Clinical Study to Compare Efficacy and Safety of Casirivimab and Imdevimab Combination, Remdesivir and Favipravir in Hospitalized COVID-19 Patients

1. INTRODUCTION

1.1. COVID-19 overview and classification

COVID-19 is an infectious viral disease caused by sever acute respiratory syndrome-corona virus 2 (SARS CoV-2) that has affected large number of people all over the world with high mortality rate. COVID-19 infection has been classified as:

1. Mild Illness: Individuals who have any of the various signs and symptoms of COVID-19 (e.g., fever, cough, sore throat, malaise, headache, muscle pain, nausea, vomiting, diarrhea, loss of taste and smell) but who do not have shortness of breath, dyspnea, or abnormal chest imaging.
2. Moderate Illness: Individuals who show evidence of lower respiratory disease during clinical assessment or imaging and who have an oxygen saturation (SpO2) ≥94% on room air at sea level.
3. Severe Illness: Individuals who have Saturation pressure of oxygen (SpO2) <94% on room air at sea level, a ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (PaO2/FiO2) <300 mm Hg, respiratory frequency >30 breaths/min, or lung infiltrates >50%.
4. Critical Illness: Individuals who have respiratory failure, septic shock, and/or multiple organ dysfunctions.

Covid-19 pandemic stimulates research works to find a solution to this crisis from starting 2020 year up to now. With ending of 2021 year, various advances in pharmacotherapy against COVID-19 have emerged.

1.2. Standard and controversial antivirals used in treatment of COVID-19 (Remdesivir and Favipravir)

Regarding antiviral drugs used in treatment of COVID-19, Remdesivir is a standard antiviral against COVID-19 and has been approved by Food and drug administration (FDA) for treatment of mild, moderate, sever and critical hospitalized COVID-19 patients. Other drugs have shown controversial antiviral activity include: favipravir, ivermectin, nitazoxanide, hydroxychloroquine, ribavirin. Favipravir became a standard antiviral which has been used for treatment of mild and moderate COVID-19 outpatients.

1.3. Advances in immunotherapy for treatment of COVID-19

Recently with the end of 2020, immunotherapy to target virus antigen has developed. Figure 1 shows two types of immunotherapy include active and passive immunotherapy. Active immunotherapy is to enhance body to produce antibodies against virus as by vaccination. Passive immunotherapy involves direct administration of prepared antibodies acting specifically against virus or administration of product containing antibodies like plasma.

There are three targets for these antibodies to work as antiviral including:

1. antibodies that prevent the virus attachment and entry
2. antibodies that inhibit the virus replication and transcription
3. antibodies that hinder various steps of the immune system response Table 1 includes various types of antibodies under investigation for treatment of COVID-19 and their targets.

1.4. Casirivimab and Imdevimab as antibodies cocktail against COVID-19

In the present study, the point of research is antibodies cocktail including REGN3048-3051(casirivimab and imdevimab).REGN3048 and REGN3051 are human monoclonal antibodies targeting the spike glycoprotein on surface of viral particles thereby preventing viral entry into human cells through the angiotensin-converting enzyme 2(ACE2) receptor, and have shown promising antiviral activity and need for further investigation to prove their benefit in COVID patients.

Previous study on REGN3048-3051 has mentioned that both efficacy and safety of this antibodies cocktail are proved in COVID-19 outpatients treatment in both low (2.4 g of REGN-COV2), or high (8.0 g of REGN-COV2) dose when compared to placebo, Efficacy is measured as

1. Virologic Efficacy Time-weighted average change from baseline in viral load through day 7 (log10 scale) in patient.
2. Clinical Efficacy Percentage of patients with one or more medically attended visits and Symptoms offset at day 7

Safety is measured as Percentage of treated patients who experience infusion related and hypersensitivity reactions and incidence of any serious and unexpected adverse effect.

This previous study concluded that efficacy is greater and more obvious in seronegative outpatients (whose immune response is not developed yet to produce antibodies against virus) and with high baseline viral load outpatients.

Now, data is available for these new antibodies cocktails. The U.S. FDA has allowed an Emergency Use Authorization (EUA) for casirivimab and imdevimab combination in the treatment and post-exposure prophylaxis of mild and moderate COVID-19 in adults and pediatric outpatients (more than12 years of age and not less than 40 kg) with positive PCR results of direct SARS-CoV-2 viral testing, and who are at high risk for progression to severe COVID-19 requiring hospitalization or causing death..

In contrast, REGN3048 and REGN3051 are still not authorized for use in patients:

• who are hospitalized due to COVID-19, OR
• who require oxygen therapy due to COVID-19, OR
• who require an increase in baseline oxygen flow rate due to COVID-19 in those on chronic oxygen therapy due to underlying non-COVID-19 related comorbidity(FDA, 2021).

Now, casirivimab and imdevimab are approved investigational antibodies, Serious and unexpected adverse effects can occur that not previously reported with their use.

Confirmed adverse effects include hypersensitivity and infusion related reactions and the study have showed that there is no difference in safety profile between intravenous (I.V) infusion and subcutaneous (S.C) injection. Data about use during pregnancy and breastfeeding mother is insufficient yet. Also, Data not support any dosage adjustment in hepatic and renal patients.

This antibody combination follows linear pharmacokinetics after its single intravenous doses with half-life of about 25 to 37 days for both antibodies. Regarding elimination, this combination is not metabolized by liver cytochrome enzymes ,and not excreted by kidneys.

Limitations of the previous study performed on antibody cocktail include:

1. short duration of follow up
2. not used much clinical relevant outcomes like mortality rate
3. Not studied the long term effect of antiviral efficacy in lowering viral load on inflammatory markers.
4. Study performed on non-hospitalized patients only and not included hospitalized patients (trial is done only on outpatients and not inpatients)

II. AIM OF THE STUDY:

1. To evaluate the efficacy of antibodies cocktail (casirivimab and imdevimab) compared to standard antiviral therapy in reducing 28-day mortality in hospitalized patients with moderate, severe or critical COVID19
2. To evaluate safety of antibodies cocktail (casirivimab and imdevimab) compared to standard antiviral therapy by monitoring of hypersensitivity and infusion related reactions or other significant adverse effects

III. PATIENTS AND POPULATION

265 COVID-19 PCR confirmed patients with indication for antiviral therapy is included in this study and will be randomized (2:1:1) into 3 groups

1. Group A: REGN3048-3051(Antibodies cocktail (casirivimab and imdevimab) )
2. group B: Remdesivir
3. group C: Favipravir

Population in this study are patients hospitalized in isolation hospital-Mansoura university.

A computer file containing a written informed consent from included patients will be provided. Paper will not be a tool for providing agreement by patients or their relatives to avoid transmission of infection.

IV. INTERVENTIONS

Population included in this study will be assigned into 3 groups with 1:2:2 ratios to receive either antibodies cocktail or standard antiviral therapy (remdesvir, favipravir).

Group A patients will receive REGN3048-3051(Antibodies cocktail (casirivimab and imdevimab) ) in low-dose regimen 1.2 gm (1200 mg of combined antibodies) diluted in 250 ml 0.9% sodium chloride solution as single I.V infusion over 30-60 minutes.

Group B patients will receive Remdesivir :

Day1 (loading dose): 200 mg (two 100mg vials) diluted in 500ml 0.9% sodium chloride solution infused I.V over 60 minutes Day 2-5 or Day 2-10 (maintenance dose): 100 mg (one 100mg vial) in 250 ml 0.9% sodium chloride solution infused I.V over 30 minutes

Group C patients will receive Favipravir :

Day 1 (loading dose): 1600 mg (8 tablets) or 1800 mg (9 tablets) orally or in Ryle tube / 12 hours Day 2-5 or day 2-10 (maintenance dose): 600 mg (3 tablets) or 800 mg (4 tablets) orally or in Ryle tube / 12 hours

Patients will be received standard of care by Physicians, Clinical pharmacist , Nurses and as guided by Egyptian COVID-19 treatment protocol.

1. METHOD

The type of this study is single blind non-RCT and is considered a Phase IV Clinical trial (post-marketing study) to report efficacy and safety of new medicine.

We use PubMed search tool to find clinical studies that performed to test efficacy and safety of developed immunotherapy in treatment of COVID-19 with about 4,000 results with focusing on antibodies developed as antiviral against COVID-19 obtaining only 70 results from which REGN-COV2, a Neutralizing Antibody Cocktail is selected with its only one clinical study up to now (REGN-COV2, a Neutralizing Antibody Cocktail, in Outpatients with Covid-19) which is published in New England Journal of Medicine on January 21, 2021.

Another resource used to obtain data is Fact Sheet for Health Care Providers- EUA OF casirivimab and imdevimab which provides clinical data about the use of this antibodies cocktail. Endnote citation software is used for citation of references.