Atea decimated as Phase II MOONSONG trial of AT-527 fails endpoint

US biopharma company Atea Pharmaceuticals’ (Nasdaq: AVIR) shares slumped 73% to $11.07 in pre-market trading today, after its COVID-19 treatment hopeful missed its clinical goal.

Phase II MOONSONG trial evaluating AT-527 in the outpatient setting did not meet the primary endpoint of reduction from baseline in the amount of SARS-CoV-2 virus in patients with mild or moderate COVID-19 compared to placebo in the overall study population, of which approximately two thirds of patients were low-risk with mild symptoms.

However, in high-risk patients with underlying health conditions, a reduction of viral load of approximately 0.5 log10 at Day 7 was observed at 550mg (prespecified subgroup analysis) and 1,100mg BID (exploratory subgroup analysis) compared with placebo.