COVID Antivirals Appear to Hold Up Against BA.2

While two monoclonal antibody combinations showed neutralizing activity against the Omicron subvariant BA.2, both required substantially higher concentrations to produce a response in patients with COVID-19, Japanese researchers said, while antivirals appeared to be less affected.

Casirivimab/imdevimab (REGEN-COV) and tixagevimab/cilgavimab (Evusheld) inhibited BA.2, but the titer of monoclonal antibodies “required for a 50% reduction in the number of infectious foci” for BA.2 was higher by a factor of 43.0 to 143.6 for the former and by a factor of 1.4 to 8.1 for the latter compared with the ancestral strain and other variants, reported Yoshihiro Kawaoka, DVM, PhD, of the University of Tokyo, and colleagues.

However, the susceptibilities of Omicron/BA.2 to the antivirals remdesivir (Veklury), molnupiravir, and nirmatrelvir, a component of Paxlovid, were similar to those of the ancestral strain and other variants of concern (50% inhibitory concentration values for these three agents that differed by factors of 2.5 to 4.5, 0.7 to 1.6, and 1.5 to 3.3, respectively), the authors noted in the New England Journal of Medicine (NEJM).

“Clinical studies are warranted to determine whether these antiviral therapies are indeed effective against Omicron/BA.2 infections,” they wrote.

Kawaoka’s group examined a biological sample of BA.2, which was isolated from a traveler from India who arrived in Japan, and tested it against the monoclonal antibodies and antivirals.