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New oral cladribine formulation for treating generalized myasthenia gravis

A Phase 3, Randomized, Double-Blind, Placebo-Controlled, 3-Arm, 3-Period Study to Assess the Efficacy and Safety of a New Formulation of Oral Cladribine Compared With Placebo in Participants With Generalized Myasthenia Gravis (MyClad)

Phase 3 Interventional Merck Healthcare KGaA, Darmstadt, Germany, an affiliate of Merck KGaA, Darmstadt, Germany · NCT06463587

This study is testing a new pill for people with generalized myasthenia gravis to see if it helps them feel better compared to a sugar pill.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment264 (estimated)
Ages18 Years and up
SexAll
SponsorMerck Healthcare KGaA, Darmstadt, Germany, an affiliate of Merck KGaA, Darmstadt, Germany Industry-sponsored
Drugs / interventionseculizumab, rozanolixizumab, ravulizumab, methotrexate, prednisone
Locations133 sites (Phoenix, Arizona and 132 other locations)
Trial IDNCT06463587 on ClinicalTrials.gov

What this trial studies

This clinical trial evaluates the efficacy and safety of a new formulation of oral cladribine in patients with generalized myasthenia gravis (gMG) compared to a placebo. The study is structured into three periods: a double-blind placebo-controlled pivotal period, a blinded extension, and a retreatment period. It aims to assess not only the immediate effects of the treatment but also its long-term safety and the pharmacokinetics of the new formulation. Participants will be monitored for sustained efficacy and the need for retreatment over time.

Who should consider this trial

Good fit: Ideal candidates include adults aged 18 and older diagnosed with generalized myasthenia gravis, particularly those with specific antibody profiles.

Not a fit: Patients with mild forms of myasthenia gravis or those not meeting the inclusion criteria may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could significantly improve the management of generalized myasthenia gravis, offering patients a new oral therapy option.

How similar studies have performed: Previous studies have shown promise with similar treatments for myasthenia gravis, indicating potential for success with this new formulation.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* Adults of ≥ 18 years of age at the time of signing the informed consent.
* Diagnosis of Myasthenia Gravis with generalized muscle weakness, meeting clinical criteria for Myasthenia Gravis Foundation of America Class II to IVa classification.

  * In participants positive for Acetylcholine receptor antibody (anti-AChR) or muscle-specific kinase antibody(anti-MuSK)
  * In participants that are autoantibody seronegative and participants who are positive for anti-low-density lipoprotein receptor-related protein 4 antibodies (anti-LRP4)
* Has a Screening and Baseline MG-ADL score more than or equal to (\>=) 6 with \>= 50 percentage (%) of the total score due to non-ocular symptoms. Screening and Baseline MG-ADL scores must be stable. The difference between the Screening and Baseline scores should not be more than 2 and there should be no reported MG exacerbation during the Screening period
* If treated with oral corticosteroids: should be on a stable daily dose for at least 3 months prior to and during screening. In such case, the daily dose of oral steroids should not exceed 20 milligrams(mg)/day for prednisone/ prednisolone or 16 mg/day for methylprednisolone
* If treated with acetylcholinesterase inhibitor should be on a stable daily dose (pyridostigmine dose ≤ 480 mg/day) for at least 3 months prior to and during screening
* Have a body weight \>= 40 kilograms
* Other protocol defined inclusion criteria could apply

Exclusion Criteria:

* Immunologic disorder other than MG or any other condition requiring chronic oral, intravenous, intramuscular, or intraarticular corticosteroid therapy. Well-controlled thyroid disease, as per the Treating Investigator or the participants regular treating physician recorded in the source documents, is not exclusionary
* Molecularly characterized or suspected congenital myasthenic syndrome, Lambert-Eaton myasthenic syndrome, inherited myopathy, muscular dystrophy, acquired myopathy or any other neurologic or systematic disease that mimics MG muscular weakness
* Active, clinically significant viral, bacterial, or fungal infection, including brain MRI findings consistent with signs of infection such as PML, or any major episode of infection requiring hospitalization or treatment with parenteral anti-infectives within 8 weeks prior or during Screening, or completion of oral anti-infectives within 8 weeks prior or during Screening. Vaginal candidiasis, onychomycosis, and genital or oral herpes simplex virus considered by the Investigator to be sufficiently controlled would not be exclusionary
* Has a history of or current diagnosis of active tuberculosis (TB)
* Active malignancy, or history of cancer
* Treatment with nonsteroidal immunosuppressants, used in gMG, such as azathioprine, mycophenolate mofetil, methotrexate, cyclosporine, tacrolimus within 4 weeks prior to randomization
* Treatment with eculizumab, rozanolixizumab efgartigimod, ravulizumab, or zilucoplan within 8 weeks prior to randomization
* History of thymectomy within 6 months prior to Screening.
* History of generalized seizures (except for history of infantile febrile seizures)
* Negative for Varicella Zoster Virus antibodies at screening
* History of myasthenic crisis in the last 12 months prior to and during screening
* History of recurrent infections (that is 3 or more infections per year) within the last 2 years
* Discontinuation of treatment with any non-steroidal immunosuppressants used in gMG, such as azathioprine, mycophenolate mofetil, methotrexate, cyclosporine, tacrolimus within the last 6 months prior to Screening
* If treated with non-steroidal immunosuppressants for gMG, the dose at Screening should not exceed 50 mg/day for azathioprine, 500 mg/day for mycophenolate mofetil, 1 mg/day for tacrolimus, 50 mg/day for cyclosporine, or 7.5 mg/week for methotrexate
* Participation in clinical study of any investigational drug within 6 months, or 5 half-lives of the investigational drug used in the previous clinical study prior to randomization, whichever is longer. However, participants with any prior exposure to cladribine may not enter the study regardless of timing of exposure
* Other protocol defined exclusion criteria could apply

Where this trial is running

Phoenix, Arizona and 132 other locations

+83 more sites — see ClinicalTrials.gov for the full list.

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Generalized Myasthenia GravisAnti-AChR antibody positiveanti-MuSK antibody positiveanti-LRP4 antibody positiveseronegative gMG
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.