CRISPR Therapeutics (CRSP) and Vertex Pharmaceuticals (VRTX) announced that The U.S. 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 U.S. in adult patients with sickle cell disease. CRISPR and Vertex expect to obtain . . .