M443 is an irreversible and specific MRK inhibitor (IC50<125 nM).

Similarly, the clonogenic assay displays a significant decrease in survival with a dose enhancement factor (DEF) of 1.6 at 10% viability. MRK depletion reduces cell viability after IR by 33% of control at 3 Gy. In both cell cultures, the IR-stimulated activation of MRK, Chk2, and p38 are greatly inhibited by 500 nM M443. Cells are seeded on coverslips, pretreated with 500 nM M443 or vehicle, exposed to 6 Gy of IR, fixed at different times after IR, and processed for immunofluorescence with the MPM2 phospho-specific antibody that specifically stains mitotic cells. The M443-treated cells fail to arrest after IR and maintained a similar mitotic index as the nonirradiated cells, in contrast to control cells. Thus, inhibition of MRK leads to inhibition of Chk2 and failure to arrest in the cell cycle in response to IR-induced DNA damage.

Treatment with M443 alone adds 5.5 days to this survival, whereas the chosen low dose of radiation does not significantly increase survival. Control mice survive with a median of 32 days after tumor cell implantation. It is displayed that the tumor-containing fraction has elevated levels of both total and active MRK (lane RB in the vehicle-treated brain). The combination of M443 and IR extend survival with a median of 16 days longer than control. Treatment with M443 does not affect the animal weight, as the weight loss observed is observed in all groups just a few days before the animals became moribund. The tumor-containing fraction from the M443-treated brain shows the total loss of MRK activity. The fractions containing the normal brain, which in the control brain show some level of MRK protein, in the treated brain also has lost MRK, suggesting that diffusion of M443 across the whole cerebellum inhibits normal MRK as well.

1820684-31-8

C31H30F3N7O2

589.61

DMSO:55 mg/mL (93.28 mM),Need ultrasonic
Powder: -20°C for 3 years
In solvent: -80°C for 2 years