Monoclonal Antibodies for Post-Exposure Prophylaxis Could Saves Lives and Money

Administering monoclonal antibodies as post-exposure prophylaxis to unvaccinated Americans age 50 and older with household members with a COVID-19 variant that is susceptible to the treatment could save millions of dollars and prevent hundreds of deaths, a new study showed.

The decision analytical model study, published in JAMA Network Open, included 1555 participants from the Regen-Cov PEP trial, with 753 receiving monoclonal antibodies as post-exposure prophylaxis (mAb PEP) and 752 in a placebo group. The REGEN-COV PEP trial tested an antibody combination of casirivimab with imdevimab given to unvaccinated COVID-19-negative participants within 96 hours of a household member testing positive for COVID-19. The decision analytical model also included data on confirmed cases for 154,136 people and vaccine coverage for 1,888 people, along with data on 1,276,716 households including 3,088,232 people.

“In this modeling study of a simulated US population, a mAb PEP for COVID-19 program was estimated to improve health outcomes and reduce costs,” the study authors, led by Abraham D. Flaxman, PhD, of the Institute for Health Metrics and Evaluation at the University of Washington, wrote. “In the setting of a susceptible variant of SARS-CoV-2, health system and public health actors would have an opportunity to improve health and reduce net payer costs through COVID-19 PEP with mAbs.”

The study modeled a month with COVID-19 transmission similar to May 2021, and 50% of exposed, unvaccinated household members age 50 and older receiving monoclonal antibodies. The model estimated post-exposure prophylaxis could prevent between 528 and 1404 hospitalizations and between 84 and 223 deaths, depending on the level of transmission.

The estimated cost of hospitalizations for COVID-19 from household exposure was $149 million to $400 million, depending on the rate of transmission. The likelihood of cost savings was highest among those aged 80 (82% in a low-transmission scenario and 100% in a high-transmission scenario). For those at a threshold of age 50, there was no probability of cost savings in a low-transmission scenario, but the likelihood of cost savings was 96% in a high-transmission scenario.

“Antibody therapies are fast acting, since their ready-made antibodies can bind to antigen immediately, in contrast to vaccines that stimulate the body to produce an immune response over weeks,” the study authors wrote. “This property of fast-acting protection makes antibody therapies potentially attractive for use in household exposure situations where unvaccinated household contacts are at high risk of acquiring infection over a short time and can be identified rapidly. However, antibodies are costly to produce, which makes it important to assess their optimal use in health economic analyses.”

Monoclonal antibodies could be beneficial in scenarios that include high transmission rates; unvaccinated people; high-risk exposure, such as within households or long-term care facilities; and among those who are immunocompromised and unlikely to mount an immune response to vaccines.

The Food and Drug Administration granted emergency use authorization for Regen-Cov as post-exposure prophylaxis for certain at-risk people but later limited the use of the antibody treatment along with bamlanivimab and etesevimab after research showed it was unlikely to be effective against the Omicron variant of COVID-19.

“Promising advances in efforts to isolate and develop mAbs with activity against a broad range of sarbecoviruses could lessen the risk of loss of activity with future SARS-CoV-2 genotypes/variants,” the study authors noted.

One variant-agnostic therapy currently under development is Humanigen’s monoclonal antibody lenzilumab, which showed promise for treating hyperinflammatory response to SARS-CoV-2 infection in recently published phase 3 trials.

The emergence of new variants doesn’t always mean monoclonal antibodies will be less effective. A recent study showed that monoclonal antibodies more effectively neutralize the newer BA.2 subvariant of Omicron than the original BA.1 subvariant.