The U.S. Food and Drug Administration on Thursday alerted patients and healthcare professionals about the withdrawal of Pfizer's sickle cell disease treatment Oxbryta. Pfizer said late on Wednesday it was pulling the drug from all markets due to risk of a painful complication and death.

The healthcare company said clinical data indicates the overall benefit of Oxbryta no longer outweighs the risk in the approved sickle cell patient population.

The company said benefits no longer outweighed the risks, with data suggesting the drug might increase the risk of pain crises and "fatal events."