OBJECTIVE: In the LixiLan-G trial, switching to iGlarLixi, a once-daily titratable fixed-ratio combination of insulin glargine 100 units/mL and the glucagon-like peptide 1 receptor agonist (GLP-1 RA) lixisenatide, improved glucose control in type 2 diabetes uncontrolled with GLP-1 RAs over 26 weeks versus continuing prior GLP-1 RA. A prespecified, 26-week, single-arm extension of LixiLan-G aimed to determine the durability of iGlarLixi efficacy and safety over 52 weeks. RESEARCH DESIGN AND METHODS: Participants with type 2 diabetes uncontrolled by GLP-1 RAs (glycated hemoglobin [HbA1c] 7-9% [53-75 mmol/mol]) were initially randomized to switch to iGlarLixi or continue prior GLP-1 RA. Those randomized to iGlarLixi who completed the 26-week primary end point period could continue iGlarLixi open-label treatment over a 26-week extension to assess durability of efficacy and safety. RESULTS: Glycemic control achieved with iGlarLixi at week 26 (mean HbA1c 6.7% [50 mmol/mol]) was maintained at week 52 (mean HbA1c 6.7% [50 mmol/mol]; mean ± SD change from baseline at week 52: -1.0 ± 0.9% [11 ± 10 mmol/mol]). Proportions of participants reaching HbA1c <7% (53 mmol/mol) with iGlarLixi were similar at week 26 (62%) and 52 (64%), as were those reaching this target without documented symptomatic (<3.0 mmol/L) hypoglycemia (57% and 58%). Safety of iGlarLixi was similar at weeks 26 and 52, with low rates of documented symptomatic hypoglycemia and gastrointestinal events. CONCLUSIONS: The efficacy and safety of iGlarLixi at the end of the 26-week randomized treatment period was maintained over the 26-week extension period in the LixiLan-G trial.