This is a double-blind, randomized, multicenter, placebo-controlled, comparative phase II dose-finding trial. The trial will be conducted with four treatment groups in the form of a parallel group comparison and will serve to compare oral treatment with daily doses of 10, 20, or 40 mg Naronapride vs. placebo for the treatment of patients with Gastroparesis.

Inclusion Criteria:

• Men and women between ≥18 and ≤75 years of age,
• Body Mass Index (BMI) ≥16 and <35 kg/m2 ,
• History of idiopathic or diabetic gastroparesis cardinal symptoms (e.g., nausea, vomiting, early satiety, postprandial fullness, bloating or upper abdominal pain) for ≥3 months,
• Evidence of delayed gastric emptying by 13C-spirulina gastric emptying breath test (GEBT) for solids with gastric emptying T1/2 ≥ 85.33 minutes (≥ 90th percentile of normative data) during the screening phase,
• Average weekly total symptom score of the ANMS GCSI-DD ≥2.0 based on the daily symptom scores recorded for at least 5 of 7 consecutive days in the week prior to Baseline,
• Participants with a type I or type II diabetes mellitus diagnosis must have a controlled diabetes mellitus defined as HbA1c ≤11% under stable antidiabetic medication,
• Exclusion of any mechanical and/or anatomical obstructions, stenosis, structural diseases, or gastric ulcers by upper gastrointestinal endoscopy during screening phase (previous endoscopic results within 12 months are acceptable, if no relevant changes in patient's disease status occurred since that time),
• No evidence of intestinal stenosis as determined by an imaging technique (i.e., either abdominal sonography, Magnetic resonance imaging [MRI] or imaging by computed tomography [CT] during screening phase (previous MRI/CT imaging or sonography results within 12 months are acceptable, if no relevant changes occurred in patient's disease status since that time),

Exclusion Criteria:

• History of major gastrointestinal surgery such as gastric bypass, anti-reflux surgery, gastric per oral endoscopic myotomy (G-POEM), gastrointestinal malignancy, colectomy,
• Intrapyloric botulinum toxin injection within 12 months,
• Gastric stimulator implant,
• Known secondary causes of gastroparesis including but not limited to Parkinson's Disease, cancer, or connective tissue diseases,