Efficacy and Safety of EN3324 (Axomadol) in Subjects With Chronic Low Back Pain

Inclusion Criteria: * 18 years of age or older * Are females who are participating abstinence or using a medically acceptable form of contraception or have been post-menopausal, biologically sterile, or surgically sterile for more than 1 year. * Have been on an unchanged regimen of analgesic medication for chronic low back pain on a daily basis for at least 3 months prior to screening; subjects taking opioids must not exceed total daily doses of 90mg oral morphine equivalent * Have a history of moderate to severe CLBP Exclusion Criteria: * Have evidence of or a history of alcohol and/or drug abuse * Have pain secondary to a confirmed or suspected neoplasm * Intend to alter their physical therapy regimen during the study. Subjects who begin or end physical therapy (either home exercises or formal therapy sessions) 2 weeks prior to screening or during the study period will be excluded from the study * Have a history or physical examination finding, which may confound pain-related data (e.g., fibromyalgia, radiculopathy)