The maker of a gene therapy for babies did not inform federal regulators about “data manipulation that created inaccuracies” until after its treatment was approved, the US Food and Drug Administration says.

The manipulated data was submitted by AveXis, a subsidiary of drugmaker Novartis, for the spinal muscular atrophy therapy Zolgensma, the FDA said.

The treatment has been criticized for its sky-high cost: $2.1 million.

Because AveXis didn’t inform the FDA of the issue until after Zolgensma was approved, the agency said Tuesday it will “use its full authorities to take action, if appropriate, which may include civil or criminal penalties,” said Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research.

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Marks said the agency “remains confident that Zolgensma should remain on the market” and noted that the inaccuracies involve “a small portion of the product testing data.” Still, he said, the submission of truthful and accurate data is “critical for the FDA to be able to protect the public health, and the law requires it.”

Zolgensma was approved in May, and the FDA wasn’t informed of the data manipulation until a month later, according to the agency.

Marks said “AveXis became aware of the issue of the data manipulation that created inaccuracies in their [biologics license application] before the FDA approved the product, yet did not inform the FDA until after the product was approved.”

Company stands behind Zolgensma

In a statement Tuesday, Novartis said it stands behind its multimillion-dollar therapy, which is approved for children less than 2 years old with spinal muscular atrophy. “We maintain that the totality of the evidence demonstrating the product’s effectiveness and its safety profile continue to provide compelling evidence supporting an overall favorable benefit-risk profile,” the company said.

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Its gene therapy subsidiary AveXis “voluntarily self-disclosed to the FDA and subsequently to other health authorities that some data previously submitted to the agency as part of our [biologics license application] was inaccurate,” the company said.

Novartis said AveXis “had become aware of allegations of data manipulation in a specific animal testing procedure used in the development of the product” and launched an investigation into the findings, sharing them with the FDA “once we had interim conclusions from our investigations.”

Therapy hailed as a ‘milestone’ for genetic disorder

In May, the FDA’s acting commissioner, Dr. Ned Sharpless, called the spinal muscular atrophy therapy’s approval “another milestone in the transformational power of gene and cell therapies to treat a wide range of diseases.” Patient groups, though, were quick to criticize the treatment’s cost.

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David Mitchell, founder of the advocacy group Patients For Affordable Drugs, told CNN at the time that “it is emblematic of our broken system that effectively forces us to pay whatever price drug corporations demand for lifesaving new drugs.”

But the group Cure SMA, which advocates for spinal muscular atrophy treatments, still hailed the treatment’s approval. “This is an important day for the SMA community. Clinical data shows that a one-time infusion of Zolgensma can change the course of SMA,” Kenneth Hobby, the organization’s president, said in May.

The disease is an inherited disorder stemming from a defective gene that leads to the death of nerve cells, affecting the muscles that allow people to walk, talk, breathe and swallow, according to the National Institute of Neurological Disorders and Stroke.

As many as 1 in 8,000 babies is estimated to be affected by one of the genetic mutations that causes it. Zolgensma, a one-time treatment, places a working copy of that gene into nerve cells before they die and symptoms develop.

In response to the FDA’s announcement Tuesday, Cure SMA said it “is investigating this issue and will report when we have further details.”