PHYSICAL ACTIVITY AND FVIII CLEARANCE: RELEVANCE FOR PERSONALIZED THERAPY IN SEVERE HAEMOPHILIA A (PHYSEMO)

In persons with severe haemophilia A (HA) infused factor VIII (FVIII) half-life and other pharmacokinetic parameters can vary according to determinants such as blood group, von Willebrand factor (VWF) level or age. However, FVIII pharmacokinetics (PK) has not been thoroughly studied in patients with severe HA as a function of daily physical activity. Patients with severe HA (FVIII \<1%) are predisposed to prolonged bleeding following even minimal musculoskeletal injuries. Potential consequences of repeated musculoskeletal bleeding are pain, arthropathy and physical disability. The key standard of care for HA patients is prophylactic infusions of FVIII concentrates (25-50 IU kg-1 infused 2-3 x/week), depending on individual response. The level of infused FVIII decreases as a function of time according to both specific PK features of each product and biochemical/genetic characteristics of the patients or different clinical conditions. Some critical points remain still unraveled, for instance, whether or not FVIII AUC is significantly affected by physical activity/exercise, in response to increased metabolic rate or subclinical/microhaemorrhages in patients with severe HA. It is known that vigorous-intensity physical activity/exercise can transiently but significantly increase circulating levels of endogenous VWF and consequently FVIII in normal subjects and in patients with moderate or mild haemophilia A. The proposed study is a Proof of Concept one as it will be aimed at investigating the relation between daily physical activity, measured by SenseWear® armband device, as number of daily steps, and PK variability of infused rec-FVIII concentrate. This kind of investigation has never been done and it is a great interest also for the evaluation of patients' quality of life.