On the surface, Viread seemed to work like AZT and Zerit, but underneath it worked better.

FORBES: The Golden Age of Antiviral Drugs

But AZT has a structural weakness (a flimsy phosphate) that viral enzymes can expel.

FORBES: The Golden Age of Antiviral Drugs

AZT, began as an orphan drug for what was then an obscure disease of the immune system.

ECONOMIST: Rare diseases: Safety in numbers | The

Barr also targeted AZT, Coumadin and Premarin.

FORBES: Lawyers In Lab Coats