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.

Pfizer’s decision Wednesday to pull its sickle cell pill off the market because of safety concerns shocked advocates and doctors, leaving many searching for answers and scrambling for ways to notify their patients about a drug that has long divided the community.

Pfizer had big hopes for a sickle-cell disease drug, as did those suffering from the disease. Things didn't turn out as planned.