Positive Results Announced for Hemophilia B Drug

Pfizer and Spark Therapeutics recently announced positive updated data from a hemophilia B clinical trial.

The phase 1/2 clinical trial studied the use of SPK-9001 in patients with hemophilia B, and additional results will be presented at the 58^th American Society of Hematology Annual Meeting.

SPK-9001 is an investigational bio-engineered, adeno-associated virus capsid expressing a codon-optimized, high-activity human factor IX variant enabling endogenous production of factor IX, Pfizer wrote in a press release.

New results being discussed are from the first 7 individuals included in the study. These patients received 1 administration of the drug at a dose of 5 X 1011 vector genomes/kg of body weight.

Investigators found that 4 of the 7 patients reached greater post-vector administration at 12 weeks, Pfizer said. These patients had stable factor IX activity levels over 30% greater than normal that persisted over time.

These patients also did not experience increased levels of liver enzymes. A participant who had not reached this goal developed an immune response to the drug, and had a drop in factor IX activity level. This patient was put on a course of corticosteroid to fix these events.

Although the patient experienced an immune response and decreased factor IX activity level, they did not have any bleeds, and did not need a replacement factor, according to Pfizer.

No other patient in the clinical trial requires the use of corticosteroids, according to the press release. No participants needed to receive infusions on factor IX concentrates to prevent bleeding, but 1 patient received a preventative infusion due to a suspected bleed.

Bleeding risks are especially serious among these patients, since nearly 60% of patients in the world with hemophilia B have severe disease. These individuals have factor IX levels less than 1%, according to the National Hemophilia Foundation.

As of August, the use of clotting factor among these patients during the 724 days after administration of SPK-9001 decreased by over 540,000 international units. Thus far, 6 participants saw improved quality of life, and increased physical activity, Pfizer reported.

The drug is currently being developed in collaboration with the 2 companies, with Spark Therapeutics conducting the phase 1/2 clinical trials under the SPK-FIX program. This program uses prior gene therapy research conducted by Spark to develop hemophilia treatments.

SPK-9001 is still being developed, and the FDA has granted the drug breakthrough therapy and orphan drug designations.

“These initial observations are encouraging, underscoring the potential of investigational SPK-9001 to deliver a potentially consistent, sustained and therapeutically meaningful level of factor IX activity through one administration,” said lead investigator Lindsey A. George, MD. “Participants in the trial did not require prophylactic factor IX infusions to prevent bleeding, including one participant who we have followed for more than eight months as of the data cutoff. We look forward to reporting additional data as we continue to document the longer-term experience with SPK-9001.”