key: cord-0690824-rwznqiib
authors: Razmi, Mahdieh; Hashemi, Farideh; Gheytanchi, Elmira; Dehghan, Masoumeh; Ghods, Roya; Madjd, Zahra
title: Immunomodulatory-Based Therapy as a Potential Promising Treatment Strategy against Severe COVID-19 Patients: A Systematic Review
date: 2020-08-29
journal: Int Immunopharmacol
DOI: 10.1016/j.intimp.2020.106942
sha: 807f7ef72f22000af15b4dc538fb3f33f3a6dc58
doc_id: 690824
cord_uid: rwznqiib

The global panic of the novel coronavirus disease 2019 (COVID-19) triggered by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to an urgent requirement for effective therapy. COVID-19 infection, especially in severely ill patients, is likely to be associated with immune dysregulation, prompting the development of novel treatment approaches. Therefore, this systematic review was designed to assess the available data regarding the efficacy of the immunomodulatory drugs used to manage COVID-19. A systematic literature search was carried out up to May 27, 2020, in four databases (PubMed, Scopus, Web of Science, and Embase) and also Clinicaltrials.gov. Sixty-six publications and 111 clinical trials were recognized as eligible, reporting the efficacy of the immunomodulatory agents, including corticosteroids, hydroxychloroquine, passive and cytokine-targeted therapies, mesenchymal stem cells, and blood-purification therapy, in COVID-19 patients. The data were found to be heterogeneous, and the clinical trials were yet to post any findings. Medicines were found to regulate the immune system by boosting the innate responses or suppressing the inflammatory reactions. Passive and cytokine-targeted therapies and mesenchymal stem cells were mostly safe and could regulate the disease much better. These studies underscored the significance of severity profiling in COVID-19 patients, along with appropriate timing, duration, and dosage of the therapies. Therefore, this review indicates that immunomodulatory therapies are potentially effective for COVID-19 and provides comprehensive information for clinicians to fight this outbreak. However, there is no consensus on the optimal therapy for COVID-19, reflecting that the immunomodulatory therapies still warrant further investigations.

The panic of novel coronavirus disease 2019 (COVID-19) triggered by SARS-CoV-2 has influenced people all over the world, which has been warned as a global health emergency [1] .

SARS-CoV-2 belongs to the single-stranded positive-sense RNA β-coronavirus family, entering the cells through applying the angiotensin-converting enzyme 2 (ACE2) receptor distributed on the surface of the heart, kidney, and intestine and particularly, lungs҆ alveolar type II (AT2) epithelial cells [2] . COVID-19 infection seems to be associated with more person-to-person transmissibility and less lethality than either severe acute respiratory syndrome (SARS) and the middle east respiratory syndrome (MERS), as the majority of the patients have experienced mild symptoms and good prognosis so far. However, it has been reported that approximately 14% of the patients with novel coronavirus pneumonia (NCP) have progressed severe or fatal conditions, along with a rising transition of the patients from the mild condition into severe pneumonia accompanied by a wide range of complications including the acute respiratory distress syndrome (ARDS), septic shock, and multiple organ failure, consequently leading to the death. Currently, management of these critically ill patients has turned into one of the principal challenges [3] [4] [5] [6] [7] .

Clinically, the COVID-19 infection is likely to provoke the immune responses in two phases, and therefore, each phase requires tailored treatment approaches. So that, at the earlier stages, the virus replicates and activates both innate and adaptive immune responses during the non-severe disease period, in which boosting the immune system may be a suitable strategy for eliminating the virus.

At the later stages associated with the expansion of severe conditions, COVID-19 is accompanied by the excessive inflammatory and dysregulated immune responses, leading to some lifethreatening obstacles [8] [9] [10] [11] . Lymphopenia and higher levels of inflammatory indicators, e.g., Ddimer and C-reactive protein (CRP), are the main characteristics of the severe COVID-19 patients, with drastically reduced numbers of the helper T cells, cytotoxic suppressor T cells, regulatory T cells, and natural killer (NK) and B cells [5, [12] [13] [14] . Additionally, a large number of the leukocytes and circulating monocytes are irregularly activated, associated with the abnormal levels of cytokines/chemokines, especially, e.g., interleukin 6 (IL-6), IL-2, IL-7, IL-10, granulocyte-colony stimulating factor (GCSF), IFN-gamma-inducible protein 10 (IP-10), and Tumor necrosis factorα (TNF-a) [15] [16] [17] [18] , eventually leading to the macrophage activation syndrome (MAS) in some patients with severe respiratory failure (SRF) [15] [16] [17] [18] [19] . All these highlight that SARS-CoV-2 might mainly induce the cytokine release syndrome (CRS), in which the magnitude of the cytokine storm is correlated with the disease severity and fatal consequences. Therefore, we need to pay close attention to the immunological status of the patients and restrain the overt inflammatory responses timely through the immunomodulators and cytokine-storm-targeted therapies to control the progression of the disease cascade and decrease the mortality among the severe COVID-19

patients [18, [20] [21] [22] [23] [24] [25] .

Seemingly, the medicines targeting the coronavirus alone might not be appropriately effective in controlling the extremely pathogenic infections and should probably be applied along with the immunomodulatory-based therapies [26, 27] . Various studies have focused on the efficacy of the immunomodulatory agents including corticosteroids, hydroxychloroquine or chloroquine, cytokine-targeted therapies (e.g., anakinra, siltuximab, or tocilizumab), passive immunotherapy (convalescent plasma and intravenous immunoglobulin), mesenchymal stem cells, and bloodpurification therapy, mostly as adjuvant therapy for treatment of the patients with severe COVID-19 and partly have reported promising outcomes. To date, numerous immunomodulators have been investigated; however, data of the available literature do not provide a complete overview. Therefore, the present systematic review was conducted to review the available evidence on the therapeutic value of the immunomodulatory agents for the management of the COVID-19 patients.

This systematic review has been registered on the International Prospective Register of Systematic

(http://www.crd.york.ac.uk/PROSPERO), with the registration number CRD42020179200. The protocol for this systematic review was conducted according to the Preferred Reporting Item for Systematic Review and Meta-analysis (PRISMA) guideline [28] .

A comprehensive search was carried out on April 21, 2020, updated on May 27, 2020, from the following main electronic databases: PubMed, Scopus, Web of Science, and Embase, for studies that focused on the efficacy of immunomodulatory medicines without any language restriction. We also checked the reference lists of all principal publications for further eligible publications. We then systematically searched for the published articles in Google, and for ongoing trials in clinical trial registries (clinicaltrials.gov). The following search strategy has been used regarding specific search tips of each database: "COVID-19" and "Immunomodulation", "Anti Inflammatory", "Mesenchymal Stem Cell", "anti-interleukin-6", "tocilizumab", "siltuximab", "Janus Kinase Inhibitor", "Anakinra", "glucocorticoids", "convalescent plasma", "intravenous immunoglobulin", "hydroxychloroquine or chloroquine" or "blood purification therapy". The details of the search strategy have been provided in Supporting Information 1.

Publications eligible for inclusion were case reports, case series, case-control and cohort studies characterizing the efficacy of immunomodulatory therapies in patients with COVID-19.

The following exclusion criteria were considered: 1) reviews, meta-analysis, and abstracts; 2) nonhuman studies; 3) The topics were not related to the review question (e.g., when the articles addressed other virus-related diseases); 4) Studies that patients received any type of anti-virals not related to immunomodulatory property; 5) studies with incomplete, non-detailed or non-useful data; 6) studies with patients coinfected with influenza virus and SARS-CoV-2; 7) COVID-19 disease in transplant recipients with long-term immunosuppression.

The selection of studies was conducted in two steps.

Step 1: two reviewers (MR and FH), independently, screened titles and abstracts of publications retrieved through the search strategies based on the inclusion criteria. Any publications that did not fulfill the eligibility criteria were excluded.

Step 2: where a publication was potentially eligible, the full text was reviewed by the same reviewers. Any disagreements were resolved by a third author.

For each eligible publication, the following descriptive information was extracted: study characteristics (first author and study country), clinical characteristics (age, sex, population), characteristics of intervention (types, dosage, frequency, etc.), and main findings (all outcomes, mortality). The primary outcome was mortality risk. Other outcomes of interest were adverse reactions, clinical laboratory benefits, and computed tomographic (CT) findings. All the retrieved information was cross-checked by MR, FH, EG, and MD.

It was not feasible to perform a meta-analysis because there were not adequate, appropriate research studies on this issue.

In the first step, a total of 1370 publications were identified from the PubMed (718) review. Fig. 1 shows a flowchart of the search and selection procedure of the studies.

Herein, the details of the ongoing clinical trials registered at the ClinicalTrials.gov by April 21, 2020, updated on May, 27 were also provided. The resulting trials were collected, were evaluated for eligibility, and were checked to remove any duplicates. After the screening procedure, 111

ongoing clinical trials were included related to the topic of the present review ( Fig. 1.) .

The main objective of these included publications and clinical trials was determining the safety and efficacy of the various immunomodulatory medicines in patients with mild/moderate-tosevere COVID-19. Tables 1, 2, and 3 present the characteristics of the publications, patients҆ demographics, therapeutic interventions, and their main findings. The enrolled trials consisted of the registry number of trials, study design, patient population, intervention, and outcomes (Supporting Information 2).

As described in Tables 1, 2, patients with systematic corticosteroid is <1-2 mg/kg/d for 3-5 days [29] .

In a retrospective study, a risk-based therapeutic strategy was developed according to the disease severity in the NCP patients, in which severely ill patients received corticosteroid immediately within the first 3 days of hospitalization in addition to the standard treatment. This treatment approach provided considerable mitigation in the clinical manifestations and imaging recovery with the mortality rate of 0% [29] , and the reduced mortality rate was also reported in the study by Wu et al. [30] . Another study reported that the early use of corticosteroid in the first 3−5 days of intensive care unit (ICU) admission could appropriately hinder the intense inflammatory storm and improve the oxygen saturation (p=0.012) [31] . Nevertheless, corticosteroids did not provide survival profit [31, 32] . Even in a case-control analysis, where the cases received the adjuvant corticosteroid (100-800mg/d) in addition to the standard treatment, elevated corticosteroid dosage led to a considerable increase in the mortality rate (P=0.003) in the matched cases [33] . Prolonged viral shedding has been reported as one of the main restrictions of corticosteroid therapy. A retrospective cohort study introduced corticosteroid as one of the influential factors for persistent SARS-CoV-2 RNA shedding (p=0.025) [34] . In contrast, other retrospective studies have shown that early and short-term administration of the low-dose corticosteroid did not prolong the viral clearance in the COVID-19 patients [29, 35] . Other publications also demonstrated that corticosteroid-containing therapy is accompanied by either hopeful or disappointing results (Table   1 ) [9, 20, [36] [37] [38] [39] [40] [41] [42] [43] .

CQ and its derivative HCQ, the food and drug administration (FDA)-approved antimalarial and autoimmune disease drugs, have been introduced as the potential broad-spectrum anti-viral chemicals. Both drugs function via modifying the endosomal pH and ACE2 glycosylation.

Additionally, these drugs possess an immune-modulatory capacity, which may synergistically reinforce their anti-viral activity in vivo. The safety profile of HCQ has made it a preferred drug for therapy in the clinics [44] [45] [46] .

A single-arm non-randomized clinical trial, aimed at evaluating the efficiency of HCQ (200 mg, 3 times daily for 10 days) on 20 SARS-CoV-2-infected patients in comparison with 16 infected control patients, showed that the HCQ administration leads to a considerable decrease in the viral load in the NCP patients within only 3-6 days compared to the controls (p= 0.001) [44] , and its effect was augmented by adding azithromycin (AZ) [44] [45] [46] . Other studies have also demonstrated the immediate recovery of the patients through the use of HCQ [47] and CQ [48, 49] . In contrast, some studies have not supported the administration of HCQ for prevention of ICU admission and/or death when used alone [50, 51] or combined with AZ [52] , or due to the life-threatening adverse reactions [53, 54] . Even a recent retrospective cohort study found the elevated overall mortality after administration of HCQ alone without AZ [55] , as observed in a randomized, phase

IIb clinical trial with a higher dosage of CQ (600 mg CQ twice per day during 10 days) [56] .

Currently, there are no guidelines for the administration of HCQ. Most studies have applied various doses of HCQ, without an optimized HCQ dosing regimen required for effective treatment and reduction of the side effects. In a study, the pharmacokinetic (PK) characteristics of HCQ at the dose of 600 mg orally were evaluated in the ICU-hospitalized COVID-19 cases and the results showed that this dosing schedule was inadequate to achieve an assumed target blood amount of 1-2 mg/L considered to be therapeutic (Table 1 ) [57] . [17] . Positive findings have also been reported by other recent studies conducted in Italy, France, and Qatar (Table 2 ) [60] [61] [62] [63] [64] [65] . However, a recent case report study announced the weak outcomes of two cases with COVID-19 after they were given one or two infusions of TCZ [66] . Two Other studies indicated an elevation in the adverse effects, including the acute hypertriglyceridemia [67] and candidaemia [68] .

The second IL-6 antagonist, namely siltuximab, approved for treatment of the Castleman's disease is a chimeric monoclonal antibody (mAb) directly binding to the IL-6 and blocks the IL-6 pathway.

In a recent study on 21 COVID-19 patients developed the ARDS, siltuximab (at the mean dose of 900 mg) administration led to the improved clinical conditions in 7 cases and stabilized state in 9

patients; however, 24% (5/21) of them suffered a deteriorating status [69] .

Anakinra, as a recombinant IL-1 receptor (IL-1R) blocker and FDA-approved rheumatoid arthritis drug, is another proposed antagonist for management of the patients with COVID-19 (Table 2) [ 70, 71] . A recent cohort study illustrated that the use of high-dose anakinra (5 mg/kg twice per day, with a mean duration of 9 days), in 29 NCP patients who had developed the ARDS, provided the survival benefit (90%) compared to the historic-control group (56%) (p=0·009), 21 days after receiving anakinra [72] .

MSCs, as the powerful immunomodulatory modalities, have been broadly applied to manage the autoimmune diseases, type 2 diabetes, and, more recently, infectious diseases. MSCs act in two ways principally, immunomodulatory functions and tissue repair abilities, making them ideal candidates to treat the diseases related to lung injury [21, 73] . In a case report on a critical NCP case who had advanced liver injury despite receiving the intensive care treatment, the patient received three intravenous infusions of 5 × 10 7 human umbilical cord MSC (hUCMSC). During 4 days of the second MSC infusion, the case was weaned from the ventilation. All the assessed markers, including CRP, alanine aminotransferase (ALT)/ aspartate aminotransferase (AST), and circulating T cell counts, returned back to the baseline ranges. No distinct adverse effects were monitored [73] . Results of a placebo-controlled trial showed that transplantation of MSCs led to the improvement of lung function and inflammatory indications, reduction of the proinflammatory cytokine TNF-α (P<0.05), and augmentation of anti-inflammatory factor IL-10 (P<0.05) within a few days compared to the standard of care (SOC)-treated group [21] . In a controlled cohort study, 41 severe NCP patients were randomly divided into 2 groups, SOC-treated group (n=29) and SOC-hUCMSCs-treated group (n=12). Within the 3rd to 7th day of therapy, the infusion of hUCMSCs noticeably accelerated the improvement of the clinical symptoms, oxygenation, and lung inflammation absorption, along with a significant reduction in the level of CRP and IL-6. The 28-day mortality was equal to 0% in the SOC-hUCMSCs-treated group, while it was equal to 10.34% for the SOC-treated group [74] . A case report study also described the therapeutic efficacy of the human umbilical cord Wharton's jelly-derived MSCs (hWJCs) on an NCP patient ( -Benefits: 1-By the third day, fever stopped in the remaining eight cases. 2-Desirable outcomes including oxygen flow and blood inflammatory biomarkers were recovered. CRP reduced slightly at d6 in all, and normalized in 5/8 patients at d11. 3-In all cases, an early chest CT scan controlled between d5 and d8.

-Adverse events: 1-Among the nine cases, a patient revealed an acute respiratory failure 6 h after the first dose of anakinra, leading to withdraw. 2-Anakinra was safe. However, mild elevation of transaminase and triglyceride was seen.

Liang China [73] The clinical outcome of hUCMSCs therapy in a critical NCP patient 

IVIG, as another passive immunomodulatory therapy, is a highly purified product comprising the polyclonal IgG obtained from the blood of healthy individuals. It binds to and neutralizes the components of the immune response and is clinically used for treatment of the autoimmune diseases. The recommended dosage of IVIG is 0.5 g/kg daily for 5 days [82, 83] [84] . A recent multicenter cohort study showed that early administration (admission ≤ 7 days) of high-dose IVIG (> 15 g/d) improved the outcomes of only critical cases with COVID-19 but not severe ones [85] . In several other studies on the severely or critically ill COVID-19 patients, although IVIG was used, it was impossible to determine the efficacy of IVIG administration on the recovery from COVID-19 (Tables 1 and 3 ) [40, 41, 86] .

Blood-purification treatments can remove the inflammatory factors and clear the pathogenic cytokines achieved using the modalities, including plasma exchange (PE), adsorption, perfusion, blood/plasma filtration, etc. A case series study reported the effectiveness of the blood purification therapy in 3 critically COVID-19 patients transferred to the ICU, who had deteriorated states despite receiving different kinds of treatments. Blood-purification therapy led to the normalization of the inflammatory markers. Eventually, 2 patients were successfully come off the ventilator and reached a stable clinical status [23] . Another case report study described that a critically COVID-19 case, who had failed to respond to the conventional interventions, was recovered promptly after treatment using the intensive PE followed by intravenous IVIG [86] . A retrospective cohort study, in which 22 patients received the continuous renal replacement therapy (CRRT) and 14 cases were given the conventional therapy (non-CRRT group), indicated that the CRRT independently led to a lower rate of mortality in the NCP cases requiring invasive mechanical ventilation [87] , unlike the results reported by Yang et al., (Table 3 ) [88] . Evaluate the possibility of CP therapy in severe NCP cases -Benefits: 1-Leukocytosis, lymphopenia and the patient's status were immediately recovered with reduction of IL-6 and CRP to baseline range since day 1 after transfusion 2-Improving of both lung abnormalities during 4 days. 3-There were no adverse effects during and following the therapy. 4-Viremia began to reduce right following the infusion of CP 

In this systematic review, an overview was presented regarding the medicines having an already known or putative role in the modulation of immunity applied for management of the patients infected with SARS-COV-2. Since the outbreak of COVID-19, there has been a comprehensive attempt to identify an effective clinical treatment scheme for control of this disease. Currently, there is no FDA-approved therapy for this pneumonia. It seems that drug repurposing demonstrated as a suitable drug discovery approach from available drugs, could partly control the disease until an effective vaccine is identified [89] .

The studies met the inclusion criteria for entering this systematic review had identified several medicines linked to the immunomodulation, i.e., corticosteroid, HCQ or CQ, anti-cytokine therapies, CP, IVIG, MSC, and blood purification therapy. Among these, cytokine antagonists, CP, and MSCs were the immunomodulators that showed more hopeful results. Available clinical experience regarding the immunomodulators for COVID-19 relies on the case reports, case series, cohorts, and case-control studies. These studies are highly heterogeneous in nature; thus, a common conclusion could not be acquired to make strong recommendations regarding application of these medicines in the routine clinical practice. It is essential to underline that although adverse events are mostly regarded as tolerable, long-term follow up remains a serious concern making it challenging to interpret the safety profiles of the drugs. The results indicated the considerable importance of the timing, duration, and dosage of the medicines for effective therapy. Fig. 2 shows a summary of the immunomodulatory therapies discussed in this review.

Amidst cytokine storm mediators, IL-6 was the cytokine highly associated with the progression of ARDS and death in the NCP patients. Recently, it has been reported that the IL-6 over-production by the circulating monocytes leads to the low human leukocyte antigen D related (HLA-DR) expression on the CD14 monocytes in the COVID-19 patients with SRF [19] . The use of a particular suppressor of the IL-6 cascade seems to be significantly functional in the treatment of NCP patients. TCZ binds to the IL-6R with high affinity [63] , while siltuximab has specificity for IL-6, and blocks the signal transductions [69] . Included clinical studies with 1-63 participants have shown that both antagonists, specially TCZ, are effective in reducing the mortality rate specially in the severely ill patients, improving the symptoms including fever resolution, oxygenation and resolved CT scans, reducing the inflammation markers (ferritin, CRP, and D-dimer), weaning from the ICU hospitalization and ventilation, and dampening the risk of disease progression to ARDS by mitigating the cytokine storm in the NCP patients [60, 62] , as applied for CRS controlling in the CAR-T therapy [90] . The recommended dose in most studies was 4-8 mg/kg for TCZ like rheumatoid arthritis, and a dosage of 11 mg/kg/day was reported for siltuximab with the infusion time of more than 1 h [58, 69] . As an IL-1R blocker, anakinra was another proposed antagonist.

High dosing of 5 mg/kg twice daily (intravenous) was applied for treatment of the NCP patients resulting in the survival benefit, amelioration of respiratory function, and decreased inflammatory markers, as applied off-label for management of the hyperinflammatory disorders [70, 72] .

However, an enhanced risk of opportunistic infections, acute hypertriglyceridemia, and anemia induced by the IL antagonists have been demonstrated among the patients with COVID-19 [68] .

Therefore, these antagonists must be prescribed for COVID-19 patients in severe phase, with precise monitoring [12] . The short half-life of anakinra (3 h) provides an immediate withdrawal and clearance from the circulation compared to TCZ with a long half-life (2-3 weeks) [72] .

Although these immunological therapies appear to be beneficial to cure NCP cases, safety hazards and substantial costs can limit the wide use of these cytokine antagonists [12] .

Improved inflammation situation following receiving the MSC-based therapy was also reported in some limited studies involving 1-41 patients with mild-to-severe COVID-19, providing lower mortality and significant recovery of the pulmonary signs. The factors considered to be vital for effective treatment include the route, timing, dose, volume, source, and duration of the MSC administration [91] . The treatment protocol used in the included publications was transplantation of hUCMSCs, intravenously, with the total number of approximately 1-2 × 10 6 cells/kg of weight, and the infusions lasted about 40 min to 1 h [21, [73] [74] [75] . MSCs are likely to enter the human body; some of them accumulate in the lungs, leading to improvement in the lung microenvironment and prevention of the pulmonary fibrosis, besides reducing the serum amounts of pro-inflammatory cytokines [73] . Similarly, a study described the improved mortality rate in the cases infected with Influenza A who had developed the ARDS using the menstrual blood-derived MSCs therapy without adverse effects in 5 patients followed-up for 5 years [92] . However, application of MSCs is associated with some limitations, including the diversity in the quality of the MSCs from various donors, transplantation of MSCs into unfavorable environments, or even undergoing the malignant transformation [91, 92] . For overcoming these barriers, an accurate assessment of the safety is needed along with a complete consideration regarding the immunosuppression of MSCs.

Strategies to boost the immune responses including CP therapy and IVIG are other emergent treatments for serious COVID-19 cases and have been successfully applied for treatment of MERS, SARS, and 2009 H1N1 pandemic with desirable efficacy and safety [81, 93, 94] . Both products, specially CP, can quickly enhance the neutralizing antibodies (Nabs), IgM and IgG levels in the serum, probably neutralizing the SARS-COV-2 and limiting the viral entry and amplification. These interventions also regulate the overactive immune system likely via Fabmediated and Fc-mediated cascades [85, 95, 96] . While high-dose IVIG (0.3-0.5 g/kg.d), purified from the healthy donors, has been proposed as an adjuvant therapy for severe NCP patients, it is not the particular antibody to any pathogen [95] . There are limited clinical data for its efficacy, and investigators have reported conflicting opinions on IVIG usage [85] . In contrast, recently, the FDA has approved the administration of plasma from the recovered donors to cure seriously ill NCP patients [97] . The key factors associated with the CP therapy are the amounts of neutralizing antibody titer, timely infusion, and suitable plasma volume. In the majority of the included studies, a dosage of 200-mL intravenous CP for each cycle (200-2400 ml depending on the severity of disease) with a high level of neutralizing antibodies could reduce the viremia and the risk of death, and tended to improve the clinical signs and shorten the course of disease without any adverse reactions [77, 93] . A recent meta-analysis study showed that CP therapy is effective for reducing the mortality rate in different types of infectious diseases [98] . Nevertheless, the outcomes of CP therapy are unforeseeable because of the diversity of sera in different donors, its limited supply, and transmission of the potential pathogens [85, 99] .

Other pharmacological agents widely used for management of the NCP infection are CQ or its derivative HCQ, and corticosteroids. In the majority of investigations, HCQ had been used orally at the dose of 200 mg, 3 times daily for 10 days alone or in combination with AZ, while the schedules for CQ administration were a bit diverse in different studies, providing quick clearance of viral load, clinical recovery, shortened time to clinical recovery (TTCR), improved pneumonia, and restoration of the immune function [12, 29, 32, 44, 48] . The former unsatisfied experiences on SARS with high-dose corticosteroids have led to the use of low-dose (MP, intravenous, <1-2mg/kg/d) and short-term (3-5 days) systemic glucocorticoids in the majority of studies, associated with recovery of body temperature, increase of oxygen saturation, reduction of inflammatory markers, and resolution of CT results [29, 41] . Included publications, with 11-1376 participants for CQ or HCQ therapies and 1-244 participants for corticosteroid therapy reported the therapeutic efficacy of all the drugs. However, a number of studies highlighted the unfavorable outcomes concerning the survival benefit of all these drugs in COVID-19 patients, even higher doses led to augmentation of the mortality risk [31, 33, 50-52, 55, 56] . Limited publications have also described the association of persistent viral RNA shedding with corticosteroid therapy [34] and cardiac toxicity, characterized by prolongation of the QT interval, with administration of CQ and HCQ in SARS-CoV-2-infected patients [54] . HCQ also has particular pharmacokinetic properties requiring certain precautions. It exhibits strong tissue tropism, with a long half-life (50 days) [100] . However, these negative findings may be partly due to the lack of adequate patient selection, along with improper dosing, timing, and duration of the therapy. Outcomes of this intervention may be improved by disease severity profiling of the patients prior to enrollment [29] [30] [31] . Therefore, despite rapidly pushing of these drugs to the clinical testing, all the three medicines should be administered with strict rules [95] .

Cytokine clearance using blood-purification modules, especially plasma exchange and continuous renal replacement therapy, has also yielded certain survival efficacy on severely and critically ill NCP individuals [23, 86] , as formerly used for controlling the cytokine storm in the patients affected with influenza virus [101] . The indications for blood-purification therapy in the patients with COVID-19 include 5-fold increase in the level of plasma inflammatory mediators, quick daily progression of the lung abnormalities, and comorbidities requiring blood-purification therapy [24, 95] . However, a study reported that the NCP non-survivors have a greater proportion of CRRT [88] , as seen for those with MERS-CoV [102] . Therefore, the blood-purification therapies are likely not to be feasible, yet, due to the controversial results reported in the literature.

Although most of the included publications have focused on the efficiency of corticosteroids and HCQ and have presented the controversial results, the trials included in the present review seemed to focus mainly on the therapies with MSCs, CP, and cytokine antagonists. Regarding the influence provided by these trials for the academic world, it should be mentioned that the framework of the trials was mostly well-designed, despite small size or the lack of randomization in some trials. It is essential to highlight that the dosing schedules applied in these trials were mostly according to the previous experiments, causing the concern that the side effects may occur in the subjects.

Notably, neither these trials have posted the outcomes, nor applicable reports existed, and the trials failed to support the patients and their clinicians. Therefore, no conclusion can be finalized concerning the safety, tolerability, efficacy, pharmacokinetics, and immunomodulatory capacity of these interventions.

The present study had several limitations. For example, majority of the included studies lacked the proper control groups and were considered to have a moderate to high risk of bias as a consequence of combining the non-randomized evaluations, poor methodological approach for selection of the participant, small sample sizes, study designs, type of interventions, therapeutic regimens, dosage of drugs, and duration of therapies. This heterogeneous style and, most importantly, the lack of appropriate control groups did not justify us to conduct a meta-analysis.

Results of this systematic review revealed that the immunomodulatory-based therapies are promising and provided a valuable therapeutic strategy to the scientific community and clinicians to fight against this outbreak in real-time situation even though other approaches and studies, including vaccine candidates, would be beneficial, but only in the future. This comprehensive systematic review of the immunomodulatory therapies applied for treatment of COVID-19 patients infected patients for the appropriate selection of the patient and therapy. Despite these encouraging findings, to date, a definitive conclusion cannot be drawn on the optimal and reliable therapy for COVID-19 because of the limited high-quality studies, the lack of control group in the majority of studies, and partly high heterogeneity, reflecting further need for firm investigations from the advanced preclinical researches and well-designed prospective randomized clinical trials. 

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Corticosteroid treatment of patients with coronavirus disease 2019 (COVID-19)

Hydroxychloroquine and azithromycin as a treatment of COVID-19: results of an open-label non-randomized clinical trial

Clinical and microbiological effect of a combination of hydroxychloroquine and azithromycin in 80 COVID-19 patients with at least a six-day follow up: A pilot observational study

Early treatment of COVID-19 patients with hydroxychloroquine and azithromycin: A retrospective analysis of 1061 cases in Marseille, France

Efficacy of hydroxychloroquine in patients with COVID-19: results of a randomized clinical trial

Treating COVID-19 with Chloroquine

Relationships among lymphocyte subsets, cytokines, and the pulmonary inflammation index in coronavirus (COVID-19) infected patients

No evidence of clinical efficacy of hydroxychloroquine in patients hospitalised for COVID-19 infection and requiring oxygen: results of a study using routinely collected data to emulate a target trial

Observational Study of Hydroxychloroquine in Hospitalized Patients with Covid-19

No evidence of rapid antiviral clearance or clinical benefit with the combination of hydroxychloroquine and azithromycin in patients with severe COVID-19 infection

Hydroxychloroquine in patients mainly with mild to moderate COVID-19: an open-label, randomized, controlled trial

QT Interval Prolongation and Torsade De Pointes in Patients with COVID-19 treated with Hydroxychloroquine/Azithromycin

Outcomes of hydroxychloroquine usage in United States veterans hospitalized with Covid-19, medRxiv

Effect of High vs Low Doses of Chloroquine Diphosphate as Adjunctive Therapy for Patients Hospitalized With Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection

Towards Optimization of Hydroxychloroquine Dosing in Intensive Care Unit COVID-19 Patients

Tocilizumab treatment in COVID-19: A single center experience

Tocilizumab treatment in severe COVID-19 patients attenuates the inflammatory storm incited by monocyte centric immune interactions revealed by single-cell analysis

Favorable changes of CT findings in a patient with COVID-19 pneumonia after treatment with tocilizumab

Off-label use of tocilizumab in patients with SARS-CoV-2 infection

Pilot prospective open, single-arm multicentre study on off-label use of tocilizumab in severe patients with COVID-19

Tocilizumab therapy reduced intensive care unit admissions and/or mortality in COVID-19 patients

Interleukin-6 blockade for severe COVID-19

Tocilizumab for the treatment of severe coronavirus disease 2019

Use of Tocilizumab for COVID-19-Induced Cytokine Release Syndrome: A Cautionary Case Report

Acute hypertriglyceridemia in patients with COVID-19 receiving tocilizumab

Tocilizumab for cytokine storm syndrome in COVID-19 pneumonia: an increased risk for candidemia?

Use of siltuximab in patients with COVID-19 pneumonia requiring ventilatory support, medRxiv preprint

Use of anakinra in severe COVID-19: a case report

Targeting the inflammatory cascade with anakinra in moderate to severe COVID-19 pneumonia: case series

Interleukin-1 blockade with high-dose anakinra in patients with COVID-19, acute respiratory distress syndrome, and hyperinflammation: a retrospective cohort study

Clinical remission of a critically ill COVID-19 patient treated by human umbilical cord mesenchymal stem cells

Treatment of Severe COVID-19 with human Umbilical Cord Mesenchymal Stem Cells

Intravenous infusion of human umbilical cord Wharton's jellyderived mesenchymal stem cells as a potential treatment for patients with COVID-19 pneumonia

Anti-SARS-CoV-2 virus antibody levels in convalescent plasma of six donors who have recovered from COVID-19

Effectiveness of convalescent plasma therapy in severe COVID-19 patients

Treatment of 5 Critically Ill Patients With COVID-19 With Convalescent Plasma

Treatment With Convalescent Plasma for Critically Ill Patients With Severe Acute Respiratory Syndrome Coronavirus 2 Infection

Treatment with convalescent plasma for COVID-19 patients in Wuhan, China

Use of Convalescent Plasma Therapy in Two COVID-19 Patients with Acute Respiratory Distress Syndrome in Korea

High-Dose Intravenous Immunoglobulin as a Therapeutic Option for Deteriorating Patients With Coronavirus Disease

Recovery of severely ill COVID-19 patients by intravenous immunoglobulin (IVIG) treatment: A case series

Effect of regular intravenous immunoglobulin therapy on prognosis of severe pneumonia in patients with COVID-19

Clinical Efficacy of Intravenous Immunoglobulin Therapy in Critical Patients with COVID-19: A Multicenter Retrospective Cohort Study

Successful treatment with plasma exchange followed by intravenous immunoglobulin in a critically ill patient with COVID-19

Effect of continuous renal replacement therapy on all-cause mortality in COVID-19 patients undergoing invasive mechanical ventilation: a retrospective cohort study

Clinical course and outcomes of critically ill patients with SARS-CoV-2 pneumonia in Wuhan, China: a single-centered, retrospective, observational study, The Lancet Respiratory Medicine

Network-based drug repurposing for novel coronavirus 2019-nCoV/SARS-CoV-2

FDA Approval Summary: Tocilizumab for Treatment of Chimeric Antigen Receptor T Cell-Induced Severe or Life-Threatening Cytokine Release Syndrome

Role of mesenchymal stem cells, their derived factors, and extracellular vesicles in liver failure

Clinical study of mesenchymal stem cell treating acute respiratory distress syndrome induced by epidemic Influenza A (H7N9) infection, a hint for COVID-19 treatment, Engineering (Beijing)

Challenges of Convalescent Plasma Therapy on COVID-19

Feasibility of Using Convalescent Plasma Immunotherapy for MERS-CoV Infection, Saudi Arabia

The pathogenesis and treatment of the `Cytokine Storm' in COVID-19

Convalescent plasma in Covid-19: Possible mechanisms of action

COVID-19 convalescent plasma transfusion

Potential effective treatment for COVID-19: systematic review and meta-analysis of the severe infectious disease with convalescent plasma therapy

Perspectives on therapeutic neutralizing antibodies against the Novel Coronavirus SARS-CoV-2

In Vitro Antiviral Activity and Projection of Optimized Dosing Design of Hydroxychloroquine for the Treatment of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)

Evaluation of plasma exchange and continuous veno-venous hemofiltration for the treatment of severe avian influenza A (H7N9): a cohort study

Clinical predictors of mortality of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) infection: A cohort study

This work was supported by Iran University of Medical Sciences (Grant # 99-1-28-18235).

The authors declare that there are no conflicts of interest.