Spark falls on Factor VIII activity data for hemophilia A therapy

Spark Therapeutics Inc. (NASDAQ:ONCE) fell $21.60 (28%) to $56.01 on Tuesday after reporting new Phase I/II data showing that the highest tested dose of hemophilia A gene therapy SPK-8011 led to lower than expected Factor VIII activity levels in two patients.

BioMarin Pharmaceutical Inc. (NASDAQ:BMRN), whose hemophilia A gene therapy is in Phase III testing, added $7.77 to $105.72 on Tuesday...