TAS6417 (CLN-081, TPC-064) is a novel EGFR inhibitor that targets EGFR exon 20 insertion mutations while sparing wild-type (WT) EGFR. IC50 values ranges from 1.1 ± 0.1 to 8.0 ± 1.1 nmol/L.
Of the 255 kinases tested, TAS6417 inhibits 25 kinases other than EGFR with IC50 values less than 1,000 nmol/L, which was 100 times higher than its IC50 value against WT EGFR. It inhibits only six kinases containing TXK, BMX, HER4, TEC, BTK, and JAK3, with IC50 values less than 10 times that against WT EGFR. TAS6417 inhibits proliferation of Ba/F3 cells driven by various EGFR exon 20 insertion mutations, with IC50 values ranging from 5.05 ± 1.33 nmol/L to 150 ± 53 nmol/L. It also suppresses the growth of cells expressing exon 20 insertion mutations of the EGFR gene, with a GI50 value of 86.5 ± 28.5 nmol/L for LXF 2478L cells and 45.4 ± 2.6 nmol/L for NCI-H1975 EGFR D770_N771insSVD cells. TAS6417 has no effect on EGFR-independent proliferation in NCI-H23 or NCI-H460 cells[1].
TAS6417 causes persistent tumor regression in vivo in EGFR exon 20 insertion-driven tumor models. The tumor regression occurrs quickly after TAS6417 treatment and persists during the treatment period. Pharmacokinetic analysis reveals that the plasma concentration of TAS6417, administered at 50 and 100 mg/kg to mice, decreases rapidly in the first 4 hours. In contrast, although the effective doses in the rat model exhibit lower maximum plasma concentration (Cmax) values than those in the mouse model, the plasma concentrations tend to be more persistent, lasting up to 8 hours. TAS6417 inhibits mutant EGFR in tumors but not WT EGFR in skin tissues. It prolongs survival of animals bearing lung cancer[1].
[1] Hasako S, et al. Mol Cancer Ther. 2018, 17(8):1648-1658.