Current issues in prophylaxisLong-acting concentrates
New formulations of clotting factor concentrates are designed to sustain the level of clotting factor concentrates in the blood for longer periods of time, meaning that less frequent and/or fewer injections will be needed to achieve the same result.
The availability of these medications could change how prophylaxis is administered. They have the potential to increase the adoption of prophylaxis among patients, to improve patient adherence, and to improve outcomes.Trough levels
Currently, the goal of prophylactic treatment is to convert a patient with severe haemophilia to a patient with moderate haemophilia by maintaining a baseline factor level (trough level) of greater than 1%. Given impending product advances and taking note that normal FVIII/FIX activity is 50%–150%, it may be time to consider whether a 1% target is sufficient to prevent bleeding.
A recent study showed that absence of joint bleeding may only be reached when approaching FVIII trough levels of 15%. The analysis also demonstrated an 18% reduction in joint bleed frequency with every percent increase in residual clotting factor activity in moderate and mild patients who are treated on demand .
Although theoretically a trough level of 15% may be ideal to achieve the absence of joint bleeding, it is, in the near term, unattainable given the high cost of treatment. However, we should aspire to an absence of joint bleeds. Moving forward incrementally from 1% to higher baseline factor levels (e.g. 3% or 5%) would be a step in the right direction.
We are entering an era in which it is becoming possible to treat an individual patient, rather than treating their disease. To be most effective, a prophylaxis protocol should be tailored to the individual based on their age, bleeding pattern, joint health, the level and timing of physical activity they engage in, their clotting factor levels, and their ability to adhere to a protocol). Prophylactic regimens should also be flexible enough to change with time as the individual patient’s circumstances change.
Knowledge of a patient’s pharmacokinetics – i.e. how the body absorbs, distributes, and eliminates a drug – is likely to help personalize prophylaxis when combined with other information.