The company said that Zolgensma was a one-time treatment for spinal muscular atrophy, a disease that affects about 1 in 10,000 births and leads to death or the need for permanent ventilation at age 2 in 90 percent of cases.
But the message comes as the administration of US President Donald Trump has promised to deal with high drug costs.
Novartis defended pricing by saying that gene therapy was a transformative new type of treatment and was 50 percent cheaper than current treatments.
"Zolgensma is a historic advance for the treatment of SMA and a single gene therapy for one time," noted Novartis CEO Vas Narasimhan in a statement, adding that the company was working with the government and insurance companies to speed up coverage.
The total cost amounts to $ 2,125 million paid over five years to $ 425,000 per year.
Zolgensma works by providing a functional copy of the defective gene responsible for SMA to stop disease progression through a single intravenous infusion.
The US Food and Drug Administration said the drug's safety had been tested in an ongoing clinical trial and a completed clinical trial in 36 patients between two weeks and eight months.
Most evidence of its effectiveness was based on the results of the ongoing experiment, which found that "patients treated with Zolgensma … showed a significant improvement in their ability to reach developmental motor milestones" including head control and the ability to sit without support.
Jerry Mendell, a physician involved in the attempt at the Nationwide Children's Hospital in Columbus, Ohio, added that "the effectiveness, delivered as a one-time treatment, is truly remarkable and provides a level of unprecedented hope for families".
The most common side effects of Zolgensma are elevated liver enzyme and vomiting, FDA says.
Gene and cell therapies utilize the biology to convert diseases ranging from congenital blindness to pediatric leukemia.