Pfizer Pauses Hemophilia A Gene Therapy Trial Due to Increased Thrombosis Risk

Compiled by Tom Li

Latest News: Despite the U.S. FDA lifting the hold on the Phase III Affine clinical study of the hemophilia A gene therapy giroctocogene fitelparvovec in March this year, Pfizer and its partner Sangamo Therapeutics voluntarily paused the development trial and began adjusting the treatment regimen after discovering that the therapy might increase the risk of thrombosis.

It is reported that Pfizer recently found that a trial participant with a high level of factor VIII developed a deep vein thrombosis below the knee. The patient had a history of thrombosis but is currently in good condition. Pfizer is also analyzing the factors contributing to this thrombosis.

The first-quarter earnings report released the other day showed that Pfizer has currently called a halt to relevant trials and is considering resuming clinical research and development work in a few months. The company expects that the clinical trial will resume in the third quarter of this year and anticipates releasing relevant trial results in the second half of 2023.

Public information shows that Hemophilia A is a genetic disease caused by the deficiency or dysfunction of coagulation factor VIII, with the normal level of human coagulation factor VIII ranging between 50%-150%.

Previously, due to a clinical hold by the U.S. FDA, Pfizer's hemophilia gene therapy development was delayed, putting it behind competitors CSL Behring and BioMarin. Both companies reportedly plan to submit approval applications to regulators before mid-year.

However, other therapies under research by Pfizer also have clinical potential for treating hemophilia, and data from several related trials are expected to be released in 2023. Marstacimab is a novel non-factor treatment candidate that has previously received Fast Track designation from the U.S. FDA for the treatment of hemophilia A and B.

In addition, Pfizer also announced last week that the U.S. FDA has allowed the Phase 3 clinical trial of its Duchenne muscular dystrophy (DMD) gene therapy fordadistrogene movaparvovec to continue. Reportedly, the therapy was put on hold by the U.S. FDA after a patient died at the end of last year.

Reference Source: Another Pfizer Gene Therapy is Free of FDA Hold, but Delay Continues