Positive Data Available: FLT180a for Hemophilia B


Recently, the International Society on Thrombosis and Haemostasis (ISTH) held its 2022 Congress from July 9th to 13th. During the conference, researchers and other stakeholders discussed research, care, and advancements within the fields of thrombosis, hemostasis and vascular biology. According to a news release from clinical-stage biotechnology company Freeline Therapeutics Holdings plc (“Freeline Therapeutics”), one such discussion centered around data from the Phase 1/2 B-LIEVE clinical study. The dose-confirmation study sought to understand more about FLT180a for patients with hemophilia B.

Interested in checking out the presentation? Just search for poster #PB0213.

FLT180a: An Overview

In an article published in ASH Clinical News, FLT18a is described as:

an experimental gene therapy that uses AAVS3, a synthetic capsid, to deliver a codon optimized F9 gene with a gain-of-function mutation to liver cells.

So far, researchers have evaluated FLT180a in the Phase 1/2 B-AMAZE and Phase 1/2 B-LIEVE studies. Within the B-LIEVE study, researchers sought to confirm the safety and efficacy of 7.7e11 vg/kg FLT180a. If confirmed as safe and effective, this dose would be used in further Phase 3 studies.

Altogether, findings from the B-LIEVE study are promising. Researchers found that:

  • A singular FLT180a dose was able to rapidly and significantly raise factor IX levels. This allowed patients to experience less bleeding and reduce the dependency on prophylaxis or factor replacement therapies.
  • FLT180a was found to be relatively safe and well-tolerated for those with hemophilia B. While some side effects did occur, these were all minor.
  • Although some patients have experienced decreased FIX expression following the treatment period, they are still expressing higher FIX expression than they did before the trial. Additionally, patients have still not required any additional treatment options or experienced any serious bleeding events.

What is Hemophilia B?

There are two main types of hemophilia, a rare bleeding disorder in which the blood lacks enough clotting factor to clot properly. Hemophilia A, or factor VIII deficiency, is considered to be the more common form. Alternately, those with hemophilia B lack clotting factor IX. Because hemophilia is a variable condition, some people may experience serious and life-threatening bleeding episodes; others may experience mild symptoms. In rare cases, people with hemophilia B may experience bleeding episodes as children which lessen over time. Typically, males are affected with hemophilia while females are carriers. Symptoms can include:

  • Prolonged bleeding after injuries, surgery, or dentistry
  • Spontaneous bleeding episodes
  • Frequent nosebleeds
  • Easy bruising
  • Bloody urine or stool (caused by urinary or gastrointestinal bleeding)
  • Joint pain, swelling, and restricted mobility
Jessica Lynn

Jessica Lynn

Jessica Lynn has an educational background in writing and marketing. She firmly believes in the power of writing in amplifying voices, and looks forward to doing so for the rare disease community.

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