SEATTLE — Oral cladribine reduced the annualized rate of relapse in patients with the relapsing-remitting form of multiple sclerosis by over half in a phase III trial presented at the annual meeting of the American Academy of Neurology.
Cladribine, an antineoplastic used primarily to treat hairy cell leukemia, has several properties relevant to the treatment of multiple sclerosis (MS): It produces a sustained reduction in numbers of CD4 and CD8 T cells and of B cells, decreases levels of proinflammatory chemokines, and crosses the blood-brain barrier, according to lead investigator Dr. Gavin Giovannoni, a neurologist at Barts and The London School of Medicine and Dentistry, London.
He and his coinvestigators enrolled patients who had definite, active relapsing-remitting MS and an Expanded Disability Status Scale (EDSS) score of 5.5 or less.
Of those patients, 433 received a lower total dose of cladribine (3.5 mg/kg), 456 received a higher total dose of cladribine (5.25 mg/kg), and 437 got a placebo. Medication was taken for only 4-5 days a month in 2-4 months a year.
“We were quite surprised,” Dr. Giovannoni said of the trial's results for the primary end point, the annualized relapse rate after 96 weeks of treatment. “Despite having a relatively low event rate in the placebo arm, there was a robust and highly significant impact on relapse rate in both [experimental] study arms.”
Specifically, in intention-to-treat analyses, annualized relapse rates were 0.14 and 0.15 in the lower- and higher-dose cladribine groups, respectively, compared with 0.33 in the placebo group. The differences corresponded to statistically significant 58% and 55% relative reductions.
Compared with their counterparts in the placebo group, patients in the lower- and higher-dose cladribine groups were significantly less likely to experience a relapse (relative risks, 0.52 and 0.54) or progression (hazard ratios, 0.67 and 0.69).
Dr. Giovannoni reported that he has received personal compensation from Merck-Serono.
The study was supported by Merck Serono S.A., Geneva, an affiliate of Merck KGaA, Darmstadt, Germany.