Pradefovir mesylate is primarily used in the treatment of chronic hepatitis B virus (HBV) infections. It functions as a prodrug of adefovir, which is an antiviral agent that inhibits the replication of the HBV virus. By converting to its active form in the liver, it specifically targets and suppresses viral DNA polymerase, thereby reducing viral load and improving liver function. This makes it a valuable option for patients requiring long-term antiviral therapy to manage HBV and prevent complications such as liver cirrhosis and hepatocellular carcinoma. Its use is often considered in cases where other antiviral treatments may be less effective or unsuitable.