CRISPR Therapeutics and Vertex Pharmaceuticals Incorporated announced that the US Food and Drug Administration (FDA) has placed a clinical hold on the Investigational New Drug Application (IND) for CTX001 for the treatment of sickle cell disease pending the resolution of certain questions that will be provided by the FDA as part of its review of the IND. The IND was submitted to the FDA in April to support the planned initiation of a phase 1/2 trial in the US in adult patients with sickle cell disease. CRISPR and Vertex expect to obtain additional information on the FDA's questions in the near future and plan to work rapidly with the FDA toward a resolution.

CTX001 is an investigational, gene-edited autologous hematopoietic stem cell therapy for patients suffering from ß-thalassemia and sickle cell disease (SCD). The planned initiation of a phase 1/2 trial of CTX001 in Europe in adult patients with transfusion dependent ß-thalassemia is unchanged, and the companies expect to initiate the trial in the second half of 2018.

CTX001 is an investigational ex vivo CRISPR gene-edited therapy for patients suffering from ß-thalassemia and sickle cell disease in which a patient's hematopoietic stem cells are engineered to produce high levels of fetal hemoglobin (HbF; hemoglobin F) in red blood cells. HbF is a form of the oxygen carrying hemoglobin that is naturally present at birth, and is then replaced by the adult form of hemoglobin. The elevation of HbF by CTX001 has the potential to alleviate transfusion-requirements for ß-thalassemia patients and painful and debilitating sickle crises for sickle cell patients.CTX001 is being developed under a co-development and co-commercialisation agreement between CRISPR Therapeutics and Vertex.

CRISPR and Vertex entered into a strategic research collaboration in 2015 aimed at the discovery and development of gene editing treatments using the CRISPR/Cas9 technology to correct defects in specific gene targets known to cause or contribute to particular diseases. Vertex has exclusive rights to license up to six new CRISPR/Cas9-based treatments that emerge from the collaboration, and CTX001 represents the first treatment to emerge from the joint research program. For CTX001, CRISPR and Vertex will equally share all research and development costs and profits worldwide.

CRISPR Therapeutics is a leading gene editing company focused on developing transformative gene-based medicines for serious diseases using its proprietary CRISPR/Cas9 platform. CRISPR/Cas9 is a revolutionary gene editing technology that allows for precise, directed changes to genomic DNA.

Vertex is a global biotechnology company that invests in scientific innovation to create transformative medicines for people with serious and life-threatening diseases. In addition to clinical development programs in CF, Vertex has more than a dozen ongoing research programmes focused on the underlying mechanisms of other serious diseases.