Martin Shkreli mocked a group of high school students who recreated his $750-drug Daraprim for $2

Sydney (AFP) — "Bad boy" pharmaceutical chief Martin Shkreli, who raised the cost of an HIV drug by 5,000 percent, has mocked a group of Sydney school students who recreated the life-saving medicine on the cheap.

The teenagers said they were spurred to try recreate the drug after Shkreli became a global figure of hate by buying the rights to Daraprim and then hiking the price in the United States from $13.50 a tablet to $750.

In response Shkreli tweeted some sarcastic remarks about the students' successful recreation of pyrimethamine, the active ingredient for Daraprim, an anti-parasitic used to treat people with low immune systems such as those with HIV.

"Labor and equipment costs? Didn't know you could get physical chemists to work for free?" Shkreli tweeted. "I should use high school kids to make my medicines! 

"And why buy my equipment when I can use the lab's for free?! And those teachers who told them what to do, they'll work for free, right."

Student James Wood said this week he and his friends, with the help of University of Sydney chemists, had started off with just $20 of the drug, and in one reaction had produced thousands of dollars' worth.

Turing Pharmaceuticals, which Shkreli used to head, continue to sell the only FDA-approved form of the drug in the US, but reportedly cut the price in half for hospitals after an outcry.

Daraprim, which figures on the World Health Organisation list of essential medicines, is cheap in most countries, with 50 tablets selling in Australia for $10.

In another tweet about the students Shkreli said: "We know they made this, how? Cause they said so?"

Several hours after being blasted on Twitter for his comments, Shkreli was more gracious in a short YouTube clip Friday.

"These Australian students are proof that the 21st century economy will solve problems of human suffering through science and technology," he said.

"We should congratulate these students for their interest in chemistry and all be excited about what is to come in this stem-focused 21st century."