AimsTo assess the effects on glycaemic control of lixisenatide vs placebo as add-on treatment to basal insulin (BI)metformin and effects on glycated haemoglobin (HbA1c) reduction in patients with insufficiently controlled type 2 diabetes (T2D). MethodsPatients (n=448) with inadequately controlled T2D were randomized (1:1) to lixisenatide or placebo as add-on to BImetformin for 24weeks after an 8-week run-in phase, during which BI was titrated to a target self-monitored plasma glucose (SMPG; 4.4-5.6mmol/L). The primary endpoint was absolute change in HbA1c from baseline to week 24. Secondary efficacy endpoints included: percentage of responders; changes in 2-hour postprandial plasma glucose (PPG); 7-point SMPG (daily average); body weight (BW); total daily BI dose; fasting plasma glucose; and safety assessments. ResultsBaseline demographics were similar in the two treatment groups. After insulin optimization during run-in, lixisenatide was superior to placebo in mean change from baseline (7.9% [standard deviation {s.d.}, 0.66] and 7.9% [0.70], respectively) to week 24 in HbA1c (least squares mean [standard error {s.e.}] change -0.62% [0.09] vs -0.11% [0.09]; P<.0001, respectively) and higher proportions of patients achieved HbA1c targets. Two-hour PPG, daily mean SMPG and mean BW were reduced further and daily BI dose was lower with lixisenatide than placebo (-1.12kg vs 0.04kg [P<.0001]; -3.0U vs -1.9U [P=.0033], respectively). Treatment-emergent adverse events were greater with lixisenatide than placebo (63.8% vs 40.8%, respectively). The incidence of symptomatic hypoglycaemia was similar (lixisenatide 15.6% vs placebo 13.5%). ConclusionsIn Asian patients insufficiently controlled on BI +/- metformin, lixisenatide was superior to placebo in glycaemic control, with a tolerability profile in line with other glucagon-like peptide-1 receptor agonists.