The development of a 'breakthrough' gene therapy to treat a form of haemophilia has the potential to save thousands of lives, researchers say.

Australian and international researchers have developed a "breakthrough" gene therapy to treat a rare form of haemophilia - a life-threatening disorder that prevents the blood from clotting.

A multi-centre clinical trial published in the prestigious New England Journal of Medicine has shown the therapy successfully stopped bleeding in nine out of 10 men with haemophilia B.

Trial lead Professor John Rasko at Royal Prince Alfred Hospital says the result represents a major milestone in the quest to find a cure for the disorder.

"We are very excited about the results, as those people in our trial have previously had to live with the risks of spontaneous bleeding every day. To prevent potentially life-threatening bleeds they have typically had to inject themselves with clotting factors every few days," he said.

"This trial has targeted haemophilia B, which affects about 500 males in Australia - with about 100 experiencing a severe form of the condition, but our next focus is targeting haemophilia A, which affects more than 2300 people."

Haemophilia B is an inherited disorder where blood does not clot properly due to missing or defective clotting factor known as IX.

Sufferers experience a wide range of bleeding episodes, usually in the joints or muscles. Over time, bleeding can cause severe arthritis, chronic pain and disability.

Trial participants were injected with a modified gene, called Factor IX, designed to produce a substance which clots the blood and then followed for almost 10 years.

For 38-year-old Mark Lee - who has undergone blood infusions up to three times a week since he was born - the therapy has been "life-changing".

"I spent my childhood wrapped up in cotton wool, unable to play football or do any of the things my mates could. I would always remind myself that there were people worse off than me, but it was still disappointing," Mr Lee said.

"I have two daughters who are carriers for haemophilia but now I know that if they have affected children it will be one injection and they can live normal lives. This goes beyond our little family currently. It will have a positive impact on all generations to come."