Impact of dose capping in insulin glargine/lixisenatide fixed-ratio combination trials in patients with type 2 diabetes

<b>Objective:</b> The LixiLan clinical trials of insulin glargine (iGlar)/lixisenatide fixed-ratio combination (iGlarLixi) investigated the safety and efficacy of iGlarLixi versus iGlar: LixiLan-O (NCT02058147) in patients with type 2 diabetes (T2D) inadequately controlled on oral antidiabetes drugs (OADs) and LixiLan-L (NCT02058160) in patients with T2D inadequately controlled on basal insulin ± OADs. In these two trials, both iGlar and iGlarLixi were titrated to a maximum (capped) dose of 60 units. We evaluated whether this may have affected the reported glycemic efficacy of iGlar, and the glycemic differences observed between treatment with iGlarLixi and iGlar. <b>Methods:</b> The efficacy of iGlar under uncapped conditions was simulated in a two-step approach. First, a model characterizing the relationship between iGlar dose and fasting self-measured plasma glucose (f-SMPG) was developed. Then, the relationship between glycated hemoglobin A1_c (A1C) and f-SMPG was established to translate simulated f-SMPG responses to A1C responses. <b>Results:</b> Most patients achieved stable f-SMPG at ∼60 units/day, with no further reduction with increasing insulin dose. In comparisons of observed/capped and simulated/uncapped changes in mean A1C from baseline to Week 30, iGlarLixi consistently demonstrated treatment benefit compared with iGlar. Uncapping resulted in a slightly higher mean iGlar dose in both LixiLan-O (+0.72 units) and LixiLan-L (+2.1 units), without marked impact on f-SMPG or A1C change from baseline. <b>Conclusion:</b> Uncapping the iGlar dose in LixiLan-O and LixiLan-L would not have led to significant improvements in mean A1C reduction in the iGlar arm, supporting the conclusion that iGlarLixi provides additional, clinically relevant glycemic control versus iGlar alone.