The US has approved a blood clot therapy that costs $3.5million per dose — making it the most expensive drug in the world.

Hemgenix is a one-off intravenous treatment for hemophilia B, a disorder in which people do not produce a protein needed to create blood clots and control bleeding.

The standard treatment currently involves regular trips to hospital for rounds of IVs that replenish levels of the missing or faulty clotting factor.

But the new therapy delivers a gene that can produce the missing blood-clotting factors into the liver.

In trials it was shown to cut the number of bleeding events expected over the course of a year by over half. It also freed 94 per cent of patients from the need for regular infusions to control the condition.

Hemophilia B accounts for 15 per cent of hemophilia patients and is prevalent in about one in 40,000 of the population, mostly men.

Like most medicines in the US, most of the cost of the new treatment will be paid by insurers — not patients — including private plans and government programs.

Hemgenix is a one-off intravenous treatment for hemophilia B, a disorder in which people do not produce a protein needed to create blood clots and control bleeding

Brad Loncar, a biotechnology investor and chief executive officer of Loncar Investments, told Bloomberg: ‘While the price is a little higher than expected, I do think it has a chance of being successful because 1) existing drugs are also very expensive and 2) hemophilia patients constantly live in fear of bleed.’ 

The US Food and Drug Administration (FDA) approved Hemgenix on Tuesday, saying it ‘represents important progress in developing innovative therapies for people impacted by the disease’.

It is estimated that about 16 million people in the US and Europe have hemophilia B, while hemophilia A affects four times as many.

Drugmaker CSL Behring announced the $3.5m price tag shortly after the FDA approval.

It claims the drug would ultimately reduce health care costs because patients will have fewer bleeding incidents and need fewer clotting treatments. 

The price exceeds that of several other gene therapies that have emerged in recent years.

Novartis’s Zolgensma for babies with spinal muscular atrophy was listed at $2.1m when it was approved in 2019..

Bluebird Bio’s treatment for the blood disorder beta thalassemia, Zynteglo, was listed at $2.8m when it was launched earlier this year. 

What is Hemophilia?

Source: CDC 

Hemophilia is usually an inherited bleeding disorder in which the blood does not clot properly. 

This can lead to spontaneous bleeding as well as bleeding following injuries or surgery. Blood contains many proteins called clotting factors that can help to stop bleeding. 

People with hemophilia have low levels of either factor VIII (8) or factor IX (9).

The severity of hemophilia that a person has is determined by the amount of factor in the blood. 

The lower the amount of the factor, the more likely it is that bleeding will occur which can lead to serious health problems.

In rare cases, a person can develop hemophilia later in life. 

The majority of cases involve middle-aged or elderly people, or young women who have recently given birth or are in the later stages of pregnancy. This condition often resolves with appropriate treatment.


There are several different types of hemophilia. 

The following two are the most common: 

  • Hemophilia A (Classic Hemophilia) This type is caused by a lack or decrease of clotting factor VIII. 
  • Hemophilia B (Christmas Disease) This type is caused by a lack or decrease of clotting factor IX. 


Hemophilia is caused by a mutation or change, in one of the genes, that provides instructions for making the clotting factor proteins needed to form a blood clot. 

This change or mutation can prevent the clotting protein from working properly or to be missing altogether. 

These genes are located on the X chromosome. Males have one X and one Y chromosome (XY) and females have two X chromosomes (XX). 

Males inherit the X chromosome from their mothers and the Y chromosome from their fathers. Females inherit one X chromosome from each parent.

The X chromosome contains many genes that are not present on the Y chromosome. This means that males only have one copy of most of the genes on the X chromosome, whereas females have 2 copies.

Thus, males can have a disease like hemophilia if they inherit an affected X chromosome that has a mutation in either the factor VIII or factor IX gene. Females can also have hemophilia, but this is much rarer. In such cases both X chromosomes are affected or one is affected and the other is missing or inactive. In these females, bleeding symptoms may be similar to males with hemophilia.

A female with one affected X chromosome is a “carrier” of hemophilia. Sometimes a female who is a carrier can have symptoms of hemophilia. In addition, she can pass the affected X chromosome with the clotting factor gene mutation on to her children. Learn more about the inheritance pattern for hemophilia.

Even though hemophilia runs in families, some families have no prior history of family members with hemophilia. Sometimes, there are carrier females in the family, but no affected boys, just by chance. However, about one-third of the time, the baby with hemophilia is the first one in the family to be affected with a mutation in the gene for the clotting factor.

Hemophilia can result in:

  • Bleeding within joints that can lead to chronic joint disease and pain
  • Bleeding in the head and sometimes in the brain which can cause long term problems, such as seizures and paralysis
  • Death can occur if the bleeding cannot be stopped or if it occurs in a vital organ such as the brain.