Dexamethasone muscle atrophy studies

Prevention of dexamethasone-induced atrophy was assessed in 9-week-old male C57BL/6 mice, grouped by body weight at the start of the study. Dexamethasone (Dexaject SP solution; Butler Schein) was administered at a rate of 23.0 μg per day by micro-osmotic pump (Durect) for 2 weeks. During dexamethasone administration, four groups of mice (n=10 per group) were subcutaneously injected with REGN1033, a combination of REGN1033 and REGN2477, ActRIIB.hFc or control antibody (25 mg kg⁻¹). Test article administration started on the day of the pump implantation (day 0) and the mice received a total of four injections (days 0, 3, 7 and 10). A separate group (n=10) was implanted with osmotic pumps delivering saline and administered control antibody (25 mg kg⁻¹) at the time indicated above. At the end of 2 weeks of treatment, mice were weighed and euthanized. Both right and left TA and GA muscles were excised and weighed.