healthHealth and Medicine

Two Groundbreaking Gene Therapy Studies Hint At Cure For Hemophilia


Robin Andrews

Science & Policy Writer

Gene therapy is making enormous leaps and bounds as of late. CI Photos/Shutterstock

Gene therapy in humans may still be in its infancy, but it’s already making some previously impossible stories a reality. From editing out the symptoms of sickle cell disease to curing two baby girls of an incurable form of leukemia, the future is already here for some.

Now, as reported by two remarkable studies in The New England Journal of Medicine, it appears that gene therapy’s making headways when it comes to hemophilia. After two pioneering experimental approaches, most of the participants in the study experienced normal levels of blood clotting, and many no longer required injections of coagulating elements that they previously needed on regular basis.


The journal, which is naturally cautious when it comes to declaring medical breakthroughs, ran an editorial entitled “A Cure for Hemophilia within Reach.”

Hemophilia doesn’t make the news that often, probably because it’s so rare. Those that have it are almost always male, and it’s usually inherited. Although patient’s symptoms vary in terms of their severity, they all have one thing in common: they aren’t able to clot their blood as usual, which means that they bleed for longer than usual. This can be anything from deeply problematic to fatal.

Currently, there is no cure. The best that can be done is the aforementioned injections, which add clotting factors to the blood. Although normal lives can be lived by those afflicted, they have to be far more cautious than others day-to-day.

The two main types of hemophilia are denoted A and B, although others do exist. The far more commonplace type A, thanks to the unusual nature of the genetics driving the condition, was thought to be far more difficult to treat using gene therapy. Type B, on the other hand, was suspected of being comparatively easier, but by no means no cakewalk.


These studies took on both, and won.

During the first study, nine men with severe hemophilia A were observed after undergoing gene therapy. These men were susceptible to bleeding in joints and soft tissue, and required regular blood clotting injections to get by.

The team altered their genes using an adeno-associated virus (AAV), a type not known to cause any disease. It’s often used in gene editing to deliver artificially engineered DNA strands into target cells.

Shortly after this single infusion, the patients produced far more factor VIII – an essential blood-clotting protein – than usual. Those that received the highest dose of the infusion had normal levels of factor VIII for up to 24 weeks, which meant that, for all intents and purposes, they didn’t have any symptoms of hemophilia A. Additionally, no adverse toxicity effects nor immune reactions were detected.


A remedy for type A was described by the editorial as being “the ultimate grail,” and one that “was not expected to be feasible soon.” Now, the grail may be within reaching distance.

A 3D rendering of factor VIII. molekuul_be/Shutterstock

The second study looked at hemophilia B, and was led by the Division of Hematology at The Children’s Hospital of Philadelphia.

This type focused on the gene associated with factor IX, which also plays a role in blood coagulation, and which those suffering from type B have defective versions of, or simply lack. Once again, after a single AAV injection, the 10 participants in this study showed sustained average concentrations of factor IX.

In both cases, the patients didn’t require conventional treatments for extended periods of time after their infusions.


Is this therapy safe in the long-term, and is it just as effective? How will a larger sample size react to the treatment? Only more research will tell, but for now, these studies represent nothing less than groundbreaking steps towards that elusive cure.


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