This is a Phase II multi-center, double-blind, placebo-controlled, randomized study in Patients with moderate to severe lung injury due to COVID-19 or other potential viral and bacterial pathogens. The study will enroll up to 40 Patients into two cohorts, randomized 1:1 to receive active study drug plus standard treatment or placebo (LRS) plus standard treatment. On the treatment (Day 0) Cohort 1 will receive a single IV dose of hMSCs Cohort 2 will receive Lactated Ringer's Solution. A second dose of MSCs or LRS will be given to Cohort 1 or Cohort 2, respectively on Day 3 after the first dose. Patients who discontinue the study before Month 1 for reasons other than adverse events will be replaced.
