[CAS NO. 391210-10-9]  Mirdametinib (PD0325901)

The improved potency of PD0325901 relative to CI-1040 is evident. A single oral dose of PD0325901 (25 mg/kg) inhibits phosphorylation of ERK by more than 50% at 24 hours post-dosing. In contrast, CI-1040 at a much higher dose (150 mg/kg) only inhibit pERK levels for roughly 8 hours, returning to control levels by 24 hours after treatment. Therefore, the dose required to produce a 70% incidence of complete tumor responses (C26 model) is 25 mg/kg/day versus 900 mg/kg/day for PD0325901 and CI-1040, respectively. Anticancer activity of PD 0325901 has been demonstrated for a broad spectrum of human tumor xenografts. After 1 week of oral administration of PD0325901 (20–25 mg/kg/day) in mice, no tumor growth is detected in mice inoculated with PTC cells bearing a BRAF mutation. For PTC with the RET/PTC1 rearrangement, the average tumor volume of the orthotopic tumor is decreased by 58% as compared with controls. In conclusion, PTC cells carrying a BRAF mutation are more sensitive to PD0325901 than are PTC cells carrying the RET/PTC1 rearrangement.