A new treatment for haemophilia could soon be developed, giving the clotting process more time to produce thrombin, according to a UK-based study.
A study published in Blood suggests that the therapy could come from factor V Leiden – a common mutation associated with excessive clotting.
Standard treatment for haemophilia is administration of the missing factor – factor VIII for haemophilia A and factor IX for haemophilia B – but this requires regular intravenous injections, which have been found to be under-effective. Some cases have also resulted in the development of antibodies that reject the factor.
Now, co-author Dr Trevor Baglin, of Cambridge University's Addenbrooke's Hospital, and his team have attempted a new approach, which is based on observations relating factor V Leiden.
“We know that patients who have severe haemophilia and also have mutations that increase clotting, such as factor V Leiden, experience less-severe bleeding,” he said.
The researchers reduced the activity of activated protein C (APC), an enzyme that promotes bleeding. This is because patients with factor V Leiden produce too much thrombin if they have defects in the anticoagulant APC mechanism.
The team, led by Professor James A. Huntington, exploited this by developing a direct inhibitor of APC and modifying serpins (serine protease inhibitors) to make them specific and efficient APC inhibitors.
To test it, they administered serpin to mice with haemophilia B and then clipped their tails. The blood loss decreased as the dose increased, with the highest dose reducing bleeding to the level of the healthy mice.
The serpin helped most of the mice to form stable clots, and those that had higher doses experienced quicker clot formation. The serpin also accelerated clot formation when added to blood samples from haemophilia A patients.
Prof Huntington added: “It is our understanding that because we are targeting a general anti-clotting process, our serpin could effectively treat patients with either haemophilia A or B, including those who develop inhibitors to more traditional therapy.”
The serpin will be developed so that it is delivered subcutaneously and will be long-acting, which, he said: “will free patients from the cumbersome thrice-weekly infusions that are necessary under many contemporary therapy regimens”.
Blood 27 October 2016
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