The withdrawal decision was prompted by clinical data indicating that the overall benefit of Oxbryta “no longer outweighs the risk” in its target patient population, the company said in a public release. Specifically, the trials outline an “imbalance” in vaso-occlusive crises and fatal events that the company will assess further. The move to stop clinical trials of the drug will last while Pfizer further reviews the available data and investigates the findings.
Sickle cell disease is a genetic blood disorder where patients have a mutation in hemoglobin, a protein found in red blood cells. This leads the protein to clump together, causing cells to have a sickle shape that can block blood vessels and carry less oxygen, leading to acute pain and anemia.
Oxbryta, whose generic name is voxelotor, is an oral small molecule drug that was first approved by the US Food and Drug Administration (FDA) for the treatment of sickle cell disease in 2019, with an EU approval granted in 2022. The drug is designed to make hemoglobin better at carrying oxygen and less prone to clumping together, making red blood cells more functional.
The treatment was previously developed by the U.S. firm Global Blood Therapeutics before the company was snapped up by Pfizer for $5.4 billion in 2022, and bagged Pfizer $328 million in revenues in 2023.
The big pharma company has notified regulators about the data and doesn’t expect the event to impact its full-year 2024 financial guidance. Nevertheless, the company’s stock price on the New York Stock Exchange slumped by more than 1% at the news yesterday (Wednesday 25th September).
Emphasizing Pfizer’s focus on patient safety, chief medical officer and head of worldwide medical and safety, Aida Habtezion, said in the company release that the Pfizer’s “primary concern is for patients who suffer from SCD, which remains a very serious and difficult-to-treat disease with limited treatment options. We advise patients to contact their physicians to discuss alternative treatment while we continue to investigate the findings from our review of the data.”
The global market for sickle cell disease was worth $2.25 billion in 2022 and is expected to grow by 20.1% per year to $9.84 billion by 2030. The main players in the market have included Pfizer with Oxbryta, Novartis with the antibody Adakveo (crizanlizumab) and Generex Biotechnology’s Emmaus Medical with Endari (L-glutamine). In 2017, Endari became the first branded drug for sickle cell disease in decades when it was greenlit by the U.S. FDA.
Another driver for the sickle cell disease market is gene therapy, with the first cell-based gene therapies – Casgevy by Vertex Pharmaceuticals and Lyfgenia by Bluebird Bio – approved by the U.S. FDA in late 2023.
