Results Summary

What was the research about?

Myasthenia gravis, or MG, is a rare disease of the immune system that causes muscle weakness. MG can cause droopy eyelids and trouble swallowing, chewing, talking, and breathing.

Medicines that suppress the immune system can help relieve MG symptoms. These medicines require routine monitoring for adverse events, such as liver damage or stomach issues. Questions remain about how these medicines compare with each other.

In this study, the research team compared two medicines for adults with MG: azathioprine, or AZT, versus mycophenolate mofetil, or MMF. The team wanted to learn how these medicines affected patient quality of life, symptoms, and other health outcomes.

What were the results?

After two years, patients who took AZT and patients who took MMF had better quality of life and fewer symptoms. Patients who took MMF reported more improvement in quality of life than patients who took AZT. But the difference was small and not meaningful.

Patients who took AZT and patients who took MMF didn’t differ in:

  • Symptom improvement and muscle strength as assessed by clinicians
  • Ability to do daily activities
  • Number of hospital stays for MG

Among patients who took AZT, 32 percent had an adverse event. The most common event was liver damage. Among patients who took MMF, 19 percent had an adverse event. The most common event was stomach issues, such as cramps or diarrhea.

Who was in the study?

The study included 82 adult patients with MG. Of these patients, 96 percent were White, 2 percent were Asian, 1 percent were Black, and 1 percent were of unknown race. The average age was 66, and 61 percent were men.

What did the research team do?

The research team enrolled patients with MG who were receiving care at one of 19 MG clinics in the United States and Canada. As part of regular care, clinicians prescribed either AZT or MMF to patients. At the start of the study and again two years later, patients completed surveys about their quality of life and ability to do daily activities. Clinicians completed surveys about patients’ symptoms, muscle strength, hospital stays, and adverse events caused by the medicines.

Patients with MG, clinicians, health insurers, and patient organizations helped design and carry out the study.

What were the limits of the study?

The research team enrolled fewer patients in the study than planned, which made it hard to detect differences between AZT and MMF. The study took place at MG clinics. Forty percent of patients had the form of MG that affects only eye muscles. Results may differ in other types of clinics and for patients with other forms of MG.

Future research could include patients with other forms of MG and those receiving care at other types of clinics.

How can people use the results?

Patients with MG and their clinicians can use these results when considering medicines to treat MG.

Final Research Report

View this project's final research report.

Peer-Review Summary

Peer review of PCORI-funded research helps make sure the report presents complete, balanced, and useful information about the research. It also assesses how the project addressed PCORI’s Methodology Standards. During peer review, experts read a draft report of the research and provide comments about the report. These experts may include a scientist focused on the research topic, a specialist in research methods, a patient or caregiver, and a healthcare professional. These reviewers cannot have conflicts of interest with the study.

The peer reviewers point out where the draft report may need revision. For example, they may suggest ways to improve descriptions of the conduct of the study or to clarify the connection between results and conclusions. Sometimes, awardees revise their draft reports twice or more to address all of the reviewers’ comments.

Peer reviewers commented and the researchers made changes or provided responses. Those comments and responses included the following:

  • Reviewers noted that the study found a statistically significant difference between the two treatments for Myasthenia Gravis, but the researchers did not consider that difference to be clinically meaningful. They asked the researchers to provide more support for this conclusion and postulate on the reasons for the smaller-than-expected difference between groups. The researchers added text to the report indicating that their difficulties with meeting their enrollment goals during the COVID-19 pandemic led to a loss of study power and was probably a main reason for the lack of a clinically meaningful difference between the two treatments.
  • The reviewers asked for more information on the involvement of patients and stakeholders as research partners in the study. The researchers added details to the engagement section of the report describing how their three stakeholders were involved starting at the point of study development when they helped to identify the outcome measures. This advisory group continued to meet with the researchers every three months to discuss issues related to the study and to provide feedback on their study recruitment plans as well as on abstracts and papers stemming from the project.
  • The reviewers questioned how the researchers could conclude that the study results were due specifically to the interventions for Myasthenia Gravis when patients might also be affected by the COVID-19 pandemic, either by contracting the illness or through side effects from the vaccinations. The researchers explained that the outcome measures they used were specific to Myasthenia Gravis. They did record occurrences of other medical illnesses during the study and no patients reported having COVID-19 in that time.

Conflict of Interest Disclosures

Project Information

Donald B. Sanders, MD, and Pushpa Narayanaswami, MD
Duke University
Prospective Multicenter Observational Cohort Study Of Comparative Effectiveness of Disease-Modifying Treatments for Myasthenia Gravis (MG)

Key Dates

August 2017
December 2022

Study Registration Information


Has Results
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Health Conditions Health Conditions These are the broad terms we use to categorize our funded research studies; specific diseases or conditions are included within the appropriate larger category. Note: not all of our funded projects focus on a single disease or condition; some touch on multiple diseases or conditions, research methods, or broader health system interventions. Such projects won’t be listed by a primary disease/condition and so won’t appear if you use this filter tool to find them. View Glossary
Populations Populations PCORI is interested in research that seeks to better understand how different clinical and health system options work for different people. These populations are frequently studied in our portfolio or identified as being of interest by our stakeholders. View Glossary
Intervention Strategy Intervention Strategies PCORI funds comparative clinical effectiveness research (CER) studies that compare two or more options or approaches to health care, or that compare different ways of delivering or receiving care. View Glossary
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Last updated: December 20, 2023