By Angus Crawford
Marty St Clair's breakthrough saved lives
It is 20 years since the world's first HIV/Aids drug came onto the market in the US.
There were complaints AZT was expensive and could have toxic side effects.
But it offered hope.
Not of a cure, but at least of a longer life for the 15,000 Americans then living with the disease.
Hope too for governments worldwide who watched as the pandemic began.
The scientist who first realised AZT could tackle HIV was Marty St Clair.
She is still working in the field for British pharmaceutical giant GSK.
"It absolutely woke me up," she told me, describing that day in November 1984.
She was doing drug trials on cells in petri dishes.
"You can imagine this was rather a boring task I was doing."
She put living cells in petri dishes. Then she added the virus.
A series of different drugs were then put in 350 samples.
If the drug failed to work the cells died and dropped off, making a hole or plaque.
Ms St Clair had to count every single plaque on every single dish.
"I was holding them up to the window," she said. "I came to 16 dishes, none of which had any plaques."
All were labelled as containing AZT.
Ms St Clair didn't believe it.
"I rang my supervisor, then I said: 'I wonder if I forgot to put the virus in these 16?'" she recalls.
"He looked at them and said: 'That's stupid, out of 350 plates you forgot to put virus in these? Of course you didn't screw up'.
"He actually believed this was the eureka moment more than I did."
It was late on Friday night. She told a few people and went home to bed.
"Monday morning - I had five or six messages saying, 'did I hear it right? Do we have something that could be used against Aids?'"
It took just three years to get AZT licensed.
"Today it's 10 or more years to get a drug to market," said Ms St Clair.
"But remember people were dying, people were being diagnosed with Aids and within just a matter of months were dead."
"It was the first ray of hope."
But it cost $188 for 100 pills - out of reach for many people.
"It was frustrating," Ms St Clair confesses. "But we were doing our very best to make it available as easily as we could."
It also had side effects.
"It was very toxic. We didn't have the battery of trials that drugs today have. We very quickly realised that was a toxic dose and reduced it over time."
HIV/Aids was spreading faster in Africa then anywhere else.
The price of the drug and poor health care systems placed it out of reach of most sufferers.
"I do believe that where you are born shouldn't determine the quality of your health care," said Ms St Clair.
"Therapies truly are out reach of a lot of patients.
"Our company has really made inroads into making drugs available for patients in developing nations."
AZT is still in use across the world, and Ms St Clair says she'll always be associated with it.
"It's our passion, it is our life's work," she said. "If it weren't for AZT I don't know where we'd be today.
"You always have to start with one - and AZT was the first."