The chief executive of Novartis on Wednesday defended the company’s decision to delay telling the Food and Drug Administration about manipulated data involving its $2.1 million gene therapy treatment, saying that it “thoroughly, aggressively” investigated the issue and that patient safety was never threatened.

V as Narasimhan , the chief executive, also indicated in a call with investors that the company was forcing out a small number of scientists who were involved in the manipulated data.

The F.D.A. on Tuesday issued an unusual public rebuke of Novartis for failing to report the falsified data before its gene therapy treatment, Zolgensma, was approved in May, even though the company had known about the issue since March. The agency said that it was continuing to investigate and that the company could face civil or criminal penalties.

Novartis and the F.D.A. have said the falsified data did not affect the safety, quality or efficacy of Zolgensma, a therapy that treats a rare genetic disease known as spinal muscular atrophy. The product will remain on the market; about 400 babies a year are born with the disorder in the United States.