Zinbryta, a drug treatment for multiple sclerosis, was withdrawn last year after concerns that the medication may have let to serious brain inflammation.

Multiple sclerosis is an autoimmune condition which affects the central nervous system (brain and spinal cord). The disease causes the body’s immune system to attack the protective sheath around nerve cells known as the myelin. This sheath helps nerves conduct electrical impulses and effectively send signals from the brain.

When the myelin is compromised by multiple sclerosis, neurological connections in the brain and spine are less effective and can lead to various neurological symptoms. Although symptoms may vary based on which parts of the nervous system is affected and how aggressive the damage is, symptoms may include: numbness; limb weakness; partial or complete vision loss; prolonged double vision; tingling; pain; electric shock sensations with certain neck movements; tremor; unsteady gait; lack of coordination; slurred speech, fatigue; dizziness; and more.

Zinbryta was approved for use by the U.S. Food and Drug Administration (FDA) in May 2016. However, as the agency noted, the intravenous immune modulating drug has always had a complex safety profile and has been linked to life threatening liver damage and serious immune system disorders.

The FDA warned about these issues and recommended that Zinbryta not be prescribed to patients with liver problems, patients taking medications affecting the liver, and patients with skin conditions including eczema and psoriasis. The agency also required patients to have tried two or more disease modifying treatments before using Zinbryta.

In 2018, encephalitis (a life threatening inflammation of the brain) was added to the list of concerns related to this drug treatment for multiple sclerosis. Unlike meningitis, which is the inflammation of the membranes covering the brain, encephalitis involves inflammation of the brain tissue.

Signs of the condition may resemble a flu including muscle pain or weakness, fatigue, fever, headache, light sensitivity, nausea or vomiting, and more. However, the condition can quickly worsen and result in symptoms including seizures, changes in behavior, confusion, and disorientation. Encephalitis needs to be treated immediately and aggressively and may be targeted with antibiotics that can cross the blood-brain barrier.

In March 2018, pharmaceutical manufacturers Biogen and AbbVie took Zinbryta off the worldwide market after the European Medicines Agency revealed eight cases of encephalitis. Seven reports from patients in Germany and one in Spain led to the sudden market withdrawal of the drug, which was announced the same day that the European Medicines Agency called for an “urgent review” of the drug treatment for multiple sclerosis.

“Given the nature and complexity of adverse events being reported, characterizing the evolving benefit/risk profile of Zinbryta will not be possible going forward given the limited number of patients being treated,” the companies said in a statement, according to CNN. “Therefore, Biogen and AbbVie believe it is in the best interest of patients to voluntarily withdraw worldwide marketing authorizations for Zinbryta.”

At the time of the recall, the FDA released a statement saying that the agency was working closely with both pharmaceutical companies “to help ensure a well-organized withdrawal from the market in the United States, and to ensure that healthcare professionals have the information they need to carefully transition their patients using Zinbryta to another treatment.”