-Weakness: Antiretroviral drugs work, in part, by looking like DNA/RNA nucleotides. The "indiscriminate" viral enzyme (reverse transcriptase) mis-incorporates the drug, stopping viral replication, while the cell's RNA higher fidelity machinery rejects it, which limits the treatment's toxicity.

One of the problems (for HIV) is that it likes to infect both actively dividing "new" white blood cells like activated T-cells, and "old" (terminally differentiated) cells like macrophages. But these old cells no longer have the same pool of DNA bases floating around, ready to be made into new DNA.