A Phase 3 interventional study of Placebo and Cladribine Low Dose in Generalized Myasthenia Gravis, sponsored by Merck Healthcare KGaA, Darmstadt, Germany, an affiliate of Merck KGaA, Darmstadt, Germany. Recruiting at 154 sites in 25 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-21.
Sponsored by Merck Healthcare KGaA, Darmstadt, Germany, an affiliate of Merck KGaA, Darmstadt, Germany (part of Merck KGaA, Darmstadt, Germany) · Phase 3, Interventional, and Treatment
The purpose of this clinical study is to determine the efficacy and safety of a new oral cladribine formulation in participants with Generalized Myasthenia Gravis (gMG) in comparison to placebo. It will also investigate the sustained efficacy, the need for retreatment, and the long-term safety of oral cladribine in gMG. An additional component is included to characterize the Pharmacokinetics (PK) of the new cladribine formulation in gMG participants. This study is divided into 3 periods: the double-blind placebo control (DBPC) pivotal period, and 2 extensions, the blinded extension (BE) and the retreatment (RT) period. Furthermore, in trial interviews will be conducted as a sub-study to MyClad with a sub-set of participants to gain an in depth understanding of the participant cladribine treatment and study experience.
330 studies on the registry are indexed under Myasthenia Gravis; 144 are open to participants now.
This study's planned enrollment of 264 is above the median of 44 across 217 interventional studies indexed under Myasthenia Gravis.
Browse Myasthenia Gravis studies →Merck Healthcare KGaA, Darmstadt, Germany, an affiliate of Merck KGaA, Darmstadt, Germany is the lead sponsor of 55 studies on the registry; 4 are open to participants now.
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Diagnosis of Myasthenia Gravis with generalized muscle weakness, meeting clinical criteria for Myasthenia Gravis Foundation of America Class II to IVa classification.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
DBPC Period: Participants will be administered with Placebo, orally as 2 separate treatment courses starting on Day 1 and at the beginning of Week 5. BE Period: Participants initially randomized to placebo matched to cladribine in DBPC period will receive cladribine Low Dose or High Dose, orally as 2 separate treatment courses starting at the beginning of Week 25 and at the beginning of Week 29 and retreated if clinically justified with placebo matched to cladribine. RT Period: If clinically justified, participants requiring retreatment with cladribine Low Dose or High Dose or cladribine supplemental dose will receive the selected dose of cladribine or matching placebo regimen.
Other: Placebo · Drug: Cladribine Low Dose · Drug: Cladribine High Dose
DBPC Period: Participants will be administered with cladribine Low Dose, orally as 2 separate treatment courses starting on Day 1 and at the beginning of Week 5. BE Period: Participants initially randomized to cladribine Low Dose in DBPC period will receive placebo matched to cladribine as 2 separate treatment courses starting at the beginning of Week 25 and at the beginning of Week 29 and retreated with cladribine supplemental dose if clinically justified. RT Period: If clinically justified, participants requiring retreatment with cladribine Low Dose regimen and/or supplemental dose will receive the selected dose of cladribine or matching placebo regimen.
Drug: Cladribine Low Dose
DBPC Period: Participants will be administered cladribine High Dose, orally as 2 separate treatment courses starting on Day 1 and at the beginning of Week 5. BE Period: Participants initially randomized to cladribine High Dose in DBPC period will receive placebo matched to cladribine as 2 separate treatment courses starting at the beginning of Week 25 and at the beginning of Week 29 and retreated with cladribine supplemental dose if clinically justified. RT Period: If clinically justified, participants requiring retreatment with cladribine High Dose regimen and/or supplemental dose will receive the selected dose of cladribine or matching placebo regimen.
Drug: Cladribine High Dose
Participants will receive placebo matched to cladribine in two courses separated by 4 weeks.
Participants will receive cladribine low dose in two courses separated by 4 weeks.
Participants will receive cladribine high dose in two courses separated by 4 weeks.
Change from Baseline in Myasthenia Gravis - Activities of Daily Living (MG-ADL) Scale Score at Week 24 During the Double-Blind Placebo Controlled (DBPC) Period
Time frame: Baseline, Week 24
Change from Baseline in Quantitative Myasthenia Gravis (QMG) Scale Score at Week 24 During the Double-Blind Placebo Controlled (DBPC) Period
Time frame: Baseline, Week 24
Percentage of MG-ADL Responders at Week 24 During the Double-Blind Placebo Controlled (DBPC) Period
MG-ADL responder is defined by achieving \>= 3 points decrease in MG-ADL score.
Time frame: At Week 24
Change from Baseline in Myasthenia Gravis Composite (MGC) Scale Score at Week 24 During the Double-Blind Placebo Controlled (DBPC) Period
Time frame: Baseline, Week 24
Percentage of Quantitative Myasthenia Gravis (QMG) Scale Responders at Week 24 During the Double-Blind Placebo Controlled (DBPC) Period
QMG responder is defined by achieving \>= 4 points decrease in QMG score.
Time frame: At Week 24
Time From Initial Cladribine Full Dose Treatment to First Retreatment or Rescue Treatment up to end of Study
Time frame: Up to End of Study (Week 144)
Number of Participants With Adverse Events (AEs) and Adverse Events of Special Interest (AESIs)
Time frame: Up to End of Study (Week 144)
Number of participants with Adverse Events (AEs) by Severity as per National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.0
Time frame: Up to End of Study (Week 144)
Number of Participants with Abnormal Laboratory Variables including Absolute Lymphocyte Count and Vital Signs
Time frame: Up to End of Study (Week 144)
Pharmacokinetic (PK) Plasma Concentration of Cladribine
Time frame: Pre-dose, 0.25, 1, 2, 3, 4, 6, 8 and 24 hours post-dose
Change from Baseline in the Revised Myasthenia Gravis Quality of Life - 15 Scale (MG-Qol15r) Score at Week 24 During the Double-Blind Placebo Controlled (DBPC) Period
Time frame: Baseline, Week 24
Number of Participants with Abnormal ECG parameters
Time frame: Up to End of Study (Week 144)
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Plan to share: Yes — IPD supporting publicly available results will be evaluated for sharing.
Supporting information: Study protocol, Statistical analysis plan, Clinical study report, Analytic code
Time frame: IPD from completed trials will be publicly available within 6 months after all of the following events: Approval of a product/new indication by major authorities (FDA, EMA, PMDA if requested) with no pending submissions Public results via primary manuscript or trial registry disclosure Legal authority to share data Privacy protections are in place If approval is not sought or development is globally discontinued, data will be publicly available within 18 months after global trial completion. Further information on how to request data can be found on our website bit.ly/IPD21
Access criteria: Qualified researchers may propose access to IPD from sponsored trials via https://vivli.org/members/ourmembers/.
Data sharing details ↗ · vivli.org
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Merck Healthcare KGaA, Darmstadt, Germany, an affiliate of Merck KGaA, Darmstadt, Germany →