Bimagrumab confirms its good long-term tolerability in sporadic inclusion myositis … and its lack of functional efficacy

Sporadic inclusion myositis is an inflammatory myopathy. It causes slowly progressive and asymmetric muscle weakness and atrophy (quadriceps, flexors of the fingers, etc.), usually beginning after the age of 50. The usual treatments for other inflammatory myopathies (corticosteroids, immunosuppressants, etc.) have no effect in inclusion myositis, which would include a part of degenerative mechanisms. 

No benefit on muscle function 

Bimagrumab, an antibody to the myostatin receptor, has been tested (NCT01423110) against placebo in 14 patients with sporadic inclusion myositis, with encouraging results. Ten countries including France then conducted a phase II / III trial called RESILIENT (NCT01925209) in 251 patients with inclusion myositis and treated for one year with bimagrumab or placebo; 211 of them then continued to receive bimagrumab once a month at a dose of 1, 3 or 10 mg / kg for up to two years as part of a double-blind against placebo and then open-label extension study. Its results, published in February 2021 by Neurology, show: 

  • an equivalent frequency of adverse reactions in the bimagrumab group (91% of participants declared at least one) and in the placebo group (89.1%), most often diarrhea (14.7%), muscle spasms ( 9.6%) or skin rashes (5.1%); 
  • a gradual decline in the distance covered on the 6-minute walk test in all groups.

These data are identical to the results of the RESILIENT trial.


Efficacy and safety of bimagrumab in sporadic inclusion body myositis: long-term extension of RESILIENT. Amato AA, Hanna MG, Machado PM et al. Neurology. 2021 Feb 17:10.1212/WNL.0000000000011626.


Long-term safety and tolerability of bimagrumab (BYM338) in sporadic inclusion body myositis Sivakumar K, Cochrane TI, Sloth B, et al. Neurology. 2020;10.1212/WNL.0000000000010417.