For $US20, a group of high school students has created 3.7 grams of an active ingredient used in the medicine Daraprim, which would sell in the United States for between $US35,000 and $US110,000.

Key points: Sydney Grammar students recreate Pyrimethamine in school lab at just $20 cost

Sydney Grammar students recreate Pyrimethamine in school lab at just $20 cost Daraprim retails in the tens of thousands in the United States

Daraprim retails in the tens of thousands in the United States Drug used to treat parasitic infection in people with weak immune systems

Pyrimethamine, the active ingredient in Daraprim, treats a parasitic infection in people with weak immune systems such as pregnant women and HIV patients.

In August 2015, the price of Daraprim in the US rose from $US13.50 per tablet to $US750 when Turing Pharmaceuticals, and its controversial then-chief executive Martin Shkreli, acquired the drug's exclusive rights and hiked up the price.

Since then, the 17-year-olds from Sydney Grammar have worked in their school laboratory to create the drug cheaply in order to draw attention to its inflated price overseas, which student Milan Leonard said was "ridiculous".

"It makes sense that if you're putting billions of dollars into research for a drug like this, you should be able to reap some profit, but to do something like this … it's just not just," he said.

Milan described the moment he realised he and his classmates had been successful.

"It was ecstatic, it was bliss, it was euphoric," he said.

"After all of this time spent working and chemistry being such a high and low, after all the lows, after all the downs, being able to make this drug, it was pure bliss."

Fellow student Brandon Lee said he could not believe the result after a year of work.

"At first there was definitely disbelief," he said.

"We spent so long and there were so many obstacles that we, not lost hope, but it surprised us like 'oh, we actually made this material' and 'this can actually help people out there'.

"So it was definitely disbelief but then it turned in to happiness as we realised we finally got to our main goal."

The 17-year-olds from Sydney Grammar recreated Pyrimethamine in their high school laboratory.

Turing Pharmaceuticals continue to sell the only FDA-approved form of the drug in the US, and last year, said federal and state health schemes answered questions of access and affordability.

Following backlash, the company lowered the cost by 50 per cent for hospitals.

University of Sydney research chemist Alice Williamson supported the boys' work through an online research-sharing platform Open Source Malaria, and said they had done "fantastically well".

"The original route that we got, so the original recipe if you like to make this molecule, was from a patent that was referenced on Wikipedia," Dr Williamson said.

"Now of course we checked to see if it looked reasonable … but the route that was up actually had one step that involved a really dangerous chemical.

"The boys had to navigate a difficult step and do this in a different way, and they've managed to do that, and they've managed to do that in their high school laboratory."

In most countries, including Australia, Daraprim is sold for between $1 to $2 per pill.

A second US-based company, Imprimis Pharmaceuticals, made an alternative compound to Daraprim — sold for US$1 a dose — but the drug is not FDA-approved.