Regeneron does a Lilly with its Covid-19 antibody

Like Lilly’s Covid-19 antibody bamlanivimab Regeneron’s REGN-COV2 has stumbled in a clinical trial of hospitalised patients. Regeneron’s Study 2066 has had its severest cohorts – subjects on high-flow oxygen and those requiring ventilation – halted for lack of a benefit, though those not requiring oxygen or on low-flow will continue. Earlier this week the NIAID-sponsored Activ-3 trial of Lilly’s bamlanivimab, combined with Veklury in hospitalised subjects, was halted in its entirety. Such findings, coupled with evidence of efficacy in less severe Covid-19 patients, make scientific sense: once the virus does sufficient damage an antibody blocking its entry can have little benefit. The one fly in the ointment, at least as far as Regeneron’s message goes, is that an outpatient study of REGN-COV2 had yielded virology data suggesting the greatest benefit in patients with highest viral load, meaning the most severely ill ones and those at greatest need. That too can be explained if it is surmised that the fittest patients are able to mount a successful response themselves, but if there is a “Goldilocks” zone for efficacy Regeneron will have to manage expectations carefully.