US FDA consultants to determine necessity for additional studies of Vertex/CRISPR gene therapy


The staff reviewers of the US Food and Drug Administration on Friday requested the regulator’s advisory panel to consider the necessity for extra investigations for the sickle cell disease gene therapy developed by Vertex Pharmaceuticals and CRISPR Therapeutics.

The therapy, known as exagamglogene autotemcel or exa-cel, utilizes the latest gene editing CRISPR technology, and is the first-of-its-kind product to reach the FDA to make a decision on approval.

The reviewers of the FDA expressed concerns about the use of this kind of gene editing which may cause unintended genomic alterations known as “off-target” and potentially induce other side effects. They, however, mentioned no concerns about the effectiveness of the therapy.

The FDA staff believed that the small size of the genetic sample used in the lab analysis of the therapy might not be enough to ensure safety, as it did not cover the diverse population of sickle cell disease patients across the United States.

They also raised doubts about the adequacy of the company’s analysis to assess the off-target risk.

RBC analyst Luca Issi observed that the FDA was mainly focusing on the risks related to the technology. However, he considered the FDA’s concerns to be minor and anticipated additional studies to be conducted only after the therapy receives approval.

Vertex and CRISPR Therapeutics are striving to get approval for the therapy as a treatment for the inherited disorder that causes red blood cells to take on a sickle-like shape due to abnormal levels of hemoglobin in the body.

If approved, the therapy might offer patients a one-time treatment option, instead of having to undergo frequent blood transfusions or take daily medications such as Pfizer’s Oxbryta.

An independent panel is scheduled to meet on Tuesday to discuss the analysis of off-target effects and determine if additional lab investigations are needed.

The FDA will make a decision on the therapy’s use in patients aged 12 years and older by December 8.

The shares of CRISPR Therapeutics and Vertex remained unchanged in early trading.

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