Gene therapy took another public step forward during a virtual presentation at a scientific conference on Friday. CRISPR Therapeutics (CRSP -0.88%) and Vertex Pharmaceuticals (VRTX 1.36%) presented updated results from studies with CTX001, the first CRISPR-based gene-editing therapy to reach human-stage testing.

Meeting goals 

In the Climb-111 trial treating transfusion-dependent beta-thalassemia (TDT), CTX001 drastically reduced patients' dependence on frequent blood transfusions. In the years leading up to the trial, Patient 1 required 34 units of red blood cells annually and Patient 2 needed transfusions at a rate of 61 units per year. At 15 months following a single infusion of CTX001, patient 1 still hasn't required a transfusion. At the five-month mark, patient 2 hasn't required a transfusion either.

Microscope close up

Image source: Getty Images.

In the Climb-121 trial treating severe sickle cell disease, an infusion of CTX001 appeared successful for the first two patients treated. Treatment with CTX001 should lead to the body producing healthy fetal hemoglobin to replace the faulty hemoglobin at the source of their blood disorders.

Patience will be required

It could be a long time before we know if Vertex and CRISPR have a new marketable treatment option for sickle cell disease. The Climb-121 trial will look for fetal hemoglobin levels of 20% or higher sustained for at least three months. The observation window doesn't begin until six months after treatment and it lasts for a year and a half.

Climb-121 and Climb-111 are intended to enroll around 45 patients, but CRISPR and Vertex had to pause conditioning and dosing newly enrolled patients entering both studies due to the COVID-19 pandemic. The companies have resumed dosing at some locations and they expect to report more data in the second half of the year.