U.S. regulator approves new treatment for rare MND subtype

The U.S Food and Drug Administration (FDA) has approved a new drug to treat people living with a rare genetic form of motor neuron disease (MND) in the United States.

On 25 April 2023 the pharmaceutical company Biogen announced that the drug tofersen, marketed as QALSODYTM in the US, has been approved by the FDA to treat people living with the SOD1-ALS subtype of MND, which affects around 2% of people living with MND.

The clinical trial is still ongoing, and information will be gathered from patients to find out the effects of the drug on life expectancy and quality of life for people living with SOD1-ALS. Tofersen has been approved on the basis that it reduces the amount of a toxic form of protein, which is known to cause the breakdown of motor neurons, in people living with the SOD-1 subtype.

Tofersen is the first drug ever to be approved to treat a genetic cause of MND, making this a big step in MND research. At the moment, tofersen is not approved for use in the UK, including Scotland, but is currently being reviewed by the European Medicines Agency (EMA) for possible use in Europe.

What is SOD1-ALS?

SOD1-ALS is a rare genetic subtype of MND, accounting for 2% of total MND cases and up to 20% of patients who have a family history of the disease.

The SOD1 gene is a piece of DNA that everyone has. This DNA contains the instructions for making an enzyme important for keeping the cells of our bodies healthy. In people with SOD1-ALS, the DNA code for SOD1 contains a mistake, meaning that their cells can’t make this enzyme properly and instead makes a mutant version that is damaging.

How does tofersen work?

Tofersen stops the faulty SOD1 code from being used to make SOD1 protein, reducing the amount of toxic material being made.

Neurofilament-light chain (NFL) is a marker of nerve cell damage and death. Tofersen reduces the amount of NFL within the blood of people with SOD1-ALS, which suggests that the drug reduces nerve cell damage in people living with this genetic form of MND.

What does this mean for people living with this subtype of MND?

The drug tofersen has yet to be approved for use within Europe, the UK and Scotland. For it to become available to people living with SOD1-ALS in the UK and Scotland, it will need to be approved by the Medicines and Healthcare products Regulatory Agency (MHRA) to make sure it is safe by British standards.

For a new drug to become available on the NHS, it must then be approved by National Institute for Health and Care Excellence (NICE) for use in England, Wales and Northern Ireland and by the Scottish Medicines Consortium (SMC) for use in Scotland.

Only after approval by these regulatory bodies will tofersen become available to people through the NHS.