A phase II randomized, double-blind, placebo-controlled safety and efficacy study of lenalidomide in lumbar radicular pain with a long-term open-label extension phase

Abstract

Objective. This phase II study assessed lenalidomide efficacy and safety. Design. Three-phase core study: 14-day prerandomization, 12-week treatment, and 52-week open-label extension. Setting. Fourteen US centers from July 2005 to July 2007. Subjects. Chronic lumbar radicular pain patients without history of nerve injury or deficit. Methods. Subjects were randomized (1:1) to doubleblind treatment with lenalidomide 10mg or placebo once daily for 12 weeks, followed by a 52-week open-label extension. A 12-week, single-center, randomized-withdrawal (1:2, lenalidomide:placebo), exploratory study with open-label extension was undertaken in 12 subjects from the core extension who were naı¨ve to neuropathic medications and with at least a two-point decrease from baseline average daily Pain Intensity–Numerical Rating Scale score. Results. Of 180 subjects enrolled, 176 had at least one postbaseline measure; 132 completed the12-week treatment phase. In the core study, no statistically significant difference in Pain Intensity–Numerical Rating Scale mean change (20.02, P50.958) was observed at week 12 between lenalidomide and placebo; proportions achieving pain reduction at week 12 and other secondary measures were comparable between lenalidomide and placebo. In the exploratory study, week 12 mean changes in Pain Intensity–Numerical Rating Scale scores were 20.05 (lenalidomide: N53) and 2.11 (placebo: N58). Mean changes in Brief Pain Inventory–short form interference scores were 23.33 and 8.38, respectively; scores at six months were maintained or decreased in 10 of 12 subjects. Conclusions. While this study does not support lenalidomide use in an unselected lumbar radicular pain population, an immunomodulating agent may relieve pain in select subjects naïve to neuropathic pain medications.