Dipeptidyl peptidase-4 inhibitor

Inhibitors of dipeptidyl peptidase 4 (DPP-4 inhibitors or gliptins) are a class of oral hypoglycemics that block the enzyme dipeptidyl peptidase-4 (DPP-4). They can be used to treat diabetes mellitus type 2.
The first agent of the class – sitagliptin – was approved by the FDA in 2006.
Glucagon increases blood glucose levels, and DPP-4 inhibitors reduce glucagon and blood glucose levels. The mechanism of DPP-4 inhibitors is to increase incretin levels (GLP-1 and GIP), which inhibit glucagon release, which in turn increases insulin secretion, decreases gastric emptying, and decreases blood glucose levels.
A 2018 meta-analysis found no favorable effect of DPP-4 inhibitors on all-cause mortality, cardiovascular mortality, myocardial infarction or stroke in patients with type 2 diabetes.
Examples.
Drugs belonging to this class are:
Other chemicals which may inhibit DPP-4 include:
Adverse effects.
In those already taking sulphonylureas, there is an increased risk of low blood sugar when taking a medicine in the DPP-4 drug class.
Adverse effects include nasopharyngitis, headache, nausea, heart failure, hypersensitivity and skin reactions. 
The U.S. Food and Drug Administration (FDA) is warning that the type 2 diabetes medicines like sitagliptin, saxagliptin, linagliptin, and alogliptin may cause joint pain that can be severe and disabling. FDA has added a new Warning and Precaution about this risk to the labels of all medicines in this drug class, called dipeptidyl peptidase-4 (DPP-4) inhibitors. However, studies assessing risk of rheumatoid arthritis among DPP-4 inhibitor users have been inconclusive.
A 2014 review found increased risk of heart failure with saxagliptin and alogliptin, prompting the FDA in 2016 to add warnings to the relevant drug labels.
A 2018 meta analysis showed that use of DPP-4 inhibitors was associated with a 58% increased risk of developing acute pancreatitis compared with placebo or no treatment.
A 2018 observational study suggested an elevated risk of developing inflammatory bowel disease (specifically, ulcerative colitis), reaching a peak after three to four years of use and decreasing after more than four years of use.
Cancer.
In response to a report of precancerous changes in the pancreases of rats and organ donors treated with the DPP-4 inhibitor sitagliptin, the United States FDA and the European Medicines Agency each undertook independent reviews of all clinical and preclinical data related to the possible association of DPP-4 inhibitors with pancreatic cancer. In a joint letter to the New England Journal of Medicine, the agencies stated that they had not yet reached a final conclusion regarding a possible causative relationship.
A 2014 meta-analysis found no evidence for increased pancreatic cancer risk in people treated with DPP-4 inhibitors, but owing to the modest amount of data available, was not able to completely exclude possible risk.
Combination drugs.
Some DPP-4 inhibitor drugs have received approval from the FDA to be used with metformin concomitantly with additive effect to increase the level of glucagon-like peptide 1 (GLP-1) which also decreases hepatic glucose production.