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
Monitoring of Anti-TFPI in Hemophilia
During the development of anti-TFPI antibodies, thrombin generation assay (TGA) was employed using both in vitro measurements (antibodies added to blood samples) and ex vivo approaches (blood samples from patients in phase II and III trials). While a significant improvement in thrombin generation was observed in all samples from patients with severe hemophilia, no correlation with clinical outcomes could be established. Notably, thrombin peak levels were consistently improved even in patients who experienced bleeding episodes. These measurements were conducted in platelet-poor plasma (PPP) with standard reagents, which may not adequately reflect the hemostatic efficacy of anti-TFPI antibodies given their mechanism of action. It is hypothesized that optimizing reagents and utilizing more appropriate biological materials could enhance TGA sensitivity, as previously demonstrated for monitoring emicizumab. The absence of a laboratory assay to monitor anti-TFPI (tissue factor pathway inhibitor) antibodies poses a significant challenge for managing patients in surgical settings and treating acute severe bleeding. This study aims to develop a reliable assay to evaluate the hemostatic efficacy of anti-TFPI antibodies and their combined procoagulant effect with factor concentrates (FVIII or FIX) or bypassing agents.
Phase 3 Clinical Project of Pegylated Recombinant Human Coagulation Factor VIII-Fc Fusion Protein
To evaluate the prophylactic efficacy of recombinant human coagulation factor Ⅷ-Fc fusion protein (FRSW117) for injection in patients with severe hemophilia A. To evaluate the safety of recombinant human coagulation factor Ⅷ-Fc fusion protein (FRSW117) for injection in patients with severe hemophilia A. Secondary purpose: To evaluate the efficacy of recombinant human coagulation factor Ⅷ-Fc fusion protein for injection (FRSW117) in hemostasis and surgical hemostasis in patients with severe hemophilia A. To evaluate the pharmacokinetic (PK) characteristics of recombinant human coagulation factor Ⅷ-Fc fusion protein (FRSW117) for injection in treated patients with severe hemophilia A. To evaluate the immunogenicity of recombinant human coagulation factor Ⅷ-Fc fusion protein (FRSW117) for injection in treated patients with severe hemophilia A.