American pharmaceutical executive Martin Shkreli has downplayed the efforts of Sydney Grammar students who have recreated the active ingredient in his company's expensive Daraprim HIV drug for just $20.

After news of the students' accomplishment went viral on Wednesday, Mr Shkreli was tagged in a number of tweets alerting him to the fact.

"Could Martin Shkreli have some competition from these school kids?" Twitter asked.

Mr Shkreli's answer was a straight "no".

"Almost any drug can be made at a small scale for a low price," he responded to one tweet.

Loading

"Learning synthesis isn't innovation," he said to another.

"You know more goes into 'manufacturing a drug' than making 5mg at lab scale with no QA right?"

The heated dialogue comes after Mr Shkreli, in 2015, controversially jacked up the price of Daraprim, used to treat HIV and malaria, from $US13.50 to $750 per pill.

One Twitter user said the school students' cheap recreation of the drug ingredient exposed how Mr Shkreli had monopolised the drug.

While Mr Shkreli may not think much of the high school students' accomplishment, their classroom re-creation has reignited the ethics debate about company price hikes on life-saving medicines.