Sitagliptin Dose Determination Study

Rationale: Sitagliptin has been extensively studied in patients with type 2 diabetes
mellitus, but there are no documented studies in the literature to establish a safe and
efficacious dose in type 1 diabetes mellitus. Our previous experience with exenatide, which
is a GLP-1 agonist and also with similar end pharmacological effects as Sitagliptin and other
related published studies suggest that to avoid immediate post-prandial hypoglycemia insulin
dose needs to be reduced when patients administer glucagon suppressors in conjunction with
insulin. Hence, the dose of insulin will be decreased by 20-50% when Sitagliptin will be
administered.

Sitagliptin will be given in three different doses to T1DM subjects within 3 months of
diagnosis and also in a group of subjects > 1 year of their diagnosis. A paired crossover
design study aims to establish an effective glucose-lowering dose that will additionally
minimize side effects. Furthermore, only 18-30 year old subjects who are diagnosed with T1DM
for a year or more will be studied initially (4 subjects) to establish safety data before
younger subjects are recruited into the study. The data will be un-blinded after the
completion of the first two adult subjects in order to analyze preliminary data and also to
reapply for funding. Data Safety Monitoring Board will meet before the initiation of the
study and before children are enrolled into the study. The safety data after the meeting will
be submitted to the IRB for review.

Specific Aim: To establish a safe and an effective glucose-lowering dose of Sitagliptin in
type 1 diabetes (T1DM) when used along with rapid acting insulin which will normalize
post-prandial hyperglycemia and reduce hyper-glucagonemia and delay gastric emptying.

Hypothesis: A dose-response effect of Sitagliptin will be observed on gastric emptying and
glucagon suppression in both new and established subjects with T1DM.

Study Design: Following informed consent (and with appropriate subject assent), each subject
with TIDM will undergo 5 study visits: Screening, Part A (Sitagliptin 25 mg), Part B
(Sitagliptin 50 mg), Part C (Sitagliptin 100 mg), and Part D (Placebo). A randomized
double-blinded trial with a 4-period crossover design will be used to establish an ideal
Sitagliptin dose for the adult age group (18-30 years). The adult study subject's and the
study staff (except one person) will be blinded to the dose of Sitagliptin and they will do
all the study Parts A, B, C and D in random order.

Montefiore Medical Center (MMC) Investigational pharmacy and one of the study staff
(excluding the PI) will be un-blinded to the protocol for doing the randomization table,
dispensing, checking the dose of study medication and scheduling the study visits (done by
the study staff person). For the pediatric age group (13-17 years) it will be single blinded
trial with single ascending dose sequential study. Pediatric study subject's will be blinded
to the dose of Sitagliptin and they all will start with the placebo part and then proceed
with the study parts with Sitagliptin 25 mg, 50 mg and 100 mg dose in a sequential order. The
participants will be admitted to the CRC on four occasions for the Parts A, B, C and D and
each admission will be 3-4 weeks apart.

Inclusion/ Exclusion Criteria Subjects with T1DM in the age group of 12-30 years without any
concomitant illnesses except treated hypothyroidism will be recruited and also have an HbA1C
less than 9 %. Menstruating women must have a negative pregnancy test. Lactating and pregnant
women will be excluded and anyone with anemia defined by Hemoglobin of less than 12 gm/dl.
Also, subjects with a history of substance abuse (evaluated by medical history and CRAFFT
questionnaire which will be administered at the screening visit) will be excluded. The
subject's should not be on any other medication which affects blood sugars.

Screening: After signing a consent form, a screening evaluation will be performed up to 28
days prior to study enrollment in the CRC for the Parts A, B, C or D. The evaluation will
consist of medical history, physical examination (including height, weight, vital signs and
tanner staging), and blood samples for clinical laboratory tests: CBC, LFTs, amylase, lipase,
creatinine and HbA1C. The approximate volume of blood drawn is expected to be 12 ml. CRAFFT
questionnaire will be administered. Also each subject will have a Dexcom™ Continuous Glucose
Monitoring System inserted. It has three parts - a glucose sensor that is inserted
subcutaneously, a transmitter which connects to the sensor electrode and is attached to the
body and a receiver which displays the glucose values. It gets updated every 5 minutes. The
subject will need to wear it for 7 days. Also, they will be asked to keep a log on diet,
insulin and exercise while wearing the CGMS. We will try to schedule the next visit with in
the 7 day period while they are on the CGMS so that they are admitted while their glucose
levels are relatively stable. We will give an extra sensor with instructions on how to wear
it in case they cannot come to the next visit with in the week.

Part A: The subjects will be admitted into the CRC around 6:30 AM. Vitals will be taken. IV
will be placed and blood will be drawn to measure Stat CBC, HbA1C, Liver function tests,
Serum Amylase, Serum Lipase and Serum Creatinine. Study will be continued only if their
Hemoglobin is greater than 12 gm/ dl. Urine pregnancy test will be done for all female
subjects prior to study. Insulin infusion through the subcutaneous pump will be continued or
long acting analog, glargine will be given as per home regimen.

BLOOD SAMPLING AND MEDICATIONS: At approximately 0700 baseline blood samples will be drawn
prior to study start for: glucose, insulin, glucagon, GLP-1, DPP-4 activity and Sitagliptin.
Also, there will be blood draws at the following time points: -240 min, -180 min, -60 min, 0
min, 4 hrs. prior to the mixed meal and at 10, 20, 30, 40, 60, 90, 120, 150, 180, 210, 240,
360 min after. The insulin pump basal rate (or glargine) will be set to continue as per home
regimen. Sitagliptin 25 mg will be administered at this point. At around 1100 (0 min), the
pre-breakfast insulin bolus of rapid acting insulin will be given at 0 min. The insulin dose
will be based on the patient's usual insulin to carbohydrate ratio. This dose will be reduced
by 20-50% and the subject will be offered a standard liquid meal of Boost High Protein Drink,
12 Oz. (360 calories, 50 g of carbohydrates and 12 g of fat) and asked to consume it within a
10-15 minute period. This will be enriched with 1 gram of [1- 13C] glucose. Expired 13CO2
will be determined in breath at -240, 0, 10, 20, 30, 40 60, 90, 120, 150, 180, 210, 240, 360
min. Lunch will be provided after 240 min and an insulin bolus of rapid acting insulin will
be given through the insulin pump (calculated according to subject's insulin to carbohydrate
ratio and sensitivity factor) or through an insulin injection. They will stay for 2 more
hours for the 360 min blood draw. Blood glucose concentrations will be measured at the
bedside using an Analox glucose analyzer. Sitagliptin being a 24 hr medication pk data will
be obtained at 0 and 360 min. For safety reasons the subject's will be put on a Dexcom CGMS
and they will wear for a week. During this period they will keep a log sheet in which they
will note the blood glucose, food and exercise activity. They will return that using a
prepaid envelope which will be provided. The subject will be discharged after this. They will
not be paid separately for transportation, parking or child care. A social security number
will be required. It will be kept confidential. For minors, compensation will be given to the
parent, but it is intended for the child.

A subject will be withdrawn from participating in the study if he/she meets any of the
following conditions: 1) develops a chronic disease 2) develops anemia 3) becomes pregnant 4)
develops a weight loss of greater than 10 pounds for unspecified reasons 5) loss of contact-
if we are unable to reach a study subject (within 2 months of screening or completion of the
first study) by phone or mail to schedule the next appointment. All study subjects (that are
withdrawn from the study) will receive a phone call and a letter notifying them that they
have been withdrawn. Blood samples will be kept for 20 years because some of the assays have
not been developed for some of the hormone analyses. Since it is difficult to perform
clinical studies in pediatrics, we feel it is better to bank blood samples and perform
hormone analyses as newer assays become available rather than repeating the study.

Treatment of Hypoglycemia: If blood glucose values in a subject are less than 55 mg/dl, IV
glucose of 5-10gm, or if blood glucose less than 50 mg/dl, 10-15 g will be administered for
countering low blood glucose to achieve euglycemia (90-130 mg/dl). 1-2 doses of IV glucose
should correct hypoglycemia. If more than 3-4 doses are required to achieve euglycemia, the
study will be terminated and the subjects will be offered a meal tray and blood sugar
rechecked to ensure euglycemia. After the completion of the first 2 study subjects, the data
safety and monitoring committee will assess safety of the protocol, as well as drug doses and
adjustments to the protocol will be made. If hypoglycemia occurs even with the reduced dose
of insulin, further reduction in insulin dose will be advised. The total blood draw volume
will be 175.4 cc (3/4 cup) for Part A, B, C and 121.4 cc (1/2 cup) for Part D.

Each study will be 3-4 weeks apart. Prior to each part, hemoglobin must be >12 g/dl and a
female subject should test negative for pregnancy. Part B: Will be identical as part A except
that Sitagliptin dose will be 50 mg. Part C: Will be identical as part A except that
Sitagliptin dose will be 100 mg. Part D: Will be identical as part A except that the study
subject will receive a placebo. In all the Parts B, C, D urine pregnancy test will be done
before the visit for all female subjects. Also after each Part A, B, C, D the subject will be
on Dexcom™ Continuous Glucose Monitoring System for 7 days and after that they will send that
back to us using a prepaid mailing envelope.

Statistical Analysis Power Calculation: Data from an earlier trial determined that the mean
area under the curve (AUC) for children with T1DM with insulin alone was 470 mg*hr/dl. The
current trial is designed to detect a 20% difference in mean AUC for glucose in the 300 min
period to 376 mg*hr/dl. In our previous study, r > 0.7 was noted between repeated measures
(in same subjects) and that the standard deviation for our excursion measure AUC is
approximately 30%. With these specifications the necessary sample size is 11 subjects. With a
40% drop out rate we would need a total of 15 subjects with TIDM. Power calculations were
based on an alpha of 0.5 and power of 80% and two-tailed test. To stratify them in to recent
onset Vs established onset we will recruit 15 of each (n = 30). Data Analysis: Blood glucose
levels will be measured and AUC will be determined for glucose for a 300 min time period for
all 4 studies and a two-tailed, repeated measures analysis of variance will be performed. A
modified paired t-test will be used for post hoc multiple comparison. Regression analysis
will be used to calculate a dose response curve for each individual and the hypothesis will
hold true at a significance of 0.05. Similar analysis will also be carried out for insulin
and glucagon. The pharmacokinetics of Sitagliptin will be analyzed by model dependent and
model-independent means. AUC, plasma clearance, half-life and steady state volumes of
distributions will be among the parameters determined. Pharmacokinetic data will be analyzed
using ADAPT II software. The initial curve fits will be performed with the weighted least
squares algorithm. Other strategies will be invoked as appropriate.

Inclusion Criteria:

1. Age of 13 to 30 years

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

3. Menstruating women must have negative pregnancy test.

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

Exclusion Criteria:

1. Having any other chronic condition except hypothyroidism stable on medications

2. On chronic medications that may affect glucose excursions

3. Hemoglobin less than 12 g/dl

4. Positive pregnancy test (based on Urine)

5. Pregnant or lactating mothers

6. Known allergy to Januvia