In vitro activity: ASP3026 shows more selective ALK inhibition in a Tyr-kinase panel than PF02341066. ASP3026 inhibits the growth of NCI-H2228, a human NSCLC tumor cell line endogenously expressing EML4-ALK variant 3, with an IC50 value of 64.8 nM.

Kinase Assay: ASP3026 inhibited ALK activity in an ATP-competitive manner and had an inhibitory spectrum that differed from that of crizotinib, a dual ALK/MET inhibitor.

Cell Assay: In mice xenografted with NCI-H2228 cells expressing EML4-ALK, orally administered ASP3026 was well absorbed in tumor tissues, reaching concentrations>10-fold higher than those in plasma, and induced tumor regression with a wide therapeutic margin between efficacious and toxic doses. In the same mouse model, ASP3026 enhanced the antitumor activities of paclitaxel and pemetrexed without affecting body weight. ASP3026 also showed potent antitumor activities, including tumor shrinkage to a nondetectable level, in hEML4-ALK transgenic mice and prolonged survival in mice with intrapleural NCI-H2228 xenografts. In an intrahepatic xenograft model using NCI-H2228 cells, ASP3026 induced continuous tumor regression, whereas mice treated with crizotinib showed tumor relapse after an initial response. Finally, ASP3026 exhibited potent antitumor activity against cells expressing EML4-ALK with a mutation in the gatekeeper position (L1196M) that confers crizotinib resistance. Taken together, these findings indicate that ASP3026 has potential efficacy for NSCLC and is expected to improve the therapeutic outcomes of patients with cancer with ALK abnormality.