Spark Therapeutics reported that although most of the patients could have their bleeding reduced by its gene therapy, one participant though did not quickly respond to oral steroids.
The patient, who was admitted to the hospital, on his choice, received two intravenous (IV) methylprednisolone infusions instead of infusions on an outpatient basis, said the company.
The company said that the event was resolved subsequently and would count as a serious adverse event (SAE).
A total of 12 participants were enrolled in the phase 1/2 trial and were subjected to a single administration of SPK-8011, including two at a dose of 5×1011 vector genomes (vg)/kg body weight, three at a dose of 1×1012 vg/kg and seven at a dose of 2×1012 vg/kg.
Spark Therapeutics said that at all three doses there has been a reduction in annualized bleeding rate (ABR) by 97% for all the participants following four weeks after vector infusion of the gene therapy. There was also a 97% reduction in annualized infusion rate (AIR) in the same timeline, said the company.
Spark Therapeutics president and research and development head Katherine High said: “The clinical and safety profile of SPK-8011 has been highly encouraging, with no FVIII inhibitors observed. Transaminase elevations above the upper limit of normal have been seen in only three of 12 participants, with no evidence of persistent transaminase elevations.
“We believe, based on the tempo and magnitude of the immune responses observed, that a prophylactic course of steroids will suppress these responses and should lead to long-term expression of FVIII above 12 percent in all participants at a dose of 2×1012 vg/kg of SPK-8011. We plan to implement this prophylactic approach to steroid administration moving forward.”
Spark Therapeutics revealed its plans to launch a phase 3 run-in study for SPK-8011 in the fourth quarter of 2018, based on the totality of the results till date.