Fig. 2

Effects of REGN1033 on muscle mass, muscle fiber area, and number and force. a Gastrocnemius anterior (GA) muscle weight after 4 weeks of treatment with REGN1033 at 0.1, 0.75, 2.5, 10, or 30 mg/kg in CB17-SCID mice. Irrelevant isotype antibody was used as control. Muscle weights were normalized by starting body weights and expressed as percent changes from isotype control. b GA and tibialis anterior (TA) muscle weights normalized by starting body weight and expressed as percent changes from isotype control in CB17-SCID and C57BL/6 mice dosed at 10 mg/kg for 3–4 weeks. c Heart weights normalized by starting body weight and expressed as percent changes from isotype control in CB17-SCID mice dosed at 10 mg/kg for 4 weeks. d H&E staining of TA muscle from isotype control antibody and REGN1033-treated CB17-SCID mice for 4 weeks. Muscle fiber size distribution (e), fiber count (f), and fiber type (g) of GA muscle from CB17-SCID mice after 4-week treatment with 10 mg/kg of control antibody or REGN1033. Muscle fiber type and number are representatives of five independent studies. h Isometric force as a function of stimulation frequency of TA muscle at the end of 3 weeks of treatment with isotype control antibody or REGN1033. Peak tetanic force (i) and specific force (j) from the experiment shown in h. All groups had 5–10 animals. Data are means ± SEM. *P < 0.05, ***P < 0.001, ****P < 0.0001 isotype vs. control