Results from three Phase II studies showed that Sitagliptin ( MK-0431 ), an investigational medicine in a potentially new class of agents for the treatment for diabetes called DPP-IV ( dipeptidyl peptidase IV ) inhibitors significantly improved glycemic control in patients with type 2 diabetes compared to placebo.
In addition, Sitagliptin was generally well tolerated, with overall adverse events similar to placebo.


In a double-blind, placebo-controlled, parallel group study, 552 patients with type 2 diabetes were randomized to one of five treatment groups: placebo: Sitagliptin ( 25 mg, 50 mg, or 100 mg ) once daily; or Sitagliptin 50 mg twice daily.

Prior to randomization, patients were enrolled in a diet and exercise regimen and, if taking other anti-hyperglycemic agents, a drug wash off period was conducted.
Patients had predominantly mild to moderate hyperglycemia.
The mean baseline HbA1c ( A1C ) was approximately 7.7 percent to 7.8 percent, with 28.8 percent of patients having a baseline A1C at or less than 7.0 percent.


After 12 weeks, treatment with Sitagliptin led to a significant mean reduction in A1C from baseline as compared to placebo with an average reduction of 0.6 percent observed in the Sitagliptin 100 mg once daily group of which the majority of these patients had mild to moderate hyperglycemia.

Observed differences in A1C between patients taking Sitagliptin and patients administered placebo were greatest in those patients with higher baseline A1C at randomization.
In patients with a A1C baseline of between 8.5 and 10 percent, a mean reduction of 0.8 percent, relative to placebo, was seen in patients randomized to the 100 mg once daily dose of Sitagliptin using data carried forward, that is including patients whether they completed the study or not.
A mean 1.1 percent reduction in A1C relative to placebo was observed in patients taking Sitagliptin 100 mg using data from patients who completed the study as per study protocol.

Treatment with Sitagliptin was well tolerated and resulted in no significant weight gain. One adverse event of hypoglycemia was reported in each of the four Sitagliptin treatment groups, compared to no adverse events of hypoglycemia reported in the placebo group.


The second dose finding study presented was a randomized, double-blind, placebo-controlled study, which evaluated the efficacy and tolerability of Sitagliptin in 743 patients with type 2 diabetes.
In this study, patients were randomized to one of six treatment groups: placebo: Sitagliptin ( 5 mg, 12.5 mg, 25 mg, or 50 mg twice daily ); or the sulfonylurea Glipizide 5 mg titrated to 20 mg daily.

Prior to randomization, patients were enrolled in a diet and exercise regimen and, if taking other antihyperglycemic agents, a drug wash off period.
Patients were characterized as having predominantly mild to moderate hyperglycemia.
The mean A1C baseline was 7.8 percent to 7.9 percent, with 20.8 percent of patients having a baseline A1C at or less than 7.0 percent.

After a 12-week treatment period, Sitagliptin significantly reduced A1C from baseline compared to placebo.
The largest mean reduction in the patients treated with Sitagliptin was 0.77 percent, in the 50 mg twice-daily treatment group.
Patients taking Glipizide showed a 1.0 percent reduction from baseline in A1C.

Treatment with Sitagliptin was well tolerated and, like placebo, resulted in no significant weight gain.
Patients treated with Glipizide had an average weight gain of 1.1 kilogram relative to placebo.
Adverse event reports of hypoglycemia were observed in four percent of patients taking Sitagliptin, 17 percent of patients taking Glipizide and two percent of patients taking placebo.


A Phase II randomized, double-blind, placebo-controlled, four-week crossover study evaluated the efficacy and tolerability of Sitagliptin in combination with Metformin versus Metformin plus placebo.

Twenty-eight patients with a mean baseline A1C of 7.7 percent receiving Metformin were randomized into one of two treatment groups following a five-week diet and exercise run in period; they received Metformin plus placebo or Metformin plus Sitagliptin 50 mg twice daily. At the end of the first four-week treatment period, patients given metformin plus placebo were then given Sitagliptin 50 mg twice daily and vice versa.

After the first four-week treatment period, results of the 24-hour weighted mean glucose for patients taking Metformin plus Sitagliptin 50 mg twice daily was 125 mg/dL as compared to 158 mg/dL in patients taking Metformin plus placebo. This corresponds to a mean glucose reduction of 33 mg/dL.

The combination of Sitagliptin and Metformin was generally well tolerated with no clinically meaningful differences in the occurrence of adverse events when compared to Metformin alone.


Sitagliptin is an investigational medicine now under development by Merck & Co., Inc. for the treatment of type 2 diabetes.
If approved, Sitagliptin would be a member of a potentially new class of antihyperglycemic agents called DPP-IV inhibitors, which block the DPP-IV enzyme that normally inactivates the incretin gut hormones GLP-1 and GIP.
Sitagliptin is thought to lower blood glucose levels by enhancing the level of active incretin hormones which increase insulin from pancreatic beta-cells and decrease glucagon from pancreatic alpha cells in a glucose-dependent manner.

Source: Merck & Co, 2005


XagenaMedicine2005