Inclusion body myositis is a progressive muscle disease that mainly affects people over 50, causing gradual weakness in the arms and legs. While there is currently no cure, understanding treatment options — both standard approaches and those being tested in clinical trials — can help patients maintain function and quality of life for as long as possible.

Understanding Treatment Goals for Inclusion Body Myositis

When it comes to managing inclusion body myositis, the focus shifts away from curing the disease and toward preserving what patients can do for as long as possible. The main goals of treatment include maintaining muscle strength, preventing complications like swallowing difficulties, and helping people stay mobile and independent. Because this condition affects each person differently, treatment plans need to be tailored to individual needs and adjusted as the disease progresses over time.^[1]

Unlike many other muscle diseases, inclusion body myositis presents unique challenges to the medical community. The disease appears to have both inflammatory and degenerative components, meaning that inflammation damages muscle tissue while abnormal protein deposits called inclusion bodies cluster inside muscle cells. These clumps of proteins may interfere with how cells function and contribute to progressive muscle weakening. This dual nature makes finding effective treatments particularly difficult.^[3]

Treatment decisions depend heavily on which muscles are affected, how quickly the disease is progressing, and whether complications like difficulty swallowing have developed. Some patients notice weakness first in their fingers and wrists, making everyday tasks like buttoning shirts or writing difficult. Others experience weakness in their thighs, leading to frequent falls and trouble climbing stairs. Medical teams work with patients to address their specific symptoms and functional limitations.^[7]

The medical community recognizes that inclusion body myositis requires a comprehensive approach that goes beyond medication. Physical therapy, occupational therapy, and speech therapy when swallowing is affected form the cornerstone of disease management. At the same time, researchers continue to investigate new drugs and therapeutic approaches through clinical trials, searching for treatments that might slow or halt disease progression.^[11]

Standard Treatment Approaches

The reality of treating inclusion body myositis is sobering: most medications that work well for other inflammatory muscle diseases simply do not work for this condition. Unlike polymyositis or dermatomyositis, which often respond to drugs that suppress the immune system, inclusion body myositis has proven remarkably resistant to these treatments. This resistance likely stems from the degenerative component of the disease, which continues regardless of inflammation control.^[4]

Early attempts to treat inclusion body myositis with corticosteroids like prednisone showed disappointing results. While these powerful anti-inflammatory medications can reduce certain markers of inflammation in the blood and decrease the number of inflammatory cells seen in muscle tissue, they do not improve strength or prevent disability. In fact, some studies suggest that long-term use of immunosuppressive treatments might modestly worsen progression, though this observation is debated and may reflect selection bias in which patients received treatment.^[13]

Similarly, other immunosuppressive medications including methotrexate, azathioprine, and cyclophosphamide have been tried without sustained success. A controlled study of methotrexate in 44 patients found no improvement in muscle strength despite significant decreases in creatine phosphokinase levels (a marker of muscle damage in the blood). This disconnect between laboratory markers and actual patient outcomes highlights the complexity of this disease.^[13]

Intravenous immunoglobulin, often abbreviated as IVIg, has also been investigated. This treatment involves infusing antibodies collected from donated blood into a patient’s bloodstream. Early small studies suggested some benefit, but larger controlled trials failed to replicate these results. However, some evidence suggests IVIg might help patients with severe swallowing difficulties, though the effect appears limited and temporary. The treatment is generally well-tolerated but expensive and requires repeated infusions.^[13]

The mainstay of management for inclusion body myositis centers on physical therapy, occupational therapy, and speech therapy. Physical therapy helps patients maintain as much muscle strength and mobility as possible through carefully designed exercise programs. Exercise is particularly important — studies have shown that appropriate physical activity can help preserve muscle function without causing harm. Light resistance training, walking, swimming, and stationary cycling can all be beneficial when done safely and consistently.^[11]

Occupational therapists assist patients in adapting to progressive weakness by teaching new ways to perform daily activities and recommending assistive devices. Simple aids like built-up utensil handles, button hooks, or reaching devices can maintain independence even as hand strength declines. For patients experiencing leg weakness, canes, walkers, or eventually wheelchairs help prevent falls and maintain mobility.^[14]

When swallowing difficulties develop — which occurs in approximately half of all patients — speech and language therapy becomes crucial. Therapists teach techniques to minimize the risk of aspiration, which occurs when food or liquid enters the airway instead of the esophagus. This complication can lead to pneumonia and represents a serious concern. Adjusting food textures, modifying swallowing techniques, and positioning changes during meals all help reduce aspiration risk.^[7]

Promising Therapies Being Tested in Clinical Trials

Despite the challenges, researchers around the world continue to search for effective treatments through clinical trials. Several experimental drugs have shown enough promise in early testing to warrant larger studies. These investigational therapies target different aspects of the disease process, from inflammation to protein accumulation to muscle regeneration.^[10]

Arimoclomol represents one such experimental compound. This drug is believed to stimulate the repair of certain proteins inside muscle cells, potentially preventing these proteins from clumping together into inclusion bodies. The rationale is compelling: if researchers can stop protein accumulation, they might slow disease progression. An initial small clinical trial in inclusion body myositis patients showed some encouraging signs. However, a subsequent larger trial failed to demonstrate improved outcomes compared to placebo. Despite this setback, researchers continue to study the compound as they refine their understanding of its effects.^[10]

Bimagrumab, also known by its experimental code name BYM338, takes a different approach. This is a human monoclonal antibody — a laboratory-made protein designed to target specific molecules in the body. Bimagrumab was developed to treat pathological muscle loss and weakness by blocking certain signals that prevent muscle growth. In a clinical trial with inclusion body myositis patients, this compound demonstrated that it could increase muscle mass. Patients literally built more muscle tissue while taking the drug. Unfortunately, difficulties with how the trial was designed led to inconclusive results about whether this muscle growth translated into improved strength or function. The medication continues to be studied for other muscle-wasting conditions, and if it receives regulatory approval, doctors might eventually use it off-label for inclusion body myositis. Importantly, this would be a treatment for symptoms rather than a cure for the underlying disease.^[10]

Follistatin, designated as AAV1-FS344 in research protocols, represents yet another innovative strategy. This is a gene therapy-delivered protein designed to increase muscle strength and function. Gene therapy works by introducing genetic material into cells to produce beneficial proteins. Follistatin has shown positive results in patients with Becker muscular dystrophy, improving walking ability. Based on these encouraging findings, researchers tested it in inclusion body myositis patients. Unfortunately, the study did not show effectiveness in this disease. This outcome illustrates a common challenge in drug development: treatments that work for one muscle disease do not necessarily work for another, even when symptoms appear similar.^[10]

Rapamycin, also called sirolimus, offers another potential avenue. This immunosuppressant drug is already approved and widely used to prevent organ rejection in kidney transplant patients. Its mechanism involves blocking certain cellular pathways related to protein production and cell growth. Researchers hypothesize that rapamycin might help in inclusion body myositis by reducing both inflammation and abnormal protein accumulation. A large clinical trial using this medication in inclusion body myositis patients is currently recruiting participants. The study is expected to be completed in 2026, at which point the medical community will learn whether this repurposed drug can benefit patients.^[10]

Ulviprubart, also known by the designation ABC008, represents a novel class of treatment called a first-in-class anti-KLRG1 antibody. This medication works by selectively removing certain immune cells that appear to damage muscle tissue in inclusion body myositis. The drug targets a specific marker on these harmful immune cells, allowing the immune system to eliminate them while leaving other immune cells intact. This selective approach might avoid the broad immunosuppression that comes with older treatments. A large clinical trial to demonstrate effectiveness in inclusion body myositis has completed patient recruitment and is expected to report results by the end of 2025. If successful, this could represent a significant breakthrough in treating the inflammatory component of the disease.^[10]

Other experimental approaches have included beta interferon-1a and etanercept, a tumor necrosis factor (TNF) alpha blocker. Beta interferon at both standard and high doses was well tolerated but produced no significant improvement in muscle strength or muscle mass. A pilot trial of etanercept did not show significant benefit in composite muscle strength scores at six months, though slight improvement in grip strength was noted with 12 months of treatment. A larger double-blind, randomized, placebo-controlled study has been conducted to further assess etanercept’s efficacy.^[13]

Some trials have explored more aggressive immunosuppression. Anti-T-lymphocyte globulin followed by methotrexate showed regional improvement in distal upper extremity strength compared to methotrexate alone, though proximal muscle groups continued to deteriorate. Alemtuzumab, a T-cell-depleting monoclonal antibody, has also been investigated. A study involving 13 patients who underwent infusion reported slowed disease progression according to some measures, though significant questions remain about this approach.^[13]

The search for effective treatments faces numerous challenges. The disease progresses slowly, making it difficult to measure whether a treatment is working over the typical timeframe of a clinical trial. Patient-to-patient variability in symptoms and progression rates complicates trial design. The lack of validated outcome measures — agreed-upon ways to measure disease severity and improvement — makes comparing different trials difficult. Additionally, inclusion body myositis remains relatively rare, so recruiting enough patients for large, definitive studies takes considerable time and coordination across multiple medical centers.^[12]

Most common treatment methods

• Physical therapy and exercise
  • Carefully designed exercise programs help maintain muscle strength and mobility
  • Activities may include light resistance training, walking, stationary cycling, and swimming
  • Exercise should be done regularly without compromising safety
  • Physical therapists develop individualized programs based on current abilities and limitations
• Occupational therapy
  • Teaches new ways to perform daily activities as weakness progresses
  • Recommends assistive devices like built-up utensil handles, button hooks, and reaching devices
  • Helps patients maintain independence despite progressive muscle weakness
  • Addresses safety concerns and fall prevention strategies
• Speech and swallowing therapy
  • Essential for patients developing difficulty swallowing (dysphagia)
  • Teaches techniques to minimize aspiration risk
  • Provides guidance on food texture modifications and safe swallowing strategies
  • Helps prevent pneumonia from food or liquid entering the airways
• Immunosuppressive therapy (limited effectiveness)
  • Corticosteroids like prednisone generally do not improve strength despite reducing inflammation markers
  • Methotrexate, azathioprine, and cyclophosphamide have shown disappointing results in clinical studies
  • Intravenous immunoglobulin (IVIg) may provide slight, temporary benefit for severe swallowing difficulties
  • Most immunosuppressive treatments are not routinely recommended for inclusion body myositis
• Experimental treatments in clinical trials
  • Arimoclomol targets protein clumping inside muscle cells
  • Bimagrumab (BYM338) aims to increase muscle mass and reduce muscle loss
  • Rapamycin (sirolimus) is being tested in a large ongoing trial expected to complete in 2026
  • Ulviprubart (ABC008) selectively removes immune cells that damage muscle tissue, with results expected by end of 2025
  • Gene therapy approaches like follistatin have been tested but did not show effectiveness