Publication date: Apr 07, 2026
Acute Respiratory Distress Syndrome (ARDS) remains a life-threatening critical illness with high mortality and limited specific therapies. This open-label, multicenter Phase I clinical trial aimed to evaluate the safety, tolerability, and preliminary efficacy of allogeneic human umbilical cord mesenchymal stem cells (hUC-MSCs, BC-U001) in patients with mild-to-moderate ARDS. A total of 12 eligible patients were enrolled into three dose groups following a “3 + 3” dose-escalation design from 2019 to 2024. All patients received standard ARDS care plus a single intravenous infusion of BC-U001, with 28-day follow-up to assess safety and efficacy as well as exploratory immunological indicators (immunoglobulins, inflammatory cytokines, lymphocyte subsets). Baseline characteristics were balanced across groups except for more severe baseline lung injury in high dose patients (P = 0. 027). No dose-limiting toxicity, treatment-related severe adverse events (SAE), or Suspected Unexpected Serious Adverse Reactions (SUSAR) were observed across all dose groups. The overall 28-day all-cause mortality rate was 8. 3% (1/12), with 0% mortality among 5 COVID-19-related ARDS patients. Efficacy analysis showed significant improvements in the middle dose group, including a marked increase in PaO/FiO (+100. 07 mmHg, P