PKMYT1-IN-9 is a highly selective, orally active inhibitor of PKMYT1 with an IC50 of 4.4 nM. It exhibits greater selectivity for PKMYT1 compared to WEE1, for which the IC50 is 32.4 μM. Additionally, PKMYT1-IN-9 demonstrates antitumor activity.

PKMYT1:4.4 nM

PKMYT1-IN-9 (Compound 36) exhibits a significant antiproliferative effect on the HCC1569 cell line (CC₅₀: 0.31 μM), but a weaker effect on the KYSE30 cell line (CC₅₀: >30 μM). It strongly inhibits the EPHA1 kinase (IC₅₀: 10.1 nM), while showing much lower efficacy against six other kinases (ABL1, ABL2, BRAF, CSF1R, LCK, and SRC) with an IC₅₀ of >60 nM. Additionally, PKMYT1-IN-9 has no reaction with GSH, does not inhibit hERG, and shows a low inhibition rate on CYP enzymes (<50%). It also demonstrates a high clearance rate in human and mouse liver microsomes (77.3 mL/min/kg at 1 mg/kg IV).

PKMYT1-IN-9 (Compound 36) administered at 15 mg/kg orally twice daily for 21 days effectively inhibits tumor growth by 53% in female NOD-SCID mice carrying xenografts derived from HCC1569 tumors (CDX model).