CRISPR Therapeutics, Vertex set for first sickle cell disease trial after FDA lifts clinical hold — just don’t look for any explanation

CRISPR Therapeutics and Vertex have resolved a clinical hold on a high-profile gene editing program — but they’re still not ready to divulge much in the way of details about the temporary derailment they got slapped with five months ago.

The partners say the FDA has now given the green light to test their sickle cell disease treatment in humans. That will likely expand the Phase I/II study the companies are on track to initiate by the end of the year, adding to sites in the UK and Canada, where they have secured clinical trial approvals.

The announcement was out just after market close Wednesday, carrying CRISPR shares $CRSP up as much as 15% after hours. It is however down again in pre-market trading, as is Vertex $VRTX, which saw a drop of almost 5%.

If successful, the trial would mark the first clinical validation for CRISPR’s ex vivo gene editing approach, which Vertex paid $105 million to partner on back in 2015.

Scientists are still trying to understand the potential harms of the tech. For Vertex — which has built its name largely on cystic fibrosis — it’s also the first bud on its new hemoglobinopathy branch.

CTX001, which involves engineering a patient’s hematopoietic stem cells such that they produce high levels of fetal hemoglobin (or hemoglobin F), will also be investigated as a therapy for beta-thalassemia. Enrollment has begun in Europe.

In a brief statement, CRISPR and Vertex remain tight-lipped about why regulators were concerned or what they did to reassure them.

A Vertex spokesperson has this to say in response to my query: “We can’t share more at this point beyond the fact that we and CRISPR Therapeutics had a productive dialogue with the FDA over recent months and answered the questions raised in their initial review of the IND.”

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Research Scientist - Immunology
Recursion Pharmaceuticals Salt Lake City, UT
Director of Operations
Atlas Venture Cambridge, MA

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