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Extended (or enhanced) half-life factor concentrates

For people with haemophilia, the use of recombinant (laboratory made) factor products hasn’t changed much in recent years. While preventative treatment (prophylaxis) has revolutionised the lives of many people with a bleeding disorder, the typical treatment regime – regular injections into a vein at least twice a week – can place a significant burden on individuals and families.

Now, a flurry of research has resulted in new factor products for haemophilia A and B becoming available in the UK. You can inject these less often, but they work just as well in preventing bleeds. In trials, patients were able to inject once or twice a week for haemophilia A and every one or two weeks for haemophilia B. Overall, they had fewer or the same number of spontaneous bleeds and no serious side effects.

Treatment patterns are worked out individually, depending on your own treatment response and bleeding pattern, but these drugs are likely to make a difference to the lives of many Haemophilia Society members. It’s likely that treatments may be used slightly differently in everyday practice to how they were prescribed in the trials, but overall we would expect many to have a reduction in frequency of treatment.

Some of these longer-lasting products have now been approved for use in the UK and more are on the way. All of them aim to increase the time that the body takes to remove the factor from the bloodstream. This means they work for longer after being injected. The researchers call this increasing the ‘half-life’ – the amount of time it takes the level of the drug in the bloodstream to reduce by half – so these drugs are collectively known as ‘extended half-life’ or EHL treatments.

There are three main ways of producing these drugs: Fc fusion, PEGylation and albumin fusion. All of these are aiming to prolong the ‘half-life’ of clotting factors VIII and IX by altering the structure of the protein molecules so that the body takes longer to clear them from the blood circulation and they therefore work for longer after being injected.