A recent multicenter randomized clinical trial has confirmed that intramuscular administration of the monoclonal antibody sotrovimab achieves virologic equivalence to intravenous infusion in adults with early, mild-to-moderate COVID-19.
The COMET-PEAK study demonstrated that both 500-milligram and 250-milligram intramuscular doses effectively reduce nasopharyngeal viral loads, offering a potential alternative to infusion-based delivery.
This finding addresses the logistical burden of intravenous (IV) therapy during epidemic surges. While IV administration was the standard for sotrovimab under previous Emergency Use Authorizations, the requirement for infusion infrastructure often limits patient access.
By proving that intramuscular (IM) injection—delivered directly into skeletal muscle—can clear the virus from the upper respiratory tract just as effectively as an infusion, researchers have opened a pathway for simpler, community-based treatment administration.
- Simplified Access: Intramuscular delivery removes the need for specialized infusion centers, potentially allowing for administration in primary care or outpatient settings.
- Virologic vs. Clinical Success: While the IM route effectively clears viral particles from the nose and throat, this does not guarantee the same level of protection against hospitalization as the higher-dose IV route.
- Safety Profile: Patients experienced only mild, transient injection-site reactions, such as localized pain or nodules, confirming the method is well-tolerated.
The COMET-PEAK study evaluated whether intramuscular administration of sotrovimab could achieve virologic equivalence to intravenous infusion in reducing respiratory viral load among adults with early, mild-to-moderate coronavirus disease 2019.
Statistical analysis confirmed that intramuscular sotrovimab remained within the strict pharmacologic equivalence boundary when compared to the 500-milligram IV standard. Specifically, the 500-milligram IM dose yielded an adjusted geometric mean ratio of 1.04, with a 90 percent confidence interval of 0.98 to 1.09, well within the predefined range of 0.5 to 2.0.
Pharmacokinetic data revealed expected physiological differences between the two delivery methods. The IV route provides immediate, high systemic bioavailability, whereas IM injection results in slower absorption and lower overall systemic exposure. Despite these differences, the viral clearance trajectories remained parallel throughout the 29-day follow-up period. By day 29, viral levels in nearly all participants had declined below the lower limits of laboratory detection.
A critical nuance in this research is the distinction between clearing the virus and preventing disease progression. The study investigators said that prior investigations, such as the COMET-TAIL non-inferiority study, found that while 500 milligrams delivered intramuscularly was non-inferior to IV infusion for clinical protection, the 250-milligram dose was associated with excess hospitalizations and had to be terminated early.
The study was funded by Vir Biotechnology and GSK, the developers of the antibody, and followed strict protocols for genomic resistance surveillance to track potential viral mutations.
| Treatment Arm | Administration Route | Geometric Mean Ratio (vs. IV) | 90% Confidence Interval |
|---|---|---|---|
| 500 mg Sotrovimab | Intramuscular | 1.04 | 0.98–1.09 |
| 250 mg Sotrovimab | Intramuscular | 1.02 | 0.94–1.11 |
While intramuscular sotrovimab was generally well-tolerated, clinicians must exercise caution for specific patient populations. Individuals with bleeding disorders or thrombocytopenia—a condition characterized by low blood platelet counts—should avoid deep intramuscular injections due to the risk of hematoma or uncontrolled bleeding at the injection site. This treatment is not intended for patients who are already hospitalized with severe respiratory distress or those requiring immediate oxygen support.
Patients who are immunocompromised or have underlying comorbidities, such as a body mass index exceeding 30 kg/m², should consult their physician regarding the current regulatory status of monoclonal antibodies in their region.
Since the United States FDA revoked the Emergency Use Authorization for sotrovimab in December 2024 due to the prevalence of the Omicron BA.2 variant, the clinical availability of this treatment remains subject to local regulatory guidance and evolving viral genomic surveillance.
