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Biosimilar medicines

A biosimilar is a highly similar copy of an existing drug. Speak to your doctor, nurse or pharmacist if you have any specific questions about your treatment.

How are drugs made?

To understand what a biosimilar is, it helps to know a bit more about how drugs are made. Drugs are broadly divided into 2 groups:

  • those made from chemical ingredients
  • those made using living cells

Many drugs have specific chemical ingredients, these are non-biological drugs. An example is the painkiller, ibuprofen.

Other drugs are made use living cells such as those from bacteria, plants or animals. These are called biological drugs. Examples include hormones such as insulin, drugs for arthritis and some cancer drugs.

Why do we have biosimilars?

All new drugs go through strict testing over many years before they have a licence for general use.

Drug companies usually patent the new drugs they develop. This means only they can manufacture and sell the drugs for a specific amount of time. In the UK a patent lasts about 20 years. After this time other drugs companies can make the drug, often at a cheaper price.   

Copies of a non-biological drug use the exact same chemicals. The exact copy is called a generic medicine. For example, ibuprofen was originally called Nurofen. Since this drug came off patent, there are a variety of identical generic versions available. 

It’s not possible to copy biological medicines exactly. When the patent for a biological medicine expires, drug companies can make a drug that is very similar to the original, but not exactly the same. These drugs are called biosimilars. A biosimilar is a highly similar copy of an existing biological drug.

As with all new drugs, biosimilars are thoroughly tested and have a licence for use.

Biosimilars flow diagram

The benefits of biosimilars

Biosimilar medicines are quite complicated and expensive to make, but they are still cheaper than the original biological medicine. The NHS is encouraging doctors to use more biosimilars as they become available. 

Using more biosimilars should bring down the cost of cancer treatment in hospital trusts. It means that the drugs are available to more people who need it. Any savings can be reinvested in healthcare.

Are biosimilars safe and effective?

Yes, all biosimilars are as safe and effective as the original biological drug. Biosimilars undergo strict testing to check they work just as well as the original drug. Biosimilars have been safely used by the NHS for several years.

How are they checked?

The organisations who licence drugs: 

  • check there are no differences in the way they work
  • looks at all information from trials used for both the original drug and the biosimilar and compare the results
  • can request new studies if needed
  • continually monitor and review all biosimilars in use

Are the side effects the same?

You should not normally experience different side effects if you have a biosimilar. As with all medicines there is a chance that you may have a new side effect. It is very important that you tell your healthcare team if you have any side effects.  

Will I be changed from a biologic medicine to a biosimilar during my treatment?

Your doctor might discuss this possibility with you. Remember, biosimilars are highly similar to the original drug. They have been tested to make sure they work in the same way. 

Your doctor or pharmacist can answer any specific questions you have. They will give you written information about the new drug. 

Examples of biosimilars in the NHS

An example of a biological medicine is trastuzumab (Herceptin). This is a targeted cancer drug used to treat breast cancer and advanced stomach cancer. Examples of biosimilars for this drug include Herzuma and Ontruzant.

Rituximab (Mabthera) is another biological medicine. It is a targeted drug used to treat chronic lymphocytic leukaemia, some types of non-Hodgkin lymphoma and some non cancer related illnesses. Biosimilars of this drug include Truxima.

Biosimilars are also used to treat other medical conditions. For example, adalimumab (Humira) is used to treat conditions including arthritis, Crohn's disease and ulcerative colitis. An example of a biosimilar for this drug includes Imraldi.