Study to Evaluate the Safety and Efficacy of ABT-712 in Subjects With Moderate to Severe Chronic Low Back Pain (CLBP)

The study used a randomized withdrawal design with an open label (OL) period prior to a double-blind (DB) period. Participants who were receiving benefit and were tolerating ABT-712 during the OL period were randomized into the DB period. Study drug was given for a total of 8 weeks, which included up to 3 weeks in OL, up to 4 weeks in DB, and a 1-week DB taper. During the OL period, all participants took increasing doses of ABT-712 until they were taking 2 tablets, twice daily. During the DB period, participants in the ABT-712 group took 2 ABT-712 tablets, twice daily throughout the 4 weeks, while participants in the placebo group took 2 placebo tablets twice daily.