In immune-mediated necrotizing myopathy (IMNM), complement activation drives muscle necrosis.

Muscle necrosis leads to the debilitating symptoms of IMNM, such as severe muscle weakness. Unfortunately, the current treatments for IMNM do not target complement.

IMNM is characterized by debilitating manifestations.

Muscle necrosis in IMNM can lead to:

  • Severe proximal muscle weakness, especially in the lower limbs
  • Markedly elevated serum creatine kinase
  • Muscle atrophy and fatty replacement
  • Dysphagia
  • Weakness in the neck
  • Myalgia
  • Around 20% of patients with the anti-SRP subtype experience extramuscular manifestations (primarily interstitial lung disease)

Anti-SRP and anti-HMGCR IMNM subtypes can be diagnosed with a definitive serologic test.

A positive result will confirm the disease in patients with anti-HMGCR and anti-SRP subtypes. While biopsies are often performed, they are not required.

 

aSkin rash rarely occurs in patients with IMNM. Significant skin involvement suggests an alternate diagnosis.
bA dedicated test may be required for anti-HMGCR antibodies. Criteria for positive results vary by commercial tests.

Panel and individual antibody tests are available for anti-SRP and anti-HMGCR autoantibodies.

Myositis antibody panels and antibody-specific tests are widely available across multiple commercial labs for anti-SRP and anti-HMGCR testing.

Current treatments for IMNM are nonspecific and inadequate.

Patients with IMNM have poor recovery rates and often relapse. At the moment, there are no FDA-approved treatments specifically developed for IMNM. Current therapies include steroids, immunosuppressive therapies (ISTs), rituximab, and intravenous immunoglobulin therapy. Despite intense immunosuppression, ~52 – 66% of patients show progression and incomplete recovery at two years.

Agents used in the current treatment paradigm.

Patients need a treatment specifically designed for IMNM.

We believe that patients need a treatment that targets the cause of muscle necrosis in IMNM. That’s why we are in the process of investigating a synthetic peptide therapy that suppresses the terminal complement cascade.

 

For more information, contact The Myositis Association:
https://www.myositis.org/