What is the mechanism of action of nucleoside reverse transcriptase inhibitors (NRTIs)?

Nucleoside reverse transcriptase inhibitors (NRTIs) work by specifically targeting the enzyme reverse transcriptase, which is critical for the replication of HIV. The mechanism of action involves integrating into the DNA synthesis process. NRTIs are structurally similar to the natural nucleosides the virus uses to create DNA from its RNA genome. When reverse transcriptase attempts to replicate the viral RNA into DNA, the incorporated NRTI acts as a chain terminator. This halts the elongation of the newly synthesized DNA strand because NRTIs lack the necessary components to continue adding nucleotides. As a result, the conversion of viral RNA into DNA cannot be completed, effectively preventing the virus from integrating into the host genome and subsequently producing new viral particles.

This action is crucial because it directly interrupts the lifecycle of HIV, making NRTIs an essential class of antiretroviral drugs in the treatment of HIV infection. By inhibiting the reverse transcriptase, they reduce the viral load and help control the infection.