Pfizer haemophilia gene therapy hits goal in final-stage study

Results may allow pharma giant to compete with treatment approved in US last month

Pfizer’s gene therapy for a haemophilia B hit its main goal in a final-stage trial, moving closer to becoming a competitor to a similar one-time treatment that costs $3.5 million (€3.3 million).

The Prizer therapy, called fidanacogene elaparvovec, was just as effective or superior to standard replacement of clotting factor in preventing annual bleeding events from haemophilia in the trial, the company said on Thursday in a statement. The drug reduced the annualised bleeding rate by 71 per cent in treated patients compared with the standard treatment, according to the statement, and bleeding that required treatment fell by 78 per cent.

The positive results may allow Pfizer to compete with CSL Behring’s Hemgenix that was approved in the US in November. When administered just once, that drug cut the number of bleeding events expected over the course of a year by 54 per cent in a trial.

While there have been advances in the treatment of haemophilia, controlling bleeding is difficult and time-consuming for patients. The standard treatment uses factor IX, a naturally occurring blood-clotting substance that patients with the disease lack. The new gene-based treatments deliver DNA to cells that can produce the missing clotting factor.


Pfizer licensed fidanacogene elaparvovec from Spark Therapeutics in 2014, agreeing to pay $20 million up front along with potential milestone payments and royalties, and later took on the final-stage trial of the gene therapy on its own. Swiss pharma giant Roche Holding bought Spark in 2019, gaining experimental treatments for other gene-based bleeding disorders.

A total of 14 serious adverse events occurred in seven patients in Pfizer’s trial, with two assessed as related to treatment, the statement said. – Bloomberg