Study of ALXN2050 in Adult Participants With Generalized Myasthenia Gravis

A Phase 2, Randomized, Double-Blind, Placebo-Controlled Multicenter Study to Evaluate the Efficacy and Safety of ALXN2050 in Adult Participants With Generalized Myasthenia Gravis

This study will evaluate the efficacy and safety of ALXN2050 (120 milligrams [mg], 180 mg) in participants with generalized myasthenia gravis (gMG).

Safety will be monitored throughout the study.

The study consists of a blinded 8-week Primary Evaluation Period (PEP) and a blinded 26-week Extended Treatment Period (ETP). After completion of 34 weeks of treatment, participants will enter an Open-label Extension (OLE) Period for up to 1.5 years.

Inclusion Criteria:

• Diagnosed with MG at least 3 months (90 days) prior to the date of the Screening Visit. Confirmation of MG must be made via the following:

  1. Positive serologic test for anti AChR antibodies at the Screening Visit, and
  2. Abnormal neuromuscular transmission demonstrated by single fiber electromyography or repetitive nerve stimulation, or
  3. Positive response to an AChEI test (eg, edrophonium chloride test), or
  4. Improvement of signs or symptoms related to MG during treatment with an oral AChEI, as determined by the treating physician

• Myasthenia Gravis Foundation of America Clinical Classification Class II to IV at the Screening Visit.

• MG-ADL total score must be ≥ 5 (with at least 50% of the score attributed to non-ocular elements) at the Screening Visit and at randomization (Day 1).

• Participants receiving treatment with protocol-specified immunosuppressive therapies, corticosteroids, or acetylcholinesterase inhibitors must have been receiving treatment and on a stable dose prior to the date of the Screening Visit, with no changes to the regimen expected during screening, the PEP, and/or the ETP.

Exclusion Criteria:

• Estimated glomerular filtration rate ≤ 30 milliliters/minute/1.73 squared meters during Screening calculated by Chronic Kidney Disease Epidemiology Collaboration.

• History of thymectomy, thymomectomy, or any other thymic surgery within 12 months prior to the Screening Visit.

• Any untreated thymic malignancy, carcinoma, or thymoma. Participants with a history of treated thymic malignancy or carcinoma are eligible for enrollment if they meet pre-specified conditions outlined in the protocol.

• Clinical features consistent with Clinical Deterioration at the time of the Screening Visit or at any time during the Screening Period prior to randomization (Day 1).

• Use of the following within the time periods specified below:

  1. Intravenous immunoglobulin G or subcutaneous immunoglobulin within the 4 weeks (28 days) prior to the Screening Visit.
  2. Use of tacrolimus or cyclosporine within the 4 weeks (28 days) prior to the Screening Visit.