The p21 activated kinase 4 (PAK4) is serine/threonine protein kinase that is critical for cancer progression. 6-Ethynyl-1H-indole derivative 55 is a potent and selective PAK4 inhibitor (Ki=10.2 nM). Compound 55 is effective in the treatment of metastatic cancer. The pharmacokinetic study of Compound 55 was carried out by Medicilon.

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