An innovative treatment for hemophilia is proving highly effective against symptoms of the disease, even if its use is still questionable due to the risk of serious side effects, AFP and Agerpres reported Thursday.

“This therapy may have the potential to improve the monitoring of patients with hemophilia,” summarized the authors of a study published in The Lancet evaluating Fitusiran’s therapeutic interest.

The molecule, which Sanofi has owned the rights to since 2018, is one of the main breakthroughs in the treatment of hemophilia, a genetic disease that affects mostly men and results in excessive bleeding caused by a clotting problem.

To prevent bleeding, hemophiliacs are usually treated prophylactically by direct administration of the clotting proteins they lack due to a genetic defect.

However, in a significant number of patients, “inhibitory” antibodies against these proteins are produced, due to which they cannot be given prophylactic treatment. Therefore, there is no other way out for them, except for prompt treatment during bleeding episodes.

For several years, research has focused on another therapeutic avenue: prophylactic treatments that, instead of directly replacing clotting proteins, aim to achieve the same result by reducing the anticoagulant effect of certain cells.

That’s the case with Sanofi’s Fitusiran, as well as another Roche-developed molecule, Emicizumab, which is already approved in the United States and the European Union (EU) against the main form of hemophilia known as type A.

Another form of hemophilia, type B, however, does not yet have a preventive treatment if patients have developed inhibitory antibodies.

Concerns about a new hemophilia treatment

Fitusiran dramatically reduced the number of bleeding episodes in both types of hemophilia, according to a study published in the Lancet of forty patients compared to twenty others who did not receive any prophylactic treatment.

As such, this treatment has the potential to be a revolutionary solution, but it still has “many unknowns,” the independent researchers who led the study, including hematology specialist Flora Paywandi, stressed in the same Lancet issue.

These “unknowns” are mainly related to the side effects of Fitusiran.

Of the forty patients treated, about ten had abnormal levels of the enzyme, indicative of serious liver problems. Also, two patients had episodes of thromboembolism, that is, the formation of blood clots that impede blood circulation.

“The potential risk of thrombosis (…) needs to be clarified,” warned Peywandi and his colleagues.