Used as an antiviral agent, particularly effective against herpesviruses and hepatitis B virus. It functions as a nucleotide analog, inhibiting viral DNA polymerase, thereby preventing viral replication. Due to its phosphonate group, it bypasses the initial phosphorylation step required by many antivirals, allowing for enhanced cellular uptake and activation. It has been investigated for use in treating chronic hepatitis B and certain herpesvirus infections, especially in cases with resistance to other antiviral drugs. Its structural design improves metabolic stability and prolongs intracellular half-life, making it suitable for less frequent dosing regimens.