Long-term effect of marstacimab on joints that bleed frequently in people living with severe hemophilia without inhibitors: A plain language summary of publication

Summary What is this summary about? This summary describes a study that looked at how well the study treatment marstacimab works in people living with hemophilia. Hemophilia is a condition that causes people to bleed more easily because their blood is unable to clot properly. Clotting is when liquid blood turns gel-like to stop uncontrolled bleeding. Bleeding can happen inside the body, in joints and muscles. A joint that has a lot of bleeds in a short period of time is called a target joint. The summary describes how well marstacimab stopped bleeding in the target joints of people living with hemophilia. Hemophilia is caused by not having enough blood clotting factors, which are proteins found in the blood that help in forming a clot and stop bleeding. People living with hemophilia either don’t make these proteins, have low amounts of these proteins, or these proteins do not work well. Some treatments for hemophilia work by replacing these clotting factors. These treatments are known as factor replacement therapy and are given directly into a vein (called intravenous, or IV for short). They are given frequently, sometimes even more than once a week. Some people living with hemophilia develop antibodies called inhibitors against the replacement clotting factors, which causes the treatment to be ineffective. If people make these antibodies, it is called hemophilia with inhibitors. A different way to treat people living with hemophilia is using treatments called non-factor replacement therapy. One type of non-factor treatment targets a protein in the blood called tissue factor pathway inhibitor, or TFPI for short. A treatment called marstacimab attaches to TFPI and stops its activity. Marstacimab is given as a regular preventative (prophylaxis) treatment. For people living with hemophilia, this helps blood to form a clot when needed. Marstacimab is taken less often than clotting factors and is given as a once a week injection under the skin (called subcutaneous), which may be easier than injecting directly into a vein. This injection is sometimes called a shot. Marstacimab offers a new way to treat people living with hemophilia without inhibitors. What were the results of the study? In this study, marstacimab reduced bleeding in target joints in people living with hemophilia without inhibitors for up to 2 years of treatment compared to previous clotting factor replacement treatment. Most target joints got better with marstacimab treatment. What do the results mean? This study showed that marstacimab once a week could help reduce bleeding in target joints for people living with hemophilia A or B without inhibitors. Marstacimab may also help resolve target joints in people living with hemophilia A or B without inhibitors who already have target joints.