The experiments demonstrate that with viewpoint of the pharmacokinetics and therapeutic effect the astatinated Fab fragment is well suited to 7.2 h half-life of ²¹¹At, since tumor uptake remains high (~10%/g) from 3 to 14 h after i.v. injection of ²¹¹At-3H11Fab, moreover, at the same dose the tumor inhibition with ²¹¹At-3H11Fab were 84.4% by weight and 86.4% by volume higher than with ²¹¹At-3H11 (67.1% and 67.8%, respectively) on 10d post last i.p. administration.