Table 1.

Challenges for siRNA and ASO Delivery

Challenge	siRNA	PS ASO
Metabolic stability	√	√
Innate immune activation	√	√
Off-target effects	√	√
Toxicity	√	√
Long duration of response	√	√
Endosomal escape	X	X

√ = solved with chemistry; X = not yet solved.

PS, phosphorothioate; ASO, antisense oligonucleotide.