The FDA has placed a partial hold on clinical trials testing a new application method for Zolgensma, Novartis’ gene therapy for the genetic disease spinal muscular atrophy, after it showed the potential to cause serious side effects in animal models.
Spinal muscular atrophy is a life-threatening condition that usually arises when the patient is between six months and a year old. It is caused by a mutation to a gene that is essential for the survival of nerve cells. Zolgensma treats the condition by delivering a healthy copy of the gene into patients’ cells by means of a viral vector.
The intravenous version of Zolgensma was approved by the FDA in May this year for patients under two years of age and isn’t affected by the hold. Instead, the hold is in place for Zolgensma injected directly into the spine. This application method is being tested in an ongoing phase I/II trial for children up to five years old because it decreases the dose required to have an effect, and reduces the risk of side effects. No safety issue has been seen in any patients so far, and Novartis released positive interim results from the lower dose patient cohorts earlier this year.
The animal studies linked the gene therapy to inflammation and damage to sensory nerve cells in the spinal cord, which could lead to sensory problems. Novartis will discuss with the FDA the next steps needed to assure patient safety and resume the trial.
Zolgensma has already been under the spotlight this year for other issues. With an initial pricing of $425,000 per year over five years in the US, it’s drawn criticism for being the world’s most expensive drug. In addition, the therapy was the central point of a data manipulation scandal this year, where a small amount of animal study data included in the FDA market approval application was revealed to have been altered by employees at the company.
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