Tolerability and Efficacy of RJX in Patients With COVID-19

For each cohort, there will be an open label Safety Lead-in (Part 1) and a placebo controlled, randomized, double-blind portion (Part 2). In Part 1, RJX will be administered daily for 7 days. In the active treatment arm of Part 2 for both cohorts, RJX will be administered daily for 7 days per cycle and patients may receive up to 2 cycles. As detailed below, patients will be allowed to receive a second 7 day cycle of therapy based on the medical judgment of the Investigator. The total RJX exposure during Part 2 could therefore be up to 14 days. Both cohorts will start and enroll in parallel and independently. A safety follow-up period will begin at Day 14/Discharge, or when treatment is discontinued, and will continue for approximately 60 days post discharge. Part 1 will be conducted at a single site and Part 2 will be conducted at multiple sites. The 2 cohorts in this study are: * Cohort 1: * Hospitalized COVID-19 patients ≥18 years without hypoxemia who are either not receiving any oxygen therapy OR are receiving supplemental oxygen via mask or nasal prongs (namely, clinical status score 4 or 5 on an 8-point ordinal scale). * Patients are required to have the following high-risk characteristics 1. Age ≥65 years AND type 2 diabetes or hypertension OR 2. Age ≥18 years with abnormal blood tests AND CRP \>50 mg/L PLUS at least 1 of the following biomarkers: 1. D-dimer \>1,000 ng/mL, 2. Ferritin \>500 µg/L, 3. High sensitivity cardiac troponin \>2 × upper limit of normal (ULN), 4. LDH \>245 U/L. * Cohort 2: * Hospitalized COVID-19 patients with hypoxemia without ARDS who are receiving either non-invasive positive pressure ventilation (NIPPV) OR high flow oxygen (namely, clinical status score 3 on an 8-point ordinal scale).