# Evaluating the efficacy of different doses of tocilizumab in treating critically ill COVID–19 patients: a single–center retrospective cohort study

## TL;DR

This study found that giving more doses of tocilizumab to critically ill COVID-19 patients did not significantly improve survival or reduce hospital complications.

## Contribution

The study provides evidence that additional tocilizumab doses do not improve mortality or clinical outcomes in severe or critical COVID-19 patients.

## Key findings

- No significant differences in 30-day or in-hospital mortality were observed between groups receiving one, two, or three tocilizumab doses.
- All groups showed favorable responses in inflammatory markers like CRP, though IL-6 levels initially increased.
- Additional tocilizumab doses did not reduce hospital stay, ventilation duration, or complication rates.

## Abstract

To evaluate the therapeutic efficacy of different doses of tocilizumab (TCZ) in patients with severe or critical COVID–19.

In this single–center retrospective cohort study conducted from January 2023 to January 2024, 56 hospitalized patients with severe or critical COVID–19 who received TCZ were included. Patients were categorized into three groups based on the number of TCZ doses administered: one dose (n = 16), two doses (n = 32), and three doses (n = 8). The primary outcomes were in–hospital mortality and 30–day mortality following the first dose. Secondary outcomes included changes in inflammatory marker levels, length of hospital stay, duration of mechanical ventilation, and incidence of complications during hospitalization.

After adjusting for potential confounders, there were no statistically significant differences in 30–day mortality (one dose vs. two doses HR 0.39; 95% CI, 0.15–1.04; P = 0.060 and one dose vs. three doses HR 0.27; 95% CI, 0.06–1.07; P = 0.067) or in–hospital mortality (one dose vs. two doses HR 0.65; 95% CI, 0.35–1.25; P = 0.090 and one dose vs. three doses HR 0.70; 95% CI, 0.40–1.50; P = 0.300) among the three groups. However, all groups showed a favorable response in inflammatory markers. Interleukin–6 (IL–6) levels initially increased after TCZ administration but subsequently declined in a fluctuating pattern. C–reactive protein (CRP) levels decreased consistently across all groups, while procalcitonin showed a modest decline. The number of TCZ doses had no significant impact on length of hospital stay, duration of mechanical ventilation, or the incidence of complications such as respiratory failure requiring mechanical ventilation, heart failure, secondary infections, thrombotic/embolic events, transaminase elevation, neutropenia, GI perforation/Haemorrhage, or acute kidney injury.

Administering additional doses of TCZ beyond the initial dose was not associated with further reductions in mortality or improvements in other major clinical outcomes in patients with severe or critical COVID–19.