Pfizer Withdraws Oxbryta After 16 Deaths in Sickle Cell Disease Trials

Global Pharmaceutical Giant Halts Distribution Following EMA Safety Review

Pfizer announced the immediate worldwide withdrawal of its sickle cell disease medication Oxbryta on September 26, 2024, after European regulators disclosed 16 patient deaths in clinical trials. The company suspended all clinical trials and expanded access programs globally, citing safety concerns about vaso-occlusive crises in treated patients. The withdrawal affects all markets where regulators approved Oxbryta, including the United States, where the drug generated $338 million in sales during 2023. The European Medicines Agency revealed that 16 of 18 total deaths occurred in patients receiving Oxbryta across two Phase III clinical trials, though regulators found no definitive causal link.

5 Key Points

• Sixteen deaths occurred in Oxbryta-treated patients across two Phase III clinical trials.
• Pfizer halted all clinical trials and expanded access programs worldwide.
• The drug generated $338 million in worldwide sales in 2023.
• Regulators approved Oxbryta in multiple markets, including the United States.
• EMA states no clear evidence links the drug directly to the deaths.

Patient Deaths Trigger Global Safety Review

The deaths emerged from two Phase III clinical trials evaluating Oxbryta’s therapeutic applications. The HOPE Kids 2 trial (GBT440-032) enrolled 236 children aged 2 to 15 years with sickle cell disease who demonstrated high stroke risks across eight countries. Using transcranial Doppler ultrasound measurements to evaluate cerebral arterial blood flow, investigators recorded eight deaths in patients receiving Oxbryta compared to two in the placebo group. The RESOLVE trial (GBT440-042) examined the drug’s efficacy in treating leg ulcers among 88 patients aged 12 and older from Brazil, Kenya, and Nigeria. This trial documented eight additional deaths during its open-label phase, prompting the EMA to note the number exceeded expected mortality rates. Pfizer also suspended a third Phase III trial, an open-label extension study (GBT440-038) examining long-term treatment safety.

Multibillion-Dollar Investment Faces Market Reversal

Pfizer purchased Global Blood Therapeutics for $5.4 billion in October 2022, positioning Oxbryta as the centerpiece of its rare hematology portfolio. The drug demonstrated rapid market growth, with worldwide sales jumping from $73 million in 2022 to $338 million in 2023. Sales reached $176 million in the first half of 2024, surpassing the previous year’s $148 million January-June performance by 19%. “The data suggest an imbalance in vaso-occlusive crises and fatal events which require further assessment,” Pfizer stated in announcing the withdrawal. The company must now restructure its rare disease strategy, particularly in treating sickle cell disease, where Oxbryta represented a cornerstone therapy.

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European Regulators Launch Urgent Investigation

The European Medicines Agency convened an “extraordinary meeting” of its Committee for Medicinal Products for Human Use (CHMP) to examine the Oxbryta deaths. “There is currently no clear evidence that Oxbryta caused any of the deaths, and information about many of the cases is still being awaited,” the EMA stated. The agency pointed to potential complications from infections, including malaria, which is particularly relevant given trial locations in malaria-endemic regions. Pfizer’s preemptive withdrawal, despite unclear causation, aligns with pharmaceutical safety protocols prioritizing patient protection over market position.

Gene-Based Therapies Transform Treatment Landscape

The FDA’s December 2023 approval of Casgevy marked a pivotal shift in sickle cell disease treatment. Vertex Pharmaceuticals and CRISPR Therapeutics developed this first-ever authorized CRISPR-based gene editing therapy, moving beyond traditional drug interventions. Simultaneously, regulators approved Bluebird Bio’s Lyfgenia, a lentiviral therapy that expands genetic treatment options. These approvals carry particular significance for sickle cell disease patients, who historically faced limited therapeutic choices. Ted W. Love, MD, former CEO of Global Blood Therapeutics and current chairman of the Biotechnology Innovation Organization, previously highlighted these treatment barriers, particularly affecting patients of African descent.