Results of efficacy parameters of spleen and liver organ volume changes measured by MRI. (A) Spleen volumes at screening were 8-54 multiple of normal (MN; normal spleen volume was calculated as 0.2% body weight): mean splenic MN was ∼ 15 MN in each group. Primary efficacy analysis at month 9 (n = 31) demonstrated significant reduction: 26.9% in the 30 U/kg/infusion subgroup and 38% in the 60 U/kg/infusion subgroup (P < .0001). At month 6, the percentage decreases were 22.2% and 29.9%, respectively (P < .0001). (B) Liver volume reduction at month 9 was 10.5% in the 30 U/kg/infusion subgroup (P = .004) 1 and 11.1% in the 60 U/kg/infusion subgroup (P < .0001). In patients with hepatomegaly (defined as liver volume > 1.5 times normal where normal volume was calculated as 2.5% body weight) reduction in liver volume was 13.9% at month 9 for both dose groups combined. The error bars represent SE.