Inclusion Criteria:

• Controlled Type I Diabetes Mellitus (glucose < 250 mg/dL) with onset < 30 years of age.
• Male or female between 18 and 70 years of age, inclusive.
• Patient has documented diagnosis of moderate to severe gastroparesis (> 30% at 2 h as determined by scintigraphy; or t1/2b > 109 min as determined by 13C-octanoic acid breath test). All of the following apply:
• Confirmed delayed gastric emptying (properly conducted gastric emptying assessments within last 6 months acceptable) AND a minimum 3 month history of relevant symptoms for gastroparesis (e.g., chronic postprandial fullness, postprandial nausea, vomiting)
• A female patient is eligible to participate if she is of:
• Non-childbearing potential defined as pre-menopausal females with a documented tubal ligation or hysterectomy; or postmenopausal defined as 12 months of spontaneous amenorrhea [in questionable cases a blood sample with simultaneous follicle stimulating hormone (FSH) > 40 MlU/mL, or a value consistent with the local laboratory standard value, is confirmatory.
• Child-bearing potential and agrees to use one of the contraception methods listed in Section 8.1 for an appropriate period of time (as determined by the product label or investigator) prior to the start of dosing to sufficiently minimize the risk of pregnancy at that point. Female patients must agree to use contraception for at least 4 days following the last dose of study medication.
• Male patients must agree to use one of the contraception methods listed in Section 8.1. This criterion must be followed from the time of the first dose of study medication through at least 4 days after the last dose of study medication.
• Body weight ≤110 kg and BMI < 32.0 kg/m2 (inclusive).
• Patient has never had a gastrectomy, nor major gastric surgical procedure or any evidence of bowel obstruction within the previous 12 months
• Dosage of any concomitant medications has been stable for at least 3 weeks, except for routine adjustments in daily insulin treatments
• HbA1c level is ≤ 10.0%
• Calculated creatinine clearance > or equal to 50 ml/min
• QTcB or QTcF < 450 msec or QTc<480msec in patients with Bundle Branch Block based on single or average QTc value of triplicate values obtained over a brief recording period.
• AST, ALT, alkaline phosphatase and bilirubin ≤ 1.5xULN (isolated bilirubin >1.5xULN is acceptable if bilirubin is fractionated and direct bilirubin <35%)
• Capable of giving written informed consent, which includes compliance with the requirements and restrictions listed in the consent form.

Exclusion Criteria:

• Patient has acute severe gastroenteritis
• Patient has a gastric pacemaker
• Patient is on chronic parenteral feeding
• Patient has daily persistent severe vomiting
• Patient has pronounced dehydration
• Patient has had clinical diabetic ketoacidosis in last 4 weeks
• Patient has a history of eating disorders (anorexia nervosa, binge eating, bulimia)
• Use of medications potentially influencing upper gastrointestinal motility or appetite within one week of the study (e.g., prokinetic drugs, macrolide antibiotics (erythromycin))
• Patient is taking opiates.
• Use of prohibited medications listed in Section 9.2 within the restricted timeframe relative to the first dose of study medication.
• History or presence of clinically significant gastro-intestinal, hepatic or renal disease or other condition known to interfere with the absorption, distribution, metabolism or excretion of drugs.
• Presence of thyroid dysfunction (NOTE: patients with abnormal TSH at screening/baseline are not eligible.

Patients with a history of hypothyroidism on a stable dose of thyroid replacement therapy are eligible to participate in the study).

• The patient has participated in a clinical trial and has received an investigational product within the following time period prior to the first dosing day in the current study: 30 days, 5 half-lives or twice the duration of the biological effect of the investigational product (whichever is longer).
• History of sensitivity to any of the study medications, or components thereof or a history of drug or other allergy that, in the opinion of the investigator or GSK Medical Monitor, contraindicates their participation.
• Where participation in the study would result in donation of blood or blood products in excess of 500 mL within a 56 day period.
• Pregnant females as determined by positive serum or urine hCG test (from the first urine of the day) at screening or prior to dosing.
• Lactating or pregnant females.
• Unwillingness or inability to follow the procedures outlined in the protocol.
• Patients deemed unable to comply with the procedures outlined in the protocol may be excluded at the Investigator's discretion.
• For male volunteers: An unwillingness of the male patient to comply with the contraception requirements listed in Section 8.1, from the time of the first dose of study medication until at least 4 days following administration of the last dose of study medication.
• A positive pre-study Hepatitis B surface antigen or positive Hepatitis C antibody result within 3 months of screening.