New Covid-19 antiviral cuts symptoms by 1.5 days

A new treatment for Covid-19 can shorten illness among adults with mild cases of the virus, according to a study in the New England Journal of Medicine.

Simnotrelvir is an oral 3-chymotrypsin-like protease inhibitor that was developed by Simcere Pharmaceutical in partnership with two Chinese academic institutions. It was approved in China under an emergency authorisation for the treatment of mild-to-moderate Covid-19 in January 2023. Like the antiviral Paxlovid (nirmatrelvir/ritonavir), it is administered in combination with ritonavir, which limits the breakdown of simnotrelvir.

In the latest phase 2-3 study, 1208 patients with mild-to-moderate Covid-19 were randomised to receive either simnotrelvir and ritonavir or a matching placebo twice daily for five days. The treatment was given within three days of symptom onset.

The researchers found that the time to sustained resolution of Covid-19 symptoms was around 1.5 days shorter in the simnotrelvir group than in the placebo group. On day five of treatment, the decrease in viral load from baseline was greater in the simnotrelvir group than in the placebo group. There were also no evident safety concerns with most adverse events recorded as mild or moderate.

According to the researchers, simnotrelvir is the most popular Covid-19 antiviral in China, and can be bought at a fraction of the price of Paxlovid.