A single intravenous (i.v.) dose of AZD5991 leads to a dose-dependent antitumor effect ranging from tumor growth inhibition (TGI) to tumor regression (TR). Ten days after treatment, AZD5991 shows 52% and 93% TGI (p<0.0001) at 10 and 30 mg/kg, respectively. At the same time point, AZD5991 at 60 mg/kg leads to 99% TR with no detectable tumors in 6 out of 7 mice, while complete TR is seen in 7 out of 7 mice in the 100 mg/kg dose group. AZD5991 also shows a dose-dependent duration of response with tumors in the 100 mg/kg group growing back later than those in the 60 mg/kg group. The magnitude of in vivo tumor efficacy is correlated with activation of caspase-3 in the tumor and concentration of AZD5991 in plasma. Treatment with AZD5991 was well tolerated at all dose levels with no significant body weight loss. A single dose of AZD5991 36 days after the first dose causes tumor regression in 4 out of 4 mice. In mice dosed with AZD5991 at 100 mg/kg on day 0 and day 1, tumors grow back later than those dosed with a single dose of AZD5991 at the same dose level[1].
