List of products in the National Drug Code with proprietary name . This medication is used to treat sickle cell disease. People with sickle cell disease have a certain abnormal protein (hemoglobin S) in their red blood cells that makes the cells stiff and irregularly shaped (sickle- or crescent moon-shaped). Voxelotor works by decreasing hemoglobin S. This effect may decrease symptoms such as tiredness, shortness of breath, and attacks of pain (sickle cell crisis).