Cure for haemophilia B on the horizon?

A new small study has bolstered hopes gene therapy could offer a single-injection cure for haemophilia B.

On Tuesday, clinical haematologist and pathologist Professor John Rasko presented an abstract to the HAA conference with top-line results from his recent phase I-II clinical trial of a new adeno-associated virus gene therapy in haemophilia B patients.

The results have been “nothing less than startling” for Professor Rasko and his colleagues, with all 10 patients maintaining a clotting factor of 25% to 35% one year after the single injection.

The gene therapy involves a modified parvovirus carrying an encoded clotting factor being injected into the patient, which travels to the liver where gene expression takes place.

In this case it was a bioengineered AAV coat-protein carrying a factor 9 gene.

Professor Rasko and his team have been refining the technique for over fifteen years in collaboration with US colleagues.

“When we first started the clinical trials, we published two papers in 2006 and 2007 where we had to inject into the hepatic artery,” Professor Rasko, Director of Cell and Molecular Therapies at Royal Prince Alfred Hospital, tells the limbic.

“At that stage the technology wasn’t advanced enough to inject into a peripheral vein.

“Now because of the way the coat protein of the virus has been bioengineered we have made it so clever, that instead of having to inject it into a vessel supplying the liver directly, we can inject it into a peripheral vein and its like a cruise missile.

The virus predominantly is taken to the liver and its genetic payload is dumped into the cells which are permanently genetically modified so that they become capable of producing the clotting factor which they previously weren’t making.”

The 10 patients involved in the trial had previously IV self-administered clotting factor 9 two or three times a week for prophalaxis or treatment for a bleed.

“A few weeks following the injection, none of the patients has needed factor concentrate and the follow-up is now over a year,” Professor Rasko said.

Two of the patients required oral steroids short-term, to manage an immune response, the other eight did not.

“The results have been nothing less than startling,” Professor Rasko said.

“It’s early days yet. But I think our fingers our crossed this will lead to an approved therapy where one injection is curative. There is evidence in the animal models (which have 10 years follow-up) to support that.”

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