MEK/ERK pathway in supporting cell survival. U0126 enhances apoptosis in human breast cancer MCF-7 cells, acute myeloid leukemia, and PC12 cells.

BI-847325 is a novel, ATP-competitive, orally available inhibitor of Aurora kinases and MEK. In in vitro studies, BI-847325 inhibited the activity of Xenopus laevis Aurora Kinase B with an IC50 of 3 nM; with IC50 values for human Aurora kinase A and Aurora kinase C being 25 and 15 nM, respectively. BI-847325 also inhibited human MEK1 and MEK2 with respective IC50 values of 25 and 4 nM. BI-847325 had been in phase I clinical trials by Boehringer Ingelheim for the treatment of solid tumours. However, there is no development reported for this study.

Selumetinib (AZD6244 or ARRY-142886) is a potent, selective, and ATP-uncompetitive inhibitor of Ras-Raf-mitogen-activated protein kinase kinase (MEK1/2). This inhibition can prevent ERK activation, disrupt downstream signal transduction, and inhibit cancer cell proliferation and survival. Selumetinib has shown tumour suppressive activity in multiple rodent models of human cancer including melanoma, pancreatic, colon, lung, and breast cancers. AstraZeneca is responsible for development and commercialization of selumetinib.

Trametinib is a reversible and specific inhibitor of mitogen-activated protein kinase kinases MEK1 and MEK2 which are involved in a RAS/RAF/MEK/ERK signaling pathway and control cell growth, survival, and differentiation. By inhibiting MEK1 and MEK2 trametinib blocks dual phosphorylation of ERK1/2 and stops cell cycling. In addition, trametinib blocks BRAF pathway in the cells with BRAF V600E mutations. Trametinib (as a single agent and in combination with dabrafenib) is approved for the treatment of unresectable or metastatic melanoma with BRAF V600E or V600K mutations.