Experimental Hemophilia A Drug Loses Effectiveness Over Time, Efficacy Questionable After 8th Year

According to a publication from Reuters, based on early clinical data, American biotechnology company BioMarin Pharmaceuticals believes that a single injection of its experimental hemophilia A drug could relieve symptoms of the condition for up to eight years. It’s effectiveness, however, begins to wane almost immediately. After eight years, the drug seems to offer little benefit to hemophilia patients.

About Hemophilia

Hemophilia is a rare disorder characterized by the ineffective clotting of blood. The bleeding episodes, caused by low-levels of clotting factors (blood proteins that facilitate clotting — such as platelets), can be life-threatening if untreated.

Normally, small cuts and minor wounds aren’t the main source of concern for hemophilia patients. Often more concerning is the threat of internal bleeding events — particularly in the joints. Internal bleeding is harder to slow with exogenous treatment, and can potentially damage important organs and tissues.

Hemophilia A, or “classic hemophilia,” is caused by a lack of a clotting protein called factor VIII. When the body detects a wound, it sends platelets and clotting factors to the breach. Platelets form a simple plug that stops some of the bleeding. Blood clotting factors, including factor VIII, then begin a series of chemical reactions that culminate in a fibrin clot — a more complete protein mesh that stops bleeding and closes off the wound.

Gene Therapy Potentially a Solution

BioMarin believes their experimental gene therapy drug, valoctocogene roxaparvovec, could be used to alleviate some of the serious complications of hemophilia A.

Data collected from two early stage trials yielded mixed results for the drug candidate, however. One study followed eight hemophilia patients for three years — the other followed seventeen for about half a year. All were administered the same valoctocogene roxaparvovec infusion.

The study suggests that the gene therapy drug’s effectiveness wanes early, plateaus for about a year, then loses effectiveness at a slow but steady rate. BioMarin researchers believe the drug could be effective for up to eight years. Beyond that, the drug offers significantly less, if any, relief from hemophilia symptoms.

Some patients in these studies additionally received injections of factor VIII proteins, which could obviously influence a hemophilia patient’s symptoms.

Though a moderate success, the gradual decline in valoctocogene roxaparvovec’s effectiveness is a serious hamper to its future potential on the market — estimates for just one treatment reach as high as $2 million (based on a 5-year projection of the average $400,000 spent annually on clotting factor transfusions for hemophilia patients). It seems unlikely that many would be willing to shell out $2 million for a drug therapy that will be effective for less than a decade.

BioMarin is researching ways to administer a second dose of the experimental drug if the first dose’s effectiveness wanes. Although the gene therapy looks to provide some relief “beyond 3 years for most patients,” it doesn’t have the lasting effectiveness to be called a “cure.”


Gene therapy drugs are some of the most expensive in the world — multi-million dollar price tags are often attached. Why is it important that gene therapies provide more lasting benefits than other standards of care, like regular transfusion or medication? Share your thoughts with Patient Worthy!

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