By Reuters

The U.S. Food and Drug Administration (FDA) has raised concerns over quality controls at a Mylan NV manufacturing plant in India, according to a warning letter from the agency dated April 3.

India-based drug manufacturing facilities have been criticised by the FDA in recent years for violating quality standards, as the agency increases oversight of key suppliers to the United States.

"Your quality system does not adequately ensure the accuracy and integrity of data to support the safety, effectiveness, and quality of the drugs you manufacture," the FDA said in the letter to Mylan.

The agency's concerns stem from an inspection in September of a facility located at Nashik in Maharashtra that produces antiretroviral therapies (ARVs) used to treat HIV.

"When something reaches a warning letter stage, it can show that the FDA is dissatisfied with the company's attempts to explain or remediate the issue," Wells Fargo analyst David Maris said.

The FDA outlined several violations at Mylan's Nashik facility, including a failure to "thoroughly investigate" unexplained discrepancies in drug batches and cited examples of "missing, deleted, and lost data".

The agency said Mylan had opened an investigation into the "lost" data, but attributed it to power interruptions, connectivity problems and instrument malfunctions.

"You could not explain why these events occurred with frequency in your laboratory, nor had you undertaken a comprehensive investigation into the problem or sought to correct it and prevent its recurrence," the FDA wrote.

Until the regulator can confirm Mylan's compliance with standard manufacturing practices, it may withhold approval of any new applications listing the firm as a drug manufacturer, the FDA said.

Mylan has nine independent sites, including the Nashik facility, that produce and supply ARVs, which helps maintain continuous supply, Mylan spokeswoman Nina Devlin told Reuters.

"In the decade that Mylan has supplied ARVs, we have never had any supply disruption due non-compliance at any site and, again, we do not anticipate any supply disruption at this time," Devlin said.

The FDA had in 2015 had sent a warning letter expressing concerns over quality controls at three Mylan facilities in the south Indian city of Bengaluru.