Patent ID: 7723509

Claim:
An iRNA agent comprising a first strand and optionally a second strand, wherein at least one subunit having a formula (I) is incorporated into at least one of the strands: wherein: X is N(CO)R 7 , or NR 7 ; Each of R 1 , R 3 , and R 9 is, independently, H, OH, OR a , OR b , CH 2 OR a , or CH 2 OR b , provided that at least one of R 1 , R 3 , and R 9 is OH, OR a , or OR b and that at least one of R 1 , R 3 , and R 9 is CH 2 OR a , or CH 2 OR b ; R 7 is T-R d , in which T is a tether comprising a hydrocarbon chain and one or more linking groups, wherein at least one of the linking groups is cleavable; and R d is a steroid radical, wherein the tether selected from the group consisting of each of A and C is, independently, O or S; and B is OH, O − , or