Abstract B287: Selective targeting of Met-kinase by RP1400 attenuates tumor progression in mouse models of gastric cancer, glioblastoma, and hepatocellular carcinoma.
Authors: Viswanadha Srikant , G Babu , Veeraraghavan Sridhar , Vakkalanka Swaroop 
Published: August 2014

Background: c-Met is a proto-oncogene that encodes the protein Met with intrinsic tyrosine kinase activity. Aberrant Met kinase activity triggers a series of unwarranted phosphorylation events and signalling processes that ultimately lead to the development of cancer. Alteration of the Met kinase signalling cascade represents an attractive approach aimed at blocking invasion and metastasis of cancer cells. Herein, we describe the biological activity and pharmacokinetic properties of RP1400, a novel, selective, and potent Met kinase inhibitor with scope to be developed as a clinical candidate for cancers mediated by dysregulated Met kinase activity.

Methods: Met Kinase activity of RP1400 was determined using an HTRF® KinEASE assay kit (Cisbio, Bedford, MA) with modifications. Met-dependent antiproliferative effect was determined in a host of Met amplified cell lines representative of various cancers. Inhibition of constitutive Met kinase phosphorylation in MKN-45 and NCI-H441 cells was measured in an ELISA assay. Subsequently, effect of the compound on Akt and Stat-5a phosphorylation, downstream markers in the Met signalling cascade, was determined. In vivo efficacy of RP1400 was evaluated in subcutaneous MKN-45 (gastric cancer), U87MG (glioblastoma), and MHCC97H (hepatocellular carcinoma) xenografts using SCID or nude mice. Pharmacokinetic behavior of the compound in plasma after single dose oral administration or IV injection was determined in Balb/c mice.

Results: RP1400 demonstrated remarkable potency against the purified Met kinase enzyme (8.9 nM) with &gt;50-fold selectivity against other kinases in a 451-kinase panel. Inhibition of Met kinase activity was accompanied by a significant reduction in constitutive Met phosphorylation in MKN-45 (28.6 nM) and NCI-H441 (1.8 nM) cells. As a consequence, Akt and Stat-5a phosphorylation were inhibited half-maximally in MKN-45 cells at 16.2 nM and 11.2 nM respectively. RP1400 caused a significant inhibition in proliferation of Met amplified cell lines including MKN-45, EBC-1, SNU-5, and MHCC97H with IC50 values ranging from 3-80 nM. Compounded with a favorable pharmacokinetic profile, in vitro potency of RP1400 translated into excellent in vivo efficacy with &gt;80% reduction in tumor growth noticed in MKN-45, U87MG, and MHCC97H xenografts at 100 mg/kg/BID/PO dose.

Conclusions: Our findings demonstrate the potency of RP1400, a novel and selective small-molecule inhibitor of Met kinase with efficacy values comparable or superior to existing Met kinase inhibitors in development. On lines with selective inhibitors, the compound displayed antiproliferative effect only in cell types harboring amplification of the Met kinase gene. RP1400 is currently undergoing extensive toxicological evaluation with clinical trials anticipated in H1 2014.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B287.

Citation Format: Srikant Viswanadha, Babu G, Sridhar Veeraraghavan, Swaroop Vakkalanka. Selective targeting of Met-kinase by RP1400 attenuates tumor progression in mouse models of gastric cancer, glioblastoma, and hepatocellular carcinoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B287.