This is a Phase 2, two-arm, randomized, double-blind, placebo-controlled multicenter study to evaluate the safety and efficacy of leronlimab (PRO 140) in patients with mild-to-moderate symptoms of respiratory illness caused by coronavirus 2019 infection. Patients will be randomized to receive weekly doses of 700 mg leronlimab (PRO 140), or placebo. Leronlimab (PRO 140) and placebo will be administered via subcutaneous injection.

The study will have three phases: Screening Period, Treatment Period, and Follow-Up Period.

A total of 75 subjects will be randomized 2:1 in this study.