Pfizer pulls sickle cell drug oxbryta, raising safety concerns
Pfizer's abrupt withdrawal of Oxbryta, a drug for sickle cell disease, has sent shockwaves through the medical community. Concerns over its safety, flagged by European regulators, led to its removal just five years after approval. Doctors and patients now face uncertainty as the sudden discontinuation poses risks, including severe anemia. The lack of transparency from Pfizer and regulatory agencies raises concerns about patient trust and the future of sickle cell treatments.
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By Lisa Jarvis
The note was only a few paragraphs long, but sent shockwaves through the community of sickle cell disease specialists: Pfizer Inc.was pulling the drug Oxbryta off the market based on evidence its benefits no longer outweighed its risks.
Concerns over the treatment were known. European regulatory authorities in July had flagged an unusual number of deaths and pain crises in clinical trials and met this week to review the data. But doctors were caught off guard by the way this unfolded. Typically, removing a drug from the market is a slow, carefully planned — even painstaking — process. Pfizer's product was yanked from pharmacy shelves just under five years after being approved.
The sickle cell community now deserves more transparency from Pfizer and health agencies about what happened to prompt such an abrupt withdrawal. The lack of open dialogue threatens to further undermine patients' already tenuous trust in the medical establishment, not to mention the burgeoning pipeline of new drugs for their disease.
Oxbryta, which arrived on the US market in 2019 and was acquired by Pfizer in 2022, is far from a cure-all. Sickle cell disease is caused by a rare genetic mutation that causes hemoglobin, the part of our red blood cells responsible for shuttling oxygen around the body, to glom together. Oxbryta prevents that glomming, in theory easing the anemia that can cause fatigue and weakness in the short term and wreak havoc on vital organs in the long term.
But its effects are modest, and some had even questioned whether it merited approval. It doesn't reduce pain, which is the biggest reason people with sickle cell end up in the emergency room. Its limitations meant that Oxbryta never became a staple in sickle cell care. Lydia Pecker, director of the Young Adult Clinic at the Sickle Cell Center for Adults at Johns Hopkins, estimates that only about 1 out of every 6 or 7 of the patients at her center had been prescribed the drug. But she and other specialists told me that some patients reported feeling much better while taking it.
The most immediate worry now is that patients suddenly will stop taking the medicine, which sickle cell specialists stress must be tapered. Anecdotal reports passed among doctors suggest abruptly ending treatment can lead to anemia so severe some people need a blood transfusion or hospitalization, says Pecker.
Yet Pfizer's surprise move means pharmacies will no longer dispense the drug, putting patients in a bind. "We're having patients and families counting how many pills they have left so we can safely wean them" says Seethal Jacob, director of the Comprehensive Pediatric Sickle Cell Program at Riley Hospital for Children in Indianapolis. Specialists are working overtime to offer families as much context as possible about why Pfizer took the drug off the market and to reassure them about the research process.
It doesn't help that is the second sickle cell drug to attract negative attention in recent years. Last year, European regulatory authorities withdrew conditional approval for a treatment called Adakveo after clinical data failed to prove it reduces pain crises.
Providing assurances about the approval process and safety of existing drugs is much more difficult when doctors have little to go on. Sickle cell experts have spent the past few days trying to piece together what prompted this unusual approach from Pfizer. They're left parsing the few paragraphs in Pfizer's press release, an equally limited notice from the Food and Drug Administration, and the public information provided by European regulatory authorities.
In an emailed statement, Pfizer emphasized its ongoing commitment to sickle cell disease and said more information would eventually arrive. "We will keep patients, regulatory authorities, investigators and clinicians informed about actions and appropriate next steps for Oxbryta. Right now, we are focused on analyzing the data and will share updates on presentation or publication timing in the future."
The problem is, doctors and their patients deserve that now. Sickle cell specialists need as much detail as possible about the circumstances of the deaths that occurred — such as the severity of the patients' disease and their level of care — so they can understand what went wrong.
More broadly, there's reason to worry the situation will shake people's faith in the clinical process. After years of neglect by the pharma industry, sickle cell research has lately experienced a mini-renaissance. Last year, two transformative gene therapies for the disease received FDA approval and a pipeline of other drugs are in development — including other treatments from Pfizer, which it told Bloomberg it continues to pursue.
But will patients now be more hesitant to sign up for the studies needed to prove they work — or be willing to try them even after they're approved? This week, some have "express[ed] fear that these drugs are not getting enough scrutiny and once again patients are being used as guinea pigs," says Sharl Azar, medical director of Massachusetts General Hospital's Comprehensive Sickle Cell Disease Treatment Center.
Doctors can only mitigate those fears if regulatory agencies and the companies come clean. They must offer more transparency and accountability about the withdrawal of Oxbryta and help the community understand what the situation means for future clinical studies.
US regulators allow treatments for rare diseases to come onto the market early based on assurances of their safety and signs of efficacy. It's always a challenge to balance the need for new treatments with the slow process of proving a drug is both effective and safe. Patients and doctors need to know what Pfizer and regulatory authorities have learned about where those scales tip.
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