Closed Loop System With Pramlintide Versus Exenatide

Diabetes complications can be minimized or forestalled with the use of intensive insulin
management. In the post-Diabetes Control and Complications Trial (DCCT) era, diabetologists
around the globe are engaged in developing better methods of improving glycemic control in
patients with type 1 diabetes mellitus (T1DM). To achieve the DCCT-recommended glycemic and
hemoglobin A1C (HbA1c) goals, in addition to physicians, engineering and pharmaceutical
companies are augmenting our ability to improve control by innovative compounds and
technologies such as continuous glucose monitoring. Despite these substantial advances,
hyper- and hypoglycemia continue to be problematic in the management of T1DM, especially in
children.

Current T1DM management involves checking blood glucose pre-prandially and once at bedtime (4
times/day), and making insulin dose adjustments based on these 4 blood glucose measurements.
This approach is woefully inadequate. Post-meal hyperglycemia is missed, and low blood
glucose is undetected until the patient has symptomatic hypoglycemia. Moreover, we depend on
patients to make appropriate dose modifications to basal rates of insulin when on the pump,
without the guidance of adequate blood glucose measurements. The continuous glucose
monitoring system (CGMS) is increasingly studied as a tool to examine glucose trends, and is
helping to combat inadequate self-monitoring. However, the CGMS still relies on the patient's
ability to make accurate insulin dose adjustments based on glucose readings. To address this
issue the closed loop system is now under investigation.

The closed loop system is developed to closely emulate physiologic insulin delivery. The
algorithm was developed by modeling beta cells and validated by hyperglycemic clamp studies
using the subcutaneous site for measurement of blood glucose and insulin delivery. The
algorithm is known as the external Physiologic Insulin Delivery (ePID). Current studies
suggest that basal requirements are detected accurately, and the algorithm responds
effectively. However, meal related elevation in blood glucose remains a challenge, as when
blood glucose levels begin to rise and are seen in the subcutaneous glucose sensor signal, it
is already too late to administer insulin in a way that will effectively minimize the
postprandial glucose peak. Improvements in the ePID algorithm have been studied to improve
the postprandial response with some success, but require user intervention for best results,
and despite that glucose excursions fail to normalize in the post-prandial period. It is
likely that further improvements in postprandial glycemia will be limited with insulin
monotherapy. Besides insulin there are other dysregulated hormones such as glucagon and
amylin, which contribute to post-prandial hyperglycemia.

The autoimmune destruction of insulin-secreting beta cells of the pancreas is presumed to
cause T1DM. In addition to insulin, other hormones such as glucagon and amylin play a role in
normalizing glucose excursions. Failure of glucagon suppression results in immediate
postprandial hyperglycemia, and a loss of glucagon response to hypoglycemia results in late
postprandial hypoglycemia. Despite the increasing use of subcutaneous continuous insulin
administration and newer insulin analogs, insulin replacement remains imperfect, and glucose
excursions are inadequately controlled in diabetes. This suggests that other factors, in
addition to diet and insulin management, may need to be addressed if postprandial glucose
excursions are to be normalized in T1DM.

The recent discovery of the hormone amylin has enhanced our understanding of postprandial
glucose homeostasis. Patients with T1DM have deficiencies of both insulin and amylin. Amylin,
a 37-amino acid polypeptide hormone, is co-secreted from the pancreatic beta cells in
conjunction with insulin in response to nutrient stimuli. Amylin, in the immediate
postprandial period, may mediate part of its effect by suppressing glucagon secretion,
resulting in the suppression of hepatic glucose production and the slowing of gastric
emptying.

Pramlintide acetate is a synthetic analog of the naturally occurring human hormone amylin. It
effectively reproduces amylin agonist activity in an equipotent fashion. Pramlintide acetate
has been reported to improve glycemic control in adults with both type 1 and type 2 diabetes
mellitus. Specifically, postprandial glucose excursions are improved with adjunctive
pramlintide use compared with insulin monotherapy.

Exenatide is a synthetic analog of exendin-4. It is FDA approved for use in adults with type
2 diabetes mellitus (T2DM). Clinical studies indicate that exenatide is very effective in
decreasing postprandial glucose excursions. The investigator's brochure for exenatide
suggested that in adults with T2DM, exenatide was well tolerated at 0.1 mcg/ kg/ dose, and
resulted in glucose lowering. Our preliminary data in children with T1DM suggests that 1.25
mcg and 2.5 mcg are good pre-prandial initial doses with a prandial insulin dose reduction of
30%. The principal mechanism of action in T1DM is suppression of glucagon, with a subsequent
suppression of hepatic glucose production and decreased immediate post-prandial
hyperglycemia. These effects result in further reduction of HbA1c beyond the reduction
observed with insulin alone. Additionally, in T2DM, exenatide delays gastric emptying, and
decreases food intake through centrally mediated mechanisms causing satiety and improved
weight control. The most notable adverse effect of exenatide is nausea, which improves with
the duration of treatment and steady dose escalation of exenatide. Hypoglycemia may occur
with concurrent use of insulin.

In the current exploratory studies we are proposing a novel way to combat immediate
postprandial hyperglycemia in subjects with T1DM by using the study medications through the
experimental closed loop system. Subjects will not be on the closed loop system prior to
eligibility, and would not have used the closed loop system at an earlier time. We will use
prandial pramlintide/exenatide in the first protocol, and test the hypothesis that this
intervention will be superior to using insulin monotherapy in the closed loop system. This
would be a Biologic, phase I, single center study and a paired, randomized, and controlled
comparison of pramlintide and insulin versus exenatide and insulin Vs insulin monotherapy
using the ePID closed-loop system for insulin delivery.

We will stratify the study subjects into the following sub-groups of 5 subjects of 22-30
years old, 4 subjects of 18-21 years old, 4 subjects of 16-18 years old. We would also begin
the study with the 22-30 year patient sub-group and then transition to the other sub-groups
after evaluating all the safety issues. 22-30 year old ones would be considered as an adult
subset, 18-21 year olds would be considered pediatric subset according to the guidelines of
FDA's Center for Devices and Radiological Health (CDRH) and 16-18 year olds are considered
typical pediatric population. At this time, Spanish-speaking subjects will not be recruited
because Medtronic Minimed as yet does not have any literature in Spanish that may be used in
explaining the study to this group of patients. When in the future Medtronic is able to
provide us with the appropriate Spanish literature, we will at that time amend the protocol
to include this group of subjects.

Study Procedure:

Screening: Screening evaluations will be performed 1-2 months prior to study enrollment, and
will consist of an informed consent, medical history, physical examination (including height,
weight, and vital signs), and blood samples for clinical laboratory tests. The clinical
laboratory tests will include a CBC to check for anemia, hemoglobin A1C (within last month),
serum electrolytes, serum amylase, Serum HCG pregnancy test for female subjects. The
approximate volume of blood is expected to be less than 5 ml.

Following informed consent (and with appropriate subject assent) if subject is found eligible
for the study, they will undergo a baseline open-loop evaluation using a Medtronic Data
logger continuous glucose monitor (Medtronic Diabetes, Northridge, CA). The data on glucose
excursions will be collected on their usual insulin dosages so as to appropriately configure
the algorithm of the closed-loop system during the inpatient admission. Basal rates and
insulin to carbohydrate ratios will be adjusted during the period between screening and the
start of the 3 studies that they will undergo subsequently.

After screening, subjects will undergo a 3-period crossover design trial in random order.

Study A Subjects will be admitted to the general clinical research center (GCRC) on the
evening prior to the study at 6 PM. For female subjects a stat serum HCG pregnancy test is
done prior to the start of the study. Two sensors will be placed in the subcutaneous tissue.
Insertion of IV line will occur between 9-10 PM. During the night hourly samples of blood
glucose will be used to adjust insulin basal or boluses so as to maintain euglycemia. Around
6 a.m. subjects will be started on the closed-loop system for the automated delivery of
insulin based on the glucose sensor measurements. An intravenous line will be inserted in the
antecubital fossa to maintain blood glucose concentrations within the normal range.

Blood samples for basal glucose, insulin, and glucagon concentrations will be drawn at minus
30, minus 10, and 0 min prior to study start.

For study A (Control): Subjects will receive meals at 0 minutes (approximately 7 AM
breakfast), 300 min (approximately Noon lunch) and dinner at 600 min (approximately 5 PM
dinner). A partial bolus of insulin will be administered prior to breakfast in addition to
closed loop system (since the system is not expected to have calibrated by the time of
breakfast).

For study B: Subjects will receive 30 mcg of pramlintide just before 300 and 600 minutes.
Pramlintide will be administered as a subcutaneous injection just prior to lunch and dinner.
A partial bolus of insulin will be administered for breakfast in addition to closed loop
system (since the system is not expected to have calibrated by the time of breakfast).

For study C: Subjects will receive 2.5 mcg of exenatide subcutaneously just before 300 and
600 min. Exenatide will be administered as a subcutaneous injection just prior to lunch and
dinner. A partial bolus of insulin will be administered for breakfast in addition to closed
loop system (since the system is not expected to have calibrated by the time of breakfast).

At 0 mins, subjects will drink a standard liquid meal of Boost High Protein Drink 9.6 oz (360
calories, 40 g of carbohydrate) over a period of 10 min. This meal will not be counted in the
final analysis since the closed loop system will not have had enough time to adjust to the
basal conditions of the meal. A partial bolus of insulin will be administered for breakfast
in addition to closed loop system (since the system is not expected to have calibrated by the
time of breakfast).

At 300 minutes, subjects will receive a solid meal based on Estimated Energy Requirements
(EER) as reported by the Institute of Medicine Dietary Reference Intakes macronutrients
report, 2002. The carbohydrate content of the meal will be 75 g. Pramlintide 30 mcg/
Exenatide 2.5 mcg will be administered subcutaneously before lunch and dinner. Insulin will
be administered based on ePID algorithm by the closed loop system in response to glucose
concentrations detected by subcutaneous sensing. Blood samples for glucose concentrations
will be drawn every 15min-half hour (more frequently immediately after meals) after
initiating closed loop system. Blood samples for hormone analysis (insulin,
pramlintide/exenatide and glucagon) will be drawn at approximately every 15 min to half hour
intervals after lunch which will be served at approximately around Noon in the first hour and
then every half to one hour until dinner. Dinner will be served at approximately around 5 PM
(the carbohydrate content of the meal will be similar to lunch). Blood glucose will be
measured at the bedside using a YSI glucose analyzer every half hour. The study will end at
885 minutes.

Total blood volume drawn for studies A, B, and C will be approximately 97cc, 133cc and 133cc
respectively.

The subject's will be always monitored by nursing staff of the CRC, study staff and the PI is
available by phone and on call during the study. Medtronic personnel will be present for the
first four studies to ensure all the equipment is working optimally and to provide guidance
related to the closed loop system.

During the study, if subject's blood glucose values are less than 70 mg/dl, oral glucose
(5-15 g) will be administered for countering low blood glucose to achieve euglycemia (90-130
mg/dl). 1-2 doses of oral glucose should correct hypoglycemia. If more than 4 consecutive
doses are required to achieve euglycemia the study will be terminated, and the subject will
be offered a meal tray and blood sugar rechecked to ensure euglycemia. Additional 0.2 cc
blood samples for glucose may be necessary to ensure safety during an episode of hypoglycemia
and these may be done before the scheduled time for blood draws.

If blood glucose by Analox machine is greater than 300mg/dl, blood ketones will be measured
and if ketones are above 1.5 mmol/L we will terminate the study.

At the end of the study the subject will be evaluated by the research staff for the need to
receive a snack. A snack will be served before discharge only if BG of subject is less than
70mg/ dl at the end of the study. If the Principal Investigator or the attending physician
feels that the subject needs to be observed for a longer period of time then it would be at
his/her discretion.

The subjects will return two additional times (2-4 weeks apart) to complete the exact same
study, with the difference that if the patient received pramlintide on the last occasion
he/she will get either exenatide or just insulin via the closed loop system at the subsequent
visits. (Total of 3 visits).

Female subjects would have a stat serum HCG pregnancy test is done prior to the start of the
study for each visit. Subjects will have stat CBC prior to initiating closed loop study.
Serum Electrolytes will be done at the onset of the study and then will be repeated if the
patient had vomiting at the end of the study. Serum amylase would be done at each visit and
the results would be tracked on the case report forms. Capillary blood glucose check would be
done when necessary as an extra safety measure in addition to subject's blood glucose being
monitored through YSI and interstitial glucose monitored through glucose sensor.

For uniformity sake, we would be using only using Insulin Aspart for the entire duration of
the study.

If at least four subjects develop grade 3 nausea, with the 30 mcg dosage of pramlintide or
with the 2.5 mcg of exenatide then the protocol would be modified so that the subjects
receive only a 15 mcg dose of pramlintide and 1.25 mcg of exenatide.

TREATMENT FOR SEVERE NAUSEA: If severe nausea develops during the study, Zofran 0.15 mg/kg IV
will be given. The maximum dose is 8 mg. If the subject still has emesis, the study subject
would be stopped.

Study drugs and study laboratory tests will be provided at no cost to the subject. The
subjects will receive $70 at screening and $210 for the three subsequent study visits. The
total compensation involved for the study would be $ 700.

Inclusion Criteria:

1. Age greater than 18 years and less than 30 years.

2. Have had diabetes for at least 1 year, and in good control (HbA1C less than 8.5 %).

3. Be on continuous subcutaneous insulin infusion using an insulin pump

4. Subjects must be otherwise healthy except for T1DM, and treated for hypothyroidism if
present

5. Menstruating women must have negative pregnancy test.

6. Hemoglobin (Hb) more than 12 g/dl

7. Weight must be equal to or greater than 50 Kg

Exclusion Criteria:

1. Any chronic disease (leukemia, asthma, inflammatory bowel disease, cystic fibrosis,
juvenile rheumatoid arthritis, etc that directly, or as a result of treatment,
directly or indirectly affect glucose homeostasis).

2. Hemoglobin less than 12 g/dl

3. Lack of a supportive family environment

4. Positive pregnancy test based on serum beta HCG in menstruating young women

5. Evidence or history of chemical abuse

6. HbA1c more than 8.5 %

7. Weight less than 50 Kg

8. History of gastroparesis and on medications that alter gastric emptying

9. History of Pancreatitis and impaired renal function

10. Hypoglycemic unawareness

11. History of sensitivity to 5-HT3 receptor antagonists

12. History of QT prolongation

13. Concomitant use of both Acetaminophen and vitamin C

14. Patients on glucocorticoid therapy

15. Known allergies to any of the study medication