The drugmaker says that the data issue only affected a test in animals, and that its $2.1m therapy remains safe to use.

Regulators in the United States want to know why Novartis failed to disclose a problem with testing data until after the Swiss drugmaker’s $2.1m gene therapy was approved.

The Food and Drug Administration (FDA) said on Tuesday that the manipulated data involved testing in animals – not patients – and it was confident that the drug, called Zolgensma, should remain on the market. The agency said it was investigating and will consider criminal penalties if appropriate.

qatar airways

Zolgensma was approved in May for children under two years old, becoming the most expensivemedicine ever. It is a one-time treatment for a rare inherited condition, spinal muscular atrophy, which destroys an infant’s muscle control.

The FDA said in a statement on Tuesday that AveXis Inc, the Novartis AG subsidiary that manufactures Zolgensma, told the agency five weeks after the approval about a “data manipulation issue” that resulted in inaccurate information about testing in animals.

The agency said the company knew about the problem before the FDA approved Zolgensma. The inaccurate data is a small subset of the testing information that the FDA evaluated.

Acting FDA Commissioner Ned Sharpless said on Twitter on Tuesday that “the agency will use its full authorities to take action”.

In a statement on Wednesday, Novartis said that after AveXis learned of alleged data manipulation in one animal testing procedure, the company immediately began investigating. Once it had “interim conclusions”, it shared them with the FDA.

Novartis did not say why it did not notify the FDA before it approved Zolgensma. Novartis stated that the animal test in question is not used in making the therapy for patients and that Zolgensma is safe and effective.

FDA staff inspected the company’s Irvine, California, manufacturing plant in recent weeks then issued a report finding several deficiencies, including not fully following quality control procedures.

Spinal muscular atrophy affects about 400 babies born in the US each year and is a top genetic cause of infant death. Zolgensma works by supplying a healthy copy of the faulty gene that causes the condition.