A cost-saving effort by NHS England to transition multiple sclerosis (MS) patients from Biogen Inc’s (NASDAQ:BIIB) Tysabri (natalizumab) to the biosimilar drug Tyruko has led to significant side effects.

At Charing Cross Hospital in London, about 170 multiple sclerosis patients experienced complications, including relapses, mobility issues, fatigue, pain, and weight gain. Some cases were severe enough to require hospitalization.

Also Read: Biogen Strengthens Pipeline With Stoke Therapeutic’s Dravet Syndrome Candidate Via Multi-Million Dollar Deal

According to The Guardian report, NHS England has been rolling out biosimilar drugs like Tyruko since April, aiming to cut costs by using alternatives to patented medications. Biosimilars are designed to be as effective and safe as the original drugs but are considerably cheaper—Tyruko costs an average of 72% less than Tysabri.

Sandoz Group AG (OTC:SDZXF) (OTC:SDZNY), a generic spin-off of Novartis AG (NYSE:NVS), manufactures Tyruko. As per The Guardian report, the initiative is part of a broader strategy to save $1.26 billion (1 billion pounds) over five years on medication expenses.

The extent of the issue remains unclear. NHS England has stated that problems have only been observed at Charing Cross, but one patient claims that individuals at 15 other hospitals have also experienced negative effects from the switch.

Approximately half of the NHS hospitals treating MS patients are currently participating in the transition to Tyruko.

Due to growing concerns, NHS England is now discussing with the Department of Health and Social Care and the Medicines and Healthcare products Regulatory Agency to assess the situation and determine potential next steps.

Imperial College Healthcare NHS Trust, which oversees Charing Cross Hospital, initially had 345 patients on Tysabri. When the transition to Tyruko began in May, the trust anticipated mild, short-term side effects but was unprepared for the severity and persistence of complications. About half of the affected patients reported worsening symptoms over several months. In response, all have now been switched back to Tysabri.

Price Action: BIIB stock is up 0.19% at $140.91 at the last check Monday.

Read Next:

• Domino’s Pizza Q4 Same Store Sales Growth Lags, Proposes 15% Dividend Hike

Photo by Tada Images via Shutterstock

UNLOCKED: 5 NEW TRADES EVERY WEEK. Click now to get top trade ideas daily, plus unlimited access to cutting-edge tools and strategies to gain an edge in the markets.

Get the latest stock analysis from Benzinga?

• BIOGEN (BIIB): Free Stock Analysis Report

This article NHS England's Transition From Biogen's Drug To Sandoz's Biosimilar Sparks Alarm As Multiple Sclerosis Patients Report Severe Effects originally appeared on Benzinga.com

© 2025 Benzinga.com. Benzinga does not provide investment advice. All rights reserved.