Clinical Pharmacology for Zituvio
Mechanism Of Action
Sitagliptin is a DPP-4 inhibitor, which is believed to exert its actions in patients with type 2 diabetes mellitus by slowing the inactivation of incretin hormones. Concentrations of the active intact hormones are increased by sitagliptin, thereby increasing and prolonging the action of these hormones. Incretin hormones, including glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), are released by the intestine throughout the day, and levels are increased in response to a meal. These hormones are rapidly inactivated by the enzyme, DPP-4. The incretins are part of an endogenous system involved in the physiologic regulation of glucose homeostasis. When blood glucose concentrations are normal or elevated, GLP-1 and GIP increase insulin synthesis and release from pancreatic beta cells by intracellular signaling pathways involving cyclic AMP. GLP-1 also lowers glucagon secretion from pancreatic alpha cells, leading to reduced hepatic glucose production. By increasing and prolonging active incretin levels, sitagliptin increases insulin release and decreases glucagon levels in the circulation in a glucose-dependent manner. Sitagliptin demonstrates selectivity for DPP-4 and does not inhibit DPP-8 or DPP-9 activity in vitro at concentrations approximating those from therapeutic doses.
Pharmacodynamics
General
In patients with type 2 diabetes mellitus, administration of sitagliptin led to inhibition of DPP-4 enzyme activity for a 24-hour period. After an oral glucose load or a meal, this DPP-4 inhibition resulted in a 2-to 3-fold increase in circulating levels of active GLP-1 and GIP, decreased glucagon concentrations, and increased responsiveness of insulin release to glucose, resulting in higher C-peptide and insulin concentrations. The rise in insulin with the decrease in glucagon was associated with lower fasting glucose concentrations and reduced glucose excursion following an oral glucose load or a meal.
In studies with healthy subjects, sitagliptin did not lower blood glucose or cause hypoglycemia.
Sitagliptin And Metformin Hydrochloride Coadministration
In a two-day study in healthy subjects, sitagliptin alone increased active GLP-1 concentrations, whereas metformin alone increased active and total GLP-1 concentrations to similar extents. Coadministration of sitagliptin and metformin had an additive effect on active GLP-1 concentrations. Sitagliptin, but not metformin, increased active GIP concentrations. It is unclear how these findings relate to changes in glycemic control in patients with type 2 diabetes mellitus.
Cardiac Electrophysiology
In a randomized, placebo-controlled crossover study, 79 healthy subjects were administered a single oral dose of sitagliptin 100 mg, sitagliptin 800 mg (8 times the recommended dose), and placebo. At the recommended dose of 100 mg, there was no effect on the QTc interval obtained at the peak plasma concentration, or at any other time during the study. Following the 800 mg dose, the maximum increase in the placebo-corrected mean change in QTc from baseline was observed at 3 hours postdose and was 8 msec. This increase is not considered to be clinically significant. At the 800 mg dose, peak sitagliptin plasma concentrations were approximately 11 times higher than the peak concentrations following a 100-mg dose.
In patients with type 2 diabetes mellitus administered sitagliptin 100 mg (N=81) or sitagliptin 200 mg (N=63) daily, there were no meaningful changes in QTc interval based on ECG data obtained at the time of expected peak plasma concentration.
Pharmacokinetics
The pharmacokinetics of sitagliptin have been extensively characterized in healthy subjects and patients with type 2 diabetes mellitus. Following a single oral 100-mg dose to healthy volunteers, mean plasma AUC of sitagliptin was 8.52 μM•hr, Cmax was 950 nM, and apparent terminal half-life (t1/2) was 12.4 hours. Plasma AUC of sitagliptin increased in a dose-proportional manner and increased approximately 14% following 100 mg doses at steady-state compared to the first dose. The intra-subject and intersubject coefficients of variation for sitagliptin AUC were small (5.8% and 15.1%). The pharmacokinetics of sitagliptin was generally similar in healthy subjects and in patients with type 2 diabetes mellitus.
Absorption
After oral administration of a 100 mg dose to healthy subjects, sitagliptin was rapidly absorbed with peak plasma concentrations (median Tmax ) occurring 1 to 4 hours postdose. The absolute bioavailability of sitagliptin is approximately 87%.
Effect of Food
Coadministration of a high-fat meal with sitagliptin had no effect on the pharmacokinetics of sitagliptin.
Distribution
The mean volume of distribution at steady state following a single 100-mg intravenous dose of sitagliptin to healthy subjects is approximately 198 liters. The fraction of sitagliptin reversibly bound to plasma proteins is low (38%).
Elimination
Approximately 79% of sitagliptin is excreted unchanged in the urine with metabolism being a minor pathway of elimination. The apparent terminal t1/2 following a 100 mg oral dose of sitagliptin was approximately 12.4 hours and renal clearance was approximately 350 mL/min.
Metabolism
Following a [14C] sitagliptin oral dose, approximately 16% of the radioactivity was excreted as metabolites of sitagliptin. Six metabolites were detected at trace levels and are not expected to contribute to the plasma DPP-4 inhibitory activity of sitagliptin. In vitro studies indicated that the primary enzyme responsible for the limited metabolism of sitagliptin was CYP3A4, with contribution from CYP2C8.
Excretion
Following administration of an oral [14C] sitagliptin dose to healthy subjects, approximately 100% of the administered radioactivity was eliminated in feces (13%) or urine (87%) within one week of dosing.
Elimination of sitagliptin occurs primarily via renal excretion and involves active tubular secretion. Sitagliptin is a substrate for human organic anion transporter-3 (hOAT-3), which may be involved in the renal elimination of sitagliptin. The clinical relevance of hOAT-3 in sitagliptin transport has not been established. Sitagliptin is also a substrate of P-glycoprotein (P-gp), which may also be involved in mediating the renal elimination of sitagliptin. However, cyclosporine, a P-gp inhibitor, did not reduce the renal clearance of sitagliptin.
Specific Populations
Patients With Renal Impairment
An approximately 2-fold increase in the plasma AUC of sitagliptin was observed in patients with moderate renal impairment with eGFR of 30 to less than 45 mL/min/1.73 m2, and an approximately 4-fold increase was observed in patients with severe renal impairment, including patients with ESRD on hemodialysis, as compared to normal healthy control subjects.
Patients With Hepatic Impairment
In patients with moderate hepatic impairment (Child-Pugh score 7 to 9), mean AUC and Cmax of sitagliptin increased approximately 21% and 13%, respectively, compared to healthy matched controls following administration of a single 100-mg dose of sitagliptin. These differences are not considered to be clinically meaningful.
There is no clinical experience in patients with severe hepatic impairment (Child-Pugh score >9).
Effects Of Age, Body Mass Index (BMI), Gender, And Race
Based on a population pharmacokinetic analysis or a composite analysis of available pharmacokinetic data, BMI, gender, and race do not have a clinically meaningful effect on the pharmacokinetics of sitagliptin. When the effects of age on renal function are taken into account, age alone did not have a clinically meaningful impact on the pharmacokinetics of sitagliptin based on a population pharmacokinetic analysis. Elderly subjects (65 to 80 years) had approximately 19% higher plasma concentrations of sitagliptin compared to younger subjects.
Drug Interaction Studies
In Vitro Assessment Of Drug Interactions
Sitagliptin is not an inhibitor of CYP isozymes CYP3A4, 2C8, 2C9, 2D6, 1A2, 2C19 or 2B6, and is not an inducer of CYP3A4. Sitagliptin is a P-gp substrate, but does not inhibit P-gp mediated transport of digoxin. Based on these results, sitagliptin is considered unlikely to cause interactions with other drugs that utilize these pathways.
Sitagliptin is not extensively bound to plasma proteins. Therefore, the propensity of sitagliptin to be involved in clinically meaningful drug-drug interactions mediated by plasma protein binding displacement is very low.
In Vivo Assessment Of Drug Interactions
Effects of Sitagliptin on Other Drugs
In clinical studies, sitagliptin did not meaningfully alter the pharmacokinetics of metformin, glyburide, simvastatin, rosiglitazone, digoxin, warfarin, or an oral contraceptive (ethinyl estradiol and norethindrone) (Table 4), providing in vivo evidence of a low propensity for causing drug interactions with substrates of CYP3A4, CYP2C8, CYP2C9, P-gp, and organic cationic transporter (OCT).
Table 4: Effect of Sitagliptin on Systemic Exposure of Coadministered Drugs
| Coadministered Drug |
Dose of Coadministered Drug* |
Dose of Sitagliptin* |
Geometric Mean Ratio
(ratio with/without sitagliptin)
No Effect = 1 |
|
AUC† |
Cmax |
| Digoxin |
0.25 mg once daily for 10 days |
100 mg‡
once daily for
10 days |
Digoxin |
1.11§ |
1.18 |
| Glyburide |
1.25 mg |
200 mg‡
once daily for
6 days |
Glyburide |
1.09 |
1.01 |
| Simvastatin |
20 mg |
200 mg‡
once daily for
5 days |
Simvastatin |
0.85¶ |
0.80 |
Simvastatin
Acid |
1.12¶ |
1.06 |
| Rosiglitazone |
4 mg |
200 mg‡
once daily for
5 days |
Rosiglitazone |
0.98 |
0.99 |
| Warfarin |
30 mg single dose on day 5 |
200 mg‡
once daily for 11 days |
S(-) Warfarin |
0.95 |
0.89 |
| R(+) Warfarin |
0.99 |
0.89 |
| Ethinyl estradiol and norethindrone |
21 days once daily of 35 μg ethinyl estradiol with norethindrone 0.5 mg x 7 days, 0.75 mg x 7 days, 1 mg x 7 days |
200 mg‡ once daily for 21 days |
Ethinyl estradiol |
0.99 |
0.97 |
| Norethindrone |
1.03 |
0.98 |
| Metformin HCl |
1,000 mg‡ twice daily for 14 days |
50 mg‡ twice daily for 7 days |
Metformin |
1.02# |
0.97 |
*All doses administered as single dose unless otherwise specified.
†AUC is reported as AUC0-∞ unless otherwise specified.
‡Multiple dose.
§AUC0-24hr.
¶AUC0-last.
#AUC0-12hr |
Effects of Other Drugs on Sitagliptin
Clinical data described below suggest that sitagliptin is not susceptible to clinically meaningful interactions by coadministered medications (Table 5).
Table 5: Effect of Coadministered Drugs on Systemic Exposure of Sitagliptin
| Coadministered Drug |
Dose of Coadministered
Drug* |
Dose of Sitagliptin* |
Geometric Mean Ratio
(ratio with/without coadministered drugs)
No Effect = 1 |
|
AUC† |
Cmax |
| Cyclosporine |
600 mg once daily |
100 mg once daily |
Sitagliptin |
1.29 |
1.68 |
| Metformin HCl |
1,000 mg twice daily for 14 days |
50 mg twice daily for 7 days |
Sitagliptin |
1.02§ |
1.05 |
*All doses administered as single dose unless otherwise specified.
†AUC is reported as AUC unless otherwise 0-∞ specified.
‡Multiple dose.
§AUC0-12hr. |
Clinical Studies
There were approximately 5,200 patients with type 2 diabetes mellitus randomized in nine double-blind, placebo-controlled clinical safety and efficacy trials conducted to evaluate the effects of sitagliptin on glycemic control. In a pooled analysis of seven of these trials, the ethnic/racial distribution was approximately 59% White, 20% Hispanic or Latino ethnicity, 10% Asian, 6% Black or African American, and 6% other groups. Patients had an overall mean age of approximately 55 years (range 18 to 87 years). In addition, an active (glipizide)-controlled trial of 52-weeks duration was conducted in 1,172 patients with type 2 diabetes mellitus who had inadequate glycemic control on metformin.
In patients with type 2 diabetes mellitus, treatment with sitagliptin produced clinically significant improvements inA1C, fasting plasma glucose (FPG) and 2-hour post-prandial glucose (PPG) compared to placebo.
Monotherapy
A total of 1,262 patients with type 2 diabetes mellitus participated in two double-blind, placebo-controlled trials, one of 18-week and another of 24-week duration, to evaluate the efficacy and safety of sitagliptin monotherapy. In both monotherapy trials, patients currently on an antihyperglycemic agent discontinued the agent, and underwent a diet, exercise, and drug washout period of about 7 weeks. Patients with inadequate glycemic control (A1C 7% to 10%) after the washout period were randomized after completing a 2-week single-blind placebo run-in period; patients not currently on antihyperglycemic agents (off therapy for at least 8 weeks) with inadequate glycemic control (A1C 7% to 10%) were randomized after completing the 2-week single-blind placebo run-in period. In the 18-week trial, 521 patients were randomized to placebo, sitagliptin 100 mg, or sitagliptin 200 mg, and in the 24-week trial 741 patients were randomized to placebo, sitagliptin 100 mg, or sitagliptin 200 mg. Patients who failed to meet specific glycemic goals during the trials were treated with metformin rescue, added on to placebo or sitagliptin.
Treatment with sitagliptin at 100 mg daily provided significant improvements in A1C, FPG, and 2-hour PPG compared to placebo (Table 6). In the 18-week trial, 9% of patients receiving sitagliptin 100 mg and 17% who received placebo required rescue therapy. In the 24-week trial, 9% of patients receiving sitagliptin 100 mg and 21% of patients receiving placebo required rescue therapy. The improvement in A1C compared to placebo was not affected by gender, age, race, prior antihyperglycemic therapy, or baseline BMI. In these 18-and 24-week trials, among patients who were not on an antihyperglycemic agent at trial entry, the reductions from baseline in A1C were -0.7% and -0.8%, respectively, for those given sitagliptin, and -0.1% and -0.2%, respectively, for those given placebo. Overall, the 200 mg daily dose did not provide greater glycemic efficacy than the 100 mg daily dose. The effect of sitagliptin on lipid endpoints was similar to placebo. Body weight did not increase from baseline with sitagliptin therapy in either trial, compared to a small reduction in patients given placebo.
Table 6: Glycemic Parameters in 18- and 24-Week Placebo-Controlled Trials of Sitagliptin in Patients with Type 2 Diabetes Mellitus*
|
18-Week Trial |
24-Week Trial |
| Sitagliptin 100 mg |
Placebo |
Sitagliptin 100 mg |
Placebo |
| A1C (%) |
N = 193 |
N =103 |
N = 229 |
N = 244 |
| Baseline (mean) |
8 |
8.1 |
8 |
8 |
| Change from baseline (adjusted mean† ) |
-0.5 |
0.1 |
-0.6 |
0.2 |
Difference from placebo
(adjusted mean† ) (95% CI) |
-0.6‡
(-0.8,-0.4) |
|
-0.8‡
(-1.0, -0.6) |
|
| Patients (%) achieving A1C <7% |
69 (36%) |
16
(16%) |
93 (41%) |
41
(17%) |
| FPG (mg/dL) |
N = 201 |
N =107 |
N = 234 |
N = 247 |
| Baseline (mean) |
180 |
184 |
170 |
176 |
| Change from baseline (adjusted mean† ) |
-13 |
7 |
-12 |
5 |
Difference from placebo
(adjusted mean† ) (95% CI) |
-20‡
(-31, -9) |
|
-17‡
(-24, -10) |
|
| 2-hour PPG (mg/dL) |
§ |
§ |
N = 201 |
N = 204 |
| Baseline (mean) |
|
|
257 |
271 |
| Change from baseline (adjusted mean†) |
|
|
-49 |
-2 |
Difference from placebo
(adjusted mean †) (95% CI) |
|
|
-47‡
(-59, -34) |
|
*Intent-to-treat population using last observation on trial prior to metformin rescue therapy.
†Least squares means adjusted for prior antihyperglycemic therapy status and baseline value.
‡p<0.001 compared to placebo.
§Data not available |
Additional Monotherapy Trial
A multinational, randomized, double-blind, placebo-controlled trial was also conducted to assess the safety and tolerability of sitagliptin in 91 patients with type 2 diabetes mellitus and chronic renal insufficiency (creatinine clearance <50 mL/min). Patients with moderate renal insufficiency received 50 mg daily of sitagliptin and those with severe renal insufficiency or with ESRD on hemodialysis or peritoneal dialysis received 25 mg daily. In this trial, the safety and tolerability of sitagliptin were generally similar to placebo. A small increase in serum creatinine was reported in patients with moderate renal insufficiency treated with sitagliptin relative to those on placebo. In addition, the reductions in A1C and FPG with sitagliptin compared to placebo were generally similar to those observed in other monotherapy trials. [see CLINICAL PHARMACOLOGY].
Combination Therapy
Add-On Combination Therapy With Metformin
A total of 701 patients with type 2 diabetes mellitus participated in a 24-week, randomized, double-blind, placebo-controlled trial designed to assess the efficacy of sitagliptin in combination with metformin. Patients already on metformin HCl (N=431) at a dose of at least 1,500 mg per day were randomized after completing a 2-week singleblind placebo run-in period. Patients on metformin and another anti-hyperglycemic agent (N=229) and patients not on any antihyperglycemic agents (off therapy for at least 8 weeks, N=41) were randomized after a run-in period of approximately 10 weeks on metformin HCl (at a dose of at least 1,500 mg per day) in monotherapy. Patients with inadequate glycemic control (A1C 7% to 10%) were randomized to the addition of either 100 mg of sitagliptin or placebo, administered once daily. Patients who failed to meet specific glycemic goals during the trials were treated with pioglitazone rescue.
In combination with metformin, sitagliptin provided significant improvements in A1C, FPG, and 2-hour PPG compared to placebo with metformin (Table 7). Rescue glycemic therapy was used in 5% of patients treated with sitagliptin 100 mg and 14% of patients treated with placebo. A similar decrease in body weight was observed for both treatment groups.
Table 7: Glycemic Parameters at Final Visit (24-Week Trial) for Sitagliptin in Add-on Combination Therapy with Metformin*
|
Sitagliptin 100 mg + Metformin |
Placebo +
Metformin |
| A1C (%) |
N = 453 |
N = 224 |
| Baseline (mean) |
8 |
8 |
| Change from baseline (adjusted mean† ) |
-0.7 |
-0 |
Difference from placebo + metformin
(adjusted mean† ) (95% CI) |
-0.7‡
(-0.8, -0.5) |
|
| Patients (%) achieving A1C <7% |
213 (47%) |
41 (18%) |
| FPG (mg/dL) |
N = 454 |
N = 226 |
| Baseline (mean) |
170 |
174 |
| Change from baseline (adjusted mean †) |
-17 |
9 |
| Difference from placebo + metformin (adjusted mean† ) (95% CI) |
-25‡
(-31, -20) |
|
| 2-hour PPG (mg/dL) |
N = 387 |
N = 182 |
| Baseline (mean) |
275 |
272 |
| Change from baseline (adjusted mean†) |
-62 |
-11 |
| Difference from placebo + metformin (adjusted mean†) (95% CI) |
-51‡
(-61, -41) |
|
*Intent-to-treat population using last observation on trial prior to pioglitazone rescue therapy.
†Least squares means adjusted for prior antihyperglycemic therapy and baseline value.
‡p<0.001 compared to placebo + metformin. |
Initial Combination Therapy With Metformin
A total of 1,091 patients with type 2 diabetes mellitus and inadequate glycemic control on diet and exercise participated in a 24-week, randomized, double-blind, placebocontrolled factorial trial designed to assess the efficacy of sitagliptin as initial therapy in combination with metformin. Patients on an antihyperglycemic agent (N=541) discontinued the agent, and underwent a diet, exercise, and drug washout period of up to 12 weeks duration. After the washout period, patients with inadequate glycemic control (A1C 7.5% to 11%) were randomized after completing a 2-week single-blind placebo run-in period. Patients not on antihyperglycemic agents at trial entry (N=550) with inadequate glycemic control (A1C 7.5% to 11%) immediately entered the 2-week single-blind placebo run-in period and then were randomized. Approximately equal numbers of patients were randomized to receive initial therapy with placebo, 100 mg of sitagliptin once daily, 500 mg or 1,000 mg of metformin HCl twice daily, or 50 mg of sitagliptin twice daily in combination with 500 mg or 1,000 mg of metformin HCl twice daily. Patients who failed to meet specific glycemic goals during the trial were treated with glyburide (glibenclamide) rescue.
Initial therapy with the combination of sitagliptin and metformin provided significant improvements in A1C, FPG, and 2-hour PPG compared to placebo, to metformin alone, and to sitagliptin alone (Table 8, Figure 1). Mean reductions from baseline in A1C were generally greater for patients with higher baseline A1C values. For patients not on an antihyperglycemic agent at trial entry, mean reductions from baseline in A1C were: sitagliptin 100 mg once daily, -1.1%; metformin HCl 500 mg bid, -1.1%; metformin HCl 1,000 mg bid, -1.2%; sitagliptin 50 mg bid with metformin HCl 500 mg bid, -1.6%; sitagliptin 50 mg bid with metformin HCl 1,000 mg bid, -1.9%; and for patients receiving placebo, -0.2%. Lipid effects were generally neutral. The decrease in body weight in the groups given sitagliptin in combination with metformin was similar to that in the groups given metformin alone or placebo.
Table 8: Glycemic Parameters at Final Visit (24-Week Trial) for Sitagliptin and Metformin, Alone and in Combination as Initial Therapy*
|
Placebo |
Sitagliptin
100 mg
QD |
Metformin
HCl
500 mg bid |
Metformin
HCl
1,000 mg bid |
Sitagliptin
50 mg bid
+
Metformin
HCl
500 mg bid |
Sitagliptin
50 mg bid
+
Metformin
HCl
1,000 mg bid |
| A1C (%) |
N =165 |
N = 175 |
N = 178 |
N = 177 |
N = 183 |
N = 178 |
| Baseline (mean) |
8.7 |
8.9 |
8.9 |
8.7 |
8.8 |
8.8 |
| Change from baseline (adjusted mean† ) |
0.2 |
-0.7 |
-0.8 |
-1.1 |
-1.4 |
-1.9 |
Difference from placebo (adjusted mean†)
(95% CI) |
|
-0.8‡
(-1.1, -0.6) |
-1‡
(-1.2, -0.8) |
-1.3‡
(-1.5, -1.1) |
-1.6‡
(-1.8, -1.3) |
-2.1‡
(-2.3, -1.8) |
| Patients (%) achieving A1C <7% |
15 (9%) |
35 (20%) |
41 (23%) |
68 (38%) |
79 (43%) |
118 (66%) |
| % Patients receiving rescue medication |
32 |
21 |
17 |
12 |
8 |
2 |
| FPG (mg/dL) |
N = 169 |
N = 178 |
N = 179 |
N = 179 |
N = 183 |
N = 180 |
| Baseline (mean) |
196 |
201 |
205 |
197 |
204 |
197 |
| Change from baseline (adjusted mean† ) |
6 |
-17 |
-27 |
-29 |
-47 |
-64 |
Difference from placebo (adjusted mean †)
(95% CI) |
|
-23‡
(-33, -14) |
-33‡
(-43, -24) |
-35‡
(-45, -26) |
-53‡
(-62, -43) |
-70‡
(-79, -60) |
2-hour PPG
(mg/dL) |
N = 129 |
N = 136 |
N = 141 |
N = 138 |
N = 147 |
N = 152 |
| Baseline (mean) |
277 |
285 |
293 |
283 |
292 |
287 |
| Change from baseline (adjusted mean † ) |
0 |
-52 |
-53 |
-78 |
-93 |
-117 |
Difference from placebo (adjusted mean †)
(95% CI) |
|
-52‡
(-67, -37) |
-54‡
(-69, -39) |
-78‡
(-93, -63) |
-93‡
(-107, -78) |
-117‡
(-131, -102) |
*Intent-to-treat population using last observation on trial prior to glyburide (glibenclamide) rescue therapy.
†Least squares means adjusted for prior antihyperglycemic therapy status and baseline value.
‡p<0.001 compared to placebo. |
Figure 1: Mean Change from Baseline for A1C (%) over 24 Weeks with Sitagliptin and Metformin, Alone and in Combination as Initial Therapy in Patients with Type 2 Diabetes Mellitus
 |
| *All Patients Treated Population: least squares means adjusted for prior antihyperglycemic therapy and baseline value. |
Initial combination therapy or maintenance of combination therapy may not be appropriate for all patients. These management options are left to the discretion of the health care provider.
Active-Controlled Trial Vs Glipizide In Combination With Metformin
The efficacy of sitagliptin was evaluated in a 52-week, double-blind, glipizide-controlled noninferiority trial in patients with type 2 diabetes mellitus. Patients not on treatment or on other antihyperglycemic agents entered a run-in treatment period of up to 12 weeks duration with metformin HCl monotherapy (dose of ≥1,500 mg per day) which included washout of medications other than metformin, if applicable. After the run-in period, those with inadequate glycemic control (A1C 6.5% to 10%) were randomized 1:1 to the addition of sitagliptin 100 mg once daily or glipizide for 52 weeks. Patients receiving glipizide were given an initial dosage of 5 mg/day and then electively titrated over the next 18 weeks to a maximum dosage of 20 mg/day as needed to optimize glycemic control. Thereafter, the glipizide dose was to be kept constant, except for down-titration to prevent hypoglycemia. The mean dose of glipizide after the titration period was 10 mg.
After 52 weeks, sitagliptin and glipizide had similar mean reductions from baseline in A1C in the intent-to-treat analysis (Table 9). These results were consistent with the per protocol analysis (Figure 2). A conclusion in favor of the non-inferiority of sitagliptin to glipizide may be limited to patients with baseline A1C comparable to those included in the trial (over 70% of patients had baseline A1C <8% and over 90% had A1C <9%).
Table 9: Glycemic Parameters in a 52-Week Trial Comparing Sitagliptin to Glipizide as Add-On Therapy in Patients Inadequately Controlled on Metformin (Intent-to-Treat Population)*
|
Sitagliptin 100 mg |
Glipizide |
| A1C (%) |
N = 576 |
N = 559 |
| Baseline (mean) |
7.7 |
7.6 |
| Change from baseline (adjusted mean† ) |
-0.5 |
-0.6 |
| FPG (mg/dL) |
N = 583 |
N = 568 |
| Baseline (mean) |
166 |
164 |
| Change from baseline (adjusted mean† ) |
-8 |
-8 |
*The intent-to-treat analysis used the patients' last observation in the trial prior to discontinuation.
†Least squares means adjusted for prior antihyperglycemic therapy status and baseline A1C value. |
Figure 2: Mean Change from Baseline for A1C (%) Over 52 Weeks in a Trial
 |
| * The per protocol population (mean baseline A1C of 7.5%) included patients without major protocol violations who had observations at baseline and at Week 52. |
The incidence of hypoglycemia in the Sitagliptin group (4.9%) was significantly (p<0.001) lower than that in the glipizide group (32%). Patients treated with Sitagliptin exhibited a significant mean decrease from baseline in body weight compared to a significant weight gain in patients administered glipizide (-1.5 kg vs +1.1 kg).
Add-On Combination Therapy With Pioglitazone
A total of 353 patients with type 2 diabetes mellitus participated in a 24-week, randomized, double-blind, placebo-controlled trial designed to assess the efficacy of sitagliptin in combination with pioglitazone. Patients on any oral antihyperglycemic agent in monotherapy (N=212) or on a PPARγ agent in combination therapy (N=106) or not on an antihyperglycemic agent (off therapy for at least 8 weeks, N=34) were switched to monotherapy with pioglitazone (at a dose of 30 to 45 mg per day) and completed a run-in period of approximately 12 weeks in duration. After the run-in period on pioglitazone monotherapy, patients with inadequate glycemic control (A1C 7% to 10%) were randomized to the addition of either 100 mg of sitagliptin or placebo, administered once daily. Patients who failed to meet specific glycemic goals during the trials were treated with metformin rescue. Glycemic endpoints measured were A1C and fasting glucose.
In combination with pioglitazone, sitagliptin provided significant improvements in A1C and FPG compared to placebo with pioglitazone (Table 10). Rescue therapy was used in 7% of patients treated with sitagliptin 100 mg and 14% of patients treated with placebo. There was no significant difference between sitagliptin and placebo in body weight change.
Table 10: Glycemic Parameters at Final Visit (24-Week Trial) for Sitagliptin in Add-on Combination Therapy with Pioglitazone*
|
Sitagliptin 100 mg + Pioglitazone |
Placebo + Pioglitazone |
| A1C (%) |
N = 163 |
N = 174 |
| Baseline (mean) |
8.1 |
8.0 |
| Change from baseline (adjusted mean† ) |
-0.9 |
-0.2 |
| Difference from placebo + pioglitazone (adjusted mean†) (95% CI) |
-0.7‡
(-0.9, -0.5) |
|
| Patients (%) achieving A1C <7% |
74 (45%) |
40 (23%) |
| FPG (mg/dL) |
N = 163 |
N = 174 |
| Baseline (mean) |
168 |
166 |
| Change from baseline (adjusted mean †) |
-17 |
1 |
| Difference from placebo + pioglitazone (adjusted mean ) (95% CI) |
-18‡ (-24, -11) |
|
*Intent-to-treat population using last observation on trial prior to metformin rescue therapy.
†Least squares means adjusted for prior antihyperglycemic therapy status and baseline value.
‡p<0.001 compared to placebo + pioglitazone |
Initial Combination Therapy With Pioglitazone
A total of 520 patients with type 2 diabetes mellitus and inadequate glycemic control on diet and exercise participated in a 24-week, randomized, double-blind trial designed to assess the efficacy of sitagliptin as initial therapy in combination with pioglitazone. Patients not on antihyperglycemic agents at trial entry (<4 weeks cumulative therapy over the past 2 years, and with no treatment over the prior 4 months) with inadequate glycemic control (A1C 8% to 12%) immediately entered the 2-week single-blind placebo run-in period and then were randomized. Approximately equal numbers of patients were randomized to receive initial therapy with 100 mg of sitagliptin in combination with 30 mg of pioglitazone once daily or 30 mg of pioglitazone once daily as monotherapy. There was no glycemic rescue therapy in this trial.
Initial therapy with the combination of sitagliptin and pioglitazone provided significant improvements in A1C, FPG, and 2-hour PPG compared to pioglitazone monotherapy (Table 11). The improvement in A1C was generally consistent across subgroups defined by gender, age, race, baseline BMI, baseline A1C, or duration of disease. In this trial, patients treated with ZITUVIO in combination with pioglitazone had a mean increase in body weight of 1.1 kg compared to pioglitazone alone (3 kg vs. 1.9 kg). Lipid effects were generally neutral.
Table 11: Glycemic Parameters at Final Visit (24-Week Trial) for Sitagliptin in Combination with Pioglitazone as Initial Therapy*
|
Sitagliptin 100 mg + Pioglitazone |
Pioglitazone |
| A1C (%) |
N = 251 |
N = 246 |
| Baseline (mean) |
9.5 |
9.4 |
| Change from baseline (adjusted mean† ) |
-2.4 |
-1.5 |
| Difference from pioglitazone (adjusted mean †) (95% CI) |
-0.9‡
(-1.1, -0.7) |
|
| Patients (%) achieving A1C <7% |
151 (60%) |
68 (28%) |
| FPG (mg/dL) |
N = 256 |
N = 253 |
| Baseline (mean) |
203 |
201 |
| Change from baseline (adjusted mean † ) |
-63 |
-40 |
| Difference from pioglitazone (adjusted mean †) (95% CI) |
-23‡
(-30, -15) |
|
| 2-hour PPG (mg/dL) |
N = 216 |
N = 211 |
| Baseline (mean) |
283 |
284 |
| Change from baseline (adjusted mean †) |
-114 |
-69 |
| Difference from pioglitazone (adjusted mean† ) (95% CI) |
-45‡
(-57, -32) |
|
*Intent-to-treat population using last observation on trial.
†Least squares means adjusted for baseline value.
‡p<0.001 compared to placebo + pioglitazone. |
Add-On Combination Therapy With Metformin And Rosiglitazone
A total of 278 patients with type 2 diabetes mellitus participated in a 54-week, randomized, double-blind, placebo-controlled trial designed to assess the efficacy of sitagliptin in combination with metformin and rosiglitazone. Patients on dual therapy with metformin HCl ≥1,500 mg/day and rosiglitazone ≥4 mg/day or with metformin HCl ≥1,500 mg/day and pioglitazone ≥30 mg/day (switched to rosiglitazone ≥4 mg/day) entered a dose-stable run-in period of 6 weeks. Patients on other dual therapy were switched to metformin HCl ≥1,500 mg/day and rosiglitazone ≥4 mg/day in a dose titration/stabilization run-in period of up to 20 weeks in duration. After the run-in period, patients with inadequate glycemic control (A1C 7.5% to 11%) were randomized 2:1 to the addition of either 100 mg of sitagliptin or placebo, administered once daily. Patients who failed to meet specific glycemic goals during the trial were treated with glipizide (or other sulfonylurea) rescue. The primary time point for evaluation of glycemic parameters was Week 18.
In combination with metformin and rosiglitazone, sitagliptin provided significant improvements in A1C, FPG, and 2-hour PPG compared to placebo with metformin and rosiglitazone (Table 12) at Week 18. At Week 54, mean reduction in A1C was -1.0% for patients treated with sitagliptin and -0.3% for patients treated with placebo in an analysis based on the intent-to-treat population. Rescue therapy was used in 18% of patients treated with sitagliptin 100 mg and 40% of patients treated with placebo. There was no significant difference between sitagliptin and placebo in body weight change.
Table 12: Glycemic Parameters at Week 18 for Sitagliptin in Add-on Combination Therapy with Metformin and Rosiglitazone*
|
Sitagliptin 100 mg + Pioglitazone |
Pioglitazone |
| A1C (%) |
N = 251 |
N = 246 |
| Baseline (mean) |
9.5 |
9.4 |
| Change from baseline (adjusted mean† ) |
-2.4 |
-1.5 |
| Difference from pioglitazone (adjusted mean† ) (95% CI) |
-0.9‡
(-1.1, -0.7) |
|
| Patients (%) achieving A1C <7% |
151 (60%) |
68 (28%) |
| FPG (mg/dL) |
N = 256 |
N = 253 |
| Baseline (mean) |
203 |
201 |
| Change from baseline (adjusted mean† ) |
-63 |
-40 |
| Difference from pioglitazone (adjusted mean† ) (95% CI) |
-23‡
(-30, -15) |
|
| 2-hour PPG (mg/dL) |
N = 216 |
N = 211 |
| Baseline (mean) |
283 |
284 |
| Change from baseline (adjusted mean† ) |
-114 |
-69 |
| Difference from pioglitazone (adjusted mean †) (95% CI) |
-45‡
(-57, -32) |
|
*Intent-to-treat population using last observation on trial.
†Least squares means adjusted for baseline value.
‡p<0.001 compared to placebo + pioglitazone. |
Add-On Combination Therapy With Glimepiride, With Or Without Metformin
A total of 441 patients with type 2 diabetes mellitus participated in a 24-week, randomized, double-blind, placebo-controlled trial designed to assess the efficacy of sitagliptin in combination with glimepiride, with or without metformin. Patients entered a run-in treatment period on glimepiride (≥4 mg per day) alone or glimepiride in combination with metformin HCl (≥1,500 mg per day). After a dose-titration and dosestable run-in period of up to 16 weeks and a 2-week placebo run-in period, patients with inadequate glycemic control (A1C 7.5% to 10.5%) were randomized to the addition of either 100 mg of sitagliptin or placebo, administered once daily. Patients who failed to meet specific glycemic goals during the trials were treated with pioglitazone rescue.
In combination with glimepiride, with or without metformin, sitagliptin provided significant improvements in A1C and FPG compared to placebo (Table 13). In the entire trial population (patients on sitagliptin in combination with glimepiride and patients on sitagliptin in combination with glimepiride and metformin), a mean reduction from baseline relative to placebo in A1C of -0.7% and in FPG of -20 mg/dL was seen. Rescue therapy was used in 12% of patients treated with sitagliptin 100 mg and 27% of patients treated with placebo. In this trial, patients treated with sitagliptin had a mean increase in body weight of 1.1 kg vs. placebo (+0.8 kg vs. -0.4 kg). In addition, there was an increased rate of hypoglycemia. [see WARNINGS AND PRECAUTIONS and ADVERSE REACTIONS ].
Table 13: Glycemic Parameters at Final Visit (24-Week Trial) for Sitagliptin as Add-On Combination Therapy with Glimepiride, with or without Metformin*
|
Sitagliptin 100 mg + Glimepiride |
Placebo + Glimepiride |
Sitagliptin 100 mg + Glimepiride + Metformin |
Placebo + Glimepiride + Metformin |
| A1C (%) |
N = 102 |
N = 103 |
N = 115 |
N = 105 |
| Baseline (mean) |
8.4 |
8.5 |
8.3 |
8.3 |
Change from baseline
(adjusted mean† ) |
-0.3 |
-0.3 |
-0.6 |
-0.3 |
Difference from placebo
(adjusted mean† ) (95%
CI) |
-0.6‡
(-0.8, -0.3) |
|
-0.9‡
(-1.1, -0.7) |
|
Patients (%) achieving
A1C <7% |
11 (11%) |
9 (9%) |
26 (23%) |
1 (1%) |
| FPG (mg/dL) |
N = 104 |
N = 104 |
N = 115 |
N = 109 |
| Baseline (mean) |
183 |
185 |
179 |
179 |
Change from baseline
(adjusted mean† ) |
-1 |
18 |
-8 |
13 |
Difference from placebo (adjusted mean †) (95%
CI) |
-19§
(-32, -7) |
|
-21‡
(-32, -10) |
|
*Intent-to-treat population using last observation on trial prior to pioglitazone rescue therapy.
†Least squares means adjusted for prior antihyperglycemic therapy status and baseline value.
‡p<0.001 compared to placebo.
§p<0.01 compared to placebo |
Add-On Combination Therapy With Insulin (With Or Without Metformin)
A total of 641 patients with type 2 diabetes mellitus participated in a 24-week,randomized, double-blind, placebo-controlled trial designed to assess the efficacy of sitagliptin as add-on to insulin therapy (with or without metformin). The racial distribution in this trial was approximately 70% White, 18% Asian, 7% Black or African American, and 5% other groups. Approximately 14% of the patients in this trial were Hispanic or Latino. Patients entered a 2-week, single-blind run-in treatment period on pre-mixed, long-acting, or intermediate-acting insulin, with or without metformin HCl (≥1,500 mg per day). Patients using short-acting insulins were excluded unless the short-acting insulin was administered as part of a pre-mixed insulin. After the run-in period, patients with inadequate glycemic control (A1C 7.5% to 11%) were randomized to the addition of either 100 mg of ZITUVIO or placebo, administered once daily. Patients were on a stable dose of insulin prior to enrolment with no changes in insulin dose permitted during the run-in period. Patients who failed to meet specific glycemic goals during the double-blind treatment period were to have up-titration of the background insulin dose as rescue therapy.
The median daily insulin dose at baseline was 42 units in the patients treated with sitagliptin and 45 units in the placebo-treated patients. The median change from baseline in daily dose of insulin was zero for both groups at the end of the trial. In combination with insulin (with or without metformin), sitagliptin provided significant improvements in A1C, FPG, and 2-hour PPG compared to placebo (Table 14). Both treatment groups had an adjusted mean increase in body weight of 0.1 kg from baseline to Week 24. There was an increased rate of hypoglycemia in patients treated with sitagliptin. [see WARNINGS AND PRECAUTIONS and ADVERSE REACTIONS].
Table 14: Glycemic Parameters at Final Visit (24-Week Trial) for Sitagliptin as Add-on Combination Therapy with Insulin*
|
Sitagliptin 100 mg + Insulin
(+/- Metformin) |
Placebo + Insulin
(+/- Metformin) |
| A1C (%) |
N = 305 |
N = 312 |
| Baseline (mean) |
8.7 |
8.76 |
| Change from baseline (adjusted mean† ) |
-0.6 |
-0.1 |
Difference from placebo (adjusted mean †,‡ )
(95% CI) |
-0.6§
(-0.7, -0.4) |
|
| Patients (%) achieving A1C <7% |
39 (12.8%) |
16 (5.1%) |
| FPG (mg/dL) |
N = 310 |
N = 313 |
| Baseline (mean) |
176 |
179 |
| Change from baseline (adjusted mean† ) |
-18 |
-4 |
Difference from placebo (adjusted mean† )
(95% CI) |
-15§
(-23, -7) |
|
| 2-hour PPG (mg/dL) |
N = 240 |
N = 257 |
| Baseline (mean) |
291 |
292 |
| Change from baseline (adjusted mean† ) |
-31 |
5 |
| Difference from placebo (adjusted mean †) (95% CI) |
-36§
(-47, -25) |
|
*Intent-to-treat population using last observation on trial prior to rescue therapy.
†Least squares means adjusted for metformin use at the screening visit (yes/no), type of insulin used at the screening visit (pre-mixed vs. non-pre-mixed [intermediate-or long-acting]), and baseline value.
‡Treatment by stratum interaction was not significant (p>0.10) for metformin stratum and for insulin stratum.
§p<0.001 compared to placebo |
Maintenance Of Sitagliptin During Initiation And Titration Of Insulin Glargine
A total of 746 patients with type 2 diabetes mellitus (mean baseline HbA1C 8.8%, disease duration 10.8 years) participated in a 30-week, randomized, double-blind, placebocontrolled trial to assess the efficacy and safety of continuing sitagliptin during the initiation and uptitration of insulin glargine. Patients who were on a stable dose of metformin (≥1,500 mg/day) in combination with a DPP-4 inhibitor and/or sulfonylurea but with inadequate glycemic control (A1C 7.5% to 11%) were enrolled in the trial. Those on metformin and sitagliptin (100 mg/day) directly entered the double-blind treatment period; those on another DPP-4 inhibitor and/or on a sulfonylurea entered a 4 to 8 week run-in period in which they were maintained on metformin and switched to sitagliptin (100 mg); other DPP-4 inhibitors and sulfonylureas were discontinued. At randomization patients were randomized either to continue sitagliptin or to discontinue sitagliptin and switch to a matching placebo. On the day of randomization, insulin glargine was initiated at a dose of 10 units subcutaneously in the evening. Patients were instructed to uptitrate their insulin dose in the evening based on fasting blood glucose measurements to achieve a target of 72 to 100 mg/dL.
At 30 weeks, the mean reduction in A1C was greater in the sitagliptin group than in the placebo group (Table 15). At the end of the trial, 27.3% of patients in the sitagliptin group and 27.3% in the placebo group had a fasting plasma glucose (FPG) in the target range; there was no significant difference in insulin dose between arms.
Table 15: Change from Baseline in A1C and FPG at Week 30 in the Maintenance of Sitagliptin During Initiation and Titration of Insulin Glargine Trial
|
Sitagliptin 100 mg +Metformin + Insulin Glargine |
Placebo +Metformin + Insulin Glargine |
| A1C (%) |
N = 373* |
N = 370* |
| Baseline (mean) |
8.8 |
8.8 |
| Week 30 (mean) |
6.9 |
7.3 |
Change from baseline (adjusted
mean)† |
-1.9 |
-1.4 |
| Difference from placebo (adjusted mean) (95% CI)† |
-0.4 (-0.6, -0.3)‡ |
|
| Patients (%) with A1C <7% |
202 (54.2%) |
131 (35.4%) |
| FPG (mg/dL) |
N = 373* |
N = 370* |
| Baseline (mean) |
199 |
201 |
| Week 30 (mean) |
118 |
123 |
| Change from baseline (adjusted mean)† |
-81 |
-76 |
*N is the number of randomized and treated patients.
†Analysis of Covariance including all post-baseline data regardless of rescue or treatment discontinuation. Model estimates calculated using multiple imputation to model washout of the treatment effect using placebo data for all subjects having missing Week 30 data.
‡p<0.001 compared to placebo. |