Study participants
The effect of empagliflozin on liver enzymes was analysed from three data sources. First, in the EMPA-REG OUTCOME® trial (NCT01131676), participants with type 2 diabetes (HbA1c 53–75 mmol/mol [7–9%] for drug-naive participants and 53–86 mmol/mol [7–10%] for those on stable glucose-lowering therapy), established cardiovascular disease, BMI ≤45 kg/m2, and eGFR (according to Modification of Diet in Renal Disease [MDRD]) ≥30 ml/min/1.73 m2 were randomised 1:1:1 to receive empagliflozin 10 mg, empagliflozin 25 mg or placebo once daily. Background glucose-lowering therapy was to remain unchanged for 12 weeks. After week 12, investigators were encouraged to adjust glucose-lowering therapy to achieve glycaemic control according to local guidelines. They were also encouraged to treat cardiovascular risk factors to achieve the best standard of care according to local guidelines throughout the trial. The trial was planned to continue until at least 691 participants had experienced an adjudicated event included in the primary outcome (three-point major adverse cardiovascular events: composite of cardiovascular death, non-fatal myocardial infarction and non-fatal stroke) [15].
Second, liver enzyme data from four Phase III trials in participants with type 2 diabetes were pooled. In these trials, participants with BMI ≤45 kg/m2, eGFR (MDRD) ≥30 ml/min/1.73 m2 (or ≥50 ml/min/1.73 m2 in the monotherapy trial) and HbA1c ≥53 to ≤86 mmol/mol (≥7 to ≤10%) were randomised 1:1:1 to receive empagliflozin 10 mg, empagliflozin 25 mg or placebo once daily for 24 weeks as monotherapy (NCT01177813) [16], add-on to metformin (NCT01159600) [17], add-on to metformin plus sulfonylurea (NCT01159600) [18] or add-on to pioglitazone with or without metformin (NCT01210001) [19]. Rescue medication could be initiated if, after an overnight fast, a participant had a confirmed plasma glucose concentration of >13.3 mmol/l during weeks 1–12 or >11.1 mmol/l during weeks 12–24.
Finally, liver enzymes were analysed in the initial 104-week period of the EMPA-REG H2H-SU trial, in which participants with type 2 diabetes, BMI ≤45 kg/m2, HbA1c 53–86 mmol/mol (7–10%) and eGFR (MDRD) ≥60 ml/min/1.73 m2 were randomised 1:1 to receive once-daily empagliflozin 25 mg or glimepiride 1–4 mg as add-on to metformin (NCT01167881) [22]. Glimepiride was initiated at a dose of 1 mg/day, with a recommendation for uptitration if fasting plasma glucose (assessed with home monitoring) was >6.1 mmol/l, to 2 mg/day at week 4, 3 mg/day at week 8 and 4 mg/day at week 12. Rescue medication could be initiated if, after an overnight fast, a participant had a confirmed blood glucose concentration of >13.3 mmol/l during weeks 1–12, >11.1 mmol/l during weeks 12–28 or >10.0 mmol/l (or HbA1c >64 mmol/mol [>8%]) after week 28.
For all the trials that contributed data to these analyses, the clinical trial protocol was approved by the relevant institutional review boards and local independent ethics committees, and all of the trials were conducted in accordance with the Declaration of Helsinki and the International Conference on Harmonization guidelines for Good Clinical Practice. Participants provided signed and dated informed consent before entering each trial.
ALT and AST measurements
In the EMPA-REG OUTCOME® trial, samples for analysis of liver aminotransferases were taken during study visits at baseline and weeks 4, 12, 28 and 52, and then every 14 weeks until the end of the trial. In the 24-week placebo-controlled trials, samples for analysis of liver aminotransferases were taken during study visits at baseline and at weeks 12 and 24. In the initial 104 weeks of the EMPA-REG H2H-SU trial, samples for analysis of liver aminotransferases were taken during study visits at baseline and at weeks 12, 28, 52, 78 and 104. In all studies, analyses of liver aminotransferases were performed by a central laboratory.
Analysis
Changes from baseline in ALT and AST were assessed using mixed-model repeated measures (MMRM) analyses, including baseline ALT or AST and baseline HbA1c as linear covariates and region, baseline BMI, baseline eGFR, study, treatment, visit, baseline HbA1c by visit interaction, baseline ALT or AST by visit interaction and visit by treatment interaction as fixed effects. The analysis of EMPA-REG OUTCOME® data included an additional factor for the last week a participant could have had an ALT or AST measurement. MMRM analyses were based on observed cases, including values after initiation of rescue medication. In analyses of EMPA-REG OUTCOME® and pooled data from the 24-week trials, analyses were performed for the pooled empagliflozin group and placebo. In each dataset, changes in ALT were analysed in all participants and in tertiles by ALT at baseline, and changes in AST were analysed in all participants and in tertiles by AST at baseline. Data are expressed as adjusted means (95% CI) or adjusted means ± SE.
In the EMPA-REG OUTCOME® trial, the contribution of changes in weight or HbA1c (individual and combined effects) to changes in ALT at weeks 28, 52 and 164 (median observation time) were assessed using MMRM analyses as described above, with additional factors for change in HbA1c or weight and, for weight analyses only, baseline weight by visit interaction. These contribution analyses were performed for all participants.