The effect of thymosin α1 on mortality of critical COVID-19 patients: A multicenter retrospective study.

BACKGROUND: Thymosin α1 therapy was commonly used in patients with coronavirus disease 2019 (COVID-19), while its impact on outcomes and which patients could benefit from thymosin α1 therapy were uncertain. STUDY DESIGN AND METHODS: Patients with COVID-19 from 19 designated hospitals between January 1 to February 29, 2020 were included, and the main exposure of interest was administration of thymosin α1. The primary outcome was 28-day mortality. Propensity score matching (PSM) was used to account for baseline confounders, cluster analysis and Cox proportional hazard model was used to account for subgroup analysis. RESULTS: A total of 771 patients were included, and 327/771 (42.4%) patients received thymosin α1 therapy. The 28-day mortality in thymosin group was significantly lower than that in control group (41.3% vs. 60.6%, p < 0.001). After PSM 522 patients were included in analysis and the 28-day mortality in thymosin α1 group and control group were 51.0% and 52.9% respectively, with no significant difference. In subgroup analyses, the association between thymosin α1 therapy and 28-day mortality appeared to be stronger among male patients (HR 0.673, 95% CI 0.454-0.998; p = 0.049). There were no benefits of thymosin α1 in 28-day mortality in other subgroups. There were two phenotypes after cluster analysis, but no benefits of thymosin α1 were shown in phenotype 1 (HR 0.823 95% CI 0.581-1.166; p = 0.273) and phenotype 2 (HR 1.148 95% CI 0.710-1.895; p = 0.442). CONCLUSION: There was no association between use of thymosin α1 and decreased mortality in critically ill COVID-19 patients. Subgroups analysis and phenotype analysis also showed no differences on mortality after thymosin α1 therapy.