Safety and Efficacy of Combined Tixagevimab and Cilgavimab Administered Intramuscularly or Intravenously in Nonhospitalized Patients With COVID-19
Authors: Bender Ignacio Rachel A. , Chew Kara W. , Moser Carlee , Currier Judith S. , Eron Joseph J. , Javan Arzhang Cyrus , Giganti Mark J. , Aga Evgenia , Gibbs Michael , Tchouakam Kouekam Hervé , Johnsson Eva , Esser Mark T. , Hoover Keila , Neytman Gene , Newell Matthew , Daar Eric S. , Fischer William , Fletcher Courtney V. , Li Jonathan Z. , Greninger Alexander L. , Coombs Robert W. , Hughes Michael D. , Smith Davey , Wohl David Alain ,   Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV)–2/A5401 Study Team, Ritz Justin , Hosey Lara , Roa Jhoanna , Patel Nilam , Colsh Kelly , Rwakazina Irene , Beck Justine , Sieg Scott , Evering Teresa , Cardoso Sandra , Corado Katya , Jagannathan Prasanna , Jilg Nikolaus , Perelson Alan , Pillay Sandy , Riviere Cynthia , Singh Upinder , Taiwo Babafenu , Gottesman Joan , Pedersen Susan , Jennings Cheryl , Greenfelder Brian , Murtaugh William , Kosmyna Jan , Gapara Morgan , Shahkolahi Akbar , Gasser Robert 
Published: April 2023

ImportanceDevelopment of effective, scalable therapeutics for SARS-CoV-2 is a priority.ObjectiveTo test the efficacy of combined tixagevimab and cilgavimab monoclonal antibodies for early COVID-19 treatment.Design, Setting, and ParticipantsTwo phase 2 randomized blinded placebo-controlled clinical trials within the Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV)–2/A5401 platform were performed at US ambulatory sites. Nonhospitalized adults 18 years or older within 10 days of positive SARS-CoV-2 test and symptom onset were eligible and were enrolled from February 1 to May 31, 2021.InterventionsTixagevimab-cilgavimab, 300 mg (150 mg of each component) given intravenously (IV) or 600 mg (300 mg of each component) given intramuscularly (IM) in the lateral thigh, or pooled placebo.Main Outcomes and MeasuresCoprimary outcomes were time to symptom improvement through 28 days; nasopharyngeal SARS-CoV-2 RNA below the lower limit of quantification (LLOQ) on days 3, 7, or 14; and treatment-emergent grade 3 or higher adverse events through 28 days.ResultsA total of 229 participants were randomized for the IM study and 119 were randomized for the IV study. The primary modified intention-to-treat population included 223 participants who initiated IM tixagevimab-cilgavimab (n = 106) or placebo treatment (n = 117) (median age, 39 [IQR, 30-48] years; 113 [50.7%] were men) and 114 who initiated IV tixagevimab-cilgavimab (n = 58) or placebo treatment (n = 56) (median age, 44 [IQR, 35-54] years; 67 [58.8%] were women). Enrollment in the IV study was stopped early based on a decision to focus on IM product development. Participants were enrolled at a median of 6 (IQR, 4-7) days from COVID-19 symptom onset. Significant differences in time to symptom improvement were not observed for IM tixagevimab-cilgavimab vs placebo or IV tixagevimab-cilgavimab vs placebo. A greater proportion in the IM tixagevimab-cilgavimab arm (69 of 86 [80.2%]) than placebo (62 of 96 [64.6%]) had nasopharyngeal SARS-CoV-2 RNA below LLOQ at day 7 (adjusted risk ratio, 1.33 [95% CI, 1.12-1.57]) but not days 3 and 14; the joint test across time points favored treatment (P = .003). Differences in the proportion below LLOQ were not observed for IV tixagevimab-cilgavimab vs placebo at any of the specified time points. There were no safety signals with either administration route.ConclusionsIn these 2 phase 2 randomized clinical trials, IM or IV tixagevimab-cilgavimab was safe but did not change time to symptom improvement. Antiviral activity was more evident in the larger IM trial.Trial RegistrationClinicalTrials.gov Identifier: NCT04518410