RN624 In Adult Patients With Chronic Low Back Pain

Inclusion Criteria: * Male or female of any race, \>18 years of age and have BMI ≤39 kg/m2 * Present with duration of chronic low back pain of ≥3 months requiring regular use of analgesic medication (\>4 days per week for the past month) * Primary location of low back pain is between the 12th thoracic vertebra and the lower gluteal folds, with or without radiation into the posterior thigh, classified as Category 1 or 2 according to the classification of the Quebec Task Force in Spinal Disorders * Must have a score of ≥4 for Low Back Pain Intensity (NRS) while on current treatment at Screening, and completes at least 4 daily pain diaries during the 5 days prior to Randomization, with an average Low Back Pain Intensity (NRS) score of ≥4 Exclusion Criteria: * Back pain due to visceral disorder (i.e. endometriosis) or Back pain due to recent major trauma (i.e. vertebral fracture, post-traumatic spondylolisthesis) * History of lumbosacral radiculopathy, spinal stenosis associated with neurological impairment, or neurogenic claudication * Osteoporotic compression fracture within the last 6 months * Known history of: Rheumatoid arthritis; Seronegative spondyloarthropathy (i.e., ankylosing spondylitis, psoriatic arthritis, reactive arthritis, inflammatory bowel disease-related arthropathy); Paget's disease of spine, pelvis or femur; Fibromyalgia; Tumors or infections of the spinal cord * Patients receiving acetaminophen only to manage their chronic low back pain * Any uncontrolled or untreated chronic disease