Study: Intramuscular, Intravenous Sotrovimab Equally Effective for Treatment of COVID-19


Intramuscular sotrovimab was not inferior to intravenous (IV) administration for the early treatment of mild-to-moderate COVID-19 in high-risk, non-hospitalized patients 12 years of age and older, according to the headline data from the randomized, multi-center, open-label COMET-TAIL phase 3 trial. Administration of the drug was effective up to 7 days after symptom onset, according to the study.

“I am pleased that [the] results demonstrated similar efficacy for sotrovimab when injected directly into the muscle compared to administered intravenously, potentially offering a more convenient option for patients,” said Hal Barron, MD, chief scientific officer and president of GlaxoSmithKline, in a press release. “We look forward to working with regulatory authorities to help make this new option available to appropriate patients with COVID-19.”

The study enrolled 983 patients, initially divided into 3 arms: 500 mg of sotrovimab given intravenously, 500 mg delivered intramuscularly, and a low dose of 250 mg delivered intramuscularly. The low dose intramuscular cohort was discontinued following a greater number of hospitalizations occurring in that cohort. In the 500 mg intramuscular arm, the rate of progression to hospitalization for more than 24 hours or death was 2.7%, compared to 1.3% in the IV arm. The adjusted difference in the rate of progression between the arms was 1.07% with a 95% confidence interval of -1.25% to 3.39%.

“This trial was conducted during the height of circulation of the Delta variant, with significant enrollment in Florida—a hot spot for this particular variant and where hospitalization rates averaged more than 10% of confirmed cases,” said George Scangos, PhD, chief executive officer of Vir Biotechnology, in the release. “We designed sotrovimab to stand up to the variants that we anticipated would occur, and these data demonstrate that sotrovimab administered via IV or IM could prove important in the fight against COVID-19 following authorization. As we approach the third year of the pandemic, we can expect that multiple treatment options will continue to be needed, particularly for high-risk patients with complex health needs.”

Low rates of serious adverse events (AEs) were reported, with grade 3-4 AEs occurring in less than 1% of both arms. GlaxoSmithKline and Vir Biotechnology are currently in ongoing discussions with the FDA regarding the existing Emergency Use Authorization for sotrovimab.


Primary endpoint met in COMET-TAIL Phase III trial evaluating intramuscular administration of sotrovimab for early treatment of COVID-19 [news release]. GlaxoSmithKline; November 12, 2021. Accessed November 12, 2021.

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