Spark Therapeutics Inc shares tumble over concerns about its gene therapy treatment for hemophilia

Shares in the gene therapy group Spark Therapeutics (NASDAQ:ONCE) plunged Tuesday after the company said an otherwise successful trial for a gene therapy treatment taking aim at hemophilia landed one patient in the hospital.

While the company’s gene therapy treatment for hemophilia A reduced bleeding and the need for infusions by 97% in the group of 12 hemophiliacs who took part in the Phase 1/2 trial, a pair of patients in the Phase 1/2 trial responded poorly to the treatment.

By the afternoon, Spark shares had slid 27.8% to US$56.01 in response to this disappointment.

The two patients who reported concerning immune responses were treated after their clotting levels dropped. After failing to respond to oral steroids, one of the two patients chose to go to a hospital to receive intravenous infusions in what Spark described as a “serious” adverse effect.

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Across the study, a total of seven out of the 12 hemophiliacs participating were forced to receive oral steroids to address an array of symptoms.

Despite the setbacks, the Philadelphia-based company is still set to introduce a Phase 3 trial for SPK-8011 in the fourth quarter of this year.

Hemophilia A, which is also called classic hemophilia, is a genetic disorder in which blood fails to clot properly.

Separately, Spark also put out its results for the second quarter Tuesday, swinging to a profit of US$80.2mln from a loss of US$74.4mln loss in the year-ago quarter.

Its revenue climbed to US$25.2mln, the bulk of which was owed to Spark’s licensing agreements with Pfizer Inc (NYSE:PFE).

As of the close of June, Spark reported cash and cash equivalents of US$656.8mln.

Contact Ellen Kelleher at [email protected]

Story by ProactiveInvestors