Analgecine , the extracts of Vaccinia -inoculated rabbit skin, effectively alleviates the chronic low back pain with little side effect – A randomized multi-center double-blind placebo-controlled phase 3 clinical trial

Abstract Background Chronic low back pain affects daily activities at home and workplaces and causes a huge economic burden. Current therapeutic options are very limited and the effects of available pharmacological agents are less than satisfactory. While NSAIDs might be effective for the short term and opioids might help with urgent pain relief and improving the life quality, their long-term use is associated with significant side effects and drug misuse or abuse. To seek alternative pharmacological agents for effective treatment, we examined the therapeutic potential of the extracts of Vaccinia variola -inoculated rabbit skin ( Analgecine, abbreviated as AGC ) in patients with chronic low back pain due to degenerative vertebral disorders. Methods In this randomized multi-center double-blind placebo-controlled phase 3 clinical trial (Chinese Clinical Trial Registry number 2009L01498), we enrolled patients (aged 26–70 years) with chronic low back pain for at least 3 months due to degenerative spinal (vertebral) disorders from 7 medical centers in China, and randomly allocated 459 participants to receive oral AGC or placebo for 28 days to study the efficacy and safety of AGC . Randomization was performed according to a centralized randomization schedule, which was blocked by study sites and generated by an unmasked statistician independent of study conduct and data analysis. Both participants and staff at each study site were masked to treatment assignment. The primary efficacy endpoint was the change of the mean pain intensity, based on an 11-point numerical rating scale, between the baseline and the last week of treatment, with the primary efficacy analysis of intention to treat. The ratio between exposed and unexposed groups was designed to be 3:1 in order to increase the likelihood of demonstrating the AGC effect upon repeated measures. Results 347 patients were assigned to receive AGC (4 units/tablet; 2 tablets twice a day) and 112 patients were to take placebo. Among them, 324 patients taking AGC and 112 receiving placebo completed the assessment. Patients receiving AGC reported significant pain relief at the end of week 2 and 3 compared to those taking placebo, with mean reduction of the pain scores as 1.7 vs. 0.9 at week 2 (p