When bamlanivimab gained initial authorization 13 months ago, it was the first drug specifically designed to arrest infections of the SARS-CoV-2 virus that causes COVID-19. Up until that point, drugs used to treat severe cases had been repurposed, such as dexamethasone or Gilead’s Veklury, which was originally developed for hepatitis and Ebola.

Bamlanivimab and etesevimab are synthetic antibodies, binding to the coronavirus’ signature spike protein and preventing the virus from entering cells and replicating further. Bamlanivimab’s authorization as a single agent was closely followed by one for a dual-antibody combination from Regeneron, and then months later Vir and GSK won clearance for a single antibody treatment.

But as coronavirus variants emerged, the U.S. government withdrew bamlanivimab as a single agent, and Lilly added etesevimab to the combination to improve effectiveness. Dual-antibody combinations are thought to be more resistant to viral mutations as the individual drugs bind to separate places on the virus.

To gain authorization in children, Lilly submitted data from use of bamlanivimab and etestevimab from pediatric patients in a study called BLAZE-1. The company found weight-based doses led to symptom resolution in five days, compared with seven days for those given the adult dose.

As injectable drugs that require patients to visit healthcare facilities, antibodies haven’t been used as widely as they could be or administered early enough in the course of disease to make a difference. Antiviral pills from Merck and Pfizer, however, may change how symptomatic cases are treated as patients could potentially treat themselves at home over just a few days.

Merck’s pill, called molnupiravir, won a close vote from an FDA expert panel last week and is expected to gain emergency authorization. However, children may not be allowed to use that pill because of the potential to cause damage to bones.

Pfizer, meanwhile, is expected to ask the FDA for emergency authorization in coming weeks.