<h4>Aims</h4>To compare up-to-date efficacy and safety data of sodium-glucose cotransporter-2 inhibitors (SGLT-2is) versus other metformin-containing oral dual-therapies (ODTs) in type 2 diabetes mellitus.<h4>Methods</h4>We updated a 2016 systematic literature review (SLR), searching MEDLINE, Embase, the Cochrane Database of Systematic Reviews, congress abstracts and SLR/meta-analysis (MA) bibliographies to identify randomised controlled trials. This evidence concerns the gene SLC5A2 and type 2 diabetes mellitus.