A Study to Evaluate the Efficacy and Safety of TAK-906 in Adult Participants With Symptomatic Idiopathic or Diabetic Gastroparesis

Inclusion Criteria

• Should have experienced symptoms of gastroparesis (e.g., postprandial fullness, nausea, vomiting, upper abdominal pain, and early satiety for at least 3 months before screening as assessed by a physician.
• Must have confirmed delayed gastric emptying by meeting 1 of the following criteria:
• Confirmed by an accepted diagnostic testing method (Gastric Emptying Breath Test [GEBT], scintigraphy, or wireless motility capsule) that is documented in the participant's medical records prior to screening; OR
• Participants without previous confirmation of delayed gastric emptying prior to screening will undergo a GEBT after they have stopped taking prohibited medications.
• Must have an average composite ANMS GCSI-DD symptom score ≥2 during the 7 days before randomization. The predominant symptom experienced by participants must not be abdominal pain.
• Must experience nausea: nausea subscale (of ANMS GCSI-DD) symptom score ≥2 at least 4 of 7 days or an average nausea subscale symptom score ≥2 during the 7 days before randomization. Nausea symptoms must not be attributable to a central disorder (e.g. motion sickness, glaucoma, menstrual cycles, migraine headache).
• Has a body mass index (BMI) of ≥18 to ≤40 kg/m^2 inclusive.
• Participant with diabetes mellitus must have glycosylated hemoglobin (HbA1c) ≤11% at screening and before randomization.
• Absence of gastric outlet obstruction confirmed by upper GI, computed tomography or endoscopy.

Exclusion Criteria

• Known secondary causes of gastroparesis including but not limited to Parkinson disease, cancer, viral illness, or connective tissue diseases.
• Predominant gastroparetic symptom is epigastric pain, diffuse abdominal pain, or pain associated with bowel movement.
• Is taking medications that affect gastric emptying including opioids, glucagon-like peptide-1 analogs (e.g., exenatide, liraglutide), amylin analogs (e.g., pramlintide), and cannabinoids.
• Prior history of gastric surgery, including but not limited to gastrectomy, gastric bypass, gastric banding, bariatric surgery, pyloroplasty, vagotomy, or fundoplication, which has manipulated the natural anatomy of the stomach.
• History of intra-pyloric botulinum toxin injection within 3 months of Screening or currently has functioning implantable electric stimulator.
• Nasogastric, percutaneous endoscopic gastrostomy, or percutaneous endoscopic jejunostomy feeding tube or inpatient hospitalization for gastroparesis within 2 weeks before the Screening Visit.
• Required parenteral nutrition for treatment of gastroparesis within 2 months before the Screening Visit.
• Previous diagnosis of gastric bezoar (the presence of retained liquid, bile, or small amounts of poorly organized food residue is permitted).
• Poor control of diabetes within 30 days prior to randomization, including diabetic ketoacidosis, hypoglycemia requiring medical intervention, admission for control of diabetes or diabetic complications.
• Elevated serum prolactin (>upper limit of normal [ULN]) at Screening.
• Has concurrent hypogonadism, current clinically significant menstrual abnormalities, such as amenorrhea or oligomenorrhea, or other clinical features of hyperprolactinemia such as galactorrhea or gynecomastia.
• Has acute or chronic liver disease meeting any of the criteria described below:
• Has an alanine aminotransferase (ALT), aspartate aminotransferase (AST) or total bilirubin >2.0 times the ULN.
• Has pre-existing liver cirrhosis that meets Child-Pugh Class B (moderate; total score 7 to 9 points) or C (severe; total score 10 to 15 points) (see Appendix B).
• Has acute or chronic hepatitis B or C virus infection, manifesting as one of the following at screening:
• Positive hepatitis B surface antigen (HBsAg) or hepatitis B core antibody (HBcAb). NOTE: if a participants tests negative for HBsAg, but positive for HBcAb, the participant would be eligible if the Investigator has documentation of other tes