U.S. Food and Drug Administration approved Inmazeb (atoltivimab, maftivimab, and odesivimab-ebgn), a combination of three monoclonal antibodies, as the first FDA-approved treatment for Zaire ebolavirus (Ebola virus) infection in adult and pediatric patients.
About Ebola virus
Zaire ebolavirus, commonly known as Ebola virus, is one of four Ebolavirus species that can cause a potentially fatal human disease. Ebola virus is transmitted through direct contact with blood, body fluids and tissues of infected people or wild animals, as well as with surfaces and materials, such as bedding and clothing, contaminated with these fluids. Individuals who provide care for people with Ebola virus, including health care workers who do not use correct infection control precautions, are at the highest risk for infection.
Mechanism of action
Inmazeb targets the glycoprotein that is on the surface of Ebola virus. Glycoprotein attaches to the cell receptor and fuses the viral and host cell membranes allowing the virus to enter the cell. The three antibodies that make up Inmazeb can bind to this glycoprotein simultaneously and block attachment and entry of the virus.
Clinical basis of approval
Inmazeb was evaluated in 382 adult and pediatric patients with confirmed Zaire ebolavirus infection in one clinical trial (the PALM trial) and as part of an expanded access program conducted in the Democratic Republic of the Congo (DRC) during an Ebola virus outbreak in 2018-2019. The PALM trial was led by the U.S. National Institutes of Health and the DRC’s Institut National de Recherche Biomédicale with contributions from several other international organizations and agencies.
In the PALM trial, the safety and efficacy of Inmazeb was evaluated in a multi-center, open-label, randomized controlled trial, in which 154 patients received Inmazeb (50 mg of each monoclonal antibody) intravenously as a single infusion, and 168 patients received an investigational control. The primary efficacy endpoint was 28-day mortality. The primary analysis population was all patients who were randomized and concurrently eligible to receive either Inmazeb or the investigational control during the same time period of the trial. Of the 154 patients who received Inmazeb, 33.8% died after 28 days, compared to 51% of the 153 patients who received a control. In the expanded access program, an additional 228 patients received Inmazeb.
The most common symptoms experienced while receiving Inmazeb included: fever, chills, tachycardia (fast heart rate), tachypnea (fast breathing), and vomiting; however, these are also common symptoms of Ebola virus infection.
Patients who receive Inmazeb should avoid the concurrent administration of a live vaccine due to the treatment’s potential to inhibit replication of a live vaccine virus indicated for prevention of Ebola virus infection and possibly reduce the vaccine’s efficacy.
Inmazeb received an Orphan Drug designation for the treatment of Ebola virus infection. The Orphan Drug designation provides incentives to assist and encourage drug development for rare diseases. Additionally, the agency granted Inmazeb a Breakthrough Therapy designation for the treatment of Zaire ebolavirus infection.
Limitation of Use
- The efficacy of INMAZEB has not been established for other species of the Ebolavirus and Marburgvirus genera.
- Zaire ebolavirus can change over time, and factors such as emergence of resistance, or changes in viral virulence could diminish the clinical benefit of antiviral drugs. Consider available information on drug susceptibility patterns for circulating Zaire ebolavirus strains when deciding whether to use INMAZEB.