This is about MS patients being switched from a life-changing treatment to a cheaper alternative without consent—leading to serious health decline, and no clear path to switch back.

I am writing to share a deeply personal and urgent story — one that is quietly affecting hundreds of people living with Multiple Sclerosis (MS), and which I fear is being driven not by science, but by NHS cost-cutting.

In late 2024, many MS patients like myself, who are being treated for severe forms of relapsing-remitting MS (RRMS), were switched from the gold-standard drug Tysabri (natalizumab) to a newer, cheaper biosimilar version called Tyruko — without adequate patient consultation, and with devastating consequences.

I was diagnosed with RRMS in 2009, though my first symptoms began in 2005. Due to the aggressive nature of my condition, my neurologist immediately placed me on Tysabri IV in September 2010. For 13 years, this drug gave me stability and hope. My symptoms improved year after year — especially my mobility — and while Tysabri doesn’t reverse neurological damage, it seemed to “dampen down” my MS in a way nothing else could. I truly thrived on it.

But on 27 December 2024, my hospital administered my first IV dose of Tyruko. Thankfully it has kept me relapse free, however, since that day, my condition has sharply deteriorated. I was hit with extreme fatigue and intense headaches, and the fatigue has never lifted. I've now received five doses, and with each one, my MS symptoms have worsened — including the return of previously dormant issues. I am now struggling to walk, and my daily functioning and independence are diminishing before my eyes.

I have since learned that I’m not alone. The MS community is full of people who were previously stable on Tysabri but are now suffering severe relapses or symptom resurgence after being switched to Tyruko. Many of us feel strongly that there is a glaring lack of long-term, real-world research into the effects of Tyruko versus Tysabri IV — especially in patients who had been doing well for years.

NICE considers Tyruko equally effective simply because it is biosimilar — meaning it is "highly similar" in structure and function to Tysabri. But that ruling allows Tyruko to piggyback off Tysabri's clinical trial data, without any substantial, independent, real-world studies on its own. We believe this is not just inadequate, it is dangerous.

To date, I have written to my hospital trust (BSOL), my neurologist, MS nurse, NHS England, PALS, my MP, the MS Trust and MS Society. My letter is co-signed by 103 fellow patients from 31 hospitals across the UK, all of whom are experiencing similar adverse effects since the switch.

I also conducted a survey of 64 patients nationwide, which, though small, paints a consistent and concerning picture of widespread suffering linked to Tyruko. These are not isolated cases.

Furthermore, NHS England has already received correspondence from Mrs Jonelle Roback, a patient at Charing Cross Hospital, who raised these concerns back in August 2024. Her case was taken seriously, and her hospital has since switched over 60% of its IV Tyruko patients back to Tysabri. Her story was reported by The Times in October 2024 and The Guardian in February 2025.

Our suffering is not limited to one hospital or region — it's nationwide. I am also in contact with a patient in Sweden, who reports the same post-switch deterioration. Patients in Sweden and Finland are now campaigning against Tyruko too.

We, the MS community, feel voiceless — and increasingly, hopeless. Many of us were stable. Some of us were thriving. Now, we are declining rapidly, and we are being told there’s no way back.

We ask everyone to shine a light on this. To ask the hard questions about how biosimilars are being introduced. And to help give voice to those who are suffering in silence.

Please, help us be heard.

We respectfully demand that:

• Patients who experience worsening symptoms after switching to Tyruko be given the option to return to Tysabri IV.
• All treatment switches to be made with full, informed patient consent.
• NHS England and individual Trusts review and transparently publish safety data from the Tyruko rollout.

This is not just about one medication. It’s about the right to choose what’s best for our bodies and futures. Please listen to patients, respect our lived experiences, and restore the option to continue Tysabri IV for those who need it.

Signed,

Julie Cowdrill,

and People living with MS, their families, and supporters