Govindarajulu Babu

Abstract B287: Selective targeting of Met-kinase by RP1400 attenuates tumor progression in mouse models of gastric cancer, glioblastoma, and hepatocellular carcinoma.

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 >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 >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.

Mechanisims of asthma and allergic disease – 1094. Pre-clinical characterization of RP3133, a novel and potent CRAC channel inhibitor for the treatment of respiratory disorders

Calcium release activated calcium channels inhibitors have a potent role in treatment of autoimmune disorders mediated dysregulated T-lymphocyte and mast cell functioning. Herein, we describe the pre-clinical of RP3133, a novel and potent CRAC channel inhibitor with scope for development as a clinical candidate for asthma.

Abstract 4489: Preclinical profile of novel, potent, and selective PI3K delta inhibitors

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Background: Phosphoinositide-3 kinase (PI3K) belongs to a class of intracellular lipid kinases that phosphorylate the 3 position hydroxyl group of the inositol ring of phosphotidylinositol. The PI3K pathway is frequently activated in human cancers and thus represents an attractive target for small molecule inhibitors. Pan-PI3K inhibitors currently in development have been associated with adverse side-effects such as insulin resistance, thus necessitating the need to develop isoform specific inhibitors of PI3K. Herein, we describe the biological and pharmacokinetic properties of representative molecules from a series of novel and small molecule PI3KΔ inhibitors with scope to be further developed as clinical candidates for hematological malignancies such as acute myeloid leukemia and Non-Hodkins lymphoma. Methods: Activity of test compounds on individual PI3K isoforms was determined by a Homogenous Time Resolved Fluorescence assay (Millipore, Billerica, MA) with modifications. Cell based selectivity assays against α, β, or γ isoforms was assessed by testing the effect of the compounds on PDGF, LPA, or c5a induced Akt phosphorylation in NIH-3T3 or RAW cells. Similarly, inhibition of cellular PI3KΔ activity was determined in a IgM induced human B-cell proliferation assay. Cell viability assay was conducted to determine the growth inhibitory effect of the compounds in cell lines representative of human acute and chronic leukaemia and lymphoma. Pharmacokinetic behaviour of compounds in plasma after single dose oral administration was determined in female Balb/c mice. Results: Among the compounds evaluated, RP5175 and RP5182 inhibited PI3KΔ activity in enzyme and cell based assays with IC50 values of 9.6 & 37.3 nM and EC50 values of 7.6 & 18.9 nM respectively. Besides, the compounds displayed a high degree of selectivity over the alpha (>500 fold), beta (>400 fold), and gamma (>15-40 fold) isoforms. Viability assays demonstrated that the compounds caused a significant inhibition in growth of THP-1, TOLEDO, and HL-60 cells. Pharmacokinetic studies in female Balb/c mice indicated good oral absorption with favourable peak plasma concentrations. Conclusions: Results demonstrate the PI3K delta selective nature of RP5175 and 5182 along with an ability to suppress proliferation of cancer cells. In vitro selectivity and potency data indicate the therapeutics potential of the compounds in hematological cancers without the deleterious effects commonly associated with the Pan PI3K inhibitors. The compounds are currently being tested for in vitro and in vivo efficacy across various cancer cell lines and xenograft models besides selectivity against other kinases. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4489. doi:10.1158/1538-7445.AM2011-4489