MiR-122 is a liver-specific microRNA (miRNA) that plays a pivotal role in regulating hepatic functions such as lipid metabolism and stress response. The observation that hepatitis C virus (HCV) could only replicate in miR-122-positive hepatocytes led to the discovery that miR-122 is essential for HCV replication, and miR-122 is now one of the crucial host factors for anti-HCV therapy. Currently, the most advanced miR-122 targeting therapy is SPC3649 (miravirsen), a locked nucleic acid-modified oligonucleotide antagonizing miR-122. This review serves to provide information on the discovery and development of SPC3649, the first miRNA-targeted drug to enter human clinical trials, and introduce other miR-122-targeting therapeutics being developed for hepatitis C.