Pfizer Begins Lead-In Study for Hemophilia B Gene Therapy

Rare Daily Staff

Pfizer said that it initiated a late-stage study to evaluate the efficacy and safety of current factor IX prophylaxis replacement therapy for hemophilia B, a lead-in that will serve as the control group for patients who enroll in the next phase of the study to evaluate the company’s experimental gene therapy to treat the rare bleeding disorder.

Hemophilia is caused by a deficiency in one of several blood clotting factors. People with hemophilia are at risk for excessive and recurrent bleeding from modest injuries, which have the potential to be life-threatening. People with severe hemophilia often bleed spontaneously into their muscles or joints, or rarely into other critical closed spaces such as the intracranial space, where bleeding can be fatal. The incidence of hemophilia B is one in 25,000 male births.

People with hemophilia B have a deficiency in clotting factor IX, a specific protein in the blood. The current standard of care requires recurrent intravenous infusions of either plasma-derived or recombinant factor IX to control and prevent bleeding episodes.

The phase 3 program was initiated following the transfer of the responsibility for Spark Therapeutics’ hemophilia B gene therapy program to Pfizer. In December 2014, Pfizer and Spark Therapeutics entered into a license agreement for the program. Under the terms of the agreement, Pfizer now assumes sole responsibility for all subsequent pivotal studies, all regulatory activities, manufacturing, and global commercialization of any products resulting from the program.

The interventional portion of the pivotal phase 3 study will enroll patients who have completed at least six months in the lead-in study. It is hoped that, once treated, patients will be able to produce factor IX themselves, rather than having to regularly inject factor IX.

In May 2018, Pfizer and Spark announced data for 15 participants in the ongoing phase 1/2 clinical trial of fidanacogene elaparvovec for the treatment of severe or moderately severe hemophilia B. The findings showed all 15 patients had discontinued routine infusions of factor IX concentrates with no reported serious adverse events or thrombotic events as of the May 7, 2018 data cutoff.

“The current data suggest immense promise for the use of this potential one-time treatment option,” said Brenda Cooperstone, senior vice president and chief development officer, rare disease, Pfizer Global Product Development.

July 17, 2018
Photo: Brenda Cooperstone, senior vice president and chief development officer, rare disease, Pfizer Global Product Development