The U.S. Food and Drug Administration (FDA) has fully rescinded its emergency use authorization (EUA) for the use of sotrovimab in treating Covid-19. The agency announced the update to the EAU on April 5.

Sotrovimab is an intravenous monoclonal antibody medication produced by GlaxoSmithKline. A monoclonal antibody solution is injected into the body to bind to a specific protein or antigen in order to induce the body’s immune system to attack that antigen. Sotrovimab was originally authorized by the FDA to combat the initial form of the SARS-CoV-2 virus. 

While monoclonal antibodies can be a potentially life-saving tool for helping to combat viruses, they are also only narrowly effective. The nature of monoclonal antibodies means that they only bind to certain antigens. When an antigen such as a virus mutates to the point that it no longer binds to the monoclonal antibodies, the medication is no longer as effective. 

According to the FDA, the Centers for Disease Control and Prevention (CDC) Nowcast data from April 5, the same date as the announcement, the ratio of Covid-19 cases caused by the Omicron BA.2 variant is above 50% in all Health and Human Services (HHS) regions. HHS regions are a series of 10 divisions that split the United States and its territories in order to provide more local on-the-ground support than coordinating responses from HHS national headquarters. 

With more than 50% of Americans infected with a variant, the effectiveness of sotrovimab at its current dosage level is no longer sufficient to justify its EUA. The removal of sotrovimab’s authorization comes on the heels of two partial removals of authorization on March 25 and 30. This follows a general trend of decreasing the prioritization of sotrovimab since February as the variants spread.

In the March 25 update, the FDA slightly tightened the scope of sotrovamib use by targeting HHS regions in the Northeast. The HHS regions affected by the March 25 update were regions 1 and 2 consisting of:

Region 1

  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island

Region 2

  • New Jersey
  • New York
  • Puerto Rico
  • The Virgin Islands

During the March 30 update, the FDA announced that due to the prevalence of the Omicron variant in HHS regions 5, 9, and 10, sotrovimab would no longer be authorized in those regions. The states and territories in those regions are:

Region 5

  • Illinois
  • Indiana
  • Michigan
  • Minnesota
  • Ohio
  • Wisconsin

Region 9

  • Arizona
  • California
  • Hawaii
  • Nevada
  • American Samoa
  • The Commonwealth of the Northern Mariana Islands
  • The Federated States of Micronesia
  • Guam
  • The Marshall Islands
  • The Republic of Palau

Region 10

  • Alaska
  • Idaho
  • Oregon
  • Washington

At the end of both previous updates, the FDA stated that they would monitor the situation and provide updates on effective treatments as the data became available. The FDA is now advising all healthcare professionals to use alternative approved or authorized medications to treat Covid infections.