The FDA on Monday approved a Global Blood Therapeutics treatment for sickle cell disease, three months before the agency’s decision was expected.
Regulators evaluated the drug, voxelotor (Oxbryta), under a pathway that allows for a speedier review using less evidence than is typically required. This pathway is reserved for drugs that address an unmet medical need. But South San Francisco-based Global Blood (NASDAQ: [[ticker:GBT]]) must conduct additional clinical trials to maintain the drug’s approval.
Sickle cell disease is an inherited disorder that causes hemoglobin, the oxygen-carrying red blood cells, to take the shape of a crescent, or sickle. These misshapen cells restrict blood flow and limit oxygen delivery to tissues, which leads to complications that include damage to the lungs and other organs, bouts of excruciating pain, and strokes. The Centers for Disease Control and Prevention estimates the disease affects 100,000 Americans.
Treatment for sickle cell includes older drugs that address the symptoms, as well as blood transfusions that increase a patient’s levels of normal red blood cells. A transplant can replace the bone marrow affected by the disease with a donor’s healthy marrow. But these transplants come with risks and they also require the bone marrow to come from a compatible donor to reduce the risk of rejection.
Potential one-time treatments are in clinical testing in the form of therapies that would address the genetic defect leading to sickle cell disease. Bluebird Bio (NASDAQ: [[ticker:BLUE]]) is testing its gene therapy as a treatment for the disorder. Partners Vertex Pharmaceuticals (NASDAQ: [[ticker:VRTX]]) and CRISPR Therapeutics (NASDAQ: [[ticker:CRSP]]) are developing gene-editing therapies, as are Sangamo Therapeutics (NASDAQ: [[ticker:SGMO]]) and its partner, Bioverativ (NASDAQ: [[ticker:BIVV]]).
Those experimental one-time therapies are still years away from being ready for regulatory review. In the meantime, Global Blood can now offer treatment in the form of a once-daily pill. Patients will need to take the drug for life, but the medicine could stop the effects of the disease. The drug was developed to block hemoglobin polymerization, which is the process that forces red blood cells into the characteristic sickle shape.
The FDA based its decision on a placebo-controlled Phase 3 study enrolling 274 patients. The main goal of the study was to show an increase in hemoglobin levels. In the group given the Global Blood drug, the FDA says the rate of increase was 51.1 percent compared to a 6.5 percent increase in the placebo group. Side effects reported from the study included headache, diarrhea, abdominal pain, nausea, fatigue, rash, and fever.
The FDA’s approval of voxelotor covers patients age 12 and older. A decision on the drug was not anticipated until Feb. 26. The approval comes less than two weeks after the regulatory agency cleared a Novartis (NYSE: [[ticker:NVS]]) therapy for a painful complication that happens when sickle cells obstruct blood circulation. That approval covers patients age 16 and older.
Global Blood says voxelotor will become available within two weeks. As a condition of the accelerated FDA nod, the company will continue testing its pill in post-approval clinical trial. That study, which will assess the risk of a stroke in sickle cell patients 2 to 15 years of age, is expected to start by the end of this year.
Public domain image of a sickle cell by Flickr user National Center for Advancing Translational Science
