Background: The SARS-CoV-2 virus enters cells via Angiotensin-converting enzyme 2 (ACE2), disrupting the renin-angiotensin-aldosterone axis, potentially contributing to lung injury. Treatment with angiotensin receptor blockers (ARBs), such as losartan, may mitigate these effects, though induction of ACE2 could increase viral entry, replication, and worsen disease. Methods: This study represents a placebo-controlled blinded randomized clinical trial (RCT) to test the efficacy of losartan on outpatients with COVID-19 across three hospital systems with numerous community sites in Minnesota, U.S. Participants included symptomatic outpatients with COVID-19 not already taking ACE-inhibitors or ARBs, enrolled within 7 days of symptom onset. Patients were randomized to 1:1 losartan (25 mg orally twice daily unless estimated glomerular filtration rate, eGFR, was reduced, when dosing was reduced to once daily) versus placebo for 10 days, and all patients and outcome assesors were blinded. The primary outcome was all-cause hospitalization within 15 days. Secondary outcomes included functional status, dyspnea, temperature, and viral load. (clinicatrials.gov, NCT04311177, closed to new participants) Findings: From April to November 2020, 117 participants were randomized 58 to losartan and 59 to placebo, and all were analyzed under intent to treat principles. The primary outcome did not differ significantly between the two arms based on Barnard's test [losartan arm: 3 events (5.2% 95% CI 1.1, 14.4%) versus placebo arm: 1 event (1.7%; 95% CI 0.0, 9.1%)]; proportion difference -3.5% (95% CI -13.2, 4.8%); p = 0.32]. Viral loads were not statistically different between treatment groups at any time point. Adverse events per 10 patient days did not differ signifcantly [0.33 (95% CI 0.22–0.49) for losartan vs. 0.37 (95% CI 0.25–0.55) for placebo]. Due to a lower than expected hospitalization rate and low likelihood of a clinically important treatment effect, the trial was terminated early. Interpretation: In this multicenter blinded RCT for outpatients with mild symptomatic COVID-19 disease, losartan did not reduce hospitalizations, though assessment was limited by low event rate. Importantly, viral load was not statistically affected by treatment. This study does not support initiation of losartan for low-risk outpatients.

Original languageEnglish (US)
Article number100957
StatePublished - Jul 2021

Bibliographical note

Funding Information:
Role of the funding source: This study was supported by Minnesota Partnership for Biotechnology and Medical Genomics (CON000000076883); the funder had no access to the dataset, and no role in the development, design, analysis, interpretation of results, or decision to publish. MAP, HV, TM, JK had access to the data. MAP made the decision to submit for publication.

Funding Information:
The authors have no financial conflicts of interest to disclose. All the authors report grants from Minnesota Partnership for Biotechnology and Medical Genomics during the conduct of the study. MAP reports also grants from Bill and Melinda Gates Foundation and grants from NHLBI, outside the submitted work.

Publisher Copyright:
© 2021 The Author(s)


  • Angiotensin receptor blocker
  • COVID-19
  • Losartan
  • RAAS

PubMed: MeSH publication types

  • Journal Article


Dive into the research topics of 'A multi-center phase II randomized clinical trial of losartan on symptomatic outpatients with COVID-19'. Together they form a unique fingerprint.

Cite this