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
Study to Provide Continued Access to Treatment for Patients Completing a Previous Trial With Efanesoctocog Alfa
This is a multinational, prospective, open-label, roll-over study in patients with haemophilia A, ≥6 years of age, who have completed participation in any of the parental studies with efanesoctocog alfa; XTEND-ed study (LTS16294), FREEDOM study (Sobi.BIVV001-001), PK comparison study (Sobi.BIVV001-003) or SHINE study (Sobi.BIVV001-004). The aim of the study is to provide patients with continuous benefit from efanesoctocog alfa treatment and to further continue clinical monitoring for safety and efficacy until efanesoctocog alfa is commercially available in each patient's respective country (or until March 2027, whichever comes first). The study starts with the Baseline Visit, which will be done in connection to the end of treatment at the EoT/EoS visit (or equivalent) in the respective parent study. Subsequent study visits (on site or phone call) will be done approximately every 13 weeks until End of Treatment. An End of Study safety phone call will be done 14 (+7) days after the End of Treatment Visit.
Safety and Efficacy Study of NGGT003 in Hemophilia A Patients
This is an early phase 1, open-label, single-center, dose-escalation pilot trial to evaluate the safety and efficacy of an intravenous infusion of NGGT003 in hemophilia A patients. NGGT003 uses adeno-associated virus (AAV) as a vector, carrying a liver specific promoter and codon optimized human FVIII gene B domain deletion mutant (hFVIII BDD), and expresses human FVIII protein in the liver through intravenous injection.