Peginterferon-lambda experimental antiviral drug can significantly speed up recovery for COVID-19 outpatients


A clinical study led by Dr. Jordan Feld, a liver specialist at Toronto Centre for Liver Disease, University Health Network (UHN), showed an experimental antiviral drug can significantly speed up recovery for COVID-19 outpatients – patients who do not need to be hospitalized.

This could become an important intervention to treat infected patients and help curb community spread, while COVID-19 vaccines are rolled out this year.

“This treatment has large therapeutic potential, especially at this moment as we see aggressive variants of the virus spreading around the globe which are less sensitive to both vaccines and treatment with antibodies,” says Dr. Feld, who is also Co-Director of the Schwartz Reisman Liver Research Centre and the R. Phelan Chair in Translational Liver Research at UHN.

According to the study, published today in Lancet Respiratory Medicine, patients who received a single injection of peginterferon-lambda were over four times more likely to have cleared the infection within seven days, when compared to a group treated with placebo.

“People who were treated cleared the virus quickly, and the effect was most pronounced in those with the highest viral levels. We also saw a trend towards quicker improvement of respiratory symptoms in the treatment group,” explains Dr. Feld—who translated his knowledge of peg-interferon lambda usage for viral hepatitis to research on COVID-19 treatment.

Participants with higher viral levels (above 1 million copies per mL) were much more likely to clear infection with treatment than placebo: 79% in the treatment arm compared to 38% in the placebo group; and virus levels decreased quickly in everyone in the treatment group.

Treatment benefits and public health impact

Rapid clearance has many benefits, particularly in those with high viral levels, as those cases are associated with more severe disease and a higher risk of transmission to others. Among the 60 patients followed in the study, five went to emergency rooms with deteriorating respiratory symptoms. Of those, four were in the placebo group, while only one was in the group which received the actual drug.

Bringing down the virus level quickly prevents people from getting worse and likely reduces the risk of spreading the disease to others. This may have important additional public health impact.

“If we can decrease the virus level quickly, people are less likely to spread the infection to others and we may even be able to shorten the time required for self-isolation,” says Dr. Feld.

Anonymous participant receives antiviral drug. Credit: UHN


Interferon-lambda is a protein produced by the body in response to viral infections. It has the ability to activate a number of cellular pathways to kill invading viruses.

The coronavirus that causes COVID-19 prevents the body from producing interferons, which is one way it avoids being controlled by the body’s immune system. Treatment with interferon-lambda activates those same virus-killing pathways in the cells.

Because interferon activates many virus-killing pathways, resistance due to ‘new strains’ of the virus, which could be an issue with some therapies, is not a concern with interferon-lambda.

Interferon-lambda is different from other interferons because it uses a receptor that is only present in some tissues in the body.

It is very active in the lung, the liver and the intestine, all places where the COVID-19 virus is able to replicate, but it is not active in other places leading to a lot fewer side effects than other interferons. In the trial, those treated with interferon-lambda had similar side effects to those who received placebo.

Peginterferon-lambda (used in this study) is a long-acting version of the drug developed by Eiger BioPharmaceuticals, which can be given as a single injection under the skin with a tiny needle (like insulin).

Next steps

This was an investigator initiated phase 2, double-blind randomized study, done in Toronto, with a total of 60 participants—30 who received the drug while 30 received placebo. The study was conducted from May to November 2020, with referrals from six outpatient assessment centres.

With these positive results, a large phase 3 trial is planned to start in the near future. Additional studies are ongoing at the University of Toronto, Harvard University and Johns Hopkins University with peginterferon-lambda in hospitalized patients, and in settings where it can be used to prevent infection in those who have been exposed.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the virus causing coronavirus disease 2019 (COVID-19), continues to be a global health threat. To date, only remdesivir and dexamethasone have demonstrated efficacy in randomized trials, but evaluated hospitalized patients only1, 2.

As with other acute viral infections, early initiation of antiviral therapy for COVID-19 may improve clinical outcomes3; yet there are few studies among outpatients. In addition to halting clinical progression, early treatment may shorten the duration of viral shedding, potentially reducing transmission and the duration of self-isolation4.

Interferons are produced as part of the innate immune response to viral infections, driving induction of genes with antiviral, antiproliferative and immunoregulatory properties5. The broad array of genes induced by interferons limits the risk of antiviral resistance and makes them optimal agents for novel viral pathogens6.

Interferon-lambdas, known as Type III interferons, exert a similar antiviral state to interferon-alpha/beta, but use a distinct receptor complex with high expression levels limited to epithelial cells in the lung, liver and intestine, resulting in fewer systemic side effects6. Interferon-lambda-1 controls respiratory viral infections in mice without the risk of promoting cytokine storm syndrome, as has been seen with Type I interferon treatment7. Additionally, interferon-lambda inhibits SARS-CoV-2 replication in cell culture and mouse models8, 9.

Peginterferon-lambda, a long-acting form of interferon lambda-1, has been evaluated in over 3,000 patients with viral hepatitis infections, demonstrating similar antiviral efficacy to interferon-alpha, but with an improved side effect profile10, 11. We performed a randomized, double-blind, multicenter, placebo-controlled study evaluating treatment with a single 180 µg subcutaneous injection of peginterferon-lambda or placebo in outpatients with COVID-19.



Of 364 individuals approached for the study, 105 did not meet inclusion/exclusion criteria and 199 eligible individuals declined to participate (Figure 1). All 60 randomized individuals received an injection and 59 (98%) completed follow-up, with one lost to follow-up after Day 3. The median age was 46 years (IQR 32-54), 35 (58%) were male and eleven (19%) participants were asymptomatic. The mean time from symptom onset to randomization was 4.51.7 days.

The median baseline SARS-CoV-2 RNA level was 6.71 (IQR 1.3-8.0) log copies/mL with 10 (33%) individuals in the placebo group and 5 (17%) in the peginterferon-lambda group having undetectable viral load on the day of randomization. Other baseline characteristics were similar between groups (Table 1).


The baseline SARS-CoV-2 RNA level was higher in the peginterferon lambda group and was significantly associated with the probability of clearance by Day 7 (OR 0.69, 95%CI 0.51- 0.87, p=0.001). Overall, by Day 7, 24/30 (80%) in the peginterferon-lambda group were negative for SARS-CoV-2 RNA compared to 19/30 (63%) in the placebo arm (p=0.15) (Figure 2a). After adjusting for baseline viral load, peginterferon-lambda treatment was significantly associated with clearance by Day 7 (OR=4.12, 95%CI 1.15-16.7, p=0.029) (Table 2).

The odds of viral clearance by Day 7 with peginterferon-lambda treatment compared to placebo increased with every log increase in baseline viral load (Figure 3). For those with baseline RNA of 10E6 copies/mL or greater, the proportion undetectable at Day 7 in the peginterferon- lambda group was 15/19 (79%) compared to 6/16 (38%) in the placebo group (OR 6.25, 95%CI 1.49-31.1, p=0.012) (Figure 2b), translating to a median time to viral clearance of 7 (95%CI 6.2- 7.8) days with peginterferon-lambda compared to 10 (95%CI 7.8-12.2) days with placebo (p=0.038) (Supplementary Figure 1).

Of those still positive at Day 7, participants in the peginterferon lambda group had lower viral loads than those in the placebo group, with 3 of 4 at 10E4 copeis per mL or lower, compared to 6/10 (60%) above 10E5 copies per mL in the placebo group (Supplementary Table 2). In contrast, in those with baseline viral load below 10E6 copies/mL, viral loads were higher in the peginterferon-lambda group, but both groups cleared very quickly; 9/11 (82%) in the peginterferon-lambda arm and 13/14 (93%) in the placebo arm were undetectable at Day 7 (OR 0.35, 95%CI 0.01-4.15, p=0.40) (Figure 2c).

The mean decline in SARS-CoV-2 RNA was significantly greater in the peginterferon- lambda than in the placebo group from Day 5 onwards (Figure 2e), with a similar effect observed when restricted to those with detectable virus at baseline (Supplementary Figure 2) or baseline viral load at or above 10E6 copies/mL (Figure 2g). Clearance was rapid in the low viral load group in both groups (Figure 2i).

No baseline covariates modified the association between baseline viral load and treatment assignment with clearance by Day 7 (Table 2, Supplementary Figure 3). Participants who were asymptomatic were more likely to have baseline viral loads below 10E6 copies/mL than those with symptoms (91% vs 27%, p<0.001).

At randomization, 5/51 (9.7%) participants with available samples were seropositive for SARS-CoV-2 S IgG antibodies, of whom 4 had undetectable SARS- CoV-2 RNA. Antibody positivity increased in both groups over time (Supplementary Figure 4). The presence of antibodies at any timepoint was associated with a corresponding lower viral load, with the association weakening with time as people cleared.


Symptoms were grouped into 7 categories (Table 3) and reported as absent/mild/moderate or severe. Respiratory and fever/systemic symptoms were most common in both groups (Figure 4). Documented temperature above 38oC was rare but only reported beyond Day 2 in the peginterferon-lambda group (Supplementary Figure 5).

Overall, most symptoms in both groups were mild and there was no difference in frequency, severity or rate of improvement of any of the 7 symptom categories between treatment groups. (Figure 3, Supplementary Table 2). A symptom was graded as severe on 20 occasions by 7 patients in the peginterferon-lambda group and on 30 occasions by 7 patients in the placebo group with somewhat different patterns.

In the peginterferon group, severe symptoms were most commonly loss of taste/smell whereas in the placebo group, fever/systemic symptoms were most frequently rated as severe (Supplementarry Table 3). Symptoms improved in both groups over time at a similar rate (Supplementary Table 2, Figure 3). Participants with baseline viral loads above 10E6 copies/mL had higher symptom scores than those with low baseline viral loads in all categories, except skin symptoms, but improved similarly during follow-up (Supplementary Table 2).

Laboratory AEs were mild and similar between groups. Aminotransferases were elevated at baseline in 3 (11%) participants in both groups and increased mildly, moreso in the peginterferon-lambda group. However, only two individuals met the threshold of Grade 3 elevation, one in each arm. No other grade 3/4 laboratory AEs were reported (Table 4).

There were no elevations in bilirubin with the observed increases in aminotransferases. Hemoglobin, white blood count and platelets were similar with no episodes of myelosuppression in either group. D- dimers were elevated in both groups at baseline but declined over time only in the peginterferon- lambda group (Day 7: placebo 841 ug/L vs peginterferon-lambda 437 ug/L, p=0.02). Other inflammatory markers including ferritin and C-reactive protein were elevated at baseline in both groups and changed minimally over time (Figure 5).

AEs outside of the directed symptom categories occurred in one participant in the placebo arm (rectal bleeding) and in two who received peginterferon-lambda (confusion, pneumonia); all deemed unrelated to treatment. One serious adverse event was reported in each group. A participant in the placebo group was hospitalized on Day 1 post-injection with progressive dyspnea attributed to worsening COVID-19, that improved over time leading to discharge on Day 3. One participant in the peginterferon-lambda group was admitted to hospital on Day 14 with shortness of breath and found to have a pulmonary embolism necessitating anticoagulation. No deaths occurred in either group.


Treatment with a single dose of peginterferon-lambda accelerated viral load decline and, after controlling for baseline viral load, reduced the time to viral clearance in outpatients with COVID-19. The treatment effect was most apparent in those with high baseline viral loads. Peginterferon-lambda was well tolerated with similar symptoms to those treated with placebo.

Results for SARS-CoV-2 diagnostic testing are routinely reported dichotomously as positive or negative, without viral load quantification. Cycle threshold (Ct) values are sometimes reported, but are only semi-quantitative, and vary by assay and even by run, such that results cannot be reliably compared.

Our inclusion of plasmid-derived cDNA standards with every PCR run allowed for quantification of SARS-CoV-2 RNA results and robust direct comparison between samples. Quantification is useful clinically as higher viral levels have been correlated with greater severity of COVID-1914, 15 and infectivity16. As people clear infection, they may have persistently very low levels of RNA detected at very high Ct values (>33), which are not infectious17.

We found that the odds of clearance were greater in all study particpants with peginterferon-lambda than with placebo after controlling for baseline viral load. However, the effect of peginterferon-lambda was most evident when baseline viral loads were above 10E6 copies/mL. While the specific threshold for transmissible virus is unknown, using a standard infectivity assay, Bullard and colleagues reported that at Ct values above 24, corresponding to approximately 10E6-10E7 copies/mL, infectious virus could not be detected16.

We observed that in individuals with low levels of virus, irrespective of their assigned group, spontaneous clearance occurred rapidly and near-universally by Day 7. This does not indicate lack of effectiveness of peginterferon-lambda at low viral loads, but rather that with such low levels of virus, treatment was not required as clearance was imminent. Indeed, 10 participants in the plaebo group and 5 in the peginterferon arm already had undetectable virus by the day of randomization.

In addition, 5 participants, all in the placebo arm, had already developed SARS-CoV-2-specific antibodies by the day of randomization. Similarly, recent evaluation of the REGN-COV2 monoclonal antibody cocktail demonstrated that individuals with the highest baseline viral loads exhibited the largest reduction in SARS-CoV-2 RNA with treatment, while those with detectable SARS-CoV-2 antibodies at baseline (45% of the study population) had low viral loads and did not benefit from therapy18.

It is likely that all antiviral strategies will be most effective early in infection and maximally beneficial to those with highest viral loads. Indeed early reports of interferon-beta use have not shown a clear benefit in hospitalized patients, however whether this relates to late introduction of therapy or possibly to the pro-inflammatory effects of Type I interferon is unknown. Ideally, antivirials would be given shortly after disease onset as rapid reduction of viral load would likely lower the risk of clinical deterioration, but also may reduce transmission, translating into significant public health benefits.

In the placebo group with high baseline viral load, 10/16 (63%) participants had detectable virus at Day 7, with 6/10 (60%) continuing to exceed 10E5 copies/mL, raising concern of persistent shedding of competent virus. In contrast, only 4/19 (21%) participants who received peginterferon- lambda had detectable virus at Day 7, all with viral loads below 10E6 copies/mL.

If these results are confirmed in larger studies, either quantitative testing could be introduced, with the added benefit of predicting those at risk of a severe clinical course, or a qualitative assay, ideally a point- of-care test, could be titrated to achieve an analytical sensitivity of ~10E6 copies/mL allowing for immediate risk stratification and determination of the need for treatment.

Indeed, this could likely already be achieved using currently available rapid antigen tests, with detection sensitivities in the range of 10-50,000 copies/mL, safely below the infectious threshold but avoiding those with extremely low viral loads who are unlikely to require any intervention19. Alternatively, given the tolerability of a single dose of peginterferon-lambda it may be reasonable to consider treatment irrespective of viral load, as a simple, universal approach.

Peginterferon-lambda was well tolerated with no identified safety concerns. Side effects of peginterferon-lambda overlap with COVID-19 symptoms, making it difficult to distinguish whether AEs were related to treatment or persistent infectious symptoms. As has been reported previously, symptoms were more prominent in those with higher viral loads.

With detailed serial symptom assessment, we found that symptoms improved in both groups over time without obvious differences. Notably, among those who were asymptomatic at baseline, there was no difference in AEs between the treatment and placebo groups. Mild, reversible transaminase elevations were seen more frequently in the peginterferon-lambda group, which have been reported previously10. Intriguingly, D-dimer levels fell with peginterferon-lambda treatment, which may be relevant given the association of high levels with more severe disease and increased all -cause mortality20-

The side effect profile and absence of hematological toxicity is consistent with the better tolerability of Type III interferons compared to Type I interferons like alpha/beta10. Treatment with interferon-lambda may be particularly attractive given reports that impaired interferon production and the presence of autoantibodies to interferon-alpha are associated with severe COVID-1923-25. Additional benefits include the broad activity of interferon lambda against multiple respiratorypathogens, including influenza, its very high barrier to resistance and a long-acting formulation that permits a single subcutaneous injection6, 7.

Study imitations include the small sample size, although clearance rates in those with high viral loads were consistent with the power calculations. Based on viral load and antibody data at the baseline visit, several participants were likely clearing the infection, an observation reported in other COVID-19 outpatient studies18.

The benefit of treatment was more pronounced in the group with a high baseline viral load, who were earlier in their course of infection. Early treatment would be optimal, or alternatively introduction of quantitative assays or calibrated qualitative tests for COVD-19 diagnosis and risk stratification could be used to identify those most likely to benefit from therapy. As a Phase II trial, the study was not powered to showed differences in transmission, which are very hard to document, or hospitalization, which would require a larger study enriched for those at high risk of complications.

However, as a first step to confirm efficacy, viral clearance is a key relevant endpoint. There were more Black participants in the placebo group, a population with reduced responsiveness to Type I interferon for treatment of viral hepatitis. However, there were similar proportions with the treatment-responsive interferon-lambda genotype (TT), which is strongly associated with response to interferon-alpha for hepatitis C infection and thought to explain most of the differential response to interferon by race26.

No effect of the interferon-lambda genotype was observed on baseline viral load or response to treatment in the interferon-lambda arm. A high proportion of eligible individuals declined to participate in the study, likely due to the listed AE profile, which reflected weekly injections for a year of treatment for hepatitis B and C infections10, 11. Importantly, the enrolled population was diverse, with individuals born in 25 different countries.

In conclusion, this is among the first antiviral therapies to show benefit among outpatients with COVID-19. Peginterferon-lambda accelerated viral clearance, particularly in those with high baseline viral load. This treatment may have potential to avert clinical deterioration, shorten the duration of infectiousness and limit required isolation time, with significant public health and societal impact.

reference link:

More information: Lancet Respiratory Medicine (2021). DOI: 10.1016/S2213-2600(20)30566-X


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