ACR Town Hall Provides Update on Oral Antiviral Therapy for COVID-19

Two oral antiviral drugs have received emergency use authorization (EUA) from the U.S. Food & Drug Administration, nirmatrelvir/ritonavir (Paxlovid) and molnupiravir. Dr. Pavia noted that nirmatrelvir/ritonavir, which is in short supply, has been shown to reduce the progression to hospitalization or death in high-risk patients by about 88% when given within five days.¹ The drug has some potentially lethal interactions with cardiac medications and antipsychotics, but has shown fewer interactions with immunosuppressive drugs, apart from cyclosporine, tacrolimus and sirolimus. He recommended that clinicians review their patients’ medicines with a pharmacist or use Liverpool University’s drug interaction checker.²

Molnupiravir is not as effective as nirmatrelvir/ritonavir for the treatment of COVID-19, but it is in greater supply and does not have the same drug interactions. However, it is contraindicated for use in children and during pregnancy. Contraception is necessary for all patients while taking the drug and for three months afterward in men.

Prevention

Meanwhile, several monoclonal antibody therapies have been developed to help prevent COVID-19. Tixagevimab/cilgavimab (Evusheld) is the only monoclonal antibody therapy that has received an EUA for pre-exposure prophylaxis to prevent COVID-19, and it is effective against the omicron variant, Dr. Saag said. Bamlanivimab/etesevimab, casirivimab/imdevimab (REGEN-COV) and sotrovimab have received EUAs for post-exposure prophylaxis; however, only the last is effective against the omicron variant.

Tixagevimab/cilgavimab has been shown to prevent serious COVID-19 outcomes for up to six months with the delta variant, but its effectiveness will likely be shorter with the omicron variant, Dr. Pavia explained. Although it may still be promising for a few months, he noted tixagevimab/cilgavimab is in very short supply and that its use will be expanded to more patients as it becomes more readily available.

Dr. Gandhi

The expert panel agreed the booster vaccine dose should be a different type of vaccine from the initial series. A fourth dose for immunocompromised patients makes a lot of sense, Dr. Gandhi said; however, a fourth dose is not likely to be approved for immunocompetent individuals. “There’s a concept called original antigenic sin, which is the idea that if you keep on training your immune system to form T cells and antibodies against the ancestral strain … then you redirect your resources to not produce T cells and antibodies against the variant you see in front of you,” Dr. Gandhi explained.

Katie Robinson is a medical writer based in New York.

References

1. Pfizer, Inc. Pfizer announces additional phase 2/3 study results confirming robust efficacy of novel COVID-19 oral antiviral treatment candidate in reducing risk of hospitalization or death. 2021 Dec 14.
2. University of Liverpool. COVID-19 drug interactions.