INTRODUCTION:

In December 2019, a novel coronavirus disease (covid-19), caused by infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was identified in China and has rapidly spread across continents^1-8.On 11 March 2020, the World Health Organization (WHO) declared a SARS-CoV-2 pandemic^9-11. As of June 2021, more than 180 million people have diagnosed with covid-19 infection and more than 3 million deaths have occurred globally. The cytokine storm mediated by overproduction of proinflammatory cytokines have been observed in critically ill covid-19 patients¹².

Cytokine storm may progress to cardiovascular collapse, multiple organ dysfunction and death rapidly. Therefore, early identification, treatment and prevention of cytokine storm are of crucial importance for recovery of patients^13-19.

Tocilizumab is a recombinant humanised monoclonal antibody of IgG1 class, which is directed against both soluble and membrane-bound forms of interleukin-6 (IL-6) receptor. In case of severe rheumatoid arthritis, systemic juvenile idiopathic arthritis, castleman’s disease, neuromyelitis optica, giant cell arteritis and cytokine release syndrome tocilizumab is highly used. It has been used to mitigate the life threatening cytokine release syndrome associated with chimeric antigen receptor (CAR) T-cell therapy^1,16,20,21. Tocilizumab has been proposed as a potential therapy for the cytokine storm syndrome associated with severe covid-19 pneumonia. Inhibition of IL-6 activity may ameliorate the inflammatory responses, reduce the detrimental effects of covid-19 and improve the clinical outcomes in critically ill patients^2,22-24.

The results of various studies and clinical trials with Tocilizumab showed divergent results . The aim of this study was to assess the effectiveness of Tocilizumab in severe covid-19 pneumonia among critically ill patients.

METHODS:

Study design and participants:

This is a retrospective, observational, single centre study done in a tertiary care hospital in Tamil Nadu region, India on patients with severe covid-19 pneumonia. We derived data from electronic health records of patients who received intensive care unit (ICU) care.

The study population was adults aged 18 years or older with covid-19, confirmed by reverse transcription-polymerase chain reaction who were admitted to ICU between April and October 2020. Eligible patients had covid-19 associated pneumonia, defined as at least one of the following: presence of 30 or more than 30 breaths per minute respiratory rate, peripheral blood oxygen saturation (SaO2) of less than 93% in room air, PF ratio (a ratio of arterial oxygen partial pressure (PaO2) to fractional inspired oxygen (FiO2)) of less than or equal to 200mm Hg in room air and lung infiltrates of more than 50% [radiologically – High resolution computed tomography (HRCT)/Chest X-ray] within 24–48 hours of hospital admission.

Exclusion criteria for the use of Tocilizumab were coexistent infections other than covid-19, use of immunomodulatory drugs in last 3 months, raised aminotransferases levels greater than 1.5 times the upper limit of the normal, neutrophils less than 1000/mm³, platelets less than 100000/mm³, bowel diverticulitis, gastrointestinal perforation, pregnant and lactating women.

The study was approved by the Institutional human ethical committee (PSG/IHEC/2020/Appr/EXP/227) with a waiver of informed consent.

Procedures:

Electronic medical records of the patients was used to obtain the data of demographics, comorbidities, symptoms, treatments, laboratory investigations, Subsequent Organ Failure Assessment (SOFA) score and clinical outcome . All patients received standard of care treatment at the intensive care unit according to hospital policy. Standard of care treatment included Methylprednisolone (1mg/kg q24h for 7 days), Remdesivir (200mg on day 1 followed by 100mg q24h for 10 days in mechanically ventilated patients and 5 days in other patients) and Enoxaparin 1mg/kg q12h.

In addition to standard treatment care, a non randomly selected subset of patients also received Tocilizumab. Patients were administered with Tocilizumab when a cytokine storm is suspected. In patients with evidence of acute respiratory distress syndrome (ARDS) within 72 hours of worsening of oxygenation the administration of tocilizumab is considered. However, the final decision to use Tocilizumab was at the discretion of the treating physician considering the affordability and willingness of patient attenders. Tocilizumab was administered intravenously at 8mg/kg (upto a maximum of 800mg). The second dose of Tocilizumab was given 12 to 24 hours apart.

Outcomes:

The primary outcome measure was ICU related and hospital related mortality. The secondary outcome measures were change in clinical status of patients measured by WHO (World Health Organisation) 7 category ordinary scale, changes in interleukin-6 (IL-6) levels, secondary infections and duration of ICU stay.

Statistical analysis:

The baseline characteristics of patients treated with Tocilizumab was compared with those treated with standard of care alone. Demographics and clinical variables of both treatment groups were summarized using median (IQR) for continuous variables and by frequency (%) for categorical variables. Continuous variables and categorical variables were compared by Mann-Whitney U test and Fisher’s exact test respectively. Statistical analysis was done with SPSS, version 26. Odd’s ratio was used to represent the effect on primary outcome and secondary outcomes such as mortality upto 28 days, clinical status at day 28 and incidence of secondary infections. Changes in IL-6 levels in the both treatment arms were compared by paired t test.

RESULTS:

The study was conducted with a sample size of 121. 83 patients received standard of care treatment whereas 38 received Tocilizumab along with standard of care. The baseline characteristics and investigations of the patients are summarized in Table 1. The median age of Tocilizumab and standard care group were 61.025 (40 – 84) and 60 (19 – 83) respectively (p = 0.66). 26 (68.4%) males and 12 females (31.5%) were included in Tocilizumab group whereas in standard of care, 61 (73.49%) were males and 22 (26.5%) were females. Diabetes, hypertension and obstructive airway disease were the most common comorbidities. Most of the patients were presented with complaints of fever, cough and breathlessness.

Median duration between onset of symptoms and hospitalization was 4.71(1 – 11) and 6.59 (1 – 21) days in Tocilizumab group and standard of care group respectively. Tocilizumab was administered a median of 10.9 days (3 – 27) from the onset of symptoms, 7.4 days (1 – 23) from the day of hospitalization and 2.1 days (1 – 3) from the day of ICU admission.

Table 1: Baseline characteristics and investigations of patients

Tocilizumab group (n = 38)

Standard of care group (n = 83)

P value

Age

Sex

Male

Female

BMI *

Comorbidities

Yes

Comorbidity count

> 3

Diabetes

Hypertension

Obstructive airway disease

Symptoms

Fever

Cough

Breathlessness

Baseline WHO 7 category

ordinal scale ^$

Inflammatory markers

Ferritin (ng/ml)

Interleukin-6 (pg/ml)

LDH (U/L)

WBC (mm³

Disease duration

Days from symptom onset

to hospitalization

Days from symptom onset

to ICU admission

SOFA score

Baseline PF ratio

(PaO₂: FiO₂)

< 100

100 - 200

61.025 (40 – 84)

26 (68.4%)

12 (31.5%)

25.1 (16.1 – 34.6)

28 (73.6%)

10 (26.3%)

12 (31.5%)

8 (21.05%)

19 (50%)

14 (36.8%)

3 (7.8%)

28 (73.6%)

12 (31.5%)

26 (68.4%)

4.5 (4 – 6)

20 (52.6%)

15 (39.4%)

3 (7.8%)

1065.9 (142 – 2000)

618 (9.2 – 5000)

565.05 (338 – 1301)

12172 (4700 – 34000)

4.71 (1 – 11)

8.5 (2 – 27)

2.5 (1 - 12)

145.6 (89 - 198)

11 (28.9%)

27 (71.05%)

60 (19 -83)

61 (73.4%)

22 (26.5%)

25.81 (16.5 – 35.2)

72 (86.7%)

11 (13.3%)

11 (13.2%)

26 (31.3%)

27 (32.5%)

19 (22.8%)

41 (49.4%)

37 (44.6%)

8 (9.6%)

42 (50.6%)

32 (38.6%)

57 (68.7%)

4.5 (4 – 6)

46 (55.4%)

30 (36.1%)

7 (8.4%)

781.6 (49.5 – 2000)

414 (1.9 – 5000)

566.1 (150.5 – 1704)

11643 (1100 – 31200)

6.59 (1 – 21)

7.8 (1 – 21)

3 (1 – 12)

143.9 (44.3 – 200)

27 (32.53%)

56 (67.46%)

0.66

0.6

0.44

0.11

1.00

0.552

1.0

0.01

0.54

1.0

0.08

0.205

0.801

0.9

0.734

0.082

0.57

0.523

BMI: Body mass index, SOFA: Sequentional Organ Failure Assessment, PaO₂: Partial pressure of oxygen, FiO₂:Fraction of inspired oxygen, LDH : Lactate dehydrogenase.

* BMI value is not available for 1 patient in Tocilizumab group and 19 patients in standard of care group.

^$ 4: Hospitalised, no oxygen therapy, but requiring medical care, 5: Hospitalised, any supplemental oxygen 6: Hospitalised, requiring NIV (Non Invasive ventilation) or HFNC (High flow nasal cannula)

Table 2 : Primary and secondary outcomes

Outcome	Tocilizumab (n=38)	Standard of care (n=83)	Effect estimate	Effect size (95% CI)	P value
Mortality upto 28 days	16 (42.1%)	27 (32.53%)	Odds ratio	1.5 (0.68 to 3.32)	0.308
Clinical status at day 28			Odds ratio 1-6 verus 7-8	1.35 (0.61 to 2.97)	0.44
1 : Not admitted to hospital, no limitation on activities 2 : Ambulatory,limitation of activities, home oxygen requirement 3 : Hospitalised, no oxygen therapy, not requiring medical care 4 : Hospitalised, no oxygen therapy, but requiring medical care 5 : Hospitalised, any supplemental oxygen 6 : Hospitalised, requiring NIV or HFNC 7 : Hospitalised, IMV or ECMO 8 : Death	15 (39.4%) 2 (5.2%) 0 2 (5.2%) 1 (2.6%) 2 (5.2%) 0 16 (42.1%)	45 (54.2%) 2 (2.4%) 0 1 (1.2%) 3 (3.6%) 3 (3.6%) 2 (2.4%) 27 (32.53%)
Duration of ICU stay	8.97 (1 – 20)	8.807 (1 – 18)	-	-	0.91
Secondary infections*	11 (28.9%)	23 (27.7%)	Odds ratio	1.06 (0.45 to 2.48)	0.88

NIV - Non invasive ventilation, HFNC - High flow nasal cannula, IMV - Invasive mechanical ventilation, ECMO - Extracorporeal membrane oxygenation

* Tocilizumab group : Bloodstream (n=9), Respiratory (n=4). 2 patients had bacteremia and respiratory infection. Standard of care group : Bloodstream (n=16), Respiratory (n=11). 4 patients had bacteremia and respiratory infection.

Figure 1 : Ventilatory support status of patients from first day of Tocilizumab therapy through 14 days follow up. HFNC - High flow nasal cannula, NRBM - Non rebreather mask, NIV - Non invasive ventilation, IMV - Invasive mechanical ventilation.

IL-6 levels were higher in patients who received tocilizumab when compared to standard of care group. A transient increase in IL-6 levels were noted in tocilizumab treated patients (see Table 3). In standard of care group, there is a decrease in IL-6 levels at day 14. No significant difference was found between two groups in the serum concentration of other inflammatory markers. One patient in Tocilizumab group had an injection site pain. There was no evidence of other adverse events in the Tocilizumab treated patients.

Table 3: Changes in interleukin-6 level

	IL-6		P value
	Baseline	At day 14	P value
Tocilizumab group	618	861	0.47
Standard of care group	414	313.15	0.51

DISCUSSION:

This is a single centre, observational study performed with covid-19 pneumonia patients admitted to medical intensive care unit, we are reporting the clinical characteristics, investigations and outcomes in 121 patients, among which 38 were treated with tocilizumab along with standard treatment. The use of interleukin-6 inhibitor Tocilizumab was not associated with reduction in mortality. Tocilizumab was not associated with statistically significant improvement in clinical outcome assessed by WHO seven level ordinal scale at 28 days. Our results were in constrast to various observational studies and randomized controlled trials (RCT) including TESTEO study^1,25-29. A RCT conducted in Brazil showed results that are consistent to our study and that study concluded that the use of Tocilizumab was not superior to standard of care in improving clinical status at day 15 and it might increase mortality in severe or critical covid-19 patients²¹. The preliminary results of COVACTA, the Roche phase 3 RCT of Tocilizumab for severe covid-19 showed a failure to meet the endpoint of reduced mortality at week four. In this study to evaluate the safety and efficacy of Tocilizumab in patients with severe covid-19 pneumonia, IL-6 inhibitor had no effect on clinical outcomes at week four, assessed with seven leven ordinal scale²⁴. The CORIMUNO trial performed in covid-19 patients also failed to show the impact of Tocilizumab on clinical outcome at 28 days³⁰.

Evidence suggests that covid-19 severity is associated with increased level of inflammatory mediators including cytokines and chemokines. As fatal covid-19 infection is characterized by cytokine storm syndrome, Tocilizumab has been approved in patient with covid-19 for its immunomodulatory effects. Interleukin receptor blockade have been reported to improve survival in covid-19 pneumonia³¹. In our study, a mild increase in IL-6 levels after tocilizumab administration was observed, whereas standard of care group showed a declining trend. Static or increased serum concentration of IL-6 after Tocilizumab administration were reported by various studies including TESTEO study. Elimination of IL-6 occur via IL-6 receptor mediated clearance. Binding of Tocilizumab to IL-6 receptor results in inhibition of receptor mediated IL-6 clearance and thereby accumulation of IL-6 in serum^1,32.

In our study, Tocilizumab treatment was not associated with statistically significant increase in secondary infections. It was not associated with major adverse events with exception of injection site pain in one patient. Few studies suggested that the use of Tocilizumab may be associated with higher risk of opportunistic infections, bacterial and fungal infections^1,2. It was noted through other studies that the length of ICU and hospital stay were lower among Tocilizumab treated patients³³. But in our study, there is no much difference in the length of ICU stay between both the groups.

As per studies, beneficial effects of Tocilizumab is related to early initiation of treatment in the course of illness. In STOP covid trial, decreased mortality was observed in tocilizumab treated patients who got admitted in ICU within 72 hours of onset of symptoms. An observational study in Spain concluded that Tocilizumab administration after 10 days of symptoms onset may decrease mortality in covid-19 pneumonia. In majority of Tocilizumab based randomized trials, 8 to 12 days is the average duration of symptoms at baseline. In our study, Tocilizumab was administered a median of 10.9 days after the onset of symptoms.

The limitations of our study is that it is an retrospective observational study and not a randomized comparison. This study was performed in a small sample size and only 38 patients received Tocilizumab. The decision on Tocilizumab initiation was taken by the treating physician based on clinical and laboratory parameters of patients, availability of the drug and affordability of patient attenders. Our study did not compare the radiological features of patients and the effect of Tocilizumab on it.

CONCLUSION:

Tocilizumab administration in severe covid-19 pneumonia patients requiring intensive care unit care was not superior to standard care alone in reducing mortality and improving clinical outcomes at day 28.

CONFLICT OF INTERESTS:

The authors declare that there are no conflicts of interest.

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Received on 15.11.2021 Modified on 08.01.2022

Research J. Pharm. and Tech 2023; 16(2):763-768.

DOI: 10.52711/0974-360X.2023.00130