The United States Food and Drug Administration has recently approved Qfitila (fitusiran) for routine prophylaxis to prevent or to reduce the frequency of bleeding episodes in adults and pediatric patients 12 years of age and older with hemophilia. It works on those with hemophilia A or hemophilia B, with or without factor VII or IX inhibitors which neutralizes antibodies. While subcutaneous Qfitilia does not replace the missing coagulation factor VII or IX, it reduces the amount of protein antithrombin, which leads to an increase in thrombin. It is an enzyme critical for blood clotting. The dosing starts at once every two months and it is also based on the FDA-cleared Innovance Antithrombin companion diagnostic test. However, as of now, there is no fixed doses of Qfitila is not approved mainly due the risk excessive clotting. It has also a boxed warning for thrombotic events and gallbladder disease.One of the most common side effects reported were viral infection, nasopharyngitis, and bacterial infection.How Was This Approved?The approval came on the basis of two randomized clinical trials that had 177 adult and pediatric male patients with either hemophilia A or hemophilia B enrolled. Among the participants with inhibitors who received the antithrombin-based dosing regimen of Qfitlia, there was a 73% reduction in the estimated annualized bleeding rate. This was seen in comparison with those who received on-demand treatment with bypassing agents. Among the participants without inhibitors receiving the antithrombin-based dosing regimen of Afitlia, there was a 71% reduction in the estimated annualized bleeding rate versus that seen in those who received on-demand treatment with clotting factor concentrates. "Today's approval of Qfitlia is significant for patients with hemophilia because it can be administered less frequently than other existing options," Tanya Wroblewski, M.D., deputy director of the Division of Non-Malignant Hematology in the FDA Center for Drug Evaluation and Research, said in a statement.What Is Hemophilia?As per the Centers for Disease Control and Orevention (CDC) it is an inherited bleeding disorder in which blood does not clot properly. It can lead to spontaneous bleeding as well as bleeding following injuries or surgeries. Blood usually has proteins called clotting factors that can help one to stop bleeding. However, people with hemophilia have low levels of either factor VII or factor IX.Hemophilia could also result in bleeding within joints which can then lead to chronic joint disease and pain. It could lead to bleeding in head and in brain, causing long term problems such as seizures or paralysis. In severe cases it can also lead to death if the bleeding cannot be stopped. The most common types of hemophilia are inherited, thus it is a condition that is present from birth. There are rare cases where hemophilia happens later in life, which is known as acquired hemophilia. Difference between Hemophilia A and Hemophilia BAs per the National Bleeding Disorders Foundation, hemophilia A, also called factor VIII (8) deficiency or classic hemophilia, is a genetic disorder caused by missing or defective factor VIII (FVIII), a clotting protein. Although it is passed down from parents to children, about 1/3 of cases found have no previous family history.Hemophilia B, also called factor IX (FIX) deficiency or Christmas disease, is a genetic disorder caused by missing or defective factor IX, a clotting protein. Although it is passed down from parents to children, about 1/3 of cases are caused by a spontaneous mutation, a change in a gene.