What are biosimilars?

PUBLISHED ON: 31 January 2018

You may have heard about biosimilars for drugs such as  trastuzumab, which will soon be used more widely in breast cancer treatment.

Emma Pennery, who heads up our team of nursing experts, explains what they are, how they work and why they aren’t identical to the original drug.


Key points

  • Biosimilars are made from living organisms instead of chemical mixtures
  • They are carefully controlled and tested for quality, safety and effectiveness
  • They are cheaper than the original patented versions
  • They are likely to be used by some breast cancer patients from this year, for example in place of trastuzumab
  • They have been used in the treatment of other diseases for some time now

How are breast cancer drugs made?

Most drugs are man-made by mixing chemical ingredients. If a company has created a unique drug they’re likely to patent it. This means no other company can copy the chemical recipe of that drug.

Once a patent has expired (usually after around 10 years), other companies can reproduce the chemical recipe of a drug and sell copies called ‘generics’. To be approved for sale, generics have to be exact copies of the original branded drug. In other words, they must have an identical chemical structure.

What are biologics?

Not all drugs are made from chemical recipes. Some, known as biological medicines or biologics, are made by a living organism such as a bacteria or yeast, a bit like yoghurt is made using living cells. These include vaccines, human insulin and some cancer drugs. 

As with chemical drugs, once a biologics patent has expired, other companies can reproduce them. But compared to copying chemical recipes, it’s much more complicated, expensive and time consuming.

What are biosimilars?

Copies of biologics are called ‘biosimilars’, not generics, because they are not identical to the original drug. 

There’s no way to make identical copies of biologics because they contain active substances and come from living things (the old saying, ‘there’s no uniformity in nature’). Instead, biosimilars are manufactured to be highly similar imitations of biologics already approved and in use. 

Hearing that a drug you’re taking for cancer treatment isn’t identical to the original may sound unnerving, but actually batches of original biologics are not identical to each other, because it’s impossible to exactly reproduce living structures. So biosimilars made by different companies will differ not only from the original drug, but also from each other. This makes approving new biosimilars more challenging.

How are biosimilars approved? 

Generics are approved when they have a chemical structure matching the original drug, but that doesn’t work for biosimilars. Instead, robust frameworks are in place to check that new biosimilars don’t differ significantly from the original drug in terms of quality, safety and effectiveness. You can read these frameworks for the NHS in England and Scotland and for the European Medicines Agency (EMA).  

Unlike generics, each new biosimilar has to be tested in clinical trials. Companies developing biosimilars have to demonstrate they are as effective and safe as the biologic they are imitating.

Once in use, biosimilars continue to be monitored for any adverse effects or outcomes.

Although new to breast cancer, biosimilars have been used for other diseases for some years. The EMA says evidence gathered over 10 years of clinical experience shows that carefully approved biosimilars can be used as safely and effectively as biologics. 

How does this benefit the NHS?

Although biosimilars are challenging to produce and more costly than generics, they are still quite a bit cheaper than biologics, so the NHS is understandably keen to use them whenever possible. NHS England aims to have at least 90% of new patients prescribed the best value biological drug within three months of a new biosimilar being launched.

The first that will be available to breast cancer patients are biosimilars of the intravenous form of the drug trastuzumab in the first half of 2018. More than one company is aiming to produce an intravenous trastuzumab biosimilar and it’s likely some breast cancer patients will be having these as part of their treatment in the near future.

If you are concerned about any aspect of breast cancer or treatment, call our free Helpline on 0808 800 6000.