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A sickled red blood cell
beside a normal one
Image by Betty Pace

The US Food and Drug Administration (FDA) has granted breakthrough therapy designation to voxelotor (previously GBT440) for the treatment of sickle cell disease (SCD).

Voxelotor is being developed by Global Blood Therapeutics, Inc., as a potentially disease-modifying therapy for SCD.

The drug works by increasing hemoglobin’s affinity for oxygen. Since oxygenated sickle hemoglobin does not polymerize, it is believed that voxelotor blocks polymerization and the resultant sickling of red blood cells.

If voxelotor can restore normal hemoglobin function and improve oxygen delivery, the therapy may be capable of modifying the progression of SCD.

The FDA previously granted voxelotor fast track designation, orphan drug designation, and rare pediatric disease designation.

The FDA’s decision to grant breakthrough therapy designation to voxelotor was based on clinical data submitted from the following studies:

  • Part A of the phase 3 HOPE study (GBT440-031)
  • A phase 1/2 study and open-label extension in adults (GBT440-001/GBT440-024), which was presented at the 2016 ASH Annual Meeting
  • The ongoing phase 2 HOPE-KIDS 1 study in children age 6 to 17 (GBT440-007), which was presented at the 2017 ASH Annual Meeting (abstract 689)
  • The compassionate access experience in adults with severe SCD who were not eligible for the HOPE study, which was presented at the 2017 ASH Annual Meeting (abstract 3545).

About breakthrough designation

The FDA’s breakthrough designation is intended to expedite the development and review of new treatments for serious or life-threatening conditions.

The designation entitles the company developing a therapy to more intensive FDA guidance on an efficient and accelerated development program, as well as eligibility for other actions to expedite FDA review, such as rolling submission and priority review.

To earn breakthrough designation, a treatment must show encouraging early clinical results demonstrating substantial improvement over available therapies with regard to a clinically significant endpoint, or it must fulfill an unmet need.

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