1. This study will test the safety and efficacy of TG-873870 (Nemonoxacin) compared with Levofloxacin in adult patients with Community-Aquired Pneumonia (CAP)
2. To investigate the population pharmacokinetics (PPK) of nemonoxacin in adult patients with CAP after continuous oral administration and determine the pharmacokinetic (PK)/pharmacodynamic (PD).

Community-acquired Pneumonia (CAP) remains a leading cause of death in both developing and developed countries. In the choice of antibacterial agents used to treat CAP, fluoroquinolones have received considerable attention because of their wide spectrum of bactericidal activity. TG-873870 (Nemonoxacin), a non-fluorinated quinolone (NFQ), is a selective bacterial topoisomerase inhibitor. This study will test the safety and efficacy of TG-873870 (Nemonoxacin) compared with Levofloxacin in adult patients with Community-Aquired Pneumonia (CAP).

Besides,the population pharmacokinetics (PPK) of nemonoxacin in adult patients with CAP after continuous oral administration and determine the pharmacokinetic (PK)/pharmacodynamic (PD).

Inclusion Criteria:

1. Ages between 18 and 70;
2. Weighs between 40 ~ 100 kg, and BMI ≥ 18 kg/m2;
3. Must have a clinical diagnosis of CAP
4. Chest X-ray shows new or persist/progressive infiltrates
5. If female, non-lactating and at no risk or pregnancy (post-menopausal or must use adequate birth control)
6. The patient is able to take the drug orally.

Exclusion Criteria:

1. Patients with CAP that, in the investigator's judgment, is severe enough to require hospitalization for intravenous antibiotic therapy and/or supplemental oxygen therapy with ICU support
2. Known or suspected severe bronchiectasis, cystic fibrosis, active pulmonary tuberculosis or infection with other mycobacteria or fungi, known bronchial obstruction, a history of post-obstructive pneumonia, other confounding respiratory diseases, such as lung cancer, malignancy metastatic to the lungs, lung abscess, empyema, suspected aspiration pneumonia due to vomiting, or non-bacterial respiratory infection (chronic obstructive pulmonary disease [COPD] is not exclusionary)
3. Clinically significant conduction or other abnormality on 12-lead ECG, or QTc interval
4. Potassium is < 3.5 mmol/L
5. Any known disease that seriously affect the immune system
6. Active hepatitis or decompensated cirrhosis;
7. Have used quinolones or fluoroquinolones within 14 days before enrollment
8. Patients who are being or will be on a long-term medication of steroids