Pilot Study to Assess Efficacy and Safety of Treamid in the Rehabilitation of Patients After COVID-19 Pneumonia

12-15 Russian centers are planned for participation in this pilot study. The study consists of three periods: screening (2 weeks), treatment period (4 weeks) and follow-up period (2 weeks after completion of treatment with Treamid / Placebo). The duration of participation in the study for each patient is no more than 8 weeks. 60 patients with fibrotic changes in the lungs after COVID-19 pneumonia are planned to be randomized. All patients will undergo a qualitative determination of coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by polymerase chain reaction (PCR). Patients will be evaluated using the Modified British Medical Research Council (mMRC) Dyspnea Scale, chest computed tomography (CT), spirometry and body plethysmography with determination of DLCO. This examination should be conducted as close as possible to the expected randomization date (no earlier than 5 days before). All eligible patients will be randomized into 2 groups in a 1:1 ratio: Treamid 50 mg daily (30 patients); Placebo (30 patients). During the treatment period (4 weeks), patients will receive 1 tablet Treamid / Placebo once a day. Patients will be advised to continue the standard program of medical rehabilitation under day inpatient or outpatient conditions (stage 3 according to the Interim Guidelines for Medical Rehabilitation after New Coronavirus Infection (COVID-19), 2020. Patients will visit the study center once a week. At the Week 1, Week 2 and Week 3 visits, Adverse events (AEs) and concomitant therapy, investigational drug registration, body weight, vital signs and Oxygen saturation (SpO2) scores, mMRC dyspnea score and spirometry will be recorded. During the Week 2 visit, physical examination, electrocardiography (ECG), complete blood count (CBC) and biochemical blood test, PK study, common urine analysis, bodyplethysmography with DLCO will also be conducted. Patients will complete the KBILD questionnaire. Also, the patients will undergo a 6-minute walk test to measure the distance the patient walks for 6 minutes and evaluate using the Borg Scale. At the Week 4 visit (the end of the therapy), registration of AEs and concomitant therapy, physical examination, measurement of height, body weight, vital signs and SpO2, ECG, CBC and biochemical blood tests, PK study and common urine analysis will be conducted. Patients will be evaluated using the mMRC Dyspnea Scale, chest CT, spirometry and body plethysmography with determination of DLCO. Patients will complete the King's Brief Interstitial Lung Disease Questionnaire (KBILD) followed by a 6-minute walk test to measure the distance the patient walks for 6 minutes and evaluate using the Borg Scale. Patient follow-up will continue for another 2 weeks. At the Week 6 visit, registration of AEs and concomitant therapy, physical examination, measurement of height, body weight, vital signs and SpO2, ECG, mMRC dyspnea score, CBC and biochemical blood tests, and common urine analysis will be conducted.