Gain of function describes a mutation in COVID-19 that causes it to do something new. This is different from most mutations, which are loss of function, causing

Gain of function describes a mutation in COVID-19 that causes it to do something new. This is different from most mutations, which are loss of function, causing it to stop doing something old. The gain of function mutation is a cleavage site, which means that a new protein can be created, which could have some new activity. This cleavage site looks like a Furin cleavage site: Furin is associated with transporting proteins inside a cell, and thus with infection. So a drug targeting the Furin pathway may block the effect of this gain of function mutation, and make COVID-19 less infections to those taking it.