FDA lifts clinical hold of Vertex/CRISPR Therapeutics’ sickle cell drug

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CRISPR Therapeutics and Vertex are currently enrolling patients in a phase 1/2 beta thalassemia trial in Europe—the first company-backed CRISPR trial—and plans to kick off its sickle cell study by year end. (Nadine Doerlé)

The FDA lifted a clinical hold it placed on Vertex and CRISPR Therapeutics’ gene-edited stem cell therapy for sickle cell disease. The companies are on track to start a human study in sickle cell by the end of the year. 

The agency placed the hold in May, delaying the treatment’s IND and the duo’s plans to start a U.S. phase 1/2 trial later this year. The candidate, CTX001, is autologous gene-edited hematopoietic stem cell therapy. This means the gene editing is done outside the body, on stem cells harvested from a patient. The cells are edited with CRISPR to become blood cells that make high levels of fetal hemoglobin and then infused back into the patient. CTX001 is expected to treat blood disorders by compensating for missing or defective adult hemoglobin. It is in development for beta thalassemia as well as sickle cell. 

While CTX001’s U.S. trial was held up, authorities in multiple other countries have approved clinical trials for CTX001, the pair said in a statement. They are currently enrolling patients in a phase 1/2 beta thalassemia trial in Europe—the first company-backed CRISPR trial—and plans to kick off its sickle cell study by year end. 

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The beta thalassemia trial is taking place at a single site in Germany and will enroll up to 12 adult patients who have transfusion-dependent beta thalassemia. 

RELATED: CRISPR Therapeutics, Vertex start first company-backed human CRISPR trial

For a time, it looked like Editas Medicine would be the first to launch a human trial, with plans to start testing a CRISPR treatment for a rare form of blindness in 2017. Manufacturing issues delayed the timeline to 2018, with CEO Katrine Bosley saying in the company’s second-quarter update that the IND filing is slated for October.  

CRISPR and Vertex initially teamed up in 2015, when the latter forked over $75 million in cash and took a $30 million stake in the former in exchange for the right to license up to six gene-editing programs. Vertex licensed CTX001 in December. It is the first CRISPR-based treatment to come out of the four-year deal. 

Analysts at Jefferies said in a note to clients: “We recently hosted VRTX partner CRSP at our Jefferies Gene Therapy Conference...and mgmt noted while both gene editing studies are expected to be enrolling patients by YE:18 (beta-thal currently enrolling and SCD set to start enrolling patients by year end), the companies do not want to announce results too early before the data matures - i.e., durability is important per VRTX commentary and it doesn't want to dribble out pieces of data one patient at a time like some competitors.

“CRSP has commented for beta-thal it would like to see: 1) high edited cell engraftment of 80%+; 2) fetal hemoglobin levels of 15-20%+ early on though the higher the better; 3) good durability is key and clean safety given unknowns for gene editing. This could be important proof of concept for early gene editing technology in 2019 (along w/ allogeneic CD-19 Phase I CAR-T for CRSP w/ data in 2019).”