About the Prevail Study

The Prevail Study is evaluating the safety and effectiveness of a study medication, called ALXN1720, in reducing symptoms in adults with generalized myasthenia gravis (gMG). This new investigational therapy differs from current treatment options, as it can be administered by the participant or caregiver after training from the site staff.

Who May Qualify

Eligible participants must:

  • Be 18 years of age or older
  • Have a documented diagnosis of myasthenia gravis
  • Have symptoms that involve weakness of more than just the eyes: e.g., affecting speech, swallowing, breathing, arm or leg movements
  • Not have had a thymectomy or other thymus surgery within the past 12 months
  • Not have a tumor of the thymus that has not been treated
Woman speaking to a crowd in a field.

There are additional eligibility criteria, which the study team will discuss with you.

About the Study Medication

The study medication is called gefurulimab ALXN1720. It has not been approved by country-specific regulatory health authorities, such as the Food and Drug Administration (FDA) in the US, to be used for gMG, and its use is being allowed for research purposes only. Participants will be assigned at random to receive either the study medication or a placebo (an inactive substance that looks like the study medication but contains no active ingredients). Neither the participant nor the study team will know which treatment option has been assigned, but in case of an emergency, the study team can quickly find out. The placebo allows researchers to fully understand the effects of the study medication.

Both the study medication and the placebo are administered as injections with single-use, prefilled syringes with safety devices.

Study Participation

Participation in the study can last up to approximately 34 months (a little over two and a half years) and consists of the following periods:


Lasts up to four weeks. The purpose of this period is to evaluate all interested individuals to see whether the study is a good match for them.

Randomized Controlled Treatment (RCT)

Lasts 26 weeks. Participants will be randomized to receive either the study medication or placebo. Both the study medication and the placebo will be administered via injection under the skin on a weekly basis. Participants will attend visits to the study site for routine assessments and procedures. Some visits will also be done remotely.

Open-Label Extension (OLE)

Lasts up to 105 weeks (about two years). All participants will receive the study medication during this period.

Safety Follow-Up (SFU) Visit

All participants must come for an in-person visit 12 weeks after receiving the final treatment dose. The SFU visit is required whether a participant withdraws early from the study or completes the OLE period.

Please note: This website is for US residents only. If you live outside the US or want additional information on the Prevail Study, please contact ClinicalTrials@Alexion.com or call (+1) 855-752-2356.

Throughout your study participation, the study doctor may perform a number of tests and procedures, including but not limited to:

Medical history review

Physical exam

Vital sign measurements

Electrocardiogram (ECG)

Pregnancy test (if applicable)

Blood and urine sample collections

Assessments of your myasthenia
gravis symptoms

See if you may qualify