What the trial was testing
The trial enrolled 25 patients with hemophilia a. The study was sponsored by Spark Therapeutics and tracked outcomes across the full group of patients who matched the trial's eligibility profile.
It was an early-stage trial — researchers are still confirming safety and getting an early look at how well the treatment works. Trials at this stage are designed to produce evidence regulators and physicians can act on — not just observations to follow up later.
What the results showed
Bleeding rates dropped 91.5% over the median three years of follow-up.
New England Journal of Medicine · 2021 · NCT03003533
These findings — that in annual bleeding rate after a one-time gene therapy infusion in 16 of 18 men — were published in the New England Journal of Medicine and represent the headline result of the study.
Researchers tracked outcomes across 25 patients enrolled in the trial. The result was consistent enough across the group that the team felt confident reporting it.
What this means for patients
For patients with hemophilia a, this result changes the calculus on what to ask their care team about. Whether it changes day-to-day care depends on factors like disease subtype, prior treatments, and where the patient is in their care journey.
What you can do now
This gene therapy (SPK-8011) is still in development and not yet FDA-approved. A different hemophilia A gene therapy (Roctavian/valoctocogene roxaparvovec) was approved by the FDA in 2023. Ask your hematologist about open trials and approved gene therapies if standard prophylaxis is not working for you.
Eligibility for the treatments mentioned above depends on specific test results and clinical history. Bring this summary, the trial name, and your most recent labs or pathology report to your next visit.
Open hemophilia a trials
Longitudinal Cohort of Thrombosis and Hemostasis Diseases
This is a multicenter, prospective, longitudinal, observational cohort study to investigate thrombosis and hemostasis diseases in Chinese patients. This study will collect basic information, diagnostic and treatment information, as well as medical expense information of patients from medical records.The incidence and risk factors of thrombosis and hemostasis diseases, the treatment methods, prognosis and medical expenses of these patients in China will be analyzed. The study will use questionnaire to measure the exposure of patients, and prospectively follow-up to collect the prognosis information.
A Gene Therapy Study of SPK-8011QQ in Adults With Severe or Moderately Severe Hemophilia A
This study will assess the safety and tolerability of SPK-8011QQ in adult males with moderately severe to severe hemophilia A.