The Basis for Weekly Insulin Therapy: Evolving Evidence With Insulin Icodec and Insulin Efsitora Alfa

Basal insulin continues to be a vital part of therapy for many people with diabetes. First attempts to prolong the duration of insulin formulations were through the development of suspensions that required homogenization prior to injection. These insulins, which required once- or twice-daily injections, introduced wide variations in insulin exposure contributing to unpredictable effects on glycemia. Advances over the last 2 decades have resulted in long-acting, soluble basal insulin analogues with prolonged and less variable pharmacokinetic exposure, improving their efficacy and safety, notably by reducing nocturnal hypoglycemia. However, adherence and persistence with once-daily basal insulin treatment remains low for many reasons including hypoglycemia concerns and treatment burden. A soluble basal insulin with a longer and flatter exposure profile could reduce pharmacodynamic variability, potentially reducing hypoglycemia, have similar efficacy to once-daily basal insulins, simplify dosing regimens, and improve treatment adherence. Insulin icodec (Novo Nordisk) and insulin efsitora alfa (basal insulin Fc [BIF], Eli Lilly and Company) are 2 such insulins designed for once-weekly administration, which have the potential to provide a further advance in basal insulin replacement. Icodec and efsitora phase 2 clinical trials, as well as data from the phase 3 icodec program indicate that once-weekly insulins provide comparable glycemic control to once-daily analogues, with a similar risk of hypoglycemia. This manuscript details the technology used in the development of once-weekly basal insulins. It highlights the clinical rationale and potential benefits of these weekly insulins while also discussing the limitations and challenges these molecules could pose in clinical practice.