Background:

Mubritinib (TAK-165) is a potent and selective EGFR2/HER2 inhibitor with an IC50 of 6 nM.

TAK-165 specifically inhibits HER2 tyrosine kinase with an IC50 6 nM and does not inhibit other types tyrosine kinase up to 25 000 nM. TAK-165 inhibits HER2 phosphorylation and its down-stream Akt and MAPK in HER2 strongly expressing cells (BT474 breast cancer cell line). TAK-165 sensitivity depends on HER2 levels of each cell line. Especially, BT474 cells which over-express HER2 strongly is highly sensitive (IC50=0.005 μM) and PC-3 cells which express HER2 very weakly is less sensitive (IC50=4.62 μM). But, HT1376 and ACHN cells that over-expressed EGFR showed high IC50 (IC50>25 μM)[1].

In the xenograft model, treatment with TAK-165 significantly inhibits growth of UMUC-3, ACHN, and LN-REC4. The antitumor effect after 14 days treatment are 22.9%, 26.0%, and 26.5% in UMUC3, ACHN and LN-REC4, respectively[1].

Reference：
[1]. Nagasawa J, et al. Novel HER2 selective tyrosine kinase inhibitor, TAK-165, inhibits bladder, kidney and androgen-independent prostate cancer in vitro and in vivo. Int J Urol. 2006 May;13(5):587-92.