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Important information about your medicine – omalizumab biosimilar switch

This webpage is for patients who are currently prescribed a medicine called omalizumab by King’s College Hospital NHS Foundation Trust.

If you are no longer prescribed this medicine, please disregard the following.

From May 2026, we will be changing the brand of this medicine from Xolair to Omlyclo. Omlyclo is known as a biosimilar medicine. This webpage provides more information about this change and what it means for you.

What is a biosimilar medicine?

A biosimilar is a highly similar version of an existing biological medicine (called an originator medicine or reference product). It is approved by the Medicines and Healthcare products Regulatory Agency (MHRA). Biosimilars match the originator medicine in terms of safety, quality, and effectiveness. They have been widely used in the NHS for many years.

Why is this change happening?

It is part of national and Trust-wide efforts to improve the use of best value medicines. All medicines made by pharmaceutical companies have a patent that lasts many years. A patent means that only the company that developed the medicine is allowed to sell it. When a patent expires, other pharmaceutical companies can manufacture and licence the medicine. This means there is more competition, which lowers the cost of the medicine.

Cost savings can be substantial, and by switching to a biosimilar, we provide you the same level of care whilst saving money that can be redirected to patient care within the NHS. We have a lot of experience with switches at King’s, across multiple specialties.

Am I likely to have side effects after switching?

As you are on omalizumab already, you are unlikely to have any new or different side effects after switching. As always, your treatment will continue to be carefully monitored. If you do have any side effects or concerns, please contact your doctor or specialist nurse.

Do I need any extra tests before switching?

No extra tests are needed specifically for the switch. You will continue to have routine blood test monitoring as advised by your clinical team.

What does this change mean for me?

  • You may notice a different brand name or delivery device (for example, a pre-filled pen or syringe) being used by your healthcare professional. This does not affect how the medicine works.
  • You will continue to receive the same level of care and clinical monitoring.
  • The way the medicine works in your body will remain the same.

Will this medicine change again in future?

No further changes are planned at the moment. However, more changes in the future are possible. For example, if another biosimilar lowers cost without affecting the quality of your care, or if there are global supply or stock issues, which may mean change is needed at short notice.

We will tell you about any future medicine changes by email, text, in MyChart, or at your appointment.

Further information and support

If you have questions or concerns about the switch, please ask at your next appointment or contact us using the details below. A member of the pharmacy team will phone you back at a suitable time. Please note that the voicemail service will close 3 weeks after you receive this communication.

Please provide the following details:

  • full name
  • NHS or hospital number
  • date of birth
  • contact number
  • the name of the department that prescribes this medicine for you
  • availability for a call back between 10am and 4pm, Monday to Friday

We encourage all patients to sign up to the MyChart app to receive reminders for appointments and test results.

For further information, go to:

The Patients Association website – information on switching to biosimilar medicines

We are here to support you throughout this transition. Thank you for your continued cooperation.