What is a biosimilar medicine?

This guidance supports the safe, effective and consistent use of biosimilar medicines – new biological medicinal products developed to be similar to existing biological medicines – to benefit patients in the NHS in England.

Information is aimed at:

  • healthcare professionals
  • integrated care boards
  • commissioners of NHS services
  • providers of NHS-commissioned services.

Biological medicines are complex medicines made or derived from a biological source. Because of the biological source and the manufacturing process, there is some variability in these medicines. The variability between batches of the same product is controlled and monitored during manufacturing, to maintain this within defined and approved limits.

Biological medicines are used to treat many conditions including cancers, diabetes, arthritis, psoriasis, neutropenia and enzyme or hormone deficiencies.

A biosimilar medicine (known as a ‘biosimilar’) contains a version of an active substance of an approved biological medicinal product, known as the reference product.

Biosimilar development aims to establish similarity between the biosimilar and the reference product based on a comprehensive comparability process. This ensures the previously proven safety and efficacy of the reference product also applies to the biosimilar.

Why should biosimilars be used?

Biosimilars are widely used in the UK and internationally for a number of conditions.

Biosimilars should be used because:

  • they offer the same clinical effectiveness and safety as their reference products, but usually at substantially lower cost
  • their approval is based on comprehensive comparability studies with the reference product, which is a well-established approach used to ensure any changes during manufacture do not affect the quality, safety and efficacy of biological medicines
  • they are interchangeable with the original biological product and with other biosimilars when approved, which is reflected in government guidance on the licensing of biosimilar products and supported by the joint EMA-HMA statement on interchangeability
  • NICE guidance for the reference product normally applies to the biosimilar
  • by increasing the cost effectiveness of medicines, biosimilars allow more patients to access treatment sooner, and release funding for innovative treatments and improvements in pathways of care
  • more biosimilar medicines are becoming available in different therapeutic areas as biological medicines lose their patent protection, and so the increased competition between biological medicines has the potential to deliver significant savings to the NHS.

How are biosimilars licensed for use?

The regulatory pathway

The Medicines and Health products Regulatory Agency (MHRA) is the UK’s medicines regulator responsible for the licensing of medicines. Its guidance on licensing of biosimilars products outlines the process for obtaining a licence for a biosimilar product.

A detailed head-to-head comparison of the biosimilar medicine with its reference product is needed to show that there are no clinically significant differences between them, and previously proven safety and efficacy of the reference product also apply to the biosimilar.

If a biosimilar has highly similar analytical and functional properties to the reference product, with data from the confirmatory pharmacokinetic trial demonstrating comparable pharmacokinetics and supporting comparable safety and immunogenicity, then all the reference product indications can be claimed by the biosimilar. Once the MHRA authorises a product as a biosimilar, the prescriber should consider it therapeutically equivalent in these authorised indications; this is supported by real-world data (Cohen et al 2022).

Post-authorisation regulation

Once authorised, MHRA subjects biosimilars to the same level of post-authorisation regulatory scrutiny as their reference products from a safety and risk benefit perspective. Subsequent manufacturing changes are assessed by the regulator to ensure that these changes do not impact on the quality, safety and efficacy of biological or biosimilar medicines.

Do biosimilars require a health technology assessment?

Biosimilars do not require a separate or additional health technology appraisal (TA) as a positive NICE TA recommendation for the reference product applies to the biosimilar.

NICE undertakes surveillance of guidance because of the loss of exclusivity when biosimilars of the technology are licensed for the same indication. A rapid update of TA guidance is scheduled to coincide with NHS Commercial Medicines Unit tenders for these technologies.

In some circumstances a review of the evidence for the biosimilar medicine may be required and NICE will consider producing an evidence summary.

Commissioning or procuring biosimilars

The benefit to the NHS (value proposition) offered by different products should be considered, taking into account overall cost, resources required, licensed indications of different products, the patient pathway, as well as other patient factors relevant to the use of the product, for example formulation of the biosimilar if different to the reference product.

The NHS procures biosimilars through national and regional procurement processes. Further information on these can be found in the NHS commissioning framework for biological medicines (including biosimilar medicines).

When deciding whether to use a biosimilar medicine the following should be considered:

  • the clinical rationale supporting its use
  • the overall value proposition it offers
  • appropriate engagement with key stakeholders
  • information to support implementation including plans and timelines for monitoring its use and the data collection that may be needed.

Prescribing biosimilars

Where a biosimilar is available, prescribers and patients are encouraged to have a shared decision-making conversation as part of their medicines review to consider using the biosimilar. This applies to both new patients and those who are already receiving the reference product.

Principles for prescribing:

  • shared decision-making approach with the patient
  • decisions should be evidence-based and are the responsibility of the prescriber; first choice of product should be based on clinical considerations
  • prescribe for approved indications as in the Summary of Product Characteristics (SmPC)
  • prescribe in line with information in the British National Formulary
  • prescribe by brand name in line with MHRA guidance, to guard against substitution in error (biosimilar medicines often use the same international non-proprietary name as their reference product)
  • inform the patient of the brand of biological medicine they are being prescribed
  • review biological medicines prescriptions regularly, following SmPC guidance.


Once authorised, a biosimilar product is considered interchangeable with its reference product. A prescriber can choose the biosimilar medicine over the reference product or vice versa and expect the same therapeutic effect in the patient; however, the products should be prescribed by brand name.

Biosimilars of the same reference product are also interchangeable.


Switching patients from one product to another (reference product or biosimilar) has become clinical practice. There is no scientific rationale to expect different clinical outcomes when switching between biosimilars of the same reference product and this is supported by real-world data.

When considering switching a biosimilar medicine, follow the prescribing principles above and also take into account:

  • whether the patient is clinically stable
  • the suitability of the product for the patient, including its delivery mechanism.

Dispensing biosimilars

Substitution, the practice of dispensing one medicine instead of another equivalent medicine at the pharmacy level without consulting the prescriber, is not permitted for any biological medicine (including biosimilars).

Patients and providers should be provided with evolving evidence and treatment guidance to support shared decision-making.

Further information

Please refer to the following resources: