Abstract #3738: Discovery of potent and selective orally active inhibitors of anaplastic lymphoma kinase (ALK)

Anaplastic lymphoma kinase (ALK), a receptor tyrosine kinase in the insulin receptor superfamily, was first identified as a chromosomal rearrangement ( NPM-ALK fusion gene) in anaplastic large cell lymphoma (ALCL). Alternate EML4-ALK gene translocation has been detected in a subset of non-small cell lung cancers (NSCLC) and single point mutations in ALK have been identified in a subset of neuroblastomas. Whereas expression of ALK is limited in normal adult human tissues, genetic studies indicate that aberrant expression of ALK is a key driver in these tumor types, which highlights ALK as an important potential target in treating human tumors. The high sequence homology of ALK with other members of the insulin receptor superfamily, presents a significant challenge in the design of ALK-selective inhibitors. Here we report the identification of a series of potent compounds that inhibit ALK both in vitro and in vivo, while maintaining >60 and 400-fold selectivity over the highly homologous insulin-like growth factor-1 receptor (IGF-1R) and insulin receptor tyrosine kinase (IRK), respectively. A representative member from this series inhibited the kinase activity of ALK, IGF-1R, and IRK with IC50s of 0.58, 38, and 262 nM, respectively, and inhibited the viability of Karpas-299 and SU-DHL-1 cells (ALCL cell lines expressing NPM-ALK) with IC50s of 32 and 8 nM, respectively. In Karpas-299 cells, inhibition of viability directly correlated with decreased cellular phosphorylation of NPM-ALK. In NCI-H3122 cells, a NSCLC cell line expressing an EML4-ALK fusion gene, a 30 nM concentration of the same compound inhibited EML4-ALK phosphorylation and cell viability by approximately 50%. For cells that do not express ALK, the IC50s for inhibition of proliferation in several control ALCL and NSCLC cell lines were >1000 nM and the IC50 for phosphorylation of IRK in hepatoma H4IIE cells was >10,000 nM. In vivo, daily oral administration of this specific lead compound to mice bearing subcutaneous xenografts of Karpas-299 cells elicited a dose-dependent antitumor effect, with near-complete tumor regression observed at the highest doses of 50 and 100 mg/kg. In rats, oral doses that achieved plasma levels that were efficacious in the Karpas-299 mouse model had no effect on either insulin or glucose levels. In conclusion, these data demonstrate that despite the high sequence homology among members of the insulin receptor superfamily, identification of ALK-selective compounds is possible and supports the clinical evaluation of such compounds in patients with ALK-driven tumors. Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 3738.