Casirivimab plus imdevimab reduced risk of hospitalization or death in patients with and without asthma

This randomized controlled trial investigated the efficacy of casirivimab plus imdevimab (CAS + IMD) in outpatients with acute COVID-19 compared to a placebo. The study population included 4057 individuals with COVID-19 and 2652 individuals without COVID-19 in home or community settings. The primary objective was to measure the time to hospitalization or death among these patients.

The intervention consisted of casirivimab plus imdevimab (CAS + IMD), while the comparator group received a placebo. The study specifically analyzed outcomes across different patient profiles, including those with atopic conditions and those with asthma, to determine if underlying sensitivities influenced treatment response.

Regarding the primary outcome of time to hospitalization or death, the results showed significant benefits for the CAS + IMD intervention. In patients without atopy, the risk was reduced by a hazard ratio (HR) of 0.26 (95% CI, 0.12-0.58; P < .001). For patients with atopic conditions excluding asthma, the risk was even lower with an HR of 0.17 (95% CI, 0.06-0.49; P < .001). Notably, in the placebo group, those with an atopic background without asthma showed a 52% lower risk compared to those with no atopy (HR: 0.48; 95% CI, 0.31-0.74; P < .001). Conversely, in the placebo group, patients with asthma only faced a 2.90 times higher risk of hospitalization or death compared to those without atopy (HR: 2.90; CI, 1.55-5.48; P < .001).

In the treatment arm, casirivimab plus imdevimab demonstrated a significant reduction in the risk of hospitalization or death for patients with asthma only, showing an HR of 0.32 (CI, 0.16-0.63; P < .001). A secondary outcome measured the change in viral load from baseline to day 7, though specific numerical values were not detailed in the primary summary.

Safety and tolerability data, including specific rates of adverse events or serious adverse events, were not reported in the provided data. However, the study noted that while atopic conditions were associated with better clinical outcomes in some contexts, the specific biological mechanisms for this association were not detailed.

Methodologically, the study noted that adjustments for imbalances in antihistamine use had little effect on the final estimates. These findings are significant because they demonstrate that CAS + IMD provides a consistent protective effect regardless of whether a patient has an atopic background or asthma.\n Clinical implications suggest that while atopic diseases may be associated with heightened susceptibility to infection, these patients—and those with asthma—may still derive significant clinical benefit from casirivimab plus imdevimab. The treatment appears effective in reducing severe outcomes across diverse respiratory profiles. Questions remain regarding the specific mechanisms of protection and the long-term durability of the intervention's effects.