Evidence from a study in healthy volunteers showing that a single, intravenous dose of bimagrumab reduced body fat, prompted researchers to examine the value of this approach in obese, type 2 diabetic patients.
The monoclonal antibody bimagrumab binds to and blocks the activity of the activin type II receptor (ActRII), promoting skeletal muscle hypertrophy and reducing body fat mass. Given this potential action, researchers from Pennington Biomedical Research Centre, Louisiana State University, in the US, hypothesised that the drug might represent a beneficial approach to the management of obese, type 2 diabetic patients. They recruited type 2 diabetes aged between 18 and 75 years with a glycated haemoglobin (HbA1C) of 6.5 to 10%, a body mass index (BMI) of 28 to 40 and a weight of between 65 and 140kg. All patients were prescribed either metformin (as mono-therapy), dipeptidyl peptidase 4 (DPP4) inhibitors, (again as mono-therapy) or a combination of both drugs, although a small number were not prescribed any diabetic medicines. These treatments were permitted because of their weight neutral effect. Eligible participants were randomised 1:1 to either Bimagrumab (10mg/kg to a maximum of 1200mg in 5% dextrose) or placebo (5% dextrose) via 30-minute intravenous infusion every 4 weeks for a total of 48 weeks and both clinicians and patients were blinded to allocation. The primary endpoint was a change from baseline to week 48 in total fat mass (FM) which was measured by dual energy X-ray absorptiometry. Secondary endpoints included change in diabetic status (HbA1C), body weight, BMI and both HOMA2 and the Matsuda index which are measures of insulin sensitivity.
A total of 75 patients were randomised to either bimagrumab (37) or placebo (38). The mean age of those assigned to bimagrumab was 60.7 years (62.2% female). At week 48, total FM decreased by a mean of 7.49 kg in the bimagrumab group vs 0.18 kg in the placebo group (p < 0.01). Similarly, there were significant reductions in BMI (2.19 vs 0.28, p < 0.001), body weight (5.90 kg vs 0.79 (p < 0.01) and HbA1C levels (0.76 vs 0.04, p < 0.05). Interestingly, the bimagrumab group also saw a significant increase in lean muscle mass compared to the placebo group (1.70 kg vs 0.4 kg, p < 0.001). However, there were no significant changes to either measure of insulin sensitivity or in use of anti-diabetic medication. Commenting on their findings, the authors noted that treatment with bimagrumab led to a small increase in lean muscle mass which is a beneficial effect given that muscle loss is typically observed when type 2 diabetes adopt a low-calorie diet.
They concluded that inhibition of ActRII may provide a novel pathway for the management of excess body fat and metabolic disturbances as seen in type 2 diabetics.
Heymsfield SB et al. Effect of Bimagrumab vs placebo on body fat mass among adults with type 2 diabetes and obesity. A phase 2 randomised clinical trial. JAMA Netw Open 2021