ABSTRACT
Background. Ensovibep is a multi-specific DARPin (designed ankyrin repeat protein) antiviral in clinical development for treatment of COVID-19. In the Phase 2 EMPATHY study, ensovibep demonstrated greater viral load decline versus placebo. Here we report (1) the efficacy of ensovibep in patients with and without anti-SARS-CoV-2 antibodies at baseline and (2) SARS-CoV-2 mutation emergence data with treatment. Methods. Eligible ambulatory patients with >=2 COVID-19 symptoms (onset within 7 days) and positive SARS-CoV-2 rapid antigen test on day of dosing, were randomized (1:1:1:1) to ensovibep (600, 225 or 75 mg) or placebo as single, IV infusion. Chemiluminescent immunoassays were used for antibody detection (SARS-CoV-2 S1/S2 IgG and SARS-CoV-2 IgM). A pre-specified subgroup analysis was performed based on baseline anti-SARS-CoV-2 antibody status. Analysis of changes in viral genome from baseline to post baseline was performed to evaluate treatment-emergent mutations. Results. Of the patients analyzed, 48.5% had anti-SARS-CoV-2 antibodies at baseline. Baseline log10 SARS-CoV-2 viral load (mean +/-SD) was similar across groups [ensovibep (all doses) 6.5 +/-1.5, placebo 6.2 +/-1.5];> 90% were infected with the Delta (B.1.617.2) variant. SARS-CoV-2 viral load reduction up to Day 8 showed similar effects in favor of ensovibep compared with placebo regardless of the presence of anti-SARS-CoV-2 antibodies (Figure 1). Patients in ensovibep 75 mg, 600 mg, and placebo groups had comparable incidences of emergent mutations, with a higher incidence in the 225 mg group. Based on analysis of 70% of the expected viral sequencing data, two mutations in the key binding residues of ensovibep were observed (Y489H and F486L) in a total of three patients treated with ensovibep. These patients either cleared virus by Day 8 or mutations were transient (occurred at a single time point but not later in the course of infection). (Figure Presented) Conclusion. Ensovibep effectively reduces SARS-CoV-2 viral load regardless of the presence of anti-SARS-CoV-2 antibodies at baseline. Furthermore, there were no emerging mutations of concern, indicating that a single dose administration of ensovibep is associated with minimal selective pressure.