Mepolizumab is a medicinal product currently in development as an add-on for the treatment of hypereosinophilic syndrome (HES). HES is a rare group of inflammatory disorders characterised by an overproduction of eosinophils (a type of disease-fighting white blood cell). When eosinophils infiltrate certain tissues, they can cause inflammation and organ damage which, over time, can impact patients’ day-to-day ability to function. Although any organ system can be involved in HES, the heart, central nervous system, skin, and respiratory tract are the most commonly affected.
Mepolizumab is given by injection and works by blocking the activity of human interleukin-5 (IL-5), an immune protein that is responsible for the production and survival of eosinophils. By blocking the activity of IL-5, the production and survival of the eosinophils is reduced. Using mepolizumab in addition to the standard of care may improve outcomes and reduce symptoms in patients with HES.
Avapritinib is in clinical development for the treatment of advanced systemic mastocytosis (SM) in adults. SM is a condition where mast cells grow uncontrollably and accumulate in body organs/tissues such as the skin, internal organs, lymph nodes and bones. Mast cells are immune cells that release inflammatory mediators that are important in the body’s allergic responses. When mast cells are present in large numbers there is a high release of these mediators leading to symptoms such as itching, fever, abdominal pain, nausea and vomiting. In advanced SM, mast cells collect in such high quantities that they lead to organ damage and dysfunction, bone fractures and anaemia.