AstraZeneca (LON:AZN) was among the first companies to develop a COVID-19 vaccine, but the firm has given up on marketing its Vaxzevria vaccine in the U.S. The company’s CEO, Pascal Soriot, announced that it had asked the FDA to withdraw its regulatory paperwork for Vaxzevria.

The vaccine developed jointly with Oxford University saw considerable success in Europe and elsewhere. But the replication-deficient chimpanzee adenovirus ChAdOx1/AZD1222 has seen waning use as mRNA-based vaccines have come to dominate the market.

In the third quarter of 2022, sales of the vaccine dropped 83% to $173 million. Earlier this year, developing countries refused tens of millions of vaccine doses.

After giving up on plans to market its COVID-19 vaccine in the U.S., AstraZeneca will focus on the monoclonal antibody cocktail Evusheld (tixagevimab/cilgavimab).

AstraZeneca developed Evusheld in collaboration with researchers at Vanderbilt University. Dr. James E. Crowe Jr., Robert Carnahan and other Vanderbilt researchers first identified the two antibodies and licensed them to AstraZeneca in June 2020.

To date, Evusheld is the only pre-exposure prophylaxis (PrEP) of COVID-19 to receive emergency use authorization (EUA). Specifically, the EUA covers its use in immunocompromised individuals unlikely to respond strongly to COVID-19 vaccination.

In October, AstraZeneca announced that Evusheld reduced the likelihood of hospitalization and death in the Phase 3 TACKLE study, which focused on adults with mild-to-moderate COVID-19.

The antibody cocktail has a durable effect. According to data from the Phase 3 PROVENT study, Evusheld offers protection against COVID-19 for at least six months.

The antibody cocktail, however, may not hold up to some variants, according to the FDA. In addition, the agency warned in October that various omicron subvariants had reduced susceptibility to Evusheld.

AstraZeneca plans to launch a rebooted version of Evusheld by the second half of 2023.

AZN shares were up 6.62% to $65.09. The company’s stock is up 11.63% thus far this year.