Spark Therapeutics Stock Tumbles after Mixed Results from Phase I/II Trial of Hemophilia A Candidate

Spark Therapeutics saw its share price tumble about 30% in early-morning trading after it reported mixed preliminary data this morning from a Phase I/II trial of its hemophilia A gene therapy candidate SPK-8001.

Shares of Spark fell 29%, to $55.03, as of 10:28 a.m., from yesterday’s closing price of $77.61. The selloff was touched off after Spark released second-quarter results in an announcement that included updates on its clinical programs.

“Based on the totality of the data in our Phase I/II clinical trial of investigational SPK-8011 for hemophilia A, we are pleased to announce our plans to initiate a Phase III run-in study in the fourth quarter of 2018,” Spark CEO Jeffrey D. Marrazzo said in a statement.

Following completion of the run-in study, Phase III participants are expected to receive 2x10 12  vector genomes (vg)/kg of SPK-8011. Spark said additional details on the Phase III ...