Glucagon-like peptide-1 (GLP-1) is a hormone of the incretin system responsible for a variety of glucoregulatory effects, including glucose-dependent secretion of insulin and inhibition of glucagon release, the effects of which are impaired in people with type 2 diabetes (T2D). Targeting this deficiency using GLP-1 receptor agonists (GLP-1RAs) is a well-established approach in T2D, with over a decade of clinical experience now accrued. This article reviews the evidence for subcutaneous GLP-1RAs and their role in T2D treatment, and explores the rationale for an oral GLP-1RA from a primary care perspective. Clinical trials and real-world studies with subcutaneous GLP-1RAs indicate that these agents have good glycated hemoglobin (HbA1 c)-lowering efficacy, an inherently low potential for hypoglycemia, and reduce body weight. Cardiovascular outcomes trials have established cardiovascular safety, and three GLP-1RAs have been proven to reduce the risk of major adverse cardiovascular events (MACE) in patients with established cardiovascular disease or at high cardiovascular risk. The most common adverse events associated with GLP-1RAs are gastrointestinal effects, which tend to occur soon after initiation and decline over time. T2D treatment guidelines recommend GLP-1RAs as a therapeutic option in various settings, including in those patients: i) not achieving HbA1 c targets after first-line metformin and lifestyle modifications; ii) at high risk of/with established atherosclerotic cardiovascular disease (regardless of HbA1c; GLP-1RAs of proven benefit); iii) not achieving HbA1 c targets on basal insulin if not already receiving a GLP-1RA. Despite the known benefits of GLP-1RAs, adherence and persistence rates are suboptimal, potentially due in part to injection-related concerns. With some patients having a preference for oral medications, the development of an oral GLP-1RA is a logical approach to improving treatment options for patients with T2D. Co-formulation of semaglutide with an absorption enhancer has enabled the development and recent approval of the first oral GLP-1RA, oral semaglutide, which has the potential to expand use of GLP-1RAs in clinical practice.
Keywords: Type 2 diabetes; glucagon-like peptide-1 receptor agonist; oral semaglutide; primary care.