Prospective Observational Long-term Safety Registry of Multiple Sclerosis Participants Who Have Participated in Cladribine Clinical Trials

Inclusion Criteria:

Prior enrollment into selected oral cladribine clinical trials as of randomization to either study drug or placebo, once participation in the clinical trial has ended
Written informed consent was given

Exclusion Criteria:

Participants who cannot be reached by telephone
Participants unable to answer the registry questionnaires and who do not have a next of kin or caregiver able to answer the registry questionnaires
Participants who - either during the lag interval or subsequently enter an interventional study