Why did Pfizer withdraw its sickle cell drug Oxbryta?
Clinical data showed the drug's benefit no longer outweighed its risks — including a higher death rate in a paediatric study — triggering an abrupt global withdrawal that disrupted patients with few alternatives.
In September 2024 Pfizer voluntarily withdrew all lots of Oxbryta (voxelotor) worldwide and halted all clinical trials and expanded access programmes. The company said the totality of clinical data showed the drug's benefit no longer outweighed its risks, citing an imbalance in vaso-occlusive (pain) crises and fatal events.
According to the Sickle Cell Disease Association of America's medical advisory committee, one study in 236 children with a higher risk of stroke recorded eight deaths in the voxelotor group compared with two in the comparison group. The withdrawal was abrupt for patients, many of whom had few alternatives, and haematologists described the sickle cell field as thrown into disarray. Pfizer said it acted in patients' interest and notified regulators promptly.