Relapses in people with multiple sclerosis treated with cladribine tablets followed for up to 5 years: a plain language summary

Neurodegener Dis Manag. 2022 Dec;12(6):303-310. doi: 10.2217/nmt-2022-0019. Epub 2022 Aug 26.


What is this summary about?: This is a summary of an article originally published in the Multiple Sclerosis Journal. The article presents the results from the CLARITY and CLARITY Extension studies, which looked at how well cladribine tablets work in treating people with multiple sclerosis (shortened to MS). Cladribine tablets are a medication approved for treating relapsing forms of MS. This study looked at how treatment with cladribine tablets affects the frequency and severity of relapses in people with MS. A relapse is when new symptoms develop or old symptoms return or get worse after a period of stability or improvement.

What happened in the studies?: In the CLARITY study, 870 people received either cladribine tablets (3.5 mg/kg, the approved dose) or placebo (a dummy pill). After the CLARITY study ended, some participants who received cladribine tablets chose to take part in a second study called the CLARITY Extension study. Of these participants, 98 were given placebo for 2 more years following an interval period of up to 10 months between participating in each study.

What were the results?: People with MS who were treated with cladribine tablets for 2 years in the CLARITY study had lower risks of any relapse compared with those given placebo. Participants taking placebo (after cladribine tablets) in the CLARITY Extension study experienced these same benefits, which continued for up to 3 more years after having received cladribine tablets in the CLARITY study.

What do the results mean?: Researchers concluded the recommended 2-year dosing of cladribine tablets may reduce the number and severity of relapses in people with MS for up to 5 years. Clinical Trial Registration: NCT00213135 ( Clinical Trial Registration: NCT00641537 (

Keywords: CLARITY; CLARITY Extension; cladribine tablets; lay summary; multiple sclerosis; plain language summary; relapse.

Publication types

  • Review
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cladribine / therapeutic use
  • Humans
  • Immunosuppressive Agents / therapeutic use
  • Language
  • Multiple Sclerosis* / drug therapy
  • Multiple Sclerosis, Relapsing-Remitting* / diagnosis
  • Multiple Sclerosis, Relapsing-Remitting* / drug therapy
  • Recurrence
  • Tablets / therapeutic use


  • Cladribine
  • Immunosuppressive Agents
  • Tablets

Associated data