NEW YORK: Novartis AG said on Wednesday it replaced the two top research and development executives at its Avexis unit after some data was manipulated from early testing of a gene therapy for infants that costs more than $2 million.

Avexis' Chief Scientific Officer Brian Kaspar and Senior Vice President of Research and Development Allan Kaspar have not been involved in any operations at Avexis since early May 2019, Novartis said in a statement.

The Kaspars are brothers. Brian Kaspar was a founder and key executive at Avexis and made more than $380 million from the company's 2018 acquisition by Novartis, according to SEC filings.

The Kaspars could not immediately be reached for comment.

Page Bouchard has taken on both those roles at Avexis as of Aug. 5, Novartis said.

The Swiss drugmaker said last week that it was in the process of "exiting" the Avexis scientists responsible for the manipulation of data on gene therapy Zolgensma. A Novartis spokesman said on Wednesday that a few other scientists beyond the Kaspars were no longer at the company but did not give any further details.

Novartis has not said who is responsible for the manipulated data.

The US Food and Drug Administration said last week that Novartis had notified regulators in June - more than a month after Zolgensma had been approved - that some of the early testing data had been manipulated.

The company had been aware of the problems for as many as two months before the drug's US approval, the FDA said, and it could face criminal or civil penalties.

Novartis said last week that it learned of allegations of data manipulation in mid-March and finished a preliminary investigation into the allegations in early May, confirming data discrepancies and raising data integrity concerns.

US Senate Finance Committee Chairman Chuck Grassley sent a letter to Novartis last week asking the company to provide details about the manipulation by Aug. 23.

Novartis acquired Avexis last year, paying $8.7 billion for the maker of the rare-disease treatment, which is expected to bring in billions of dollars in sales.

Zolgensma - the world's most expensive drug - was approved as a one-time treatment for spinal muscular atrophy (SMA) in late May.

The disease often leads to paralysis, breathing difficulty and death within months for babies born with the most serious Type I form. SMA affects about one in 10,000 live births, with 50% to 70% having Type I disease, and is the leading genetic cause of death in infants.