Pilot phase: the first 100 patients will be randomized in two groups to receive OKZ or placebo (50 patients per group). Early futility analysis will be performed based on the results obtained in the pilot period after 100th patient completed Visit 29. Enrollment will be paused after randomization of 100th patient, then interim analysis will be performed when all 100 patients complete Visit Day 29 or discontinue the study.Based on results of the pilot phase analysis the study could be stopped.~Pivotal phase: inclusion of patients until targeted sample size is reached and performing final safety and efficacy analysis.~Maximum expected study duration for each patient is 62 days, including 2 days of screening, 1 day of study drug administration, and 59 days of follow-up.~The study will include following periods:~Screening period lasting up to 48 hours prior to Day 1. After signing the informed consent by the patient or the legally acceptable representative or when prior consent of the patient is not possible, and the subject's legally acceptable representative is not available, after obtaining documented approval/favorable opinion for individual cases by the Institutional Review Board / Independent Ethic Committee (IRB/IEC), investigator will assess the subject's eligibility for the study.~Treatment period lasting from the beginning of Day 1 visit to 23:59 of the Day 1.~Eligible patients will be randomized to one of two treatment groups to receive a single subcutaneous injection - OKZ 64 mg or placebo in addition to standard COVID-19 therapy according to institutional guidelines;~Follow-up period lasting from 00:00 of the Day 2 to 23:59 of the Day 60. If the patient is discharged earlier than Day 15, at Days 15 and 29 5-point clinical status scale will be assessed at the study site visit or by phone interview. If the patient is discharged after Day 15, but earlier than Day 29, at Day 29 5-point clinical status scale will be assessed at the study site visit or by phone interview. The end of study is Day 60, when 5-point clinical status scale will be assessed by phone interview.~Up to 376 randomized patients (full sample size) will be included in the study according to preliminary estimation.
The primary objective of the study is to evaluate the efficacy of a single dose of OKZ (64 mg) vs placebo in addition to standard therapy in patients with severe SARS-CoV-2 infection (COVID-19) at Day 29.