New England Journal of Medicine March 04, 2021

Baricitinib plus Remdesivir for Hospitalized Adults with Covid-19

Andre C. Kalil et al. (ACTT-2 Study Group)

Bottom Line

The ACTT-2 trial demonstrated that combining the JAK inhibitor baricitinib with remdesivir significantly reduced recovery time and decreased serious adverse events compared to remdesivir alone in hospitalized adults with COVID-19.

Key Findings

1. The median time to recovery was significantly shorter in the baricitinib plus remdesivir group compared to the control group (7 days vs. 8 days; rate ratio for recovery, 1.16; 95% CI, 1.01 to 1.32; P=0.03).
2. The most pronounced benefit in recovery time occurred among patients receiving high-flow oxygen or noninvasive ventilation at baseline (10 days vs. 18 days; rate ratio, 1.51; 95% CI, 1.10 to 2.08).
3. Patients assigned to the combination treatment had 30% higher odds of experiencing an improvement in clinical status at day 15 (odds ratio, 1.3; 95% CI, 1.0 to 1.6).
4. The 28-day mortality rate was numerically lower in the combination group but the difference did not achieve statistical significance (5.1% vs. 7.8%; hazard ratio for death, 0.65; 95% CI, 0.39 to 1.09).
5. Serious adverse events were significantly less frequent in the baricitinib combination group (16.0% vs. 21.0%; difference, -5.0 percentage points; 95% CI, -9.8 to -0.3; P=0.03).
6. The incidence of new infections was significantly lower in patients receiving baricitinib (5.9% vs. 11.2%; difference, -5.3 percentage points; 95% CI, -8.7 to -1.9; P=0.003).

Study Design

Design
RCT
Double-Blind
Sample
1,033
Patients
Duration
28 days
Median
Setting
Multicenter, 8 countries
Population Hospitalized adult patients with laboratory-confirmed SARS-CoV-2 infection and evidence of lower respiratory tract involvement (radiographic infiltrates, SpO2 ≤94% on room air, or requirement for supplemental oxygen, mechanical ventilation, or ECMO).
Intervention Baricitinib (4 mg daily for up to 14 days) plus Remdesivir (200 mg loading dose, then 100 mg daily for up to 10 days)
Comparator Matching placebo plus Remdesivir (same dosing schedule)
Outcome Time to recovery up to day 29, defined as either hospital discharge or continued hospitalization for infection-control purposes only.

Study Limitations

The study was largely conducted before corticosteroids (e.g., dexamethasone) became the universal standard of care for hypoxemic COVID-19 patients, limiting the ability to assess baricitinib's additive benefit over systemic steroids.
The trial was powered for a primary outcome of time to recovery rather than mortality, which is a softer clinical endpoint.
The study follow-up was limited to 28 days, preventing the evaluation of long-term outcomes or potential delayed sequelae related to profound immunomodulation.
The observed mortality reduction did not meet statistical significance, limiting definitive conclusions regarding a survival benefit.

Clinical Significance

ACTT-2 provided critical proof-of-concept that targeting dysregulated inflammation with a JAK inhibitor (baricitinib) safely accelerates recovery and reduces progression to severe respiratory failure in COVID-19. It notably dispelled concerns that adding a potent immunosuppressant to an antiviral would increase secondary infections; rather, it reduced them. This pivotal evidence led directly to the FDA Emergency Use Authorization for baricitinib in hospitalized patients requiring supplemental oxygen.

Historical Context

The Adaptive COVID-19 Treatment Trial (ACTT) platform was launched rapidly during the initial phase of the global pandemic. ACTT-1 established remdesivir as the first antiviral to show clinical benefit. Recognizing that severe COVID-19 is driven heavily by a hyperinflammatory 'cytokine storm', ACTT-2 investigated the combination of remdesivir with baricitinib, an oral JAK1/JAK2 inhibitor. Although its publication coincided with the RECOVERY trial's validation of dexamethasone—which rapidly changed the standard of care—ACTT-2 laid the groundwork for using targeted immunomodulators in viral sepsis and severe pneumonia.

Guided Discussion

High-yield insights from every perspective

Med Student
Medical Student

How do the mechanisms of action of baricitinib and remdesivir complement each other in the treatment of COVID-19, particularly regarding the biphasic nature of the disease?

Key Response

Tests understanding of viral replication vs. hyperinflammatory phase. Remdesivir inhibits the viral RNA-dependent RNA polymerase targeting the early viral replication phase, while baricitinib is a JAK1/2 inhibitor that mitigates the downstream cytokine storm in the later hyperinflammatory phase, and uniquely may also inhibit viral entry via AAK1.

Resident
Resident

Given the known boxed warnings for JAK inhibitors regarding thrombosis and immunosuppression, how does the ACTT-2 safety data influence your decision to prescribe baricitinib in a hospitalized COVID-19 patient who is already at high risk for VTE?

Key Response

Residents must weigh risks and benefits using trial safety data. Surprisingly, ACTT-2 showed fewer serious adverse events and no increase in VTEs or new infections in the baricitinib group. This suggests that by controlling the underlying severe COVID-19 inflammation, which itself drives thrombosis and ARDS, the drug reduces overall thrombotic and infectious risk in this specific acute setting.

Fellow
Fellow

The ACTT-2 trial demonstrated the greatest recovery benefit of baricitinib in patients receiving high-flow oxygen or noninvasive ventilation (baseline ordinal score 6). How do you integrate these subgroup findings with data on dexamethasone, and when might you choose baricitinib over or alongside corticosteroids?

Key Response

Fellows must navigate overlapping therapies. Corticosteroids became standard of care concurrently. Because ACTT-2 largely evaluated baricitinib without baseline steroids, fellows must recognize that baricitinib provides profound benefit in the pre-intubation hyperinflammatory window, making it a critical choice when steroids are contraindicated or as an escalated adjunct in rapidly progressing hypoxemia.

Attending
Attending

The paradoxical reduction in secondary infections observed in the baricitinib arm challenges classical infectious disease dogma regarding immunosuppressives. What does this teach us about the pathophysiology of severe viral sepsis, and how should it reframe our clinical hesitations about using targeted immunomodulators in critical illness?

Key Response

Attendings appreciate paradigm shifts. Classical teaching dictates that immunosuppression worsens infection risk. ACTT-2 demonstrated that dampening the dysregulated host immune response (cytokine storm) actually preserves barrier tissue integrity and prevents immune exhaustion, resulting in fewer secondary bacterial/fungal infections and changing our risk-benefit calculus for immunomodulation in viral sepsis.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD
PhD

ACTT-2 utilized a proportional odds model to evaluate clinical status on an 8-point ordinal scale at day 15. What are the statistical assumptions of the proportional odds assumption in this context, and how might violations of this assumption due to disproportionate mortality rates in critical care subgroups skew the interpretation of the treatment effect?

Key Response

Focuses on advanced statistical methodology. Proportional odds (shift analysis) assumes the treatment odds ratio is constant across all cut-points of the ordinal scale. In COVID-19, mortality (the worst outcome) might not shift proportionally compared to milder respiratory outcomes, meaning a single summary odds ratio could mask heterogeneity of effect across different severity thresholds.

Journal Editor
Journal Editor

During the ACTT-2 enrollment period, the RECOVERY trial results established dexamethasone as the standard of care for severe COVID-19, leading to concurrent steroid use in some late-enrolled ACTT-2 participants. As a reviewer, how would you critically evaluate the potential for this mid-trial external event to confound the efficacy and safety signals of baricitinib?

Key Response

Editors look for external factors contaminating trial validity. The unblinded adoption of steroids in approximately 11% of patients post-RECOVERY could dilute the measured effect size or alter the safety profile of baricitinib. A rigorous review would require scrutinizing sensitivity analyses excluding or adjusting for steroid use to ensure the baricitinib effect remains independently robust.

Guideline Committee
Guideline Committee

Based on the ACTT-2 findings and subsequent trials, how should current clinical practice guidelines position baricitinib in the treatment algorithm for hospitalized COVID-19 patients requiring oxygen, specifically regarding its recommendation grade compared to IL-6 inhibitors like tocilizumab?

Key Response

Guideline committees must synthesize ACTT-2 with overlapping evidence. Currently, NIH COVID-19 Treatment Guidelines recommend baricitinib (Level AI) alongside dexamethasone for patients on high-flow O2/NIV. The committee must weigh ACTT-2's strong safety profile, ease of oral/enteral administration, and rapid onset against tocilizumab, often positioning baricitinib as the preferred immunomodulator when IL-6 inhibitors are unavailable or when aiming to minimize secondary infection risks.

Clinical Landscape

Noteworthy Related Trials

2020

ACTT-1 Trial

n = 1062 · NEJM

Tested

Remdesivir for up to 10 days

Population

Hospitalized adults with COVID-19

Comparator

Placebo

Endpoint

Time to recovery

Key result: Remdesivir was superior to placebo in shortening the time to recovery in adults hospitalized with Covid-19.
2021

RECOVERY Trial (Dexamethasone)

n = 6425 · NEJM

Tested

Dexamethasone 6mg daily for up to 10 days

Population

Hospitalized patients with clinically suspected or confirmed SARS-CoV-2 infection

Comparator

Usual care

Endpoint

28-day mortality

Key result: Dexamethasone reduced 28-day mortality among patients receiving invasive mechanical ventilation or oxygen alone.
2021

COV-BARRIER Trial

n = 1525 · Lancet Respir Med

Tested

Baricitinib 4mg daily for up to 14 days

Population

Hospitalized adults with COVID-19 and elevated inflammatory markers

Comparator

Placebo added to standard of care

Endpoint

Progression to high-flow oxygen, non-invasive ventilation, invasive mechanical ventilation, or death by day 28

Key result: While the primary composite endpoint was not significantly reduced, baricitinib treatment led to a significant relative reduction in 28-day all-cause mortality.

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