By Crystal Lindell

Pfizer is voluntarily taking its sickle cell disease medication Oxbryta (voxelotor) off the market, amid concerns that it could be causing deaths and other complications. Doctors are being told to stop prescribing Oxybryta and to start sickle cell patients on other medications. 

Pfizer said its decision was based on clinical data showing the overall benefits of Oxbryta no longer outweighs the risks. In postmarketing studies, patients taking Oxbryta had higher rates of a vaso-occlusive crisis, a condition that causes severe pain when mis-shaped red blood cells block the flow of blood to tissues and organs. Patients taking the medication also had higher death rates. 

The company said it was also discontinuing all clinical trials of Oxbryta and expanded access programs worldwide. Oxbryta has been on the market since 2019. The medication works by preventing red blood cells from becoming C-shaped and breaking down too quickly.

Pfizer’s announcement delivers another setback to sickle cell patients, who already lack treatment options and face discrimination in the healthcare system. There aren’t many treatments for sickle cell disease (SCD), a lifelong inherited blood disorder that can cause complications starting in early childhood and lead to shortened life expectancy.

The lack of treatments is due in part to the fact that SCD is relatively rare in wealthier countries. It primarily impacts those whose ancestors are from sub-Saharan Africa, an under-served patient population. About 100,000 Americans have SCD, a number so low it discourages drug makers from developing medications to treat it. Over 8 million people worldwide have SCD.

Many sickle cell patients have also borne the brunt of opioid phobia in the United States. They often end up having to go to the ER during pain flares, where many are treated as drug seekers. 

‘This Is a Step Backward’

The National Alliance of Sickle Cell Centers released a statement saying the Pfizer recall was disappointing. But they were glad that Pfizer was re-evaluating Oxbryta to see which SCD patients may still benefit from it..

"At this time, the risks are too great but there may be an opportunity in the future to better understand how to optimize this medication (and all) medications in sickle cell disease,” the organization said. 

It urged sickle cell patients currently taking Oxbryta to make an appointment with their doctor and emphasized that patients should not stop taking the drug abruptly. Instead, they should work out a weaning plan with their care team. 

“Don’t lose faith,” they said. “This is a step backward but we will stay on the path to better outcomes for everyone.”

The organization added that these types of issues highlight the importance of long-term follow-up with a sickle cell center and of clinical registries like GRNDaD, an international registry developed to track the effectiveness of SCD treatments.

“We encourage everyone to see a sickle cell specialist annually to review what is and what is not working for them,” the organization said. “We all know that sickle cell disease is highly variable, many people are different and respond differently to medications. We need to better understand these differences to identify which medication will work best for which people."

An article in MedScape explained that Pfizer’s decision to recall Oxbryta (voxelotor) came amid increased scrutiny of the drug by the European Medicines Agency (EMA). 

EMA began a review of voxelotor in July after data from a clinical trial showed that a higher number of deaths occurred with the drug than with placebo. Another trial showed a higher  number of deaths than expected. 

Pfizer’s Aida Habtezion, Pfizer’s Chief Medical Officer, said the recall was in the best interest of patients. 

“Our primary concern is for patients who suffer from SCD, which remains a very serious and difficult-to-treat disease with limited treatment options,” Habtezion said. “We advise patients to contact their physicians to discuss alternative treatment while we continue to investigate the findings from our review of the data.”

Patients, physicians, pharmacists, or other healthcare professionals with questions about Oxbryta should contact Pfizer at 1-800-438-1985.