The Use of Mebendazole in COVID-19 Patients: An Observational Retrospective Single Center Study

Background An in-silico screen identified mebendazole with potential antiviral activity that could be a repurposed drug against SARS-CoV-2. Mebendazole is a well-tolerated and cheap antihelminthic agent that is readily available worldwide and thus could be a therapeutic tool in the fight against COVID-19. Methods This is an observational retrospective study of PCR-confirmed COVID-19 patients who received mebendazole with the intention-to-treat. The study included an inpatient cohort (157 inpatients) and an outpatient cohort (185 outpatients). Of the 157 inpatients and 185 outpatients, 68 (43.3%) and 94 (50.8%) received mebendazole, respectively. Patients who presented within the same timeframe but did not receive mebendazole were used as controls. Patients received standard-of-care treatment including remdesivir, dexamethasone, and anticoagulants as deemed necessary by the treating physician. The following clinical outcomes were evaluated: for the inpatient cohort, length of stay (LOS) at the hospital, need for ventilation (combined invasive and noninvasive), and mortality; for the outpatient cohort, time to symptom resolution, need for hospitalization, and mortality. Results For the inpatient cohort, the median age did not differ between the treatment and control groups; 62 (56, 67) vs. 62 (56, 68), P, and there was a comparable proportion of males in both groups; 43 (63%) vs. 55 (62%), P=0.85. The hospital LOS was 3.5 days shorter in the treatment group compared to the control group (P < 0.001). There were fewer patients who required invasive or noninvasive ventilation in the treatment group, 2 (2.9%) vs. 7 (7.9%), and the mortality rate is lower in the treatment group, 3 (4.4%) vs. 8 (9.0%), though the differences did not reach statistical significance. For the outpatient cohort, the median age was lower in the treatment group compared with the control group; 40 (34, 48) vs. 48 (41, 54), P < 0.001. There was a comparable proportion of males between both groups; 50 (53%) vs. 52 (57%), P=0.59. Patients in the treatment group were 3.3 days closer to symptom resolution (P < 0.001). There were numerically fewer patients requiring hospitalization in the treatment group compared with the control group, 3 (3.2%) vs. 6 (6.6%), though this did not reach statistical significance (P=0.33). Conclusion In this retrospective observational study, the use of mebendazole in COVID-19 patients was associated with shorter hospitalizations in the inpatient cohort and shorter durations of symptom resolution in the outpatient cohort. The findings from this small observational study are hypothesis-generating and preclude drawing conclusions about clinical efficacy. Further studies are needed to examine the role of mebendazole in the treatment of COVID-19 patients.


Introduction
SARS-CoV-2 was identifed in late December 2019 as the causative agent of a severe acute respiratory syndrome named COVID-19 [1][2][3]. COVID-19 was ofcially declared a pandemic by the World Health Organization (WHO) on March 11th, 2020. Te virus has since propagated worldwide, causing an unprecedented incidence of morbidity and mortality. At the time this manuscript was written, there were 283 million reported cases and 5.41 million deaths worldwide. Tere are currently a large number of trials that are testing various antiviral agents that target viral proteins that are critical for viral replication. A clinicaltrials.gov search at the time this manuscript was written (in August 2022) found over 400 clinical trials testing antivirals against SARS-CoV-2 that are either active or pending, with over 100 similar clinical trials that have been completed. Tese antivirals include new and repurposed drugs targeting viral proteins that are critical for viral replication, such as the proteases (main protease (M pro ) and papain-like protease) and RNA polymerase. For example, the frst FDA-approved antiviral drug against SARS-CoV-2 was remdesivir, which was originally developed for the Ebola virus and has been successfully repurposed as a SARS-CoV-2 RNA polymerase inhibitor. Recently, Merck pharmaceuticals announced that molnupiravir, an oral antiviral agent, decreased the risk of hospitalization from COVID-19 by about 30% [4][5][6]. Also, Pfzer announced the clinical outcomes for their oral SARS-CoV-2 M pro inhibitor, Paxlovid, that reduced the risk of hospitalization or death by 89% (within three days of symptom onset) and 88% (within fve days of symptom onset) compared to placebo [7,8]. Both drugs were granted by the U.S. FDA Emergency Use Authorization. Tese new drugs, however, are unlikely to be widely available worldwide soon.
In March 2020, a preprint identifed a number of FDAapproved drugs with potential antiviral activity against SARS-CoV-2 in vitro [9]. Tis study performed an in-silico screen to identify FDA-approved drugs that can potentially inhibit SARS-CoV-2 M pro . One of the top hits identifed in that report was mebendazole, which is a widely used benzimidazole broad-spectrum oral antihelminthic agent [10]. Subsequently, in vitro antiviral screening demonstrated the inhibitory profle of mebendazole on SARS-CoV-2 viral replication at low micromolar concentrations, which is achievable at therapeutic doses. Te study also performed pharmacokinetic (PK) studies in mice, which confrmed drug levels in bronchoalveolar lavage (BAL) samples within the IC50 range. Tis is an important fnding since the failure of many repurposed drugs is linked to the mismatch between IC50 concentrations and therapeutic drug levels that can be safely achieved in vivo. Mebendazole was frst approved in 1971, and since then it has become widely available worldwide due to its efectiveness, cheap price, and low adverse efects; it is on the WHO list of essential medicines [11,12]. Mechanistically, mebendazole is believed to inhibit microtubule formation in parasites, resulting in their eventual death [13,14]. In addition, mebendazole is currently being studied as a potential anticancer agent, where it was found to impact a wide range of targets, including angiogenesis and multidrug resistance protein transporters, among others [15].
Given its availability, favorable side efect profle, and lack of widely available and cheap oral antiviral agents against SARS-CoV-2, mebendazole has been administered of-label to PCR-confrmed COVID-19 patients with an intention-to-treat. Here we report the results of a retrospective analysis of two patient cohorts from a single center in Cairo, Egypt.

Study Population.
Tis is a single-center observational study that included all comers with a diagnosis of COVID-19 from June 1st to August 30, 2020. Te diagnosis of COVID-19 pneumonia was confrmed in all patients via SARS-CoV-2 RT-PCR. Patients who required hospital admission (inpatients) and those who were managed at home (outpatients) were included. Te decision to admit patients was based on the managing provider's discretion, guided by clinical conditions and laboratory parameters.

Management Protocol.
All patients received standard care at the discretion of the treating providers. Treatment included remdesivir, prednisone, and anticoagulation. Patients were ofered mebendazole as an alternate therapy to hydroxychloroquine and ivermectin (which were included in some COVID-19 treatment protocol guidelines in Egypt [16]) when these drugs were not available. Mebendazole was administered at 500 mg BID for a maximum duration of 14 days. Te study population was then stratifed into those who received mebendazole (treatment) and those who did not (control). Te treatment assignment was not randomized and was based on the provider's discretion in line with the patient's preferences, and the patients were informed of this of-label treatment.

Statistical Analysis.
Continuous variables are presented as the median (interquartile range; IQR), and discrete variables are presented as counts (percentage). Outcomes of interest for inpatients were mortality, hospital LOS, and the requirement of ventilation (either noninvasive such as CPAP and BiPAP or invasive mechanical ventilation). Outcomes of interest for outpatients were duration to symptom resolution (patient becoming afebrile in addition to symptomatic improvement of any of the following symptoms: cough, fatigue, and sore throat), hospital admission, and mortality. For demographic and clinical variables in Table 1, we compared the continuous variables using the two-sample ttest and the discrete variables using Fisher's exact test.
For discrete outcomes of interest variables in Table 2, Fisher's exact test was performed without adjusting for covariates due to the small number of events. In contrast, the efects of mebendazole treatment on the continuous variables-hospital LOS for the inpatients and duration of symptoms for the outpatients-were estimated by the ftting of multiple linear regression models including the demographic and clinical covariates backward selected by the Akaike information criterion. All statistical analyses were performed using R (v3.6.3).
Te comparisons of demographic and clinical variables are summarized in Table 1, and outcomes are summarized in Table 2.

Inpatient Cohort
3.1.1. Baseline characteristics. Te median age (year) did not difer between the treatment and the control groups, 62 (56, 68) vs. 62 (56, 67), and there were almost equal proportions of males in both groups, 43 (63.2%) vs. 55 (61.8%). Te prevalence of diabetes and hypertension was low and balanced between the two groups.

Outcomes.
None of the patients were deceased. Tere were numerically fewer patients requiring hospitalization in the treatment group compared to the control group, 3 (3.2%) vs. 6 (6.6%), though this did not reach statistical signifcance. However, excluding those transferred to hospitals, the patients in the treatment group had a shorter duration of symptoms resolution (day), 4 (3, 4) vs. 7 (6,8), P < 0.001. Adjusting for the demographic and clinical covariates, the time to symptom resolution of patients in the treatment group was 3.3 days shorter than those in the control group P < 0.001.

Discussion
Te rapid devastation caused by COVID-19 has prompted an unprecedented race to fnd safe and efective therapies to reduce the morbidity and mortality caused by this once-in-acentury pandemic. Not surprisingly, repurposing approved drugs has been at the forefront of these eforts, as this allows prioritization of drug candidates with known favorable safety profles. Hundreds of basic and clinical studies identify potential disease modifers, ranging from immune modulators to drugs targeting various host and viral pathways involved in viral entry or replication. In the current retrospective study, an association was observed between mebendazole use and improved clinical outcomes in both inpatients and outpatients.
No increase was observed in mortality, worsening clinical outcomes, or abnormal laboratory fndings associated with mebendazole treatment in the current study. In addition, no patients discontinued mebendazole due to intolerance. It is important to note here that the maximal dose of mebendazole typically used for hydatid disease is up to 50 mg/kg/day for up to 4 weeks [17], and thus the dose used in the current study is considered modest (all patients weighed >50 kgs). Te dose of 500 mg BID used in the current study was primarily driven by the availability of 500 mg pills in Egypt (trade name Verm1).
From a pharmacokinetic perspective, the reported IC50 for mebendazole on SARS-CoV-2 in Vero6 cells was approximately 1.5 μM. Mebendazole is highly plasma proteinbound and has a volume of distribution of 1-2 L/Kg, indicating that it is not restricted to the intravascular compartment. Rodent PK studies reported earlier indicate that free mebendazole concentrations in BAL samples exceed the IC50 observed in vivo, which suggests that, from a theoretical perspective, it is possible for therapeutic doses of mebendazole to be achieved in COVID-19 patients, specifcally in the lung tissue. It is important to note, however, that we did not perform PK studies in humans and we are unsure of the in vivo IC50 needed for inhibition of viral replication, and thus these observations, although based on in vitro and animal data, remain speculative from a clinical perspective.
Mebendazole is generally well tolerated, with mild reported adverse efects including abdominal pain, diarrhea, nausea, fatulence, vomiting, and loss of appetite. Few patients had experienced severe and rare adverse efects, such as seizures, convulsions, and hypersensitivity reactions [18]. Mebendazole toxicity is mainly related to gastrointestinal adverse efects, but higher doses can lead to neutropenia and thrombocytopenia, which have direct contraindications for COVID-19 patients [19]. Since the administered regimen is within the therapeutic index of mebendazole, we did not observe any signifcant side efects that required the drug to be discontinued in the current population. It is important to note that there were some diferences in patient demographics and baseline characteristics that may have impacted the observed results. For example, for the inpatient cohort, the median temperature and oxygen saturation on admission were slightly lower in the mebendazole group. In addition, the mebendazole group had lower CRP levels and a higher percentage of patients with abnormal renal function. Importantly, fewer patients in the mebendazole group received corticosteroids. For the outpatient cohort, pertinent diferences include the median age, which was 8 years lower in the mebendazole group. It is unclear how these patient demographics may have impacted the overall observed effect. For example, while younger age is associated with better prognosis and lower rates of complications [20], lower oxygen saturation [21] and abnormal renal function [22] upon presentation are associated with worse prognosis.
As noted earlier, numerous approved drugs have been tested in COVID-19 patients following initial observations of antiviral efects in tissue culture. Notable examples include hydroxychloroquine and ivermectin [23,24], both of which have been used worldwide and even implemented in treatment protocols. An important caveat of using these two drugs, despite their clear antiviral efect in vitro, is the unfavorable pharmacokinetic profles. Both of them showed an IC50 against SARS-CoV-2 in the low micromolar range, which is not achievable to meet the therapeutic plasma concentrations in vivo. Eventually, higher doses of ivermectin are required to attain the therapeutic plasma concentrations, which can lead to serious adverse efects such as ataxia, convulsions, severe neurotoxicity, and coma [25]. In contrast, we have previously performed PK studies on mebendazole in mice, which indicate that the therapeutic plasma concentration for the administered dosage regimen in vivo is well correlated with the reported IC50 ranges against SARS-CoV-2 in vitro [26].
Finally, it is imperative to caution against using data from the current observational study to guide therapy. Results from the current study should be considered hypothesis-generating to guide decision-making for potential future randomized controlled clinical trials. We conclude that mebendazole administered at 500 mg BID appears to be safe in COVID-19 patients in both inpatient and outpatient settings, and that future randomized controlled clinical trials are warranted to evaluate the efcacy of mebendazole as an oral antiviral agent against SARS-CoV-2.

Data Availability
Te data will be made available upon request in accordance with institutional policy.