CCT245737 (SRA737)

A potent inhibitor of recombinant human CHK1, CCT245737 (SRA737) has an IC50 of 1.4±0.3 nM (mean±SD, n = 3, EZ Reader II assay). There is > 1,000-fold selectivity for CHK1 versus the functionally important kinases CDK1 and CHK2 (IC50=1.26-2.44 and 9.03 μM, respectively), and at least a 90-fold selectivity against cross-reacting kinases such as ERK8, PKD1, RSK1 and 2. It potently inhibits cellular CHK1 activity (IC50 30-220nM) and enhances SN38 cytotoxicity in multiple human tumor cell lines and human tumor xenograft models. This compound can abrogate an induced G2/M arrest. It has high cell permeability, as measured by transport across a CaCo2 cell monolayer^[1].

Mouse oral bioavailability of CCT245737 (SRA737) is complete (100%) with extensive tumor exposure. It shows significant single-agent activity against a MYC-driven mouse model of B-cell lymphoma. An i.v. dose of 10mg/kg into BALB/c mice gives a peak plasma concentration of 4μmol/L, with a half-life of 2.86h, an AUC0-∞ of 9.96μmol.h/L, a plasma clearance of 2.1L/h/kg and a large volume of distribution (0.19L). The equivalent oral dose gave an almost identical profile with an AUC0-∞ of 10.4μmol.h/L showing complete oral bioavailability (F = 105%). In a word, this compound shows complete oral bioavailability with linear pharmacokinetics and high tumor/plasma ratios consistent with extensive tumor exposure. Adequate tumor drug exposure takes a significant antitumor activity^[1].

Cytotoxicity of CCT245737 (SRA737) is determined as the drug concentration that gave 50% inhibition of tumor cell proliferation (GI50) using a 96h (i.e. 4-doublings) Sulforhodamine B (SRB) assay. Inhibition of its intracellular CHK1 activity is measured using a cell based ELISA for the abrogation of an induced G2 checkpoint (mitosis induction assay, MIA).

• https://pubmed.ncbi.nlm.nih.gov/26295308/