Updated project metadata. Coronavirus disease 2019 (COVID-19) is an unprecedented global threat caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The COVID-19 pandemic is a global health crisis. Recent reports have exposed an astonishing case fatality rate of 61.5% for critical cases, increasing sharply with age and for patients with underlying comorbidities. Mass spectrometry (MS)-based proteomics has the potential to become an ideal technology to be applied in this urgent situations, because it can quickly deliver substantial amounts of clinical and biological information from blood plasma or serum in an untargeted fashion. Furthermore, these MS-based proteomic workflows for biomarker discovery and profiling are well established. However, only two studies have presently applied proteomics to serum of COVID-19 patients with moderate proteome depth. Therefore, it is necessary to gain a more detailed understanding with in-depth proteome of plasma or serum to develop prognostic or predictive protein markers. In this study, we performed in-depth proteome profiling of undepleted plasma samples using BoxCar acquisition method from an exploratory cohort comprising ten COVID-19 patients to identify candidate biomarkers for disease severity evaluation.