**3. Tocilizumab as drug**

Tocilizumab, an immunosuppressive monoclonal antibody drug having the traditional name Actemra and Atlizumab, has been reported to be effective against COVID-19 in several countries such as China, France, Italy, Switzerland and Qatar Xiaoling [12, 13]. The drug is known to treat patients with hyperinflammatory syndrome and acute respiratory failure [14]. The drug is sold in the European Union (EU) under the trade name RoActemra and in the United States as Actemra [15, 16]. The drug was first approved in 2005 as an orphan drug in Japan, used in the treatment of Castleman's disease [17]. Nowadays, Tocilizumab has acquired license for EU, to be used alone or in combination with DMARDs [disease-modifying antirheumatic drugs]. This combined therapy is used in the treatment of rheumatic arthritis in adults, systemic form of juvenile idiopathic arthritis (sJIA) in children above 2 years and with the polyarticular form of juvenile idiopathic arthritis (pJIA) in children more than 2 years of age [17]. This drug displays a long elimination halflife. Several studies were conducted to find out whether the drug is useful or not.

In a single centre study in Brescia [Italy], having an gathering of 100 patients, 8 mg/kg [max 800 mg] of the drug was advised to be given to patients by two consecutive intravenous infusions 12 hr. apart. Significant clinical improvement was observed in this case [18]. In another study by Alattar et al. [19] at Quatar, 25 patients having COVID-19 were administered with Tocilizumab, one to three median doses of the drug individually [4.8 mg/kg]. Tocilizumab was associated with dramatic decline in inflammatory markers, radiological improvement and reduced ventilatory support requirements [19]. In a 61-year-old man with COVID-19 symptoms, with a history of kidney transplantation, 324 mg Tocilizumab was administered via subcutaneous route along with hydroxychloroquine that helped in prevention of the disease and did not require mechanical ventilation [20]. However, contrary reports do exist, that reports that Tocilizumab was not effective for preventing intubation or death in moderately ill hospitalized patients with COVID-19 [21].

#### **4. USFDA approval**

The drug Actemra (tocilizumab, Genentech, Inc., South San Francisco, CA) was approved by USFDA to be used for the treatment of Rheumatoid Arthritis (RA), Giant Cell Arthritis (GCA), Polyarticular Juvenile Idiopathic Arthritis (PJIA), Systemic Juvenile Idiopathic Arthritis (SJIA) and Cytokine Release Syndrome (CRS) [22]. However, despite of recommendation of NIH on usage of Tocilizumab for COVID-19 treatment, it has not yet received approval of USFDA.

#### **5. Dosage of tocilizumab for COVID-19 treatment**

The use of Tocilizumab is recommended as per the US NIH guidelines only for clinical trial studies [23]. The preference is mainly given to hospitalized patients with increasing oxygen demand with or without elevated markers of systemic inflammation. As per the recommendations, Tocilizumab (single intravenous [IV] dose of tocilizumab 8 mg/kg actual body weight up to 800 mg) in combination with dexamethasone (6 mg daily for up to 10 days) is advised to be administered in certain hospitalized patients experiencing rapid respiratory decompensation due to COVID-19 [24].
