Question: What is saxagliptin's role in diabetes treatment trials compared to vildagliptin and sitagliptin?

Context:
 up to October 1st, 2013.", "Saxagliptin.", "Vildagliptin.", "an extensive Medline, Embase and Cochrane Database search for 'vildagliptin', 'sitagliptin', 'saxagliptin', 'alogliptin', 'linagliptin' and 'dutogliptin' was performed up to 1 March 2013.", "An extensive Medline and Embase search for 'vildagliptin', 'sitagliptin', 'saxagliptin', 'alogliptin', 'linagliptin', and 'dutogliptin' was performed, collecting all randomized clinical trials on humans up to March 1, 2011.", "An extensive Medline, Embase, and Cochrane Database search for \"vildagliptin\", \"sitagliptin\", \"saxagliptin\", \"alogliptin\", \"linagliptin\", and \"dutogliptin\" was performed, collecting all randomized clinical trials on humans up to October 1st, 2013.", "the words \"sitagliptin,\" \"vildagliptin,\" \"saxagliptin,\" \"alogliptin,\" \"linagliptin,\" and/or \"dutogliptin.\" Completed but unpublished trials were identified through a search of the ClinicalTrials.gov website,", "Sitagliptin (MK- 0431), Saxagliptin, Melogliptin, Linagliptin (BI-1356), Dutogliptin, Carmegliptin, Alogliptin and Vildagliptin (LAF237).", "Of these, two have been approved for clinical use in the United States: sitagliptin and saxagliptin. Additionally, linagliptin, vildagliptin and alogliptin are currently in phase III development in the United States while studies with another DPP IV inhibitor, dutogliptin, have been terminated (2).", "We conducted a search on MEDLINE, Embase and Cochrane Collaborative database for randomized controlled trials (RCTs) of DPP-4 inhibitors and metformin as initial combination therapy or as monotherapy in patients with T2DM by the end of December 2012, using the key words 'alogliptin', 'dutogliptin', 'linagliptin', 'saxagliptin', 'sitagliptin', 'vildagliptin' and 'metformin'.", "Given as monotherapy, linagliptin, sitagliptin, and vildagliptin (but not saxagliptin) met the equivalence criterion when compared with one another. Given in combination with metformin, linagliptin, saxagliptin, sitagliptin, and vildagliptin showed an equivalent effect whereas alogliptin did not satisfy the equivalence criterion.", "Additionally, linagliptin, vildagliptin and alogliptin are currently in phase III development in the United States while studies with another DPP IV inhibitor, dutogliptin, have been terminated (2). Alogliptin was approved for use in Japan under the trade name Nesina\u00ae in April 2010 (3).", "Any DPP-4 inhibitor (vildagliptin, sitagliptin, saxagliptin, linagliptin or alogliptin).", "An extensive search of Medline and the Cochrane Library (any date up to December 31, 2010, restricted to randomized clinical trials, published in English) was performed for all trials containing, in any field, the words \"sitagliptin,\" \"vildagliptin,\" \"saxagliptin,\" \"alogliptin,\" \"linagliptin,\" and/or \"dutogliptin.\" Completed but unpublished trials were identified through a search of the ClinicalTrials.gov website, using the same keywords as above.", "A systematic review and meta-analysis of randomised controlled trials (RCTs) of DPP-4 inhibitors (vildagliptin, sitagliptin, saxagliptin, linagliptin and alogliptin) on HbA1c were conducted.", "Several clinical trials have studied the addition of GLP-1 receptor agonists [exenatide BID (twice daily), lixisenatide, albiglutide] or DPP-4 inhibitors (vildagliptin, sitagliptin, saxagliptin, alogliptin, linagliptin) to ongoing insulin therapy or adding insulin to ongoing therapy with a GLP-1 receptor agonist (liraglutide).", "Testing the therapeutic equivalence of alogliptin, linagliptin, saxagliptin, sit