A US company that raised the price of a drug for treating a deadly parasitic infection by more than 5,000 per cent says it will roll back some of the increase.

Turing Pharmaceuticals CEO Martin Shkreli said the new price would make Daraprim more accessible.

"We've agreed to lower the price of Daraprim to a point that is more affordable and is able to allow the company to make a profit, but a very small profit," Mr Shkreli said.

The company obtained rights to sell the drug, the only US-approved treatment for toxoplasmosis, in August. It hiked the price overnight from $13.50 per pill to $750.

Turing had said it would use profits to improve the drug's formulation and develop new, better drugs for the infection. It also stressed that some patients can get financial aid from the company to receive the drug.

But the price hike sparked outrage from medical groups representing doctors who care for patients with HIV and other infectious diseases, because Daraprim treats patients with compromised immune systems.

Hillary Clinton called Turing's price hike "outrageous". While campaigning for the Democratic nomination for president, she outlined a broad plan aimed at holding down the cost of prescription drugs.

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