Efficacy and Safety of Low-Dose, Rapidly Infused Bamlanivimab and Etesevimab: Phase 3 BLAZE-1 Trial for Mild-to-Moderate COVID-19

Introduction: The monoclonal antibody therapies bamlanivimab (BAM) + etesevimab (ETE) received emergency use authorization (EUA) from the US Food and Drug Administration (February 9, 2021) for treatment of mild-to-moderate COVID-19. The EUA of BAM + ETE was revoked (December 14, 2023) due to the high prevalence of BAM + ETE-resistant variants of SARS-CoV-2. Efficacy and safety of 700/1400 mg and 2800/2800 mg BAM + ETE are well established and published; however, efficacy and safety of 350/700 mg BAM + ETE have not been disclosed to date.

Methods: This portion of phase 3, BLAZE-1 trial (J2X-MC-PYAB) enrolled patients (between June 17, 2020 and April 9, 2021) with mild-to-moderate COVID-19 within 3 days of laboratory diagnosis of SARS-CoV-2 infection. In total, 354 patients with at least one risk factor for severe COVID-19 were enrolled, randomized (2:3), and infused with placebo (N = 141) or 350/700 mg BAM + ETE (N = 213), over ~ 8 min. Primary endpoint was to assess proportion of patients with persistently high SARS-CoV-2 viral load (PHVL) (log viral load > 5.27) 7 days after infusion.

Results: Patients were aged (mean) 53 years, 49.7% female, and 82.7% White. Seven days after drug infusion, 10.8% (95% confidence interval: 6.6, 15.0; p < 0.001) of BAM + ETE-treated patients and 34.8% (26.9, 42.6) of placebo-treated patients had PHVL, and the viral load change from baseline (least square mean [standard error]) was - 3.50 (0.15; p < 0.001) in BAM + ETE-treated patients versus - 2.51 (0.19) in placebo-treated patients. The majority of treatment-emergent adverse events were considered mild or moderate in severity (BAM + ETE: 6.6%; placebo: 14.2%). No deaths were reported.

Conclusions: Consistent with previous studies, patients treated with BAM + ETE (350/700 mg) had a significantly lower proportion of PHVL and greater reduction in viral load compared with placebo. The overall safety profile is consistent with higher doses of BAM + ETE. Infusions of over ~ 8 min did not result in meaningful increase in incidence of TEAEs compared to higher doses of BAM + ETE administered over 30-60 min.

Trial registration: Clinical trial.gov identifier, NCT04427501.