Pfizer’s sickle cell crisis
Pfizer’s $5.4bn acquisition of Global Blood Therapeutics was already on shaky ground given underwhelming sales of the group’s sickle cell drug Oxbryta – and now it looks like a complete write-off. On Wednesday Pfizer said it was withdrawing Oxbryta and discontinuing all active trials after seeing data suggesting an increase in vaso-occlusive crises and fatal events. The group didn’t give more details, but a recent notice from the EMA said the deaths had been seen in trials evaluating Oxbryta in sickle cell patients at high risk of stroke, and in those with leg ulcers, a complication of sickle cell disease. The agency said there was no clear evidence that Oxbryta caused the deaths, but Pfizer clearly isn’t taking any chances. The group still has a couple of other clinical-stage assets from the Global Blood deal, but the omens aren’t good: osivelotor is a next-generation version of Oxbryta, designed to be more potent, while inclaclumab recently had a late-stage trial terminated owing to poor recruitment, and results have yet to emerge from another study that completed in June. Pfizer said the development wouldn’t affect its 2024 financial guidance, but the deal now looks like an expensive misstep for the struggling group.
Pfizer’s sickle cell pipeline
| Product/project | Mechanism | Status |
|---|---|---|
| Oxbryta (voxelotor) | Haemoglobin S polymerisation inhibitor | Withdrawn, trials discontinued Sep 2024 following data suggesting imbalance in vaso-occlusive crises and fatal events. Hope Kids 2: 8 deaths with Oxybryta, 2 with placebo; Resolve: 8 deaths in open-label part |
| Osivelotor (PF-07940367) | Haemoglobin S polymerisation inhibitor | Ph2/3 in SCD; primary completion Oct 2028 |
| Inclacumab | Anti-P-selectin MAb | Ph3 Thrive-132 terminated Mar 2024 owing to recruitment problems; Thrive-131 completed June 2024; both in SCD VOCs |
Note: SCD=sickle cell disease; VOC=vaso-occlusive crisis. Source: OncologyPipeline & clinicaltrials.gov.
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