
FDA releases second Pfizer gene therapy from clinical hold, as hemophilia program gets OK to restart
The FDA has released a clinical hold on Pfizer and Sangamo’s hemophilia A gene therapy after ordering the companies to stop the trial last year due to concerns about blood clots.
Just a week after Pfizer announced the FDA had unleashed its gene therapy for Duchenne muscular dystrophy from a clinical hold — which was paused as one patient died and others experienced severe side effects — another one of its gene therapy programs has been given the green light to resume, Pfizer announced during its Q1 earnings call yesterday.
However, the company anticipates it won’t restart the Phase III trial until the third quarter of this year, Pfizer CSO Mikael Dolsten noted during the meeting. In the meantime, Pfizer needs to get approval of their updated study protocols from the FDA, according to their Q1 earnings news release.
Pfizer voluntarily paused the study late last year after patients experienced abnormally high levels of factor VIII, an essential blood clotting factor. In hemophilia A, patients lack a functional gene for making factor VIII, meaning that they have very low factor VIII levels at under 50%. In people without hemophilia A, factor VIII levels usually range between 50% and 100%, but in the Pfizer trial, patients had factor VIII of above 150%, putting them at risk for blood clots.
Soon after Pfizer paused the trial, the FDA slapped on a clinical hold.
One patient in the trial experienced deep vein thrombosis below the knee, Pfizer noted in the news release. That patient had a history of blood clots before the trial began, which is an exclusion criteria for participating in the study. However, the patient is now doing well, Pfizer said.
Now with the clinical hold gone, Pfizer and Sangamo may have a chance to catch up to BioMarin, as the biotech plots to return to the FDA with its gene therapy this year. BioMarin’s gene therapy was rejected by the FDA two years ago after multiple reports of factor VIII levels dwindling in patients just years after they received what is supposed to be a long-term fix.
Pfizer expects a readout from their hemophilia A program sometime in the second half of 2023.