7-Hydroxystaurosporine (UCN-01) is a protein kinase inhibitor which is under development as an anti-cancer agent in the USA and Japan. Although UCN-01 was originally isolated from the culture broth of Streptomyces sp. as a protein kinase C-selective inhibitor, its ultimate target as an anti-cancer agent remains elusive. As a single agent, UCN-01 exhibits two key biochemical effects, namely accumulation of cells in the G1 phase of the cell cycle and induction of apoptosis. Both these effects may be important for its anti-cancer activity. As a modulator, 7-Hydroxystaurosporine enhances the cytotoxicity of other anti-cancer drugs such as DNA-damaging agents and anti-metabolite drugs through putative abrogation of G2 and/or S phase accumulation induced by these anti-cancer agents. 7-Hydroxystaurosporine had been in phase II clinical trials Life Sciences for the treatment of T-cell lymphoma, malignant melanoma, pancreatic cancer, small cell lung cancer, acute myeloid leukemia, ovarian cancer. However, the research was either discontinued or suspended.

LY2606368 (Prexasertib) is a small-molecule Chk-1 inhibitors invented by Array and being developed by Eli Lilly and Company. Lilly is responsible for all clinical development and commercialization activities. LY2606368 is advancing in Phase 2 clinical trials for cancer. Prexasertib preferentially binds to and inhibits CHK1 and, to a lesser extent, inhibits CHK2. Chk-1 is a protein kinase that regulates the tumor cell's response to DNA damage often caused by treatment with chemotherapy. In response to DNA damage, Chk-1 blocks cell cycle progression in order to allow for repair of damaged DNA, thereby limiting the efficacy of chemotherapeutic agents. Inhibiting Chk-1 in combination with chemotherapy can enhance tumor cell death by preventing these cells from recovering from DNA damage.

PF-477736 is a selective, potent and ATP-competitive Chk1 inhibitor. Compound was tested in combination with gembcitabine in phase I clinical trials in patients with advanced solid tumors.

MK-8776 (SCH900776) is inhibitor of CHK1. It was tested in clinical trials against acute myeloid leukaemia, solid tumors and lymphoma.

AstraZeneca was developing AZD-7762 for the treatment of solid tumours. AZD-7762 is a potent inhibitor of Chk1 that binds in the ATP binding pocket (IC50 of 5nM; Ki of 3.6nM). AZD-7762 has activity on a range of other kinases {examples with a < 5 fold selectivity included Rous sarcoma oncogene cellular homolog (SRC) family members (e.g., Fgr, Fyn, lymphocyte-specific protein-tyrosine kinase [Lck], and Lyn, but not SRC), Flt1/3, colony stimulating factor receptor (CSF1R), RET, Abelson tyrosine kinase (Abl), and checkpoint kinase 2 (Chk2)}. It is not known if these in vitro kinase inhibitions translate into an effect in vivo. In combination with DNA-damaging agents (gemcitabine, topotecan, doxorubicin, and cisplatin), AZD-7762 inhibits tumour cell growth in vitro with a mode of action that correlates with Chk1 inhibition and abrogation of the Gap 2 (G2) and S phase checkpoints. Rightward shifts in 50% growth inhibition (GI50) values over DNA-damaging agents alone ranged from 5- to 20-fold with gemcitabine demonstrating the largest shifts followed by topotecan. In combination with radiation, AZD-7762 enhances tumour cell growth inhibition and death with survival enhancement ratios ranging from 1.7 to 1.9. Triple combinations with AZD-7762, gemcitabine, and radiation yield the largest survival enhancement ratios. AZD-7762 had been in phase I clinical trials by AstraZeneca for the treatment of solid tumors. However, this study was terminated for the safety reason in 2011.

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.

SAR-020106 is an ATP-competitive, potent, and selective inhibitor of CHK1, a serine/threonine kinase associated with DNA damage-linked S and G(2)-M checkpoint control. SAR-020106 is a potent radio- and chemosensitizer in tumor cell lines and in vivo xenograft models.