Rationale for, Initiation and Titration of the Basal Insulin/GLP-1RA Fixed-Ratio Combination Products, IDegLira and IGlarLixi, for the Management of Type 2 Diabetes

Type 2 diabetes (T2D) is a progressive disease affecting glucose regulation and a major cause of morbidity and mortality globally. Many patients are not escalated up the treatment ladder appropriately despite failing to achieve glycemic control, with barriers such as fear of hypoglycemia, weight gain, and treatment burden recognized as factors. Exogenous basal insulin is titrated to address control of fasting plasma glucose and may preserve residual β-cell function, thus promoting a greater endogenous prandial insulin response. Native glucagon-like peptide-1 (GLP-1) is a peptide hormone secreted by the gut in response to nutrient ingestion; it increases insulin secretion, inhibits glucagon secretion, and prolongs gastric emptying, thereby lowering overall food intake. As its glucose-lowering action is glucose dependent, a GLP-1 receptor agonist (GLP-1RA) achieves these benefits with a lower risk of hypoglycemia compared with other diabetes therapies. Two products, an insulin degludec/liraglutide combination (IDegLira) and an insulin glargine/lixisenatide combination (IGlarLixi), were approved for use in adults with T2D by the US Food and Drug Administration in 2016. The efficacy and safety of these two basal insulin/GLP-1RA combination products were studied in the DUAL program (NCTs 01336023, 01392573, 01676116, 01618162, 01952145, and 02298192) and the LixiLan program (NCTs 02058160 and 02058147). Compared with basal insulin, insulin/GLP-1RA fixed-ratio combinations are superior at reducing HbA_1c with weight neutrality or weight loss rather than weight gain, as well as reduced hypoglycemia rates, and reduced insulin-dose requirement with IDegLira. A combination of different medications may often be required to achieve glycemic control, and fixed-ratio combination products allow such therapies to be given in simple regimens. Clinical trial data for these products highlight the great potential of these agents, not merely their efficacy and safety but also their ease of use and decreased injection burden for patients.