(Bloomberg) -- Pfizer Inc.’s gene therapy for a hemophilia 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. 

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

The positive results may allow Pfizer to compete with CSL Behring AG’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% in a trial. 

While there have been advances in the treatment of hemophilia, 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 upfront 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 AG 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. The shares rose 0.5% at 9:55 a.m. in New York.  

(Updates shares in final paragraph. A previous version of this story corrected the company name in the second paragraph.)

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