Zidovudine (ZDV, AZT) has an azide (N3)
group instead of a hydroxyl (OH) group on its pentose sugar. Once the phosphate
group of the zidovudine bonds to OH of the last deoxyribonucleotide in the strand,
no further free deoxyribonucleotides can attach. (The phosphate groups of free
deoxyribonucleotides can only bond to OH groups, they are unable to bond to N3
groups.) This results in an incomplete provirus.