A randomized, double-blind, parallel-arm, phase II, explorative study investigating the efficacy and safety of orally administered N-Acetylcysteine (NAC) versus placebo in patients with history of SARS-Cov-2 infection and residual respiratory impairment.

Inclusion Criteria:

1. Age ≥18 and ≤90 years.
2. History of hospitalization for COVID-19 pneumonia, as documented by positive RT/PCR testing for SARS-Cov-2 infection (nasopharyngeal swab) and suggestive radiological findings at the chest CT scan.
3. Resolution of SARS-CoV-2 infection as defined by negative RT/PCR testing (nasopharyngeal swab).
4. Evidence of residual interstitial lung abnormalities (including any of the following: ground glass, reticulation, or consolidation with overall extent ≥5% of total lung volume) on chest high resolution CT scan (performed during screening or within 30 days from screening visit) AND

One or more of the following:

• DLco ≤ 70 % of predicted value at screening
• Oxygen desaturation at 6-minute walk test (6MWT) ≥4% from baseline value at screening.
• Total Lung Capacity ≤ 80 % of predicted value at spirometry performed at screening
• Exertional dyspnea at screening, as defined by MMRC ≥1

Exclusion Criteria:

1. Evidence of resting respiratory failure, as defined by PaO2 ≤60 mmHg (FiO2 21%) at blood gas analysis at screening.
2. History of interstitial lung disease, or evidence of interstitial lung disease at screening that suggests any of the following: idiopathic interstitial pneumonias; lung diseases related to exposure to fibrogenic agents or other environmental toxins or drugs; other types of occupational lung diseases; granulomatous lung diseases; pulmonary vascular diseases; systemic diseases, including vasculitis, infectious diseases (Other than SARS-Cov-2 infection) and connective tissue diseases.
3. History of other types of respiratory diseases, including disorders of the airways, lung parenchyma, pleural space, mediastinum, diaphragm, or chest wall that, in the opinion of the Investigator, would impact the primary protocol endpoint or otherwise preclude the subject's participation in the study.
4. Any other known disease, medical conditions or blood test abnormalities that in the opinion of the Investigator may put the patient at risk because of participation, interfere with study procedures or cause concern regarding the patient inability to participate in the study.
5. Concomitant treatment with oral corticosteroids and/or other immunosuppressive drugs.
6. Pregnancy status.
7. Incapacity of providing valid informed consent.