Pfizer's sickle cell drug candidates are not affected by Oxbryta reduction

(Bloomberg) — Pfizer Inc. said it will press ahead with development of its potential drugs for sickle cell anemia, despite the company's decision to withdraw an approved treatment for the disease after more patients died than acceptable and complications occurred in clinical trials.

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Taking all the data into account, the benefits of Oxbryta therapy “no longer outweigh the risks,” Pfizer said in a statement on Wednesday. The company, which also announced it would halt clinical trials while it investigated the results, said separately that the measures would have no immediate impact on its experimental drugs for the disease.

“This decision is specific to Oxbryta. We are continuing to advance our pipeline,” a Pfizer spokesperson said in response to questions from Bloomberg News, referring to the company's other SCD candidates, including inclacumab and osivelotor (GBT-601). “We will provide updates as they become available.”

The company will review all available data to determine next steps if necessary, the spokesman said.

The New York-based pharmaceutical company's announcement that it was withdrawing Oxbryta from the market came on Wednesday, just one day before the European Medicines Agency was due to discuss the drug. In July, the European regulator began reviewing the therapy after finding a higher number of deaths than expected in two studies.

According to Pfizer, the data showed an “imbalance in vaso-occlusive crises and fatal events that requires further investigation.” Vaso-occlusive crises are painful complications that commonly occur in patients with sickle cell anemia.

Oxbryta was once hailed as the first therapy of its kind to target the root cause of sickle cell anemia. Pfizer acquired the original developer, Global Blood Therapeutics, in 2022 for $5.4 billion.

In recent conference calls, the company had also discussed the potential of follow-on programs from its acquisition of Global Blood Therapeutics. In particular, CEO Albert Bourla said that GBT-601, which showed promise in a mid-stage trial late last year, could be a “potential step-up to Oxbryta.”

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