Analysis of the factors predicting clinical response to tocilizumab therapy in patients with severe COVID-19

•Improvement at 14 days occurs in 63.3% of severe COVID-19 treated with tocilizumab.•Early administration of tocilizumab is associated with better clinical response.•A recruitment window of 48 hours from admission in tocilizumab randomized clinical trials is advisable. Controversy remains about the efficacy of tocilizumab (TCZ) for the treatment of severe COVID-19. We aimed to analyze the profile of TCZ-respondent patients. We retrospectively analyzed a cohort of patients with severe COVID-19 who received off-label TCZ after recommendation by a local committee and were admitted to the University Hospital “12 de Octubre” until May 2020. The primary end point was a significant clinical improvement (SCI) on day 14 after administration of TCZ. Factors independently related to SCI were analyzed by multivariate logistic regression models. Of 428 (63.3%) patients treated with TCZ, 271 (63.3%) experienced SCI. After adjustment for factors related to unfavorable outcomes, TCZ administration within the first 48 hours from admission (odds ratio [OR]: 1.98, 95% confidence Interval [95% CI]: 1.1–3.55; P = 0.02) and ALT levels >100 UI/L at day 0 (OR: 3.28; 95% CI: 1.3–8.1; P = 0.01) were independently related to SCI. The rate of SCI significantly decreased according to the time of TCZ administration: 70.2% in the first 48 hours from admission, 58.5% on days 3-7, and 45.1% after day 7 (P = 0.03 and P = 0.001, respectively). TCZ improves the prognosis of patients with COVID-19 the most if treatment starts within the first 48 hours after admission.