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

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 double-blind 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 naive 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 (-0.02, P=0.958) 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 -0.05 (lenalidomide: N=3) and 2.11 (placebo: N=8). Mean changes in Brief Pain Inventory-short form interference scores were -3.33 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 naive to neuropathic pain medications.